التقييم الحسي ل لأغذية sensory evaluation of food

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ألغذيةألغذيةالتقييم الحسي لالتقييم الحسي ل Sensory evaluation of Food

علي كامل الساعد علي كامل الساعد أ.د أ.د المحاضر/ المحاضر/

رئيس الجمعية األردنية للتقييم الحسي

عضو الجمعية البريطانية للتقييم الحسي

كلية الزراعة/الجامعة األردنية ،عمان/األردنكلية الزراعة/الجامعة األردنية ،عمان/األردن

email :[email protected] :[email protected]

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Introduction

• Sensory evaluation is commonly used in quality control and product development of food.

• Sensory evaluation is made by the senses of taste, smell, vision , touch and hearing

• When the food is eaten, the complex sensation that results from the interaction of our senses is used to measure the food quality

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Objective &Subjective methods

• Food quality can be measured either objectively by using instruments like determination of protein using Kjeldahl method, or objectively by using people in the sensory evaluation method

• The importance of sensory analysis has grown more and more inspite of the availability and widespread of highly sensitive measuring instruments such as HPLC, GC, AAS …etc

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Comparing instruments with sensory tests

• Presently, food analyst are certain that optimal measurement of food quality can be achieved by coordinating between instrumental and sensory evaluation

• In the instrumental analysis, there is a limit where no signal appears such as 1 ppm

• While human senses which can be called biological detectors may still perceive an odor or taste which has a concentration less than 1 ppm

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Comparing instruments with sensory tests

• The instrument can analyse only one component while human senses can give a total impression of aroma, taste and texture

• Accordingly, sensory analysis is very important and equals if not superior to the instrumental methods in the field of food product development

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History

• Modern sensory analysis started only before 70 years in the Scandinavian countries (1940)

• Ten years later (1950), the European countries used the sensory analysis in their food firms

• By 1970, sensory analysis developed into a science. It is now being taught in many European and American universities. University of California at Davis as example offers a degree program in sensory analysis

• Many food firms in the west offer industrial courses in sensory analysis for their employees

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Establishing of sensory groups

• Establishing of scientific sensory groups started only before about 15 years (1999).

• The 1st one was established in UK by The Institute of Food Science &Technology.

• There are special conditions to be a member in

• such sensory groups.

• These sensory groups aim at dissemination of food sensory evaluation culture through workshops, seminars and conferences

• Fortunately, the Jordanian Sensory Group is being established these days and it is expected to start its activities very soon.

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Sensory groups

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Sensory groups

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Sensory groups

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الجمعية األردنية للتقييم الحسي لألغذية

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ISO and Sensory evaluation

• The International Standard Organization (ISO) started before about 20 years, standardization of the sensory testing methods and a significant work has been achieved.

• Good and reliable sensory results can be obtained and analyzed statistically only if exact and standard scientific sensory testing methods are applied.

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• Terms related to sensory analysis:• Panelists: persons who test the food and judge

it is named panel, panelist, assessors or judge. Panelist may be one person or several hundred depending on the type of the sensory evaluation method.

• Testing Area: A special room or lab should be designed for carrying the sensory tests. This room should have partitions to separate panelists and has suitable stools, proper lighting, openings and a source of water.

• The proper testing time was found to be later morning or mid afternoon.

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Sensory laboratory

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Sensory laboratory

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Sensory terms

• Sample preparation for sensory evaluation :• Kitchen: a well equipped kitchen is necessary to

prepare food samples for sensory evaluation.• Number of samples to be given, time or duration

between offering samples, soaking or using water…etc. are important factors that should be taken into consideration.

• Selecting the proper panel test and in this respect, we have many tests where each one suits a special purpose, among the different panel tests we have :

• Uniformity in samples is important,

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• Serving temperature should be selected properly according to the type of food. For beverage a temperature of 10-15 ºC is suitable while for ice cream a temperature of -1 ºC is recommended. In hot food like hamburger a temperature of 60 ºC is adviced.

• Containers:colorless or white , identical containers should be used for each sample to be tested. Disposable paper or plastic containers are preferable.

• Quantity of sample, in the case of difference test, this quantity is 16 ml for liquid or about 28 g for solid , and in preference test the quantity is doubled.

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Sensory terms• Number of sample to be tested by panelist, it is is

variable and depends on the type of the food to be tested and the experience of panels. However, a preliminary test should be conducted to determine how many samples can be given to the panelists to evaluate them properly.

• Coding which means giving a code or a number to the samples to be tested is important and should not affect the results. It is not recommended to give numbers like 1, 2 or A, B ; but it is better to code the samples with a three digits numbers.

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Sensory terms

• Rinsing is also a step in sensory testing, it is recommended to rinse your mouth with worm water after testing fatty foods; in cheddar cheese it is adviced to rinse with water , then to wait 5 minutes before testing the next sample .

• Information about the sample: little information should be given about the sample to be tested , otherwise the decision of the panels will be affected by these information. For this reason the persons involved in the preparation of the tested samples should not be included in the test.

Sensory terms• The panelists can be grouped to trained panelists, semi trained panelists and untrained panelists. • In case of trained panelists a number of 4-5 is enough for the

test, • while for semi trained a number of 10-20 is preferable and • for untrained person, the larger the best. • Panelist should be of good health and should stop smoking,

eating and drinking before 30 minutes of the test. The panelists should be trained.

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Sensory Quality Attributes

• Food quality which can be detected by our senses can be divided to 3 main factors:

• Appearance factors• Textural factors• Flavor factors• Appearance factor can be judged by sight and touch

senses. They include size, shape, pattern, wholeness, damage and defects.

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• Appearance factor also includes color, glossy, transparency, turbidity and consistency (gel, flow, viscosity and spread)

• Textural factors include the food properties which can be judged by both mouth feel and hand feel.

• Mouth feel properties include chewiness, fibrousness, gritteness. Mealiness and stickiness.

• Hand feel properties include the softness, firmness and juiceness.

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Sensory evaluation and quality of food

• Sensory evaluation is considered one of the most important tools used in measuring food quality.

• There are some quality parameters that can not be measured accurately by instruments and the role of instruments is complementary to sensory evaluation.

• Examples for such situation are the different tastes and odors.

• Accordingly, we will focus on some quality parameters that have to be measured sensorial.

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Sensory terms• There are a special sheets or questionnaire for each sensory

test, the results should be tabled and analyzed statistically to find if there is a significant difference or not.

• Factors affecting sensory evaluation: • expectation error (more information.• Logical error (yellow color in potato) • Suggestions.• Contrast effect (poor or good sample).• Stimulation error (other variables).• Halo effect (more than one factor) .• Motivation (importance).• Positional (bias i.e. very simple different and selection the

middle sample).

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• Flavor factors quality parameters can be judged by the two senses taste and smell.

• Under taste, we can find the terms salty, sour, bitter, and sweet.

• Under odor , we can find the terms acid, burnt and fragrant.

• Under the off-flavors we can find the terms over-cooked, stale, enzymatic, chemical and contaminated.

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• Flavor factors (taste and odor) are subjective and difficult to be accurately measured.

• It is possible to find hundreds of descriptive terms regarding flavor depending on the type of food.

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Complexity of flavor factor• Flavor in food is very complex, • an example is coffee flavor where more than 600

compounds responsible for coffee flavour have been separated and identified

• and inspite of the great progress in the analytical instrumentation in this field like the use of gas chromatography techniques in identifying the flavor components,

• flavor of food still a complex subject and not yet fully understood, specially with regard to the response of buds on the tongue to the different tastes.

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Flavor factors are subjective

• Flavor factors include taste and odor (smell, aroma) and can be detected by either tongue or nose. Taste and odor are largely subjective and as a result hardly to be accurately measured.

• Subjective: can be described as sweet… etc.• Objective: can be measured and take a value as in ash,

protein…etc.• Since flavor factors are subjective, there is a large possibility

for difference of opinion regarding evaluation. However this is expected due to:

• People differ in their sensitivity to detect taste and odor.• If they detect them correctly, people differ in their preference.

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Effect of color and texture on the flavor

• Another thing which is important here is the effect of color and texture on the flavor of the food. During evaluation of flavor, color, and texture often interfere with the evaluation of the flavor.

• As an example flavor of chery and strawberry is associated by people with the red color. Also people frequently judge the thicker food (texture) as richer in flavor.

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Methods for measuring flavor

• Panel Tests or Taste Panels

• Measuring Flavor:

• Volatile material by GC

• Flavor contributing substances by chemical and physical means as: sugar, salt and acid.

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Measuring flavor of food

• All these are research quality tools, but when it comes to the consumer quality acceptance, the above chemical, physical, and instrumental methods, can not work. The only means is to measure the quality using people.

• Measuring flavor of food:• We have to use the panel tests; in conducting panel

tests, many points should be considered such as the panelists or judges: their number, trained or semi-trained or untrained; testing room: the light, color of tables, chairs, ventilation and so on.

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Methods for Sensory Evaluation

• Many methods for sensory evaluation are available but the food quality control or product developer should be familiar with the advantage and disadvantage of each method and should select the method which properly suit the property to tested or examined in the food.

• Sensory evaluation methods can be classified to 3 groups as follow:

• Difference test.

• Preference tests.

• Descriptive tests.

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• Difference tests include the following methods:

– Triangle test

– Duo-Trio test

_ Simple paired comparison test.

– Scheffe paired comparison test

– Multiple paired comparison test.

– Ranking.

– Scoring.

– Ratio-scaling.

• Each of the above methods is applied for certain evaluation test and has its own method of data analysis.

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• Descriptive Test: • Flavor profile test.• Texture profile test.• Preference Tests: • Paired comparison and Multiple compression

preference tests.• Ranking• Hedonic scale test

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Choosing the proper panel test

• - Hedonic scale tests• - Triangle tests.• - Multiple comparison test. • - Ranking test: taste the following food samples and

arrange them 1st, 2nd. 3rd and so on according to your preference.

• Collecting sheets, tabulating, statistical analysis and giving conclusions.

• These tests are applicable not only for evaluation of flavor factor but also for other food quality factors.

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1st labRecognition test for the four basic tastes

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Recognition test for the four basic tastes

Our senses of odor or smell and taste are as important as our senses of vision and hearing regarding the test sensation.

Tongue and the hard palate are of interest for such sensation.

The four basic tastes are sweet and it is sensed at the tip of the tongue salty or saline are sensed at the tip and edge of the tongue, the third taste is the sour and it is sensed at the edge of the tongue. The fourth taste is the bitter and it is sensed at the back of the tongue .

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• In this lab we will practice the four basic tastes.• Sucrose soln will be used at two conc. i.e 0.4 and

0.6% to indicate the sweet taste. • Sodium chloride will be used for salty taste, and

tow conc. will be used i.e 0.08 and 0.16% . • Three conc. of citric acid (0.02 , 0.03 , and

0.04%) .will be used for identifying the sour taste.

• Bitter taste will be identified using quinine sulphate two conc. will be used i.e 5 and 10 ppm.

• Another soln will be given as a neutralizing agent, it will be water at 40c.

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Preparation of stock and working solutions

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Samples Preparation

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Water Quality

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Glassware and cleanliness

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Coding of Samples

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Preparation of stock and working solns.

• Trained personal, • weighing and quantitative transference• volume of the sample• (test soln II) • Sweet taste (sucrose) : 20g / 100ml (20%) stock soln .

(0.4%): 10ml from stock ------ 500ml (test soln I)

• (0.6%): 15ml from stock ---- 500ml (test soln II)

• Salty taste (sodium chloride):10g/100ml(10%)stock soln 0.08 4ml / 500ml (test soln I)

• 0.15 7.5ml / 500ml

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Preparation of stock and working solns.

• Sour taste (citric acid) : 1 g/100 ml (1 %) stock soln • 0.02 10ml / 500ml (test soln I)• 0.03 15ml / 500ml (test soln II) • 0.04 20ml / 500ml (test soln III)•

• Bitter taste (quinine sulphate) : 50mg /1000ml (0.005%) stock soln

• 5 ppm 50ml /500ml (test soln I) • 6 ppm 120ml / 1000ml (test soln II)• As you remember we can use three methods for preparing soln, the

1st is % w/w (weight / weight), the 2nd is % w /v and the 3nd is % v/v

•

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Taste testing technique

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Taste testing technique

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Results presentation and discussion

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Test sheet filling

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3rd Lecture: Odour recognition test

• We can smell while breathinng, but we perceive odours more intensely by sniffing.

• The sniffing technique, however, should not be applied to all odorants as some of them have a pungent component causing pain.

• We can taste an odorous substance on the tongue (without taking it into the mouth) by the von Skramlik test.

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• Odours can be memorized as one memorizes a foreign language.

• A panel leader with comprehensive technical knowledge and skill will be able to provide many memorization aids so that the panelist’s learning time can be considerably shortened.

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Objectives of Odour recognition test

• The main objective for such test is to train our odour memory.

• Odour can be memorized as one memorizes foreign language.

• It is recommended not to offer more than 3 odours per session to beginners.

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• Some facts have to be taught to beginners.

• In many cases we do not recognize odours which we encounter daily, because we do not pay attention to them.

• These fact always surprises the participants during their first odour recognition tests.

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• Do not make excessive demands upon beginners. It is better to present two or three odours per session over a longer period of time than to give up after 20 odorants in one session.

• No one is necessarily a good test subject because he is able to recognize a number of odours in the first sessions.

• These may have been familiar to him but not to others

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• Of more importance is the ability to memorize unknown odours and to be able to characterize them in detail.

• This ability is later required in descriptive tests (on food quality, off-notes etc.).

• In order to avoid fatigue, different (not similar) odours should be presented in one session.

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• In the literature, it is always recommended that ‘panellists should have good health, and should not suffer from chronic colds’.

• No hints are given, however, as to improve health.

• For many persons the causes for chronic colds and/or a blocked nose are unknown.

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• Medical literature explains that chronic colds may have their origin in suppurated dead teeth and/or root residues.

• As the nerves have been killed and removed, inflammation and suppuration remain undetected because they do not cause pain.

• Chronic sinusitis can also cause constant colds.

• After following medical advice, better results have been obtained from such panellists.

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• The difference between single and complex odours is not only dependent upon the odorants but also upon the background of the candidate.

• Eau de Cologne, for example, is described as a ‘single odour’ by many beginners.

• The trained perfumer, however, analyses the single character notes of this ‘complex odour’.,

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• A number of odorants have, in addition to their odour, a pungent component which causes pain.

• Some people are excessively sensitive to pungency which makes it impossible for them to perceive the odour of the sample.

• In this case, one drop of the odorant is added to 50 or 100 ml of water.

• In smelling the aqueous solution (Or suspension) the pain causing pungency becomes so weak that the odour is perceived without difficulty.

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• When tasting this solution the odour can be perceived more intensely as it becomes more volatile when warmed in the mouth.

• This technique should always be used by persons who are more taste-sensitive than odor-sensitive.

• Once the odour has been perceived in this way it will be more easily perceived by smelling at

a later time

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Anatomy of the nose

• The nose has the task of smelling as well as warming and filtering of the air we breath before it passes to the lungs.

• There are three horizontal folds in the nose where air passes through during breathing (area a) , (area b) and area “R”.

• Area “a” for normal breathing while “b” for sniffing. • The upper part of the nose “R” which is called

olfaction region is for odour sensation (fig 1).

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Human Nose Passages and Folds

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Physiology and smelling technique

• The inspired air does not stream through the upper part of the nose (R area) in ordinary breathing ,

• to make air reach to the “R” area sniffing is needed for this purpose.

• Sniffing for three times is satisfactory for odour sensation otherwise fatigue is encountered .

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Von Skramlik test

• The main objective of this test is to prove that the presence of odorants in air is not sufficient to cause odour sensation.

• It is done by closing the nose by fingers and by inhaling and exhaling through the mouth for an odorant.

• After practicing by the mouth for at least 3 times, while the bottle of the odorant is close to the lips, the mouth is closed and the nose is opened.

• At this time the odour sensation takes place.

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Von Skramlik test

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Reccommendations

• Large no of odors may cause physical and mental exhaustion for several days.

• Large no of odorants as well as the order of their presentation my cause odor fatigue.

• It is advised to smell sweet odor like vanillin after having smelled fruity one like lemon oil or vice versa.

• By such technique we can avoid odor fatigue.

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Reccommendations

• It is recommend to exclude subjects suffering for cold during odor recognition test.

• Sometimes, it is difficult to exclude them, so they can have special treatment to cancel the cold effect. This can be achieved by special medical treatment (teeth repair) or by taking Japanese medicinal herb oil.

• Odorants having pain causing component should not be inhaled in a concentrated form but diluted

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Samples preparation and presentation

• Most odorant are presented either in 10% or 1% soln.

• Solvent might be water or ethanol. • Solid sample might be ground and diluted with

sugar such as cinnamon.

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• Sample solutions are presented either on smelling strips or on soaked cotton wool. Filter paper might also be used to such purposes.

• Time intervals between sample preparation and odor sensation is variable.

• Some should be prepared on the day of sensation others before one week such as slightly rancid coconut flakes.

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Taste and odor blindness

• Sometime we may find subjects that are bitter taste blinders.

• This is very dangerous since consuming of 7 and 60 raw bitter almond kernels are fatal for children and adults respectively.

• The same apply also for odor blind subject.

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• Benzaldehyde which is formed due to hydrolysis of amygdaline (a glycoside in almonds and apricot) is not poisonous and smell similarly to better almond note

• but hydrocynamic acid formed due to the hydrolysis of amygdaline is poisonous

• and this explains why odor or taste blindness may be sometimes very dangerous.

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2nd lab : odour recognition test

• Our today lab will concentrate on the odour recognition test as well as the Von Scremlik test.

• A special sheet will be distributed for you and some odor samples.

• Yon have to practice the odor sensation and to fill the sheet with the correct answer.

• Don’t forget to describe the odor you examine.

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• Before odor recognition test you have to try the Von Scramlik test.

• A discussion will follow the test to see our correct or wrong answers.

• Results might be presented on the blackboard. • In case of significant incorrect answers we have to

repeat the tests more than one time with more concentration and sometimes with concentrated odorants.

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Aroma recognition test

Anatomy of the nose : In the last week during demonstrating of odour

recognition test it was mentioned that there are 3 folds in the nose i.e.

(a) , for normal breathing , (b) for sniffing and (R) which is called olfaction region for odor

sensation.• The aroma of a product can be perceived both by

smelling and tasting for example, coffee aroma

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Further derails about the anatomy of the noseThe nose has two openings; the nostrils are the

anterior nares and the openings at the back of the throat are the posterior nares or choana.

Regarding aroma, its perception is achieved by two means i.e.

by the nostril or what is called the anterior nares (smelling) and

by the posterior nares or what is called choana (tasting).

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Physiology of aroma perception

• As shown in Fig. 6.3, two paths lead to the regio olfactoria (R); externally through the nostrils (a), and internally through the choana (b).

• The odorous constituents of a substance are frequently more strongly perceived by tasting than by smelling.

• When taking the sample into the mouth, it becomes warmed and the odorous constituents become more volatile.

• This is the reason why, in odour recognition tests, tasting instead of smelling was suggested for people having difficulties when smelling.

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Demonstration of the physiology of Aroma

perception

In order to distinguish between aroma perceived by smell and aroma perceived by taste, the nose has to be blocked.

The panel leader demonstrates the exercise without reference to the test substance (cinnamon sugar).

He gives the following instructions: Hold beaker Z with the sample at a distance of

about 20 cm.

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Remove the aluminium foil cover, but do not look into the beaker and do not smell the sample!

Take one spoonful of the sample, but hold it away from you.

Block your nose with the other hand and keep it blocked while you ‘take the sample into your mouth (see Fig. 6.4).

Chew the sample with your mouth open (in order not to suffocate).

Analyse the aroma (flavour). You will perceive only ‘sweet’.

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Slurping a special test technique

• As swallowing samples is not wholesome , a special technique was devcloped by coffe and tea testers called slurping.

• It replaces the sensory action of swallowing • In swallowing , the aroma filled air is

pressed into the regio olfactoria via the posterior nears .

• This also occures in slurping but takes more effort.• For some people , it may take a long

time to learn the correct technique of slurping.

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• The following has to be donc vcy qLnckly . close the mouth and keep it c ose w n C YOU open t e nose. n y now w ien you he able to perceive the aroma of... (the participants shou 1(1 write down or tell what they prcccive). This exercise is so impressive that it should never be left out The story of the apple and tJI OfliOll in the literature , it is. stated that commmutcd apples and onions cannot be differentiated from one another when tasted with eyes and nose closed also ,there is many similar pairs of samples I —red wine and unsweetened black coflc. 2—a raw apple and raw potato. 3-a tomato and an orange. 4-d ii uteci raspberry syrup and sweetened milk Samles which cannot be differentiated when tasting withcyes and nose closed, it is important that the samples differ merely in their odorous constituents . if one milk samples is sweetened with sugar ( 42 . 75 gm sucrose to 1 litre whole milk ) and the other with vanillin sugar ( 42 . 75 gin vanillin sugar (5 small packages) to I litre whole milk) no differentiation is possiple . another suitable comparison is scalded milk versus burned milk . (it is rcommended that the samples be pourccI through a sieve befor taste-testing.) *sarnpi iresentation masking the colour with red or with sodium vapour light the colour differences are often not completely masked coloured glasses or plstic backers offer another way to masking coloures, colouring of samples is another wa’ of masking colour and is in common use in the confectionery industry ( colouring of candies ) and mostly wc we use red light for colour masking. Also ,that important to keep glasses odou rfree , by fill it with 3-5 % acetic acid and soak over night then rinsing with clear water.

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The story of apple and onion

Apple and onion can’t be differentiated from each other when are properly prepared i.e. peeled and ground twice (the texture should not be a variable).

The work should be in pairs, the question to be asked : Is it apple or onion?

The samples should be given randomly and their no. should be 4 pairs at least.

The eyes and nose should be closed. Such test will teach us the importance of the

olfaction region

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Aroma recognition test

• Different foods are given to the students to get experience with various types of food aroma.

• Fruit and vegetable juices are widely used for such purposes.

• Juices used are either natural or diluted.• Color differences have to be masked by

colored light, by using colored beakers or by coloring the samples.

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• Aroma recognition tests for juices will be conducted using special forms.

• One of the sheets will be for aroma recognition by smelling, while the other by tasting.

• Each form also include aroma description. • Another sheet or form containing the results

will be distributed to evaluate your results. • In case of incorrect results for any juice, you

have to test again , to get familiar with the aroma of that juice.

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Off-notes

Off-notes such as coated or rancid flavor are of vital important with regard to the aroma recognition in the food industry.

Milk is highly sensitive food and widely used for aquiring the off notes.

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• Two test groups will be organized on the off notes using milk.

• The 1st to identify the bitter , watery , cooked , scorched and sour aroma.

The 2nd test to identify or demonstrate the metallic, cardboard , rancid , cooked aroma or flavor.

All the off- notes tests will be practiced using the smelling and tasting technique.

Don’t forget not swallow the sample , only chew it and describe , then recognize the aroma.

It is better not to see the sample.

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األخرى الطعومAdditional Sensation

Tastes perceived during tasting can be classified to basic tastes and additional tastes or sensation.

