11

Teacher Professional Development ProgrammeTeacher Professional Development ProgrammeKnowledge Enriching Series forKnowledge Enriching Series for

New Senior Secondary Technology and Living:New Senior Secondary Technology and Living:Food Science and Technology StrandFood Science and Technology Strand

Item 1: Food StudiesItem 1: Food Studies

Food Preservation IIFood Preservation IIProfessor Peter CK CheungProfessor Peter CK Cheung

Food and Nutritional SciencesFood and Nutritional SciencesThe Chinese University of Hong KongThe Chinese University of Hong Kong

22

Outlines for Food Preservation I and IIOutlines for Food Preservation I and II

Purpose of food preservationPurpose of food preservationFactors causing food deteriorationFactors causing food deteriorationPrinciples of food preservationPrinciples of food preservationThermal and nonThermal and non--thermal methods of thermal methods of food preservationfood preservationEmerging methods of preservationEmerging methods of preservation

33

Thermal methods of food Thermal methods of food preservationpreservation

Methods of heat treatmentMethods of heat treatment

–– Pasteurization Pasteurization –– Blanching Blanching –– CanningCanning (commercial sterilization)(commercial sterilization)

44

Objectives of thermal treatmentObjectives of thermal treatment

To eliminate pathogensTo eliminate pathogensTo eliminate or reduce spoilage To eliminate or reduce spoilage organismsorganismsTo extend the shelfTo extend the shelf--life of the foodlife of the foodTo improve palatability of the foodTo improve palatability of the food

55

BlanchingBlanchingHeat treatment of vegetables in boiling, salted water to Heat treatment of vegetables in boiling, salted water to inactivate enzymes, kill microorganisms and retain inactivate enzymes, kill microorganisms and retain color (chlorophyll)color (chlorophyll)Typical example: Typical example: 100100ooC for 1 min to inactivate C for 1 min to inactivate peroxidaseperoxidase

PasteurizationPasteurizationHeat treatment of milk adequate to kill potential Heat treatment of milk adequate to kill potential harmful microorganisms harmful microorganisms Destroy pathogensDestroy pathogensPurposes:Purposes:To rTo reduce bacterial counteduce bacterial countTo iTo inactivate enzymesnactivate enzymesTo eTo extend shelfxtend shelf--lifelife

Mild heat treatment/ thermal processingMild heat treatment/ thermal processing

66

Different methods of pasteurizationDifferent methods of pasteurization

LowLow--temperature hold method (LHT): typical temperature hold method (LHT): typical conditions of conditions of 6363ooC for 30 min C for 30 min before cooled before cooled to 7to 7oCCHighHigh--temperature shorttemperature short--time (time (HTSTHTST): typical ): typical conditions ofconditions of 71.571.5ooC C and hold and hold for for at least at least 15 15 secsec before cooled to 10before cooled to 10ooCCUltrahighUltrahigh--temperature (UHT): 138temperature (UHT): 138ooCC for at for at least 2 seconds; extreme pasteurization that least 2 seconds; extreme pasteurization that kills all microorganisms for keeping milk in a kills all microorganisms for keeping milk in a closed, sterile container at room closed, sterile container at room temperaturetemperature

77

Table 1 Some examples of convention pasteurization treatments

in bulk30 min60-65.6Vinegar*in common30 min65.6Carbonated Drinks*bottled in bulk30-60sec85-87.8 oCApple Juice*

30 min76.7 oCGrape Juice*

30-90 min65.6-85oCDried fruitsbottled hotdepends60oCBeerbottled hotdepends62.8oCFruit Wines*in bulk1 min82-85oCGrape Wines*HTST16-20 sec82.2oCIce-CreamLTH30 min71.1oCIce-CreamUHT2 sec137.8oCMilkHTST15 sec71.7oCMilkLTH30 min62.8oCMilk

RemarkTimeTemperatureProduct

*depends on the acidity

88

Severe Heat treatment/ thermal processingSevere Heat treatment/ thermal processingSterilization (in Sterilization (in CanningCanning))

IIntensive heat treatment that kills ntensive heat treatment that kills allall the the pathogens and microorganisms, including pathogens and microorganisms, including their their sporesspores, in food. , in food. RRelatively long shelfelatively long shelf--life (i.e., more than six life (i.e., more than six months) in a hermetically months) in a hermetically sealedsealed container container withoutwithout other supplementary preservation other supplementary preservation measures.measures.

