Centre of Food Science & TechnologyInstitute of Agricultural Sciences

Banaras Hindu UniversityVaranasi-221005

Detection of Dilution and Threshold test in

relation to Food Product

ContentsIntroductionTypes of testsSensitive testThreshold testTypes of thresholdPoints to be considered in threshold testsPreparation of the test or working solutionNumber of solutions to be prepared for test solutionsFactors affecting threshold test results Dilution testPreliminary testConclusion Reference

IntroductionIntroductionSensory Evaluation

A scientific discipline used to evoke, measure,

analyze and interpret reactions to those

characteristics of food and materials as they are

perceived by senses of sight, smell, taste, touch

and hearing.

-IFT; USA

Types of tests

Different tests are employed for food evaluation

Types of tests

Different tests are employed for food evaluation

The s

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of p

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test

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for c

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g th

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ion

will

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Sensitive testSensitive test

Sensitive test are done to assess the ability of individual

to detect different tastes, odors and feel the presence of

specific factors like astringency or hotness

These tests are used to select and train panel members

for evaluating the quality of products containing spices,

salt and sugar

E.g. Tomato ketchup or sauces

Threshold testThreshold test

Sensitive threshold to measure the ability of an individual

to smell, taste or feel specific characteristics in food or

beverages or pure substances are used frequently in

selecting for evaluations in product research and

development

They are used to establish intensity of sensory response

of a food or food components

Threshold testThreshold test

Threshold is defined as a stastically determined

point on the stimulus scale at which a transition in

a series of sensations or judgments occur.

Types of thresholdTypes of thresholdMainly three types

Stimulus detection threshold Recognition

identification threshold

Terminal saturation threshold

Types of thresholdTypes of thresholdMainly three types

Magnitude of stimulus at which a transition occurs

from no sensation to sensation

Minimum concentration at

which a stimulus is correctly identified

Magnitude of a stimulus above

which there is no increase in the

perceived intensity of the stimulus

Stim

ulus

dete

ction

thre

shold Detection threshold

Differences threshold

Stim

ulus

dete

ction

thre

shold

Magnitude of stimulus at which a transition occurs

from no perceived sensation to a perceived sensation

Least amount of change of a given stimulus necessary to

produce a change in sensation

Types of ThresholdTypes of ThresholdDetection (absolute)

threshold

Point at which the substance is differentiated from the

background

Recognition threshold Point at which the substance is correctly named

Difference threshold Point at which the change in concentration is noted

Terminal threshold Point at which no further intensity increase in found

with increasing concentration

Consumer rejection

threshold

Point at which a consumer preference occurs for a

sample not containing the substance

Sensory Evaluation Of Food

Points to be considered in threshold Points to be considered in threshold teststests

Preparation of stock and working solutions

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

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.

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 not accepted in threshold tests:

Water used in preparation

chlorinated water,

Too hard water,

The following types of H2O are accepted in threshold tests:

heavily deionized water,

demineralized water ,

distilled water.

Preparation of H₂O for threshold purposes

Boiling of fresh H₂O for 10 minutes in an uncovered

enamel pot or glass beaker at least

15 cm in diameter.

Obtained boiled water is cooled then filtered

and the first portion is discarded.

Preparation of the working Preparation of the working solutionsolution

It is advised to prepare two kinds of concentration series of

testing solution

Number of solutions to be Number of solutions to be prepared for test solutionsprepared for test solutions

Many investigators advise to have 10-12 testing solutions with

a gradual concentrationTaste Initial

concentrationFinal (10th solution) concentration

Sweet taste 0.00 1%(0.0, 0.05, 0.1, 0.2 ….1%)

Salty taste 0.00 0.2%Sour taste 0.00 0.035%Bitter taste 0.00 0.0003%Caffeine taste 0.00 0.030%

Quantity of testing solution

500 ml for 15 testers

1000 ml for 30 testers

Factors affecting threshold test Factors affecting threshold test resultsresults

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

Sour insensitivity who lacks gastric acid;

Bitter insensitivity slightly improved by training;

Salty insensitivity by teeth filling on having denture plate.

Oversensitivity for sweet taste who with too much gastric

acid.

Sex; women were found to be more sensitive to sweet and

salty while men are more sensitive to sour.

Age; sensitivity for sweet and sour decrease with age.

Alcohol affect widely the sensation of the four basic tastes.

Dilution testDilution test

Dilution test are designed to established the smallest

amount of an unknown material, developed as a substitute

for a standard product, that can be detected when it is

mixed with the standard product

e.g. oSynthetic orange ingredient with natural flavoroDried whole milk in fresh milkoMargarine in butter

Continue….. Continue…..

The quality of test materials is represented by the

dilution no.

Percentage of the

test material in the

mixture of the

standard product

Bigger the dilution no.

the better the quality of

the test material

Preliminary testPreliminary test

Established the higher and lower %of the test material in the mixture

Define a series of mixture Represent the upper & lower limits

Usually 6 are enough, although 8 may be used

if greater precision is desired

Simple paired difference test Test series against the

standard starting with the

mixture containing the lower

% of test substanceObtain 15-20 judgment for each sample of series

Where the frequency of the

difference judgment just

reaches the 5% significance

level % of the test material in

That Mixture is the dilution no.

Conclusion Conclusion Useful in analyzing complex processed food

Help in studying the flavor secrets of successful

products & also the influence of variety, processing,

ageing, storage etc.

Useful for where a minimum detectable difference of

an additive or of an off flavour are to be established

ReferencesReferencesSensory evaluation of food: Principles & Practice

by Harry T. Lawless, Hildegarde teymann

Food science by B Srilakshmi

Handbook of Analysis & Quality Control for Fruit &

Vegetable Products by S. Ranganna

Basic Principles of Sensory Evaluation by American

society for testing & materials

Principles of Sensory Evaluation of food by M.A. Amerine,

R.M. Pangborn, & E.B. Roessler

Modern Sensory Methods of Evaluation Wine by M.A.

Amerine, E.B. Roessler & F. Filipello