As you know, the basic tastes include, sour, sweet bitter and salty.

The additional sensations include temperature sensations, pain sensations. Touch sensations, kinesthetic sensations, sound sensations and color sensations.

Temperature, pain and touch sensations are called cuteneous sensations.

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I. Temperature Sensation

الدافيء : • بالطعم اإلحساس أوال Some foods and beverages are preferably consumed at

specific temperatures. Tea and coffee and soups are consumed hot or warm at about 60 C.

Other foods like soft drinks are consumed cold at about 5 – 10 C, while ice-cream is consumed very cold at 0 C.

Cold and warm or hot sensations are not caused only by tasting hot or cold foods and drinks, but there are some substances that can cause such sensations.

There are coolness receptors and heat receptors on the tongue where consuming some food sensitizes these receptors.

As you see in the table below

• Ia. Warm sensations and mixed warm and pain sensations

• Warm Sensation

• a. warm (15 % Ethanol)

• b. Warm (Powdered Cinamon)

• c. Burning (Warm+Pain) (Powred Ginger)

• d. Neutrilizing Agent ( Butter)

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Table 7.1. Exercise 1a. Warm sensations perceived while tasting and mixed sensations of warm and pain

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• Ib. Cooling, cold and very cold sensations• Cold Sensation• Cool Sensation (Cocoa butter or cocoa fat)• Cold Sensation (Menthol)• Very Cold Sensation (Eucalyptus Oil)

Cooling sensations are due to the stimulation of coolness receptors or sensitizing them through absorption of health by such substances.

It is important to open your mouth and draw in some air to feel the cold sensation.

It is important to take a neutralizing agent after completion of each excersize and before starting a second one.

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II. Pain Sensation

Tasting or smelling of some substances may cause pain sensation.

This pain sensation ranges between very slight pain or tart to a high pain or burning sensations.

Many terms are used to describe the pain sensations and their increasing intensity and as appear in the following table.

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Pain Sensation

باإللم : • اإلحساس ثانيا IIa. Pain sensations ranging from tingle to pain• Tingle and slight pain (Carbonated beverage)

II.b. Pain sensations ranging from astringent to buckery

• Astringent (0.3 % Alum)• Pronounced astringent (Undiluted lemon juice) or (0.4 % alum)• Pukery (0.5 % alum)• Neutrilizing agent: (Milk chocolate)

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• II.c Pain sensations ranging from sharp to burning

• Pungent or pronounced sharp

• ( 5 % Acetic acid or vinegar)

• Burning ( Pepper)

• Neutralizing agent (Butter)

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III. Touch sensations

• It includes pressure and tactile sensations. It is difficult to differentiate between these two sensations and only trained panalists can do that.

• If you touch the back of your hand with your finger tip without moving back and forth you will have the pressure sensation.

• Since there this no movement, pressure sensation is called static sensation.

• Tactile sensation can be felt as before but with moving the tip of the finger back and forth. So tactile sensation is called dynamic sensation.

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Pressure and tactile sensations

• Sensation of different particle sizes are included under the tactile sensation.

• It is clear from the table bellow that small, medium and large particle size can be perceived while tasting.

• Pressure and tactile sensations as appear from the table cover the pairs of opposite

• Sensation.• Touch sensations also include the fat and oil

feeling or coating.

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• الحبيبات ثالثا: بحجم اإلحساس• III.a.Pressure and tactile sensations: Particle size

• Sandy (Small particle size)• (Calcium carbonate)• gritty (Medium particle size)• (Semolina)• Grainy (Large particle size)• (Rice)

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الزيتي • أو الدهني بالطعم اإلحساس• II. III.b.Pressure and tactile sensations:

Oil feeling or coating

• Smooth (Butter)

• Oily:Oil feeling or coating

• (Olive oil)

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• III.c.Pressure and tactile sensations: Opposite pairs

• Mouthfilling (Fullcream UHT milk)• Watery or flat (Skim UHT milk)

•( ) الحركية : الحسية والصالبة النعومة رابعا• Kinesthetic sensation• Soft (White bread)• Medium hard (Zwieback)• Very hard (Hard candies)

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IV.Kinesthetic sensations

• Kinesthetic sensations are perceived while tasting. In this sensation we use our muscle or power so it is sometimes called sensation of resistance.

• When we chew tough meat we will experience strong resistance while when we chew tender meat we experience little resistance.

• Many terms are used to describe the kinesthetic sensations as appears from table IVa.

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Kinesthetic sensations

واللزوجة : • الهشاشية خامساوالغضاضة واإلنقصافية

• IV.a.Kinesthetic sensations: Hardness

• Hard candies----------- very hard

• Zwieback -------------- medium hard

• White bread ----------- soft

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• IV.b.Kinesthetic sensations: Brittle• Very brittle (Potato chips or corn flakes)• Crackly (Cookies or biscuit)

• IV.c.Kinesthetic sensations: Thin and thick Soups

• IV.d.Kinesthetic sensations: sticky and slippery

• Sticky----------- dry whole milk powder• Slippery -------- raw egg white

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V. Sound sensation

• During the consumption of some hard foods, we get a sound sensation.

• Mainly three terms are used to describe the sound sensation as appear in table V.

• Table V. Sound sensation• a.Crackly--------------- biscuit or cookies• b.Crunchy-------------- Chips• c. Moist Crispy------- Pickles (slightly moist crisp)

• Raddish (pronounced moist crisp)

• Cookies (dry crispy)

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العتبة إختباراتThreshold tests

• The recognition tests for the four basic tests are considered qualitative tests. While the thresholds tests are quantitative tests.

• In the thresholds tests we aim at determining the concentration at which the particular basic tests can be recognized.

• We are measuring the sensitivity of the test subject or determining his threshold.

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Threshold types

• Threshold types: there are four threshold types:• The first threshold types is called the detection or

stimulus threshold. • In this type of threshold tests, it is reached when the

solution of the basic taste is given in such a concentration where it tastes different than the water and the basic taste is unrecognizable.

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The second threshold type

• The second threshold type is the recognition threshold.

• Here the solution of the basic taste is given in such a concentration where the taste can be correctly recognized when.

• We reach to this point we can say that we reached to the recognition threshold, and the concentration value is called the threshold value such as 0.15% NaCl.

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Third threshold type

• The third threshold type is the difference threshold. • It is defined as the concentration of the solution of the

particular taste where a difference in taste can be tested or recognized.

• Trained panel can detect or recognize difference in taste at 10% concentration 1%, 1.1%, 1.2%,…etc. of NaCl while for beginners a concentration of 30% is needed to detect the difference: 1%, 1.3%, 1.6% of NaCl…etc.

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The fourth threshold type

• The fourth threshold type is the terminal threshold.

• It is defined as the concentration of the basic taste solution where above it, an increase in the concentration can't be detected or recognized.

Information value of threshold tests

• A low recognition threshold obtained with an aqueous series does_not necessarily correspond to a high sensitivity to foods.

• Therefore threshold tests should not play too important a role in a, sensory course.

• We regard them as a basic exercise but shall pay more attention to tests with foods as we do not consume only aqueous solutions in our daily life.

Combination of threshold tests with intensity exercises

• It is suggested that we first detetmine the approximate threshold by presenting a series with large graduations and high concentrations (see Tables 9.1—9.4, part a).

• For each concentration the intensity has to be defined. • We will discover that we are not able to differentiate

between small concentration differences because the human senses are better able to differentiate qualities (e.g. different odours) than quantities (different intensities).

• Therefore, scales should not be used (especially in quality rating) with any finer graduations than can be differentiated.

• For the determination of the exact threshold value concentration series with finer graduations are presented (see Tables 9.1—9.4, part b).

• The results will become even more exact when difference tests are applied (as will be shown in Chapter 10).

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Points to be considered in threshold tests

• preparation of the concentration series– Preparation of stock solution: it is advised when preparation of solution of

increasing intensity or concentration to prepare first a stock solution and to prepare a working solution with the different intensity or concentration from this stock solution.

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• For sweet basic taste the concentration of stock solution is 20% or 20g sucrose/100 ml; the concentration is wt/vol.

• For salty basic taste, the concentration of the stock solution is 10% NaCl or 10g/100 ml.

• For the sour taste, the concentration of the stock solution is 1% citric acid

• For the bitter taste the stock solution is either 0.05% caffeine or quinine hydrochloride.

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• To prepare solution such as 0.05% w/v quinine hydrochloride.

• We weigh 0.125g which is equal to 125 mg very precisely using a high sensitive balance,

• dissolve it in little quantity of H2O then transfer quantitatively to 250 ml volumetric flask and add water till we reach to the mark.

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Water used in preparation

Quality of water is very important for sensory evaluation of foods in general and for threshold tests in particular.

The following types of H2O are nor accepted in threshold tests:

o chlorinated water,

o Too hard water,

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Water used in preparation

o heavily deionized water,

o demineralized water ,

o distilled water.

o The types of H2O may exhibit unacceptable odor, mask sweetness, introduce bitterness or susceptible to microbial contamination like demineralized water.

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Preparation of H2O for threshold purposes

• Many researches recommended to prepare the H2O for threshold purposes in special way.

• The method includes the boiling of fresh H2O for 10 minutes in an uncovered enamel pot or glass beaker at least 15 cm in diameter.

• The obtained boiled water is cooled then filtered and the first portion is discarded.

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Preparation of the test or working solution

• It is advised to prepare two kinds of concentration series of testing solution.

• One with the upper concentration for beginners and the second with lower concentration for trained persons.

• This mean that the graduation between the upper concentration solution is large like 0.10, 0.15, 0.20 %... etc.

• While a finer graduation is found in the lower concentration solution for trained persons like .0.10, 0.12, 0.14…etc.

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Number of solutions to be prepared for test solutions

• Many investigators advise to have 10-12 testing solutions with a gradual concentration.

• For a sweet taste, an initial concentration of 0.00 and final concentration 1% (0.0, 0.05, 0.1, 0.2…1%) is prepared.

• For salty taste, the initial concentration is 0.00 and the final or the tenth solution is 0.2%.

• In sour taste, the initial concentration is 0.00 and the tenth solution concentration is o.o35

• For bitter taste the final concentration is 0.0003 in case

of quinine HCL and 0.030% for caffeine.

• The quantity of testing solution is 500 ml for 15 testers and 1000 ml for 30 testers.

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Coding of solutions and beakers

• It is better to have the same coding on beakers and volumetric flasks having the prepared test solutions from 2 digital numbers like from 11 to 20 or 21 to 30 or 31 to 40 and so on.

• The beakers also should have the code number of panelist between two brackets such as 11(2) for panelist number 2 and solution with the code 11.

• Since it is advised to have two threshold tests at a sessions, twenty beakers of two different colors is preferred.

• The quantity of tested sample is about 30 ml.

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• The beakers should be arranged in a manner to save time and avoid disturbancy.

• In case one taste is tested only, the beakers should be in one line with increasing number... 11.12.13…etc. in case of two series ( Sweet and Sour) the sweet series be in front and the sour behind.

• With regard to the time of the test, it is suggested not to have or to run the threshold test on empty stomach. Suitable time is one hour after breakfast or one hour after lunch.

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Explanation of the test

• First the mouth is rinsed with the control water to be familiar with its taste.

• Testing of samples is started by beaker 11 as example. Then followed by 12 and so on.

• It is very Important to note that swallowing of the sample is not allowed.

• Only the sample moved around in the mouth in such away to come in contact with all part of the tongue.

• Also do not repeat testing any sample.

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• After rinsing the mouth with the sample number 11 we have to ask the following question: does it tastes sweet, bitter, sour or salty?

• If the answer is it likes water a (0) is marked on the sheet.

