食品工程学品质变化速度课件

现代食品工程学AdvancedFoodEngineering/EngineeringPropertiesofFoodsTel:Fax:E-mail:LectureforpostgraduatestudentAutumnof20102科学回答：是什么？为什么？技术回答：做什么？怎么做？科学是发现，技术是发明。科学是创造知识的研究技术是综合利用知识于需要的研究工程：依靠、使用复杂的系统、工具、设备或装备来完成的工作。

食品加工中的品质变化速度VelocityofQualityChangeduringFoodProcessing食品加工操作（处理）：物理性机械的，扩散的，热的操作。如洗净，浸渍，发泡，混和，过滤，抽提，结晶，冷冻，浓缩，干燥等。化学性反应的操作。如化学反应，酶反应，微生物发酵，杀菌，烹饪等。

内容:品质变化速度式设定;感官性状的变化（味道、气味、色泽、质地）；营养成分的变化（碳水化合物、蛋白质、脂质、维生素等）；氧化（酶促和非酶促；油脂氧化、维生素氧化、血红蛋白氧化等）；着色（酶促着色、非酶促着色）；漂洗；糊化（糊化与老化）；蛋白质变性（加热、冻结、其他）；其他品质变化（盐渍、糖渍、醋渍、薰蒸等）

QualityincludessafetyqualityandsensorialqualityFoodsafety:thatisthefreedomfromharmfulchemicalormicrobialcontaminationsattheproduction,processing,distributionandconsumption.Majorsensorialqualityattributesoffoodsaretexture,color,flavor,appearanceandnutritivevalue,someundesirablechangesmayoccureitherpriortoorduringdistributionand

consumption.

B.Chemicalchangeschemicalreactionsleadtodeteriorationoffoodqualityorimpairmentofsafety-non-enzymaticbrowning(Maillardreaction=reducingsugar+aminoacid)-lipidhydrolysis/oxidation-proteindenaturation-proteincross-linking-proteinhydrolysis-oligo-andpolysaccharidehydrolysis-polysaccharidesynthesis-degradationofspecificnaturalpigment-glycolyticchanges

SensoryQualitya.Lipidoxidