2/25/14Fennema'sFood ChemistryFoodScience&TechnologyFourthEdition.Foodpreservation:food safetyfood qualitySrinivasan DamodaranKirkLParkirPrefaceEditoeContrihuLPart IIMinor Food Compon437Chapter 1 Introduction to Fod ChemisrChapter 7Vitamin439ORFeSrininaanDmodaaErkLsAae FE Gngiry Ill523Chapter8Mscrad15PartI Major Food ComponentsDnirD. AfiChaper2Waerand lce.1T571Chapter9CokoriDnidSRridandOuenRFennmhynShuert83Chaper3Caubohydrate639Chapter10FaAomerNBeMifterandKeryC.Hdeyberr CLndChapter4Lipids.155Chapter 11 Food Additive689DJulianMCleennanfEriADeterrCLondid217Chapter5AminoAcidk,Peptides,andProtcimChaper1zBicotneSohstDceNntpadTosi751SinivanmDuaduaCh.onga,MohumedM.Rafand Gretia GhnChapter6Earymes331KrkLPonkin
2/25/14 1 Food Science & Technology • Food preservation: food safety food quality
2/25/142WaterandIceDavidSReidandOwenR,Fenema781Part I Food SystemLess important783Chapter 13 Dispersed Systems: Basik: ConsidentPiter Wiolatraand Tier VlietCONTENTSBigChapter14Physical and Chemicad Interactices of Compoteets in Food SystemZitistuw ESiorsli.JoePodorneendSrdsivmsDomolan22ThePhysiERF23Chapter15ChanacteristicsofMilk885TheWnMdec24NisWnddESuuiigoodChapter16PgsiologyandChemistryofESbleMusckeTisse923PGoleSwmharg, louling LXing, ad Wirn ChiongCupler17PoathanvestPysiologyofEdiade Plamt Tissu975JegroyK.BrrchtMantARomor,NormmrEHoand,andGrodyWChiuNR#R带18Chupter18 Impactof Bioceechnology onFoodSupply andQuality1051MfarfinaNreedl-MeGiwghlin282R419WaterActvityadKelutiveVapoePy4中学学学学务院Chmnistn29.1ltrodactiorZ9.2DetisitionandMcauremem2.9.3Teapersture Dependesce101RESOOURRENZ1o Molecular Mohiliy ad Food Suabilit02heEseRaDninn2.10.3TheNetMoisheS2.1L.1DefinitioroandZonesfMokulMohiyaFoodSrah2.11.2Temperature DepesdkenTheStaeDhstrm2.113 Hysterei2.10.61pnceofaPhoin2.114 Hydraton S2.10.62InterpratingaSaeDiapam2.12Relative Vapor Pressure and Food Stahilay2.10fTheEateruyoeFouilihciumandKnetc213.0210.tExuiling heCaneeptteCenglesFoodSyuem2131TheeenthRve.MMS2.10.65 1entifying te A格FUedentandaeheBdeafwerieEo1072.14 Cnnco42
2/25/14 2 Less important
2/25/14Food SafetyFood Quality·Chemical.Nutrition.Biochemical.Sensoryflavorappearance.MicrobiologicaltextureWater&FoodS9*-:Wateristheprinciplecomponentoffoods.a子S+S.Waterfunctionsasamediumfor4chemicalreactions一.Waterfunctionsasamediumfor=microbiologicalgrowthas3
2/25/14 3 Food Safety • Chemical • Biochemical • Microbiological Food Quality • Nutrition • Sensory flavor appearance texture Water & Food • Water is the principle component of foods. • Water functions as a medium for chemical reactions. • Water functions as a medium for microbiological growth
2/25/14Phases or States ofWaterPhases orStates ofWater.Stateofwaterdependson.Solid (ice)temperatureand pressure.·Liquid.Atconstantpressure it requires heattochangetemperatureand state.·Gasorvapor·At constanttemperature,it requireschanges inpressuretochangestateTemperature changePhasechange1 calorie of heat per gram of water is required to raise the:Ice to liquidwaterrequires 80cal/g at0Ctemperature of water one°C:10 g ice at 0C requires:-To raise the temperature of 100 g water from 10 to 20 °C10x80=800 caloriesrequires10 x 100 = 1000 calories."Ice Diet"One calorie is not the same as one food Calorie:1Calorie (food calorie)=1000 calorieOne Joule is 0.2390 cal (1 J= 1N -M)·800Calorieswillmelt8.000gice1 J is the energy required to lift a small appleonemeterstraightup.4
2/25/14 4 Phases or States of Water • Solid (ice) • Liquid • Gas or vapor Phases or States of Water • State of water depends on temperature and pressure. • At constant pressure it requires heat to change temperature and state. • At constant temperature, it requires changes in pressure to change state. Temperature change • 1 calorie of heat per gram of water is required to raise the temperature of water one ºC. • To raise the temperature of 100 g water from 10 to 20 ºC requires 10 x 100 = 1000 calories • One calorie is not the same as one food Calorie • One Joule is 0.2390 cal (1 J = 1N . M) 1 J is the energy required to lift a small apple one meter straight up. Phase change • Ice to liquid water requires 80 cal/g at 0 ºC • 10 g ice at 0 ºC requires: 10 x 80 = 800 calories • Ice Diet • 1 Calorie (food calorie) = 1000 calorie • 800 Calories will melt 8,000g ice