• If the answer was that the sample tastes different than water but the taste quality can't be recognized, then we write a question mark(?) on the sheet.

• The test is continued with samples 13, 14 and so on.

• There is another column in the test sheet specific for intensity of the taste.

• Numerical value have to be given to intensities rather than descriptive words i.e. sour 1, sour 2, sour 3 instead of very weak sour, weak sour, and sour. Stronger concentration will be given number 4 and the strongest number 5.

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Transparency number 1 shows the test sheet and how it can be filled correctly.

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Factors affecting threshold test results

– Insensitivity for the 3 basic tastes; sour, bitter and salt:

– sour insensitivity to observed with people who lacks gastric acid;

– bitter insensitivity is innate and can only be slightly improved by training.

– Salty insensitivity cab be caused by teeth filling on having denture plate.

– This insensitivity can be improved by changing food habits such as adding less or little salt to food.

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– Oversensitivity for sweet taste: it is observed in people with too much gastric acid.

– Sex may affect the threshold test, women were found to be more sensitive to sweet and salty while men are more sensitive to sour.

– Age also affect the threshold test. It is observed that sensitivity for sweet and sour decrease with age.

– Alcohol was found to affect widely the sensation of the four basic tastes. After Two hours of taking only 25ml ethanol, the trained panel subject was not able to differentiate between the four basic tastes.

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• - presentation of results and discussion: will be during the exercises.

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التحليل اإلحصائي. أهمية التحليل اإلحصائي1

ال يخفى على أحد الدور المهم واألساسي •للتحليل اإلحصائي في مجال التقييم الحسي إذ

ذهب البعض الى أبعد من ذلك وقالوا بأنه ال تقييم حسي بدون تحليل إحصائي، أي ال قيمة

اختبارات الحسية الاللنتائج المتحصل عليها من إذا لم يؤخذ في الحسبان تحليل النتائج إحصائيا.

وينسحب ذلك على األمور الخاصة بتطوير •المنتجات الغذائية أو على أمور ضبط جودة

األغذية. ومن هنا يالحظ أن جميع طرق التحليل الحسي •

التي تم تطويرها واعتمدت كمواصفة دولية تشمل ضمن بنودها على جزء خاص بالتحليل

اإلحصائي للنتائج المتحصل عليها بتلك الطريقة.

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. المراحل التي تمر بها عملية التحليل 2اإلحصائي

* مرحلة تصميم التجربة إحصائيا ويشمل ذلك عدد •العينات, عدد المقيمين، الطريقة التي ستستخدم في

التقييم الحسي، استمارة اإلختبار الحسي ..... الخ.*مرحلة تقديم وفحص وتلخيص نتائج التحليل الحسي وقد •

يشمل ذلك عمليات جدولة البيانات الحسية وتحويلها الى منحنيات ورسومات.

*مرحلة التحليل باستخدام إحدى الطرق اإلحصائية •المناسبة

*تشمل المرحلة الرابعة واألخيرة الوصول الى •االستنتاجات بناء على نتائج التحليل اإلحصائي. فمثال لو

كان عندنا نوعين من البسكوت وتم تقييمهما حسيا وحللت النتائج احصائيا ففي المرحلة الرابعة يتم االستنتاج

واتخاذ القرار المتعلق بأي نوع من البسكوت تم تفضيله من قبل المستهلك.

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. بعض المصطلحات المهمة في مجال 3التحليل اإلحصائي للبيانات الحسية

• Data value and data set• Observations• Variables• Null hypothesis and alternative hypothesis• Types of error and how to measure• Variance• Probability and significance• One tailed and two tailed experiments

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STATISTICAL ANALYSIS OF THE RESULTS (DATA)

• (a) Fundamentals of statistics

• *In order to facilitate the understanding of statistics some basic terms are explained as follows:

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• Null hypothesis

• *This is a very important term in statistics.

• For our purposes it will be the assumption that a result is based solely on chance.

• This would mean in our example that a test subject is simply guessing and is therefore completely unqualified as a panel member.

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• We now want to find out what requirements must be fulfilled by a test subject in order for him to be considered qualified or,

• which is the point at which the null hypothesis can be rejected.

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• Alternative hypothesis• *While, in the problem described, the null

hypothesis states that the result is due to chance or guessing,

• the alternative hypothesis states that it is not due to chance;

• the test subject is able to differentiate correctly.

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• Level of error • *In the example with five testing pairs, the null

hypothesis (result by chance or guessing) has been rejected.

• It might, however, occur that a test subject has passed this qualification test merely by guessing.

• In this case, the null hypothesis has been unjustifiably rejected, and is called level of error (α).

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• Error of the first and second kind• *When the null hypothesis has been unjustifiably

rejected, this is an error of the first kind. • This means, in the case of the second type of paired

difference test (with same and different samples in each pair),

• that differences have been found where they have not existed (pair with same samples).

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• *When the alternative hypothesis has been unjustifiably rejected, this is an error of the second kind.

• This means that no differences have been found although the samples were different.

• The latter error easily occurs when unqualified test subjects are kept on the panel.

• Therefore, it requires that only the best test subjects be selected.

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• (b) Statistical analysis of paired difference tests• Table 10.1.6 reveals whether differences between two

samples have been found simply by chance or whether they can be considered significant.

• This table, which refers only to one-tailed tests, contains data for three levels of significance or three limits for α, the level of error.

• In the case of a 5% level of error, the stronger tasting sample can be correctly identified simply by chance (the null hypothesis has been unjustifiably rejected), in one out of 20 cases.

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• *In this example, the statistical significance (given in percentage) is S = 100 - α = 95%.

• This means that the result is significant, or is secure at the 5% level of significance,

• which is marked on the head of the table as α = 0.05 or with one asterisk (*).

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• *In the case of a 1% level of error, there is a danger that in one out of 100 cases the stronger tasting sample has been correctly identified simply by chance.

• In this case, the statistical significance (given in percentage) is S = 100 – α= 99%.

• The result is then highly significant or secure at the 1% level of significance,

• which is marked on the head of the table as α = 0.01 or with two asterisks (**).

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• *In the case of a 0.1% level of error, there is a danger that in one out of 1000 cases the stronger tasting sample has been correctly identified simply by chance.

• In this case, the statistical significance (given in percentage) is S = 100 - α = 99.9%.

• The result is then very highly significant or secure at the 0.1% level of significance,

• Which is marked on the head of the table as

• α = 0.001 or with three asterisks(***).

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• The statistical significance increases as the level of error decreases.

• Let us analyse statistically the results of the three exercises which we have carried out.

• We start by counting the number of judgements, which is equal to the number of test subjects multiplied by the number of pairs:

• 20 (number of test subjects) X 4 (number of pairs) = 80 (number of judgements)

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للتقييم العينات تقديم في العشوائيةالحسي

ترميز • أو بترقيم يتعلق فيما اتجاه أو رأي من أكثر يوجداإلختبار لنوع أن كما الحسي التقييم ألغراض العينات

. ذلك على تأثير الحسيأعداد • استعمال فيها يتم التي اإلختبارات بعض فهناك

مثل لترميزها رقمين . 23، 22: 21من حالة ... وفي الخ : الترقيم عمليات في الحروف تستخدم العتبة اختبارات

. .... الخ و هـ، د، ج، ب، أ،الحسي • التقييم مجال قي العاملين أغلب فإن ذلك ومع

. العينات لترميز أرقام ثالثة من أعداد استعمال يفضلونأن • يجب العينات تقديم طريقة أن بالذكر جدير هو ومما

استخدام بمكان الضرورة ومن للعشوائية يخضعوالمسماة بذلك الخاصة .Random digit الجداول

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بالعشوائية الخاص Random digit tableالجدول

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اإلحصائي التحليل في المستخدمة الطرقالحسية للبيانات

وكما • إحصائيا الحسية البيانات لتحليل طرق ثالثة تتوفريلي:

ولكل • اإلحصائي بالتحليل خاصة جداول استخدامجداول فتتوفر بها الخاصة الجداول حسي تقييم طريقة

الترتيب ( بطريقة مقارنة )Ranking test خاصة إلختبارات وأخرى

. )Paired comparison test األزواج ( وهكذا من • بشيء له التعرض وسيتم التباين تحليل استخدام

الحقا التفصيلحاسوبية • برامج استخدام ومنها خاصة طرق استخدام

خاصة

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Analysis of variance

• Chewiness

• --------------------------------------------------------------------

• Brands

• --------------------------------------------------------------------

• Judges A B C D Total

• ---------------------------------------- ------------------------------- -

• 1 2.2 1.9 3.2 0.2 7.5

• 2 2.5 1.0 4.2 2.0 9.7

• 3 3.3 3.0 4.0 1.5 11.8

• 4 2.6 5.4 4.2 1.3 13.5

• 5 2.6 4.3 5.1 0.1 12.1

• 6 2.2 3.4 4.7 1.9 12.2

• 7 2.4 3.6 5.5 3.2 14.7

• 8 1.6 3.9 5.7 1.8 13.0

• --------------------------------------------------------------------------

• Total 19.4 26.5 36.6 12.0 94.5

• ----------------------------------------------------------------------------

• Mean 2.4 3.3 4.6 1.5

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Correction factor (CF) = 94.52/32 = 8930.25/32 = 279.07Sum of squares, samples=(19.4

2 + 26.52 + 36.62 + 12.02)/8 – CF

=2562.17/8 – CF =320.27 - 279.07 =41.20Sum of squares, judges =(7.52 + 9.72 + 11.82 + ... + 13.02)/4 – CF =1152.17/4 – CF =288.04 - 279.07 =8.97Sum of squares, total = (2.22 + 2.52 + ... + 1 .82 – CF

= 347.09 - 279.07= 68.02

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• Analysis of variance table• ----------------------------------------------------------------------------------• Source of df SS MS F• Variation• ----------------------------------------------------------------------------------• Samples 3 41.20 13.73 16.1 5*• Judges 7 8.97 1.28 1.51• Error 21 17.85 0.85• Total 31 68.02• ---------------------------------------------------------------------------------

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• The F value for samples is 16.15. • According to Chart 3 in the Appendix,

page 65, if the F value exceeds 3.07 there is a significant difference at the 5% level (*) and if it exceeds 4.87 there is a significant difference at the 1% level (**).

• There is a significant difference at the 1% level for samples so the value is marked with two asterisks. There is no significant difference for judges.

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• Many statistical tools are used to test the differences between means and if these differences are significant or not.

• Among these tests:• Tukey's Test, • Multiple range test, and• Least significant test (LSD)• LSD = t X SE• The standard error of the mean is calculated by the

equation:• SE = √0.85/8• = √ 0.1062• = 0.32

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• The t value is taken from( t) table for 21 degrees of freedom and it is 2.08.

• Least significant difference=2.08 X 0.32 =0.67

• Sample scores:A B C D

• 19.4 26.5 36.6 12.0

• Sample means:2.4 3.3 4.6 1.5

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• The sample means are arranged according to magnitude.• C B A D• 4.6 3.3 2.4 1.5• Each mean is compared with the others to see if the difference

is 0.67 or more.• C - D = 4.6 - 1.5 3.1 > 0.67• C- A = 4.6 - 2.4 = 2.2 > 0.67• C - B = 4.6 - 3.3 = 1.3 > 0.67

(least significant difference)• B - D = 3.3 - 1.5 = 1.8 > 0.67• B - A = 3.3 - 2.4 = 0.9 > 0.67• A- D = 2.4 - 1.5 = 0.9 > 0.67

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• The results are shown using letters to indicate differences:

C B A D• 4.6a 3.3b 2.4c 1.5d• Any two values not followed by the

same letter are significantly different at the 5% level. Sample C is significantly more chewy than all the others. Sample B is more chewy than sample D.

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الحسي التقييم طرق : طرقاالختالف

Difference tests• Objective of the method• Difference tests are analytical methods. The

panel members act like an instrument whose task is to analyse whether or not there is a difference between two samples.

• As the differences are very small, these tests are quite difficult.

• They require high sensitivity which, however, can be acquired through training.

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Questioning

• The question ‘which is the odd sample' or 'which sample is stronger' is posed in such a way that no hedonic answer can be given.

• This is necessary in order to keep the method strictly analytical.

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Special requirements to be met by the samples

• If only the odour, taste or flavour has to be analysed, the samples must have the same appearance, shape, temperature, and consistency, and equal amounts have to be presented.

• Otherwise bias might occur.

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Methods of Application

• Difference tests are used in • product testing and • panel training • and panel selection. • Not all five methods are, however, equally suitable.• The five main difference test methods are:• 1. The paired difference test• II. The triangle test• 111.The duo-trio test• IV. Ranking tests• V. Multiple Comparison Difference Test

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Difference threshold

• Last week the threshold terms were explained to you;

• (1) stimulus or detection threshold,

• (2) recognition threshold,

• (3) terminal threshold.

• (4) The fourth is the difference threshold. It is defined as that concentration at which the difference is recognized.

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Difference threshold

• Beginers receive samples with a 30% difference (e.g. 1%, 1.3% sodium chloride solution).

• With training and much concentration during the test, a difference threshold of 10% can be reached (e,g. l.0, 1.10 % sodium chloride solution).

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Information value of difference tests

• In contrast to tests with a concentration series, difference tests can determine whether or not a test subject is suited for sensory analysis.

• A low difference threshold not only for aqueous solutions for the four basic tastes but mainly for foods is a quality of a good sensory analyst.

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Special requirements

• Difference tests require a high degree of concentration.

• Final panel selection should not be made during training time, as some candidates may learn slowly but show considerable improvement with time and perseverance.

• Such improvement may not be observed with people who learn easily by memorization.

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Number of tests and test subjects

• Managers often have difficulty concentrating due to their busy schedules and are, therefore, not suitable as permanent panel members.

• Number of test subjects• For difference tests, at least ten people should be

available, but panels with 20 or 30 members are better.

• Number of tests• More important than the number of tests carried

out in a sensory laboratory is the thorough planning and execution of sensory tests.

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PAIRED DIFFERENCE TEST 1.1 EXPLANATION OF THE METHOD

• Directional paired difference test• Several pairs are given to each panel member. • Each pair consists of a control sample K (e.g.

apple juice) and an analytical sample A (e.g. apple juice with sugar added).

• Pairs differing only in concentrations can also be presented (A = low, B = higher concentration)

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• The objective of the method is to state whether the two samples can be differentiated.

• The question posed may be: which sample in each pair is sweeter (saltier, more sour, more fruity, more rancid, more aromatic, more crisp, etc.).

• Only one question is posed in one test.

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• Sample arrangement• The position (left or right) of the analytical (or the

more concentrated) sample in each pair is arranged randomly by consulting tables of random digits. By changing the sample arrangement from test to test, guessing is avoided.

• Examples of sample arrangements are:• KA AK AK BA AB AB • AK or AK or KA BA AB BA

• AK KA AK BA AB AB• KA KA KA BA BA AB

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Second type of the paired difference test

• Pairs with the same and different samples are presented.

• The question is posed whether the samples in each pair are identical or different.

• Possible sample arrangements are: AK, KA, KK, AA. • In practice, this type of paired difference test is used

mainly for the training and checking of test subjects.

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Exercise

• Comparison of Natural apple juice and Sweetened apple juice

• The goal of this exercise is to become familiar with the differences in sweet intensity.

• It is, therefore, better suited for the determination of the intensity differences.

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Number of samples and sample amount

• Number of samples• Four pairs per single person, these are called a 'set'.

• Sample amount• 30 ml per single sample. • When using four pairs per test subject, 120 ml of

0.018% tartaric acid (sample A) and 120 ml of 0.021% tartaric acid (sample B) are needed.

• For 15 persons, about 2 L of each sample are needed.

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Sample preparation

• Sample preparation• As has been explained earlier.• Tasting beakers• Eight tasting beakers are required per person.• The beakers are coded: 21, 22, 23, 24, 25, 26, 27, 28. • It will be explained later (see triangle tests) why we

use these codes. • The beakers are arranged in pairs, the pair with the

lowest numbers in front and pairs with higher numbers behind.

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Sample preparation

• On the test sheet, the pair with the lowest number is written on the first line and that with the highest on the last line.

• This is frequently not done by beginners who also place, for example, the beakers of all four pairs in a row or mix up the left with the right beaker and vice versa.

• Care must also be taken so that distribution errors do not occur.

Paired difference test questionnaire

• Test product: Apple juice Name: • Test subject No.: 15 Date: You will receive several pairs of apple juice samples. Please write the pair

with the lowest number on the first line and that with the highest on the last line.

• Circle in each pair the number of the more sweet tasting sample. Retasting is allowed.

Taste quality to be tested: Sweetness of apple juice • Sample numbers Remark• 21 22 • 23 24• 25 26• 27 28

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Table 10.I.3 - Paired difference test

• (Example of filled out test sheet)Test product: Apple juice Name:

• Test subject No.: 15 Date: You will receive several pairs of apple juice samples. Please

write the pair with the lowest number on the first line and that with the highest on the last line.

• Circle in each pair the number of the more sweet tasting sample. Retasting is allowed.

Taste quality to be tested: Sweetness of apple juice • Sample numbers Remark• 21 (22) • (23) 24• (25) 26• 27 (28)

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Example of a sample arrangement

• According to Table 10.1.7, which uses random digits, the samples have to be arranged as follows:

• -----------------------------------------------------------------

Random digit Even/odd number Underline the Sample codes

8 Even number Right code 21 22

1 Odd number Left code 23 24

5 Odd number Left code 25 26

6 Even number Right code 27 28

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• This means that the more sweet apple juice is poured into the beakers with the underlined codes (22, 23, 25, 28) and the less sweet apple juice into the remaining beakers (21, 24, 26, 27).

• Sample coding• The same codes are used for all participants of a

course so that the results can be discussed immediately after the test.

• In regular tests, however, each panel member receives samples with different codes.

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Statistical analysis of the obtained results In Paired difference test, the obtained results are statistically analyzed

using special table as below

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Difference tests: 2. TRIANGLE TEST

• 2.1. EXPLANATION OF THE METHOD• (a) Simple (classical) and extended triangle

test• Importance• The triangle (or triangular test) is the most

widely used of all different tests.

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Objective of the method

• In the simple or classical triangle test the only task is to find out whether or not there is a difference between two samples.

• In the extended triangle test, there are additional tasks.

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Simple triangle test

• Three samples are presented, two are alike, one is different. The question posed is: "which is the odd sample?" Either the control sample (K) or the analytical sample (A) are presented in duplicate, thus allowing six combinations:

• AKK KAK KKA and• KAA AKA AAK• (Similar combinations are possible when

comparing two commercial samples A and B).

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• The samples can be arranged in a triangle (hence the name), but are usually presented in a row.

• Samples having an after-taste should not be duplicated as this would make the test too difficult

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Extended triangle test

• Additional tasks may be defining the degree of difference (triangle-intensity or triangle-directional test), and/or characterizing the difference.

• When descriptions are too difficult, noting the panel member's preference (for either the duplicate or the odd sample) may provide hints for product development.

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• More information will be obtained, however, when the reasons for the preference can be characterized in detail by the panel members.

• Reasons for Primary emphasis on exercises with the extended triangle test

• Panel results which only indicate a significant difference between two samples are of little value in industrial practice.

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• In quality control and in research and development further information is required:

• How can the difference between the samples be characterized?

• Was the preference for the one or the other sample significant?

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Method Application

• The triangle test is of equal importance in product testing and in panel training and selection.

• Problems to be solved in product testing are manifold.

• In industry, production may suddenly be halted because an off-note has been detected.

• What is its origin?

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• Has the addition of salt or a spice component been forgotten in the manufacture of cookies?

• Did oil from a machine come into contact with the chocolate during its liquid stage?

• Has a new packaging material caused an odour transfer?

• What else might have caused an off-note?

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• In research and development it is not sufficient simply to note a difference between samples.

• The kind of difference must be characterized to provide sufficient information for further work.

• Is the new composition as successful as the former one?

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• The lack of raw materials due to war or a poor harvest in the country of origin might have forced a change in composition.

• Or, a food law may no longer allow the use of a successful ingredients in flavour compositions.

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• The flavour chemist wants to know which of his fractions has interesting and typical flavour compounds to be further investigated.

• Triangle tests are also important in storage tests (what change has occurred?)

• and in the comparison of competitive products (is there a difference?

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• What are the characteristics?

• Which product is preferred?).

• Different manufacturing processes may also cause aroma changes (e.g., spray drying vs. freeze drying).

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Simple (classical) triangle test

• Comparison of natural and artificial pepper oil• Test product Pepper oil

Name Test subject No.: Date:• You will receive a set with 4 pairs each having three

samples. • Two of these samples are identical and the other is

different. • Circle the number of the odd sample. • Re-tasting is allowed.• Sample numbers: Remarks:• 32 34 36; 42 44 46; 52 54 56; 62 64 66

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Storage tests

• Storage tests are becoming increasingly important due to the legal requirement of stating "keeping time" on product packages.

• Therefore, as many triangle tests as possible should be made with stored foods.

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• The storage time can be shortened by keeping the samples (milk, fats, meat products) at room temperature as against refrigerated.

• For safety reasons, only odour tests should be made.

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• Cookies, chips and extruded peanut snacks are stored on trays in order to expose a large surface to light and air.

• The optimal storage time has to be determined in pre-tests with a small group of test subjects.

• Attention must also be paid to texture changes especially with crisp foods.

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)b (Samples

• Sample coding• In the literature, it is recommended that 1, 2, 3 or

a, b, c not be used as codes. • According to psychologists there is a danger of

choosing sample 2 or sample b as the odd one. • Psychologists, therefore, have proposed three-

digit random numbers as codes. • Bias for the sample numbered "2" has not been

observed either in our laboratory.

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• According to our observations, three-digit numbers provide no guarantee against bias.

• By presenting samples with codes such as 738, 955 and 231 there was a tendency to choose the sample with the lowest code number (231) as the odd one.

• We have solved this psychological problem by using either even (2,4,6 or 12, 14, 16 or 22, 24, 26) or odd number codes (1, 3, 5 or 15, 17,19 or 23, 25, 27 etc.).

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• The number of samples per session depends upon

the test material, and the fatigue it may cause. The degree of difficulty also has to be

considered.

• During our intensive courses, we were forced to present a large number of samples within one and half days.

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• Participants had come a long distance and had to gain as much practical experience as possible in a short time.

• Outside of these courses, however, we present only one or two triangles in one session.

• In special cases, panel members have to come to a second session. This procedure provides optimal testing conditions.

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Sample arrangement:

• Only during courses is the same sample arrangement used for all participants in order to save time during the subsequent discussion of results.

• In our daily tests for research, development, etc., samples are presented in random order to each test subject.

• This can be done even with the same sample codes.

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• On the master sheet, the A-samples of each triangle are underlined.

• On the master sheet, the beaker with the A-sample is underlined.

• Two numbers are underlined in the same triangle when the A-sample occurs in duplicate.

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c) Number of sessions

• As already mentioned, the thorough planning and execution of sensory tests is more important than the number of tests carried out.

• Inexperienced panel leaders frequently call for too many sessions which are ill planned.

• They prepare the samples in a rush, are not ready when the panel members arrive, state at the last moment colour and/or temperature differences, and prepare insufficient sample amounts.