99

Sterilization (in Sterilization (in CanningCanning))

Intrinsic factors of food affecting Intrinsic factors of food affecting sterilization conditionssterilization conditions::Heat penetration characteristics of foodHeat penetration characteristics of foodpH of the foodpH of the foodComposition of foodComposition of food

1010

Sterilization of canned foodsSterilization of canned foods

Canning of food before sterilization

Vertical retort for sterilization of canned foods

1111

Sterilization (in Sterilization (in CanningCanning))

CCommercial sterilizationommercial sterilization conditionsconditions::Temperature ranges from Temperature ranges from 116116 -- 121121ooCCHeating time (D values) : 12D conceptHeating time (D values) : 12D conceptThermal Death time (TDT)Thermal Death time (TDT)

1212

Sterilization of Canned Foods

Table 2

12

Murano, 2003

2

1313

Table 2. Table 2. Overview of Mild and Severe Heat Overview of Mild and Severe Heat TreatmentsTreatments

ExamplesCanning

ExamplesPasteurization, blanching

DisadvantagesFood is overcookedMajor changes in texture, flavor,

and nutritional quality

DisadvantagesShort shelf lifeAnother preservation method

must be used, such as refrigeration or freezing

AdvantagesLong shelf lifeNo other preservation method is

necessary

AdvantagesMinimal damage to flavor, texture,

and nutritional quality

AimsKill all bacteriaFood will be commercially sterile

Aims Kill pathogensReduce bacterial count (food is

not sterileInactive enzymes

Severe Heat TreatmentMild Heat Treatment

1414

LowLow--temperature treatment/ cold temperature treatment/ cold storagestorage

RefrigerationRefrigeration/chilling/chilling

Freezing

1515

ChillingChillingtemperature between temperature between --1 to 81 to 8 ooCCpurpose: to reduce biochemical and purpose: to reduce biochemical and microbial changes => extend shelf life of microbial changes => extend shelf life of fresh and processed foodsfresh and processed foodscharacteristics: minimal sensory and characteristics: minimal sensory and nutritional changesnutritional changesin combination with fermentation, in combination with fermentation, irradiation, pasteurization, etc. as post irradiation, pasteurization, etc. as post treatment treatment

1616

Table 3

1717Figure 3

1818

Chill injuryChill injury

tropical, subtropical (<10tropical, subtropical (<10--1515 ooCC) and some ) and some temperate fruits (<5temperate fruits (<5--1010 ooCC))caused by maintaining temp below a specific caused by maintaining temp below a specific optimum for the fruit in concern resulted in the optimum for the fruit in concern resulted in the physiological changes as browning (surface physiological changes as browning (surface discoloration), undiscoloration), un--ripening, blemishing (pitting, ripening, blemishing (pitting, collapse of tissue), etc. collapse of tissue), etc. Mechanisms: membrane lipid structure/enzyme Mechanisms: membrane lipid structure/enzyme conformational changes, loss of conformational changes, loss of compartmentalizationcompartmentalization

1919

Chill Injury after long time storageChill Injury after long time storage

2020

2121

Freezing and frozenFreezing and frozen--food storagefood storagefood temp below freezing point food temp below freezing point water forms ice (change in state)water forms ice (change in state)for almost all kinds of food (fruit for almost all kinds of food (fruit –– whole, whole, puree, concentrates; vegetables, seafood, puree, concentrates; vegetables, seafood, meat, baked food, readymeat, baked food, ready--toto--eat prepared eat prepared food)food)

How does freezing preserve food?How does freezing preserve food?low temperaturelow temperaturelow water activitylow water activity

2222(Fellows, 2000)

Figure 4

2323Figure 5

2424

Delgado and Rubiolo, 2005

Figure 6aFigure 6b

Figure 6dFigure 6c

2525

Changes in food during fChanges in food during frrozen storageozen storage

RecrystallizationRecrystallizationFreezer burFreezer burnn (dehydration)(dehydration)Residual chemical (lipid oxidation) and Residual chemical (lipid oxidation) and enzymatic reaction (plant originenzymatic reaction (plant origin--polyphenoloxidasepolyphenoloxidase, , lipoxygenaselipoxygenase; animal ; animal originorigin-- proteolyticproteolytic and and lipolyticlipolytic enzymesenzymesColloidal substanceColloidal substance/physical/physical change (starch change (starch syneresissyneresis; emulsion breakdown); emulsion breakdown)

2626

Mechanisms of migratory Mechanisms of migratory recrystallisationrecrystallisation in in foods during frozen storagefoods during frozen storage

caused by fluctuation of storage temp.caused by fluctuation of storage temp.heat entering a freezer => melting of ice crystal on heat entering a freezer => melting of ice crystal on food surface nearest to heat source => ice crystal food surface nearest to heat source => ice crystal reduces in size => reduces in size => vapourvapour pressure increases Vs pressure increases Vs inside of freezer => migration => dehydration near inside of freezer => migration => dehydration near the region of the heat source => when temp falls the region of the heat source => when temp falls => no => no recrystallisationrecrystallisation of water vapor, but migrated of water vapor, but migrated and joined with other ice crystals => bigger size=> and joined with other ice crystals => bigger size=> quality loss as in slow freezingquality loss as in slow freezing

2727

(Brennan et al., 1990)Figure 7

2828

Freezer burnFreezer burn

loss of moisture from food to storage loss of moisture from food to storage environment environment characterized by: lighter characterized by: lighter colourcolour (microscopic (microscopic cavity previously occupied by ice can cavity previously occupied by ice can change the wavelength of reflected light) change the wavelength of reflected light) foods with large surface area/volume ratio foods with large surface area/volume ratio e.g. IQFe.g. IQFminimized by packagingminimized by packaging

2929

Freezer Burn of Red MeatFreezer Burn of Red Meat

3030

Moisture rMoisture removalemovalProduct concentrationProduct concentration

Evaporation; distillation; Evaporation; distillation; ultrafiltrationultrafiltration; dialysis; dialysis

DehydrationDehydrationSun drying; Drum dryingSun drying; Drum dryingFreeze drying; Smoking; Spraying dryingFreeze drying; Smoking; Spraying dryingControlling factors: temperature, humidity, Controlling factors: temperature, humidity, pressure, and portion sizepressure, and portion sizeDeterioration: color, flavor, textural changes due Deterioration: color, flavor, textural changes due to enzymatic activities; nonto enzymatic activities; non--enzymatic reaction enzymatic reaction ((MaillardMaillard browning); oxidative spoilage by fat browning); oxidative spoilage by fat oxidation oxidation

3131

3232

Figure 8

Murano, 2003

3333

Freeze Drying: the Sublime SolutionFreeze Drying: the Sublime Solution

www.ofd.com

3434

www.ofd.com

Commercial freeze drying equipment

3535

3636

NonNon--thermal methods of thermal methods of food preservationfood preservation

3737

Acidity controlAcidity control

Control of pH of a food through the use of Control of pH of a food through the use of acidulantsacidulantsHighHigh--acid foods (pH < 4.6)acid foods (pH < 4.6)SporeSpore--forming bacteria generally do not forming bacteria generally do not grow in foods having pH values of 4.5 and grow in foods having pH values of 4.5 and lessless

3838

Present in baking powder as potassium Present in baking powder as potassium tartratetartrate saltsaltOccurs naturally in grapesOccurs naturally in grapes

TartaricTartaric

As calcium propionate, effective antimicrobial agentAs calcium propionate, effective antimicrobial agentProduced in some cheesesProduced in some cheeses

PropionicPropionic

Provides flavor and tartness in beveragesProvides flavor and tartness in beveragesEnhances juiciness in meats (as phosphate)Enhances juiciness in meats (as phosphate)

PhosphoricPhosphoric

Provides flavorProvides flavorOccurs naturally in applesOccurs naturally in apples

MalicMalic

Provides tartnessProvides tartnessLacticLactic

Provides flavor, decreases pH, acts as chelating and sequesterinProvides flavor, decreases pH, acts as chelating and sequestering agentg agentOccurs naturally in citrus fruitsOccurs naturally in citrus fruits

CitricCitric

As sodium benzoate, effective antimicrobial agentAs sodium benzoate, effective antimicrobial agentOccurs naturally in cranberriesOccurs naturally in cranberries

BenzoicBenzoic

Provides flavor, decreases pHProvides flavor, decreases pHSodium acetate is salt form present in vinegarSodium acetate is salt form present in vinegar

AceticAcetic

CommentCommentAcidAcid

Table 3 Examples of acidulants used in the food processing industry. Acetic acid is present in vinegar, while the acid salt sodium acetate can be used as an additive to decrease a food’s pH. Citric acid is present in citrus fruits; malic acid is a component of apples; and all of these acids also can enhance food flavor. Sodium benzoate and calcium propionate are acid additives that are effective antimicrobial agents. One type of inorganic acid, namely phosphoric, is used extensively in foods and beverages.

3939

Use of packagingUse of packaging

Packaging functionsPackaging functions

Control of packaging atmosphere

For fresh meat

For anything!For convenience

For poultry

For seafoodFor produceFor dairy

For cheeseFor small goods

4040

Packaging functionsPackaging functionsPreserve spoilage of color, flavor, odor, and Preserve spoilage of color, flavor, odor, and texturetexturePrevent contamination by biological, physical, Prevent contamination by biological, physical, chemical hazardschemical hazardsPrevent loss or absorption of waPrevent loss or absorption of waterter and oxygenand oxygenPrevent tampering (neckbands/shrinkPrevent tampering (neckbands/shrink--film sleeves)film sleeves)Communicate information with Communicate information with ingredients/nutrition factsingredients/nutrition factsFacilitate marketingFacilitate marketing

4141

Controlling packaging atmosphereControlling packaging atmosphere

Vacuum Vacuum ––no entry/escape of air, carbon no entry/escape of air, carbon dioxide, waterdioxide, waterModified Atmosphere Packaging Modified Atmosphere Packaging (MAP) (MAP) –– gas flush (nitrogen and inert gas flush (nitrogen and inert gases)gases)Active packaging Active packaging –– sachet: oxygen (iron sachet: oxygen (iron oxide); carbon dioxide (calcium oxide); carbon dioxide (calcium hydroxide); water, ethylene (potassium hydroxide); water, ethylene (potassium permanganate), ethanolpermanganate), ethanol

4242

Aseptic packagingAseptic packaging

Independent sterilization of both foods Independent sterilization of both foods and packaging material with assembly and packaging material with assembly under sterile environmental conditionsunder sterile environmental conditions

4343

Tetra Aseptic packagesTetra Aseptic packages

(Source: Tetra Pak Inc.)

4444

Figure 7a Tetra Brik ®aseptic packaging material layers (Source: Tetra Pak Inc.)

Figure 7b Illustration of roll-fed packaging material being formed into Tetra Briks. (Source: Tetra Pak Inc.)

4545

Figure 8 Aseptic packagingFellows, 2000

4646

Minimal processing of foodsMinimal processing of foods

NonNon--thermal methods with no thermal methods with no substantial increases in product substantial increases in product temperaturetemperaturePreserve foods with greater retention Preserve foods with greater retention of and/or insignificant detrimental of and/or insignificant detrimental effect on nutritional and sensory effect on nutritional and sensory qualityqualityHigher consumer appeal and premium Higher consumer appeal and premium pricesprices

4747

ElectroElectro--heating (radioheating (radio--frequency, microwave frequency, microwave and and ohmicohmic heating)heating)High pressure High pressure processing (HPP)processing (HPP)High voltage electrical High voltage electrical dischargedischargeHigh intensity lightHigh intensity lightUltrasoundUltrasoundModified atmosphere Modified atmosphere packagingpackagingJet Jet impactationimpactation

Gamma radiationGamma radiationLasers and masersLasers and masersMicrofiltrationMicrofiltrationXX--raysraysCryogenic thermal Cryogenic thermal shockshockImmobilisedImmobilised enzymesenzymesActive packagingActive packagingOzoneOzoneNitrous oxideNitrous oxide

Table 4. Table 4. Examples of novel processes that may have Examples of novel processes that may have applications for minimal processing of foodsapplications for minimal processing of foods

(Fellows, 2000)

4848

TheoryTheory of Food Irradiationof Food IrradiationIonization of water byIonization of water byγγrays and electronsrays and electrons to produce to produce ions and free radicalsions and free radicalsRadiolysis: subsequent reactions caused by products Radiolysis: subsequent reactions caused by products of ionization to destroy microof ionization to destroy micro--organisms, insects and organisms, insects and parasites in irradiated food parasites in irradiated food

Figure 10

4949

Rate of destruction of microRate of destruction of micro--organisms by radiationorganisms by radiationResistance to irradiation: viruses>spore forming bacteria>vegetaResistance to irradiation: viruses>spore forming bacteria>vegetative cells tive cells

and nonand non--spore forming bacteria>insects and parasitesspore forming bacteria>insects and parasites

Figure 11

5050

NoneNoneLong term ambient storage of meat Long term ambient storage of meat (outside permitted dose)(outside permitted dose)

Up to 50Up to 50

Algeria, Bangladesh, China, CubaAlgeria, Bangladesh, China, CubaPotatoes, garlic, onionsPotatoes, garlic, onions0.10.1--0.20.2Inhibition of sproutingInhibition of sprouting

Argentina, Brazil, Chile, ChinaArgentina, Brazil, Chile, ChinaFruit, grain, flour, cocoa beans, dry Fruit, grain, flour, cocoa beans, dry foodsfoods

0.10.1--22DisinfestationDisinfestation

----PorkPork0.10.1--66Inactivation/control of Inactivation/control of parasitesparasites

China, France, Netherlands, South China, France, Netherlands, South Africa, USAAfrica, USA