2/25/14PhasediagramofWaterTemperaturecontrolLiquidot1e0C1 atm,IceandliquidwatermixtureTemperature=0°℃Solid.Liquidwaterand steamTemperature=100TriplepointVapor.At normalpressure(oneatm)thetemperature cannotgo aboveiooC with liquid waterpresent.TemperatureFressurecookerLiquidLiquid121℃oro°CRetort100°℃oPC100°C1atm1atmSolidSolidssVaporVaporSubliminationor freezedriedTemperatureTemperature5
2/25/14 5 Temperature control • Ice and liquid water mixture Temperature = 0 ºC • Liquid water and steam Temperature = 100 ºC • At normal pressure (one atm) the temperature cannot go above 100 ºC with liquid water present. Temperature Pressure 1 atm 0ºC 100ºC Phase diagram of Water Temperature Pressure 1 atm 0ºC 100ºC 121 ºC Temperature Pressure 1 atm 0ºC 100ºC Sublimination or freeze dried
2/25/14Density=masspervolumeH,O(liq) = 0.9998 (0°C)= g/mLH,O(ice)= 0.9168 (0°C)Freeze DriedFor a constant weightof water.FreezDriedLower densityresults in volumeexpansionIceliquidThermal Conductivity of Ice is about four times fasterThermal Conductivity of Ice is about four times fasterthan Liquid Waterthan Liquid WaterThawingFreezing+10C-20C-20C+10C-20C+10C
2/25/14 6 H2O(liq) = 0.9998 (0ºC) H2O(ice) = 0.9168 (0ºC) For a constant weight of water: Lower density results in volume expansion Density = mass per volume = g/mL liquid ice +10C -20C +10C -20C Thermal Conductivity of Ice is about four times faster than Liquid Water Freezing -20C +10C -20C +10C Thermal Conductivity of Ice is about four times faster than Liquid Water Thawing
2/25/14DescribingWaterinFoodsAmajorProblemTo manage water we must first be able to describe andquantify water that is in a foodSeveral approaches:.Inthedevelopmentofstablefood1)Watercontent.%H0(traditionalproducts,amajorproblemisgettingthe simple in concept and measurement2) Water activity,aw (1950's →)water in foods to stay inplace.Thataccounts for effects of solutes anddifferences betweenmeanstoprevent itfrommigratingfromfoodsplacetoplace.3) Molecular mobility, T, (Slade & Levine, 1988)-treatsfoodaspolymermatrix,wateraskeyplasticizer- glass transition explains some irregularities in adataEach approach is individually imperfect, together they arecomplimentaryWaterAvailabilityRelativeHumidityof Food!:Water content offoodp=watervaporpressureabove foodPo--Useful knowledge, but...DP, = water vapor pressureabove pure water=DoesnotaccountforhinderedwaterwaterRelative Humidity = p/ pax100food.NeedmeasureofwateravailabilityofwaterWait for equilibrium thenRH= ERH= p/p, x 100Water activity (a,)= p/p。 (0<a,<1)
2/25/14 7 A major Problem • In the development of stable food products, a major problem is getting the water in foods to stay in place. That means to prevent it from migrating from place to place. Describing Water in Foods To manage water we must first be able to describe and quantify water that is in a food Several approaches: 1) Water content, %H20 (traditional) – simple in concept and measurement 2) Water activity, aw (1950s →) – accounts for effects of solutes and differences between foods 3) Molecular mobility, Tg (Slade & Levine, 1988) – treats food as polymer matrix, water as key plasticizer – glass transition explains some irregularities in aw data Each approach is individually imperfect, together they are complimentary. Water Availability • Water content of food – Useful knowledge, but. – Does not account for hindered water • Need measure of water availability of water Relative Humidity of Food! p p = water vapor pressure above food po water po = water vapor pressure above pure water Relative Humidity = p/ po x100 Wait for equilibrium then RH = ERH = p/po x 100 Water activity (aw) = p/po (0 < aw<1) food
2/25/14Water Sorption CurveWaterMovement(samefoodwithdifferentmoisturecontents)raJoe0.90.5ERH=50%0r90%?50%≤ERH<90%0.20.40.60.81.0AwTable I, Water Content of Various Foods Dried toCaseStudy#1:RaisinBranaw=0.70Multi-componentfoodinsamepackageWater Content,Food%, wt/wt- want flakes crispy,raisins moist throughout shelf lifeNuts49.Fundamentalproblem:watermigration7Whole milk powder- Water activity values determine direction of water710CocoamigrationSoybeans913Dried whole egg10highawlowa,Skimmed milk powder10Dried lean meat and fish10Rolled oats11RaisinBranRice1215Pulses1215Dried vegetables1222Wheat flour, noodles13-15Raisins: high awDried soup mixes1321Driedfruits1825Flakes:lowaw8
2/25/14 8 Water Movement (same food with different moisture contents) ERH = 50% or 90% ? 0.5 0.9 50% < ERH < 90% Water Sorption Curve Case Study #1: Raisin Bran • Multi-component food in same package – want flakes crispy, raisins moist throughout shelf life • Fundamental problem: water migration – Water activity values determine direction of water migration – high aw low aw Raisin Bran Raisins: high aw Flakes: low aw
2/25/14alins soneP/BFoure 20Resorption isotherme for various foods and biological substances. Temperature20C, except fornumber1,which is 40'C:(1)confection (main component powderedsucrosel, (2) spray-dried chicory extract, (3) roasted Columbian coffee, (4)pig panereesextraetpowder, (5) nativerice starch. (From Ref,127.)Texture and waterBanewaruarae3iHICURE2.3SMiaovedesoceragarus.RadiuafmGingmiSaitidesatvarian0.20.80.40.6valalAutraffieDeid19581InfmntfFafnea.SoseyefOmcdlelatLinPP.41-41
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2/25/14Table3.Effectof WaterActivityonMicroorganism-InducedFood SpoilageTable 4.Water Activity of Confectionery Products*Probable SpoilageWater ActivityType of ProductFoodaOrganisms0.750.84Fondant0.901.00BacteriaCottage cheese, fresh meat0.590.76Fruit jellies0.850.90Bacteria and moldsMargarine0.650.70MarzipanSweetened condensed milkYeasts0.630.73MarshmallowBacteriaWhipped butter0.600.70Turkish delight0.800.85YeastsChocolate syrup, fruit syrups0.530.66LicoriceXerophilic moldsDried figs0.750.800.510.64Gums and pastillesJamsMolds and yeasts0.370.50Chocolate0.700.75YeastsConfections<0.48ToffeeMolasses0.650.70Osmophilic yeasts<0.30Boiled sweets0.600.65Xerophilic moldsDried fruitHoneyOsmophilic yeastsChemical reaction rates are affected by water activityGeneral TechnologyStructureBody Dertived From1. Hard Candy (1.5% Water)High Visoosity Glass2. Jelles-Various (25% Waten)High molecular weight colloidal nework3. Caramels (2% Water)Milk ProteinsVery Fine Sugar Crystallzation4Fondant (10-12% Water)5.Lozenges Compressed 8Low Molsture, Fine Sugar CrystalsExtruded (0.5%Water)5. Marshmalow (14-25% Water)Collidaly Set Foam7. Nougat (7-12% Water)High Viscosity Glass Foam ar Fine SugarCrystalization Foam8. Hard Panned Coating (0.2% Water)Sugar Crystalization0.20.40.60.81:09. Liquorice = Jelly Related (7% Water)Low Moisture, Wheat Gluten9w-10. Cream Pastes (7-8% Water)Sugar Crystallization and Colloidally SefWater Activity10
2/25/14 10 General Technology Structure Body Derived From 1. Hard Candy (1.5% Water) High Viscosity Glass 2. Jellies – Various (25% Water) High molecular weight colloidal network 3. Caramels (2% Water) Milk Proteins 4. Fondant (10-12% Water) Very Fine Sugar Crystallization 5. Lozenges – Compressed & Extruded (0.5%Water) Low Moisture, Fine Sugar Crystals 6. Marshmallow (14-25% Water) Colloidally Set Foam 7. Nougat (7-12% Water) High Viscosity – Glass Foam or Fine Sugar Crystallization Foam 8. Hard Panned Coating (0.2% Water) Sugar Crystallization 9. Liquorice – Jelly Related (7% Water) Low Moisture, Wheat Gluten 10. Cream Pastes (7-8% Water) Sugar Crystallization and Colloidally Set Water Activity Rate of reaction or growth Chemical reaction rates are affected by water activity