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• Such panel leaders should not be surprised when the test subjects lose interest in sensory analysis and find all kinds of excuses not to participate in further sessions.

• The experienced panel leader can convince a project leader that hurried tests provide only questionable results.

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• He always pre-tests to determine optimal requirements for sample preparation and presentation, and to select the appropriate test method.

• This enables him to obtain maximum information with a minimum of panel sessions.

• This is very important for the requirements of the practice, is cost saving, and provides the most useful results for research.

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)d (Test sheets

• An example of a correctly filled out test sheet for the simple (classical) triangle test is shown in Table 10.11.3 (see also Fig. 10.II.1).

• Table 10.11.10 shows a test sheet for the extended triangle test with several tasks.

• The test sheets may differ in some ways from those reported in the literature.

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• Industrial practice requires streamlining.

• Therefore, the code number of the odd

sample is not written in a special column.

• It is sufficient to circle it as was done in the paired difference test (Table 10.1.3).

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Simple (classical) triangle test

• Comparison of two brands of black currant nectar

• In case of colour differences, this test has to be done under red light or the samples have to be presented in dark-blue ATL-glasses. Two triangles are presented. The following codes are used:

• 43 45 47 (first triangle) BBA• 54 56 58 (second triangle) ABB• The number of the odd sample is underlined on

the master sheet.• The sample amount is 30 ml per beaker. Care

must be taken to have sufficient sample material

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Table 10.II.4 - Simple (classical) triangle test

• Comparison of Labeneh• Test product: Labenah Name:• Test subject No.: Date:• You will receive a set of one triangle with three

samples. Two of these samples are identical and the other is different. Circle the number of the odd sample. Retasting is allowed.

• Sample numbers: Remarks:• 32 34 36

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Testing sequence

• The samples in each triangle are tested from left to right, thus guaranteeing that random order has been followed.

• This refers especially to daily tests with a random sample arrangement, but should also be followed during courses.

• Retasting is allowed• This can, however, cause fatigue if it is done too often. • Frequently, the first impression is the correct one. • Triangle tests require much concentration which is

acquired through training.

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Hints for beginners

• It may be helpful to describe the odour, taste and flavour of each sample before continuing to the next one.

• This allows neutralizing between the samples which is not otherwise possible if the subject has a poor memory.

• Early sample description training is a great advantage for more difficult test methods (flavour profile test). Notes can be made on the back of the test sheet.

• As a neutralizing agent for the black currant nectar, water at 35-40 "C is sufficient.

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Presentation of results at the blackboard

• To provide a summary of the group's achievement, the number of responses are tallied as shown below.

• First triangle• 43 45 47• / / //// ////• Only at the very end is the code of the odd sample

circled by the panel leader, as shown below:• 43 45 (47)• / / //// ////• The differentiation is highly significant and can be

recognized without statistical tables.

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Presentation of the results at the notice board

• The results of all triangle tests are tabulated separately from those of the paired test in a record form as shown in Table 10.11.5.

• This provides a quick visual survey of the achievements of each test subject.

• Differentiation is even better when the plus signs are written in red and the minus signs in black.

• The sensitivity of single test subjects towards the various test materials can also be easily recognized.

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• People who are not sensitive to rancidity should not be chosen for tests with fats, whereas rancid-sensitive test subjects should be selected to participate especially in arbitration analyses.

• A separate record form with the test subjects' numbers and names has to be prepared for the panel leader.

• Test subject numbers may change.

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• For staff planning, a record of each test subject's achievement over a period of several years is important.

• In our fragrance and flavour manufacturing industry, only test subjects with good sensory abilities over a period of about three years have a chance to be appointed to positions requiring sensory sensitivity (as perfumers, flavourists, sensory analysts, etc.).

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(c) Extended triangle tests with several tasks

• In industrial practice, it is as important to characterize the single sample and the duplicate as it is to determine the sample preference.

• Sometimes characterization of the samples is not consistent enough to provide sufficient information for further product development.

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• It may, however, be valuable to state that the preference goes in one direction (e.g, when comparing a new flavouring composition with an old one which can no longer be used because of changes in food law regulations).

• It may also be valuable to state about equal preference for the two flavouring compositions (e.g. in the case of imitating a competitor's flavouring composition).

Multiple Comparison Difference TestQuestionare for difference test

III. DUO-TRIO TEST

• EXPLANATION OF THE METHOD• The due-trio test is so called because it is

intermediate between the duo (paired) and the trio (triangle) test.

• The test subject receives one sample marked control (K) and one or several pairs of samples. Each pair contains one control sample and one analytical sample (A) in random order.

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• The question posed is: 'Which is the different sample in each pair?'

• It can also be asked: "Which sample in each pair is identical to the control?

• The latter question is frequently preferred as it seems easier to answer.

• To avoid confusion it is recommended that the same question be used for all tests.

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• Sample arrangement• There are two possible sample combinations:• K-KA or K-AK• For several pairs consult Table 10.1.7 (ten thousand

random digits, p. 200).• Example of possible sample arrangements• K A K K K A K K A K A K• K A A K K A A K• K A A K K A K A• A K A K K A K

A, etc.

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Application

• Because the duo-trio test requires little retasting it is used with samples having a sharp or burning taste (pepper) and/or a lingering aftertaste (bitterness).

• As p (probability) = 1/2, more tests are required for statistically significant results than in the triangle test with p = 1/3.

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• This method is also advantageous for the recognition of off-notes.

• When the sample with the off-note is presented in the labelled control beaker, training time is considerably shortened.

Exercise

• Two commercial brands of bitter chocolate are presented.

• To avoid differences in appearance the samples are cut into small pieces or even grated. A red light can also be used.

• Sample presentation is shown in Fig. 10.111.1 and a correctly filled out test sheet in Table 10.111.1.

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Re-tasting

• Re-tasting only the sample identical to the labelled control not only saves time but also avoids fatigue, especially when more than two pairs are presented (e.g. fruit juices).

• Errors which frequently occur in testing the first pairs will easily become obvious.

• Suitable neutralizing agents

• for confectionery products are rose-hip tea and/or water at 35-40 "C.

• Cider vinegar with honey can also be used as follows: 2 tea spoonsful of cider vinegar and 1-2 tea spoonsful of honey are put in a drinking glass and filled with cold or warm water.

• Dissolve the honey well.

test sheet

• Test product: White cheese Name:• Test subject No.: Date:• You will receive a control sample and several pairs of • samples.• In each pair circle the number of the sample which tastes • different to the control. • Re-tasting is allowed.

• K 41 42• 43 44

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Table 10.1II.1 -Duo-trio test

• (Example of a correctly filled out test sheet)• Test product: Bitter chocolate Name:• Test subject No.: Date:• You will receive a control sample and several pairs of • samples.• In each pair circle the number of the sample which tastes • different to the control. • Re-tasting is allowed.

• K 41 (42)• (43) 44

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Statistical analysis

• For statistical analysis of the duo-trio test consult Table 10.11.12 (p. 219) for significance in paired tests.

• Both of these tests (comparison of two commercial brands of chocolate, and of natural and artificial pepper oil) are two-tailed as only the test result reveals whether or not the samples are different.

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Statistical analysis

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Tabulation of test results

• In Chapter 10.II., a triangle test with pepper oil (natural vs artificial) was described. We also used the duo-trio test for methodological comparison.

• As shown in Table 10.III.2, significant results were not achieved in the triangle test but very highly significant results were achieved in the duo-trio test.

• The labelled control not only facilitated the differentiation but also made frequent re-tasting of the burning pepper-oil samples

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III. Ranking tests

• 1. EXPLANATION OF THE METHOD

• Importance and application

• When using difference tests (paired, triangle, duo-trio test), only two samples can be compared at the same time.

• In practice, however, a series of samples (commercial products, flavour

• compositions) may have to be judged

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• and their quality pre-selected (which samples are better, which medium, and which are poor quality).

• This pre-selection helps to save time, and material (if there is only a small quantity of the competitor's product available or if the yield of the production is very small).

• For such purposes, ranking test is used. The ranking test is also widely applied in hedonic tests.

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• Testing task

• A series of samples has to be ranked either:

• (a) in increasing intensity of a property (sweetness, saltiness,

(b) aroma/flavour, rancidity);

• (c) for quality (comparison of competitive products, flavours, etc.);

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• (d) for hedonic properties (like/dislike, Preference, acceptability).

• This method has the advantage that more than two samples can be compared at the same time (in difference tests, only two samples can be compared at the same time).

• A disadvantage can be inexact results in the case of small differences and large variations.

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• Sequence of exercises• Never start with quality ranking,

especially with beginners. • Prerequisites for such ranking are not only

the ability to differentiate well, but also extensive product knowledge.

• Quality ranking is done preferably in an advanced course after completion of exercises on quality description and scoring.

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• Beginners should start by ranking the intensity of the various senses (odour, taste, colour., texture).

• Ranking the degree of preference is best done with a larger group of laymen, as trained panellists are already too knowledgeable to be representative of the consumer’s likes and dislikes.

• We shall, however, conduct such a test to get acquainted with the test sheets and the statistical analysis of the data.

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RANKING TEST IN ORDER OF INCREASING INTENSITY OF TASTE (Four basic tastes)

• (a) With sucrose solutions• Concentrations: 0.1, 0.4, 0.5, 0.8, 0.8, 1.0, 1.5, 2.0

g/100 ml solution. • Sample preparation: see Table 9.1, p. 165.• Sample amount: 30 ml per person.• Marking the beakers: A, B, C, D, E, F, G, H. (The

beakers for the recognition test for the four basic tastes can be re-used).

• For sample coding see Table 1l.2, P.256.

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• Beaker arrangement: in alphabetical order.• Test instructions: The test subjects are told that

they will receive a sucrose concentration series in random order.

• The task is to rank the samples in increasing order of intensity.

• Two samples, however, will have the same concentration and must be so noted.

Details of the test

• To avoid taste fatigue from too frequent retasting, it is recommended that the approximate intensity of each sample first be determined and written on the test sheet (Table 11.1)

• *After completion of the series, the final intensity is to be determined.

• It will become superfluous to re-taste samples with extreme intensities (weakest and strongest sample).

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• Samples with questionable intensity difference are compared preferably in pairs (Fig.11.1).

• Finally, the samples are ranked in increasing order of intensity and the result written on the lower line of the test sheet (Table 11.1).

• Do not forget to mark the samples with the same concentration.

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Table 11.1 - Ranking test (Example of a filled out test sheet)

• Name: Test subject No.: Date:• You will receive, in random order, samples which differ in intensity for one property. In this test the property is:

Sweetness• Start by determining the approximate intensity of each sample and applying the given intensity scale. Frequent

retasting will not be necessary. Note that two samples have the same intensity.• Finally, rank the samples in order of increasing intensity. Retest only samples with questionable intensity. Mark

the duplicate sample.• • Sample Intensity Intensity scale• codes (preliminary) final• A (2) 3 1= very weak• B 2 2 = weak• C (5) 4 3 =medium strong• D (2) 1 4 = strong • E (4?) 4 5 = very strong F (1) 2• G (4+) 5• H 3• Final ranking• Sample codesB D F A H E C Gweakest strongestIntensity intensityDuplicate A + H

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Ranking test

• Name: Test subject No.: Date:• You will receive, in random order, samples which differ in intensity for one property. In this test the property is:

Sweetness• Start by determining the approximate intensity of each sample and applying the given intensity scale. Frequent

retasting will not be necessary. Note that two samples have the same intensity.• Finally, rank the samples in order of increasing intensity. Retest only samples with questionable intensity. Mark

the duplicate sample.• • Sample Intensity Intensity scale• codes (preliminary) final• A 1 = very weak• B 2 = weak• C 3 =medium strong• D 4 = strong• E 5 = very strong• F• G • H • Final ranking• Sample codes•• weakest strongest• intensity intensity

• Duplicate:

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Aids for beginners

• Avoid too frequent re-tasting; remember that the first impression is usually correct.