Soft fruit, fresh fish and meat at 0Soft fruit, fresh fish and meat at 0--44℃℃

22--55Extension of chill life from Extension of chill life from 5 days to 1 month5 days to 1 month

China, South Africa, USAChina, South Africa, USAExtended storage of fresh fruitExtended storage of fresh fruit22--55Control of mouldsControl of moulds

Belgium, Canada, Croatia, Czech Belgium, Canada, Croatia, Czech Republic, Denmark, Finland, France, Republic, Denmark, Finland, France, Iran, Netherlands, South Africa, Iran, Netherlands, South Africa, Thailand, VietnamThailand, Vietnam

Spices, frozen poultry, meat, Spices, frozen poultry, meat, shrimpsshrimps

2.52.5--1010Destruction of pathogensDestruction of pathogens

HungaryHungaryWine corksWine corks1010--2525Sterilization of packaging Sterilization of packaging materialsmaterials

Belgium, Canada, Croatia, Czech Belgium, Canada, Croatia, Czech Republic, Denmark, Finland, Israel, Republic, Denmark, Finland, Israel, Korea (Rep.), Mexico, South Africa, Korea (Rep.), Mexico, South Africa, USA, VietnamUSA, Vietnam

Herbs, spicesHerbs, spices77--1010SterilizationSterilization

Countries with commercial Countries with commercial processingprocessing

Examples of foodsExamples of foodsDose rangeDose range((kGykGy))

ApplicationApplication

Table 5 Applications of food irradiation

Adapted from Ley (1987), Guise (1986a), Goresline (1982), Anon (1985), Loaharanu (1995) and Wilkinson and Gould (1996).

5151

Table 6 Table 6 Advantages and limitations of Advantages and limitations of Gamma RadiationGamma Radiation

InsecticidalInsecticidal

Improvement in flavor in some Improvement in flavor in some foods (e.g. strawberries)foods (e.g. strawberries)

Suitable for dry foodsSuitable for dry foods

Suitable for largeSuitable for large--scale production scale production Low energy costsLow energy costs

Little loss of food qualityLittle loss of food quality

Difficult to detectDifficult to detectReliableReliable

Changes in flavor due to Changes in flavor due to oxidation oxidation

Permitted in some countries Permitted in some countries

Meat and fishMeat and fish‘‘PoliticsPolitics’’ of nuclear energyof nuclear energySuitable for nonSuitable for non--microbial microbial applications (e.g. sprout inhibition)applications (e.g. sprout inhibition)

PackagingPackagingPoor consumer Poor consumer understandingunderstanding

Suitable for sterilizationSuitable for sterilization

Herbs and spicesHerbs and spicesLocalized risks from radiationLocalized risks from radiationExcellent penetration into foods Excellent penetration into foods Fruit and vegetablesFruit and vegetablesHigh capital costHigh capital costWell established and understoodWell established and understood

Examples of commercial Examples of commercial applications and productsapplications and products

LimitationsLimitationsAdvantagesAdvantages

(Fellows, 2000)

5252

Recommended Recommended bbasic referencesasic references

Food Processing Technology: Principles Food Processing Technology: Principles and Practice by P. Fellows and Practice by P. Fellows ((20002000)), 2nd , 2nd edition, CRC Press.edition, CRC Press.

Food Processing Handbook by J.G. Food Processing Handbook by J.G. Brennan (2006), WileyBrennan (2006), Wiley--VHCVHC

Understanding Food Science and Understanding Food Science and Technology by Peter S. Technology by Peter S. MuranoMurano (2003), (2003), Thomson WadsworthThomson Wadsworth

5353

Advanced readingAdvanced reading for for Emerging Preservation TechnologiesEmerging Preservation Technologies

New trends in food processing by New trends in food processing by SenoransSenorans et al. et al. in Critical Reviews in Food Science and Nutrition, in Critical Reviews in Food Science and Nutrition, 43(5):50743(5):507--526 (2003)526 (2003)Tasks of food technology in the 21st century by M. Tasks of food technology in the 21st century by M. KarelKarel in Food Technology 54(6):56in Food Technology 54(6):56--64 (2000)64 (2000)Applications and potential of ultrasonic in food Applications and potential of ultrasonic in food processing by processing by KnorrKnorr et al. in Trends in Food et al. in Trends in Food Science & Technology 15:261Science & Technology 15:261--266 (2004)266 (2004)Advances in the use of high hydrostatic pressure Advances in the use of high hydrostatic pressure for processing cereal grains and legumes by for processing cereal grains and legumes by EstradaEstrada--GironGiron et al. in Trends in Food Science & et al. in Trends in Food Science & Technology 16:194Technology 16:194--203 (2005)203 (2005)