乳制品的加工,结构和性质.ppt

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1、Manufacture,Structure and Properties of Dairy ProductsMilk Processing,Milk Powders,and Recombined MilkSummaryCommon unit processes in milk processingSeparationClarificationHomogenizationHeat-treatmentMilk powder dryingProtein separationMilk ProcessingFull-fatSemi-skimmed(half fat)Skim(low or non-fat

2、)Raw Milk ProcessingRaw MilkSeparatedClarifiedHeat-treatedPackedStandardisedSkim-milkFull-CreamCreamClarification and SeparationClarificationremoval of solid impurities Separation skimming,separation of fat from skim milkStokes Law(Creaming)vs =2a2Drg/9h0 a=particle radiusDr=density difference betwe

3、en particle and aqueous phaseg=gravitational constanth0=aqueous phase viscosityCentrifugal ClarifierMilk inMilk OutCentrifugal SeparatorMilk inSkim milkCreamHeat TreatmentsSterilisationPasteurisationUltra-heat treated(UHT)In-Can/Bottle SterilisationHigh-temperature long time processTypically 105 oC

4、for 20 minGives long shelf-lifeCaramelised or cooked flavoursExtensive protein damageIn-Can/Bottle SterilisationUsed for paediatric formulations and enteral formulations where sterility is essentialRotary RetortRotary RetortPasteurizationLeast intensive heat-treatmentTypically 62-65 oC for 30 minute

5、s,71-74 oC for 15 s,or 88.3 oC for 1sKills pathogensShort shelf-lifePlate Heat ExchangerPlate Heat Exchanger Simulationhttp:/ oC for 4-15 s,combined with aseptic packingkills thermophileslong shelf life(6 months)short time=less heat damageUHTTwo types of heatingdirect e.g.injection of steam into pro

6、ductindirect using heat exchanger(e.g.plate)UHTDirectIndirectT(oC)Time(s)70 oCProduct damagerangeMilk PowderStandardised milkHeat treatedEvaporatedDriedTypes of Milk PowderWhole milk powder(WMP)Skim milk powder(SMP or NFDM)Types of Milk PowderWMPSpray dried roller driedSMP low heat SMPmedium heat SM

7、Phigh heat SMPSpray DryingCo-currentair flowCounter-currentair flowLow TLow THigh THigh TSpray Drier Demonstrationhttp:/ Protein ProductsFunctional properties emulsificationgelationthickeningnutritionMilk Protein ProductsPrecipitated caseinsMembrane concentrated whey proteins milk protein concentrat

8、esPrecipitation of Milk ProteinpH 4.6OrChymosinCasein ManufactureMilkSkim milkDe-fattingAcid caseinRennet caseinLactic caseinPrecipitationMineral acidchymosinLactic acid bacteriaWhey streamCaseinate ManufactureAcid caseinSodium caseinateCalcium casenateNaOH +heatCa(OH)2 +heatTotal Milk ProteinateSki

9、m MilkForm whey/-cn complex Heat +Slightly alkalinePrecipitationAcid caseincaseinatingNaOHCa(OH)2Ca TMPateNa TMPate-lactoglobulin/-casein complexHeat+alkaliMembrane ConcentrationWhey proteins only precipitate in high saltalternative is ultrafiltrationUltrafiltrationProteinLactose+mineralsWaterHigh p

10、ressureWhey Protein ConcentrateWhey streamUltrafiltration +dryingLactic WPCAcid WPCRennet WPCCheese WPCLactose+mineralsMilk Protein ConcentrateSkim MilkConcentrated milkMPC 70ultrafiltrationdryingMPC 85MPC 56Micellar CaseinSkim MilkConcentrated milkMicellar caseinmicrofiltrationdryingRecombined/Reco

11、nstituted MilkManufactured where fresh milk not availableMiddle EastSouth East AsiaReconstituted MilkWMP is shipped to dairy plantreconstituted with water to same total solids as milk heat-treated and packedRecombined MilkSMP and anhydrous milk fat(AMF)shipped to recombining plantfat is homogenised

12、with SMP to same fat content and total solids as fresh milkRecombined MilkSMPAMFHomogeniseHeat-treatPackPrinciples of HomogenizationEffect of HomogenizationFormation of small,stable fat dropletsrecreates artificial milk fat globule membranenot same as in fresh milkproperties differentHomogenizationA

13、lso used to reduce particle size in fresh milkfat droplets more stable to creaming(Stokes Equation)vs =2a2Drg/9h0TaskMilk proteins are used as ingredients in a wide range of manufactured food products.Summarize the main products that milk proteins are found in.Choose one particular food product where milk protein is an important ingredient and describe the function of the protein is this particular food.