• Rinsing the mouth thoroughly with water at 35 'C may be a great help when judging intensifies.

• Start rinsing with the first sample, do not wait until fatigue sets in.

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Presentation of results at the blackboard

• During courses with 15 participants, the results of five test subjects are written on the blackboard.

• From these it can be seen whether or not the results are the same or varied.

• Then a line is drawn and the correct ranking order is presented by the panel leader.

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Examples of results at the blackboard

• Results B F D A H E G C• of Participants H F D A B E C G• B F D A H E C G• B F D A H G E C• B D F A C H E G• Correct order B D F A H E C G

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Presentation of results at the notice board

• In this case, it is easier to survey results when correct ones are marked with a plus sign (+) and incorrect ones with the given letter (Table 11.2).

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)b (Ranking test with sodium chloride solutions

• Concentrations: 0.08, 0.09, 0.1, 0,1, 0.2, 0.3, 0.4, 0.5% (w/v).

• Sample preparation: see Table 9.2, p. 166.• Example of results: see Table 11.2, p. 256.• (c) Ranking test with citric acid solutions• Concentrations: 0.003, 0.01, 0.02, 0.03, 0.03, 0.04,

0.05% (w/v).• Sample preparation: see Table 9.3, p. 167.

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RANKING TEST IN ORDER OF DEGREE OF PREFERENCE

• Samples suitable for this test are different kinds of food.

• The simplest way is to buy competitive products in supermarkets.

• Differently flavoured samples (such as chocolate) can also be used as shown below.

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• Number of samples• Do not use more than three to four samples for

beginners. • Also, in real tests, limit the number to four to five

to avoid fatigue.Coding

• This is better done with letters than with numbers. This is not true, so we will use numbers of three digits.

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Test instructions

• The samples are tested in a specified order. Those which are liked best are placed to the left, those liked least to the right.

• An example of a test sheet is shown in Table 11. 11. The best liked sample gets the first place in ranking, the least liked the last (fourth).

• The other samples are ranked in between.

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Evaluation of the results

• This can be done as shown in Table 11.12. The given rank positions (1 = first, 2 = second, 3 = third, 4 = fourth) are listed below the sample code.

• This procedure is, however, too time consuming to be used during courses.

• The rank sum is easier and faster to determine by using the tabulation chart of Milhlhausen as shown in Table 11.13a.

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• The rank positions (1, 2, 3, 4) are written in a column on the left side, and the box head contains the sample codes (916, 517, 480,650).

• The results of the participants are tallied. • When the rank order 517, 480, 916, 650 has

been given by a participant:• the stroke for 517 is written in the box for the

first the stroke for 480 is written in the box for the second

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• the stroke for 916 is written in the box for the third the stroke for 650 is written in the box for the fourth rank position (see Table 11.13a).

• After the results of all participants have been entered in the various boxes of the

evaluation chart, • the number of the results in each box are added

together and then multiplied by the rank position number (first rank position number:

X 1, second: X 2, third: X 3, fourth: X 4).

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• The rank sum for each sample is obtained by adding the single sums in each column (see Table 11.13b).

• The lowest rank sum indicates the best liked sample, the highest rank sum the least liked sample.

• The rank sums of Tables 11.12 and 11.13b are identical, but have been obtained in different ways.

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Table 11.11-Ranking the degree of preference

• Test product: chocolate Name:• Test subject No.: Date:• You will receive four samples. Please rank them in order of your degree of

preference.• Write to the very left the code of the sample you like best (to which you give the first

position in the degree of preference) and to the very right the code of the sample you like least.

• Mark the degree of preference for the other samples in between.• ---------------------------------------------------------------------------------• Sample Code• • ---------------------------------------------------------------------------------------------------------• 1. rank 2. rank 3. rank 4. rank• position position position position• (most liked) (least liked)• ----------------------------------------------------------------------------------------------------------

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Table 11.11-Ranking the degree of preference (Example for a filled out test sheet)

• Test product: chocolate Name:• Test subject No.: Date:• You will receive four samples. Please rank them in order of your degree of

preference.• Write to the very left the code of the sample you like best (to which you give the

first position in the degree of preference) and to the very • right the code of the sample you like least.• Mark the degree of preference for the other samples in between.• ---------------------------------------------------------------------------- • Sample Code• 517 480 916 650

• ------------------------------------------------------------------------------------------------• 1. rank 2. rank 3. rank 4. rank• position position position position• (most liked) (least liked)• ------------------------------------------------------------------------------------------------•

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• Table 11.12 - Results of ranking the degree of preference with• differently flavoured chocolate samples• --------------------------------------------------------------------------------------• Test Rank position given for the samples• Subject -------------------------------------------------------------------------• No 916 517 480 650 • ---------------------------------------------------------------------------------------• 1 3 1 2 4• 2 1 3 2 4• 3 2 1 3 4 4 4 2 1 3• 5 1 2 3 4• 6 2 1 3 4• 17 3 1 4 2• ---------------------------------------------------------------------------------• Rank sums 44 21(**) 42 63(**)• of the samples

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Statistical analysis of the data

• Table 11.14 shows whether or not the result is significant • and Table 11.15 shows whether or not it is highly significant•

Table11.13a-Tabulation chart for ranking tests (with listing of one result)• ----------------------------------------------------------------------------------------• Sample codes• 916 517 480 650• -----------------------------------------------------------------------------------------• 1. Rank position /• -------------------------------------------------------------------------------------------• 2. Rank position /• -------------------------------------------------------------------------------------------• 3. Rank position /• -------------------------------------------------------------------------------------------• Rank position /

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Table 11.13b - Ranking the degree of preference with chocolate Samples (Use of the tabulation chart of Table 11.13a)

Sample codes• 916 517 480 650 • (a) (b) (a) (b) (a) (b) (a) (b)• ---------------------------------------------------------------------------------• 1. Rank // ///// ///// /• position //// • (2X 1) = 2 (14X 1) =14 (IX 1) =1• ---------------------------------------------------------------------------------------• 2. Rank ///// // ///// /• position / /// • (6X2) = 12 (2X2) = 4 (8X2) =16 (1X2) =2• 3. Rank ///// / ///// ///• position / //• (6X3)=18 (1X3) =3 (7X3) =21 (3X3 )=9• ------------------------------------------------------------------------------------------• ------------------------------------------------------------------------------------• 4. Rank /// / ///// /////• position /// • (3X4) =12 (1X4) =4 (13X4) =52 • ------------------------------------------------------------------------------------------- • Rank sum 44 21** 42 63**• of the 916 517 480 650 • samples• -------------------------------------------------------------------------------------------• (a)= number of judgments.• (b)= rank sum of the respective rank position

• ----------------------------------------------------------------------------------------

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Detail from Table 11.14

• Rank totals required for significance at the 5% level • (α ≥ 0.05)• No. of Number of treatments or samples ranked • Repli 2 3 4 5 6 7 8 9

• (17) 22-29 27-41 32-53 38-64 43-76 48-88 53-100 58-112 • 22-29 28-40 35-50 41-61 48-71 54-82 61-92 67-103

• ---------------------------------------------------------------------• The four-figure blocks in Table 11.4 represent: • lowest insignificant rank sum, • any treatment - highest insignificant rank sum, • any treatment; lowest insignificant rank sum,• predetermined treatment - highest insignificant rank

insignificant rank sum, predetermined treatment.

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• For our exercise (number of responses = 17, number of ranked samples = 4, and any treatment), we find in Table 11.14 "32-53".

• This means that 32 is the lowest insignificant rank sum and 53 the highest insignificant rank sum.

• In our exercise, sample 517 had the lowest rank sum: 2l.

• This rank sum is not only lower than 32, from Table 11.14, but also lower than 30, from Table 11.15. This means that the placement of sample 517 in the first rank position is "highly significant"

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• or, in other words; among the four chocolate samples, sample 517 is liked best.

• The placement of sample 650 in the fourth rank position, with the rank sum of 63, is also highly significant.

• The highest rank sum, from Table 11.15, is 55. This means that among the four chocolate samples, sample 650 is liked least.

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Detail from Table 11.15

• Rank totals required for significance at the 1% level (α ≥0.01)

• No. of Number of treatments or samples ranked • Replications ------------------------------------------------------------ 2 3 4 5 6 7 8 9• 17 20-31 25-43 30-55 35-67 39-80 44-92 49-104 53-117 • 21-30 26-42 32-53 38-64 43-76 49-87 55-98 60-110• The rank sums of the samples 480(= 42) and 916 (= 44) are

within the ranges 32-53 (Table 11.14) and 30-55 (Table 11.15). Their rank position is not significant.

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• If it is of interest, the ranking test can be supplemented by a triangle test with these two samples and the additional question of preference asked.

• The results of ranking tests are not always as clear as in our exercise.

• Variations may have several causes: the samples were too similar in their character (aroma. flavour);

• excessive demands were made upon the test subjects (too many samples, fatigue due to a lingering aftertaste); or none of the samples were acceptable (liked).

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PREFERENCE TESTS

• Preference tests include the paired comparison test, the multiple comparison test, the hedonic scale, and ranking tests.

• Sample questionnaires and examples of these methods follow.

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Paired comparison test

• The paired comparison test used in preference testing is similar to that used for difference testing.

• When testing preferences, the panellist is presented with two coded samples and is asked which he prefers, such as in the next questionnaire.

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QUESTIONNAIRE FOR PAIRED COMPARISON TEST

• NAME DATE• PRODUCT• Taste the two coded samples in the following order: • 317 225• Which of these two samples do you prefer?

• Comments:

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EXAPAPLE ON PAIRED PREFERENCE TEST

• To determine which of two spice combinations was preferred in a drop cookie, a paired comparison preference test was used. Fifty panellists compared the two cookies.

• Twenty-five panellists tasted a cookie from treatment A first and the other 25 tasted a cookie from treatment B first.

• Thirty-five of the fifty panellists preferred the cookies from treatment B.

• According to statistical Chart, this indicates a significant preference at the 1 % level.

• If 33 persons had preferred one cookie over the other, it would have been significantly preferred at the 5% level.

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Multiple Comparison Difference TestQuestionare for difference test

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Ranking the degree of preference

• Test product: chocolate Name:• Test subject No.: Date:• You will receive four samples of chocolate having the code Nos:. 517,

480, 650, and 916.• Please rank them in order of your degree of preference.• Write to the very left the code of the sample you like best (to which you

give the first position in the degree of preference) and to the very right the code of the sample you like least.

• Mark the degree of preference for the other samples in between.• -------------------------------------------------------------------------------• Sample Code• • --------------------------------------------------------------------------------------------• 1. rank 2. rank 3. rank 4. rank• position position position

( position• (most liked) (least liked)• ----------------------------------------------------------------------------------------------------------

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Hedonic Scale Test

• *The most commonly used scale for preference testing is the nine-point hedonic scale.

• The term "hedonic" is defined as "having to do with pleasure."

• It should only be used in connection with scales in which the panelist expresses his degree of liking or disliking, such as in the following sample questionnaire.

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• QUESTIONNAIRE FOR HEDONIC SCALE

• NAME DATE

• PRODUCT

• Taste these samples and check how much you like or dislike each one

• 148 914 579 777• like extremely like extremely like extremely like extremely• like very much like very much like very much like very much• like moderately like moderately like moderately like moderately • like slightly like slightly like slightly like slightly• neither like nor dislike neither like nor dislike neither like nor dislike neither like nor dislike • dislike slightly dislike slightly dislike slightly dislike slightly• dislike moderately dislike moderately dislike moderately dislike moderately • dislike very much dislike very much dislike very much dislike very much• dislike extremely dislike extremely dislike extremely dislike extremely •• Comments:

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EXAMPLE FOR HEDONIC SCALE TEST

• The ratings for each sample are given numerical values ranging from like extremely (9) to dislike extremely (1).

• The results are analysed by analysis of variance, which has been already described before.

• If only two treatments are evaluated, the mean scores received by each can be compared using the t-test.

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Analysis of variance

• Chewiness

• --------------------------------------------------------------------

• Brands

• --------------------------------------------------------------------

• Judges A B C D Total

• --------------------------------------------------------------------

• 1 2.2 1.9 3.2 0.2 7.5

• 2 2.5 1.0 4.2 2.0 9.7

• 3 3.3 3.0 4.0 1.5 11.8

• 4 2.6 5.4 4.2 1.3 13.5

• 5 2.6 4.3 5.1 0.1 12.1

• 6 2.2 3.4 4.7 1.9 12.2

• 7 2.4 3.6 5.5 3.2 14.7

• 8 1.6 3.9 5.7 1.8 13.0

• --------------------------------------------------------------------------

• Total 19.4 26.5 36.6 12.0 94.5

• ----------------------------------------------------------------------------

• Mean 2.4 3.3 4.6 1.5

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Correction factor (CF) = 94.52/32 = 8930.25/32 = 279.07Sum of squares, samples=(19.4

2 + 26.52 + 36.62 + 12.02)/8 – CF

=2562.17/8 – CF =320.27 - 279.07 =41.20Sum of squares, judges =(7.52 + 9.72 + 11.82 + ... + 13.02)/4 – CF =1152.17/4 – CF =288.04 - 279.07 =8.97Sum of squares, total = (2.22 + 2.52 + ... + 1 .82 – CF

= 347.09 - 279.07= 68.02

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• Analysis of variance table• ----------------------------------------------------------------------------------• So df SS MS F• Variation• ----------------------------------------------------------------------------------• Samples 3 41.20 13.73 16.1 5*• Judges 7 8.97 1.28 1.51• Error 21 17.85 0.85• Total 31 68.02• ---------------------------------------------------------------------------------

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• The F value for samples is 16.15. • According to Chart 3 in the Appendix, page 65, if the

F value exceeds 3.07 there is a significant difference at the 5% level (*) and if it exceeds 4.87 there is a significant difference at the 1% level (**).

• There is a significant difference at the 1% level for samples so the value is marked with two asterisks. There is no significant difference for judges.

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• Tukey's Test is used to determine which samples are signifi-• cantly different. The standard error of the mean is calculated.• SE = √0.85/8• = √ 0.1062• = 0.32• The value from Chart 4 of the Appendix, page 67, for four• samples and 21 degrees of freedom is 3.95.• Least significant difference = 3.95 X 0.32 = 1.3• Sample scores: A B C D• 19. 26.5 36.6 12.0• Sample means: 2.4 3.3 4.6 1.5

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DESCRIPTIVE SENSORY ANALYSIS

• A group of highly trained panellists examine the flavour or texture of a product to provide a detailed descriptive evaluation of it.

• The most commonly known descriptive methods are the flavour profile and the texture profile.

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The flavour profile is the description of the flavour and aroma of a food product.

The description names the perceptible factors, the intensity of each factor, the order in which the factors are perceived, aftertaste, and overall impression.

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• The texture profile is the description of the textural characteristics perceived in a food product, the intensity of each factor, and the order in which they are perceived.

• Mechanical characteristics are described qualitatively and quantitatively;

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• geometrical characteristics are described qualitatively and semi-quantitatively;

• the description of fat and moisture characteristics depends on the product being studied.

• Hardness, fracturability, chewiness gumminess, adhesiveness, and viscosity are mechanical properties.

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• Examples of geometrical properties are grittiness, coarseness, and fibrousness.

• Descriptive analysis is a valuable tool in difference testing and in product development work.

• It provides a complete description of sample differences and guides the product developer in modifying product characteristics to meet consumer demands.

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• *The training of profile panels requires considerable time and the members must possess a high degree of motivation and interest.

• Once trained, however, the panel can provide thorough and reliable descriptions of products in a short time.

• Since the descriptive panel members work together as a group, forceful members could have undue influence on the other panellists and hence, change the results.

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• A method of sensory evaluation called quantitative descriptive analysis was developed at the Stanford Research Institute.

• During preliminary sessions the sensory properties of the product are identified by a trained panel.

• Samples are made up to illustrate the different properties so that the panel agrees on the meaning of each term used.

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• During these sessions the judges work together as a group and discussion is encouraged.

• *The panel members decide the sensory properties that should be evaluated and they also develop the language to be used. During evaluation sessions the panellists work individually.

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• *The scale used is an interval scale consisting of a horizontal line (15 cm) long with anchor points (1.3 cm) from each end and usually, but not necessarily, having a mid point.

• Each anchor point is usually labelled with a word or expression.

• A separate line is used for each sensory property to be evaluated.

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• Each judge records his evaluation by making a vertical line across the horizontal line at the point that best reflects his perception of the magnitude of that property.

• After the panelists have completed their judgments, the experimenter superimposes a grid dividing the line into 60 units, to assign a number between 0 and 60 to each rating. These values are then tabulated.

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QUESTIONNAIRE FOR DESCRIPTIVE ANALYSIS WITH SCALING

• NAME DATE• Please evaluate the firmness of these sample of frankfurters.• Make vertical lines on the horizontal line to indicate your rating of the

firmness of each sample.• Label each vertical line with the code number of the sample it represents.• Please taste the samples in the following order:• 572 681 437 249

• ___________________________________

• • very soft very firm•

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Definition of texture and flavour

• Both of these terms are not only frequently used in the literature, but are also defined in different ways. This makes their understanding difficult.

• 1. DEFINITION OF CONSISTENCY, STRUCTURE AND TEXTURE

• These terms were defined in such a way that they can be differentiated clearly. Physical properties are limited by their connotation in consistency, structure and texture.

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• These terms cannot be used synonymously even though all can be characterized rheometrically by similar force action methods.

• * Rheology was defined as the science of deformation and flow of substances.

• All substances flow only their flow behaviour is different.

• After deformation, the particles return to their original position.

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(a) Definition of consistency

• Consistency describes a substance's compactness, the connection of its elements, density, firmness or viscosity, and its resistance or plastic behaviour (action) during continuous changes of form.

• Its plastic behaviour can be described as a deformation curve, forming curve or flow curve in the case of viscous substances.

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(b) Definition of structure

• Structure describes a substance's set-up, construction, granular make-up, textile construction (as macrostructure, microstructure and molecular structure) and, depending on network structure or structure power, as liquid, semi-firm and firm foods.

• The terms 'firmness' or 'softness' are also used. • Even though not exactly defined, they descriptively

evaluate consistency and structure as well as density and hardness properties of substances.

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• The crosslinks of polymers considerably influence the firmness of these high molecular weight substances.

• In the case of products of plant origin the fruits and bulbs (tubers) evaluated as cell turgor of the cell condition.

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(c) Definition of texture

• *Texture describes a substance's tissue structure. The term is derived from the word textile. Textile manufacturers produce, through spinning and weaving, materials of various 'textures'.

• *Psychophysical investigations made by food technologists about 30 years ago led to a classification of hedonic sensations perceived through the mouth which are important to the modern consumer.

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• In modern sensory analysis, texture is characterized by detailed subdivisions of the help of tactile and pressure sensations perceived through biting, chewing and swallowing.

• This has led to a deeper understanding of the

texture complex of foods.

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• When judging foods by tasting, properties such as softness in biting, ease of disintegration into fragments, connection of the fibres, and other pressure and softness sensations on the tongue, hard palate and cheeks are considered.

• An easy to bite, tender, firm but soft and juicy texture seems to be the most acceptable to the consumer. As can be seen, sensual enjoyment is derived from functional properties.

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• The following definition have been proposed for texture:

• "Texture is the composite of those properties which arise from the physical structural elements and the manner in which it registers with the physiological senses".

• The term texture, therefore, encompasses all properties of foods which are perceived by the kinesthetic and tactile senses in the mouth, e.g. tenderness, density, granular structure, fragility, humidity, etc.

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Following are 96 texture descriptions and material properties

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• *The importance of texture as a 'sensory quality complex' is very well explained in the introduction of the mentioned publication.

• *Texture and juiciness are of utmost, top-rate importance for the palatability (eating value) of meat and other foods.

• Prepared, ready-to-eat meat must be first of all tender and juicy.

• Too firm, tough, coarse or dry meat texture is not appealing and it will always be rated low in consumer tests."

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• *Among all quality properties, the texture of many foods is the most sensitive (delicate) and most changeable, especially during cold storage and freezing-thawing processes, and in all cooking processes.

• In prepared meat, a high texture quality is related to excellent culinary art and precise time-temperature cooking.

• Careless routine preparation can change an originally tender piece of meat into a dry, leather-like product.

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• *The 96 descriptive texture designations and product properties listed can be classified by adding intensifies to the descriptions, e.g. 'little - slight - very - strong - complete - predominant' etc. The range of this descriptive scaling is, however, variable and subjective.

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• *It is most difficult to determine precisely the border values of 'tender - almost tender- slightly tender, etc.' while chewing. In principle, each scaling point should have the same meaning for each test subject. This is only possible when work is done in an objectified way.

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Analytical texture evaluation

• *For a sensory record of textural features of any food, the different physiological, tactile and pressure sensations are analytically evaluated in sequence of their perception, and their intensifies defined. The bite, chew and swallow process is divided into three stages.

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• *Depending upon the product, 5 to 6 scale points are used for the mechanical perceptions in the mouth. Over 20 mechanical and kinaesthetic properties are evaluated sensorial in sequence of their perception and their intensifies defined.

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• *The following features (characteristics) belong to the mechanical properties: hardness, cohesiveness', adhesively, density and viscosity, factorability, cheesiness and gumminess (referring to hardness and connection of particles).

• *Geometrical features are particle size, hardness and fibre orientation.

•

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• Texture profile analysis• *The mentioned analytical texture evaluation has

been worked out in the research laboratories of the General Foods Corporation, and is known as General Foods Texture Profile Analysis (TPA). It is used in research and development in American, Japanese and Latin American countries. Sensory reference standards form the basic for the scale points.

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• *There exist, for example, nine steps for hardness, seven steps for brittleness, seven steps for cheesiness, etc. Panel training and selection is explained and described in detail. The texture analysis belongs to the so-called 'high school' of sensory analysis. The TPA requires knowledge of the product and of the physiology of chewing, as chew number, chew speed and amount of saliva are related to texture.

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• *There exist instrumental methods for evaluating texture, and over one hundred instruments, such as the shear apparatus, compress meters, electrometers, cuterr devices, consist meters and viscosimeters which measure various physical properties, but which are not always correlated with sensory results.

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• *For measuring the various texture profile features (characteristics),

• the classical General Foods Texturometer is used.

• Exact measurements are made according to a compression principle (squeezing and comminuting) providing texture profilograms.

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• *Sensory and instrumental texture meacerement is a special psycho

• physical (and auditive) science and is open to all those with real interest. It requires, however, profound knowledge of the specific product and sensitivity.

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• 2.FLAVOUR• Definition• *Two definitions can be found in literature. In the first case, the • term flavour includes the four basic tastes and the aroma • perceived through tasting. * Standards organizations of different countries increasingly • use the second definition:FLAVOUR- total impression of taste, • odour, tactile, kinesthetic, temperature and pain sensations • perceived through tasting.

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*The cooperation of the various factors in aroma and

flavour development is illustrated very well in the following Fig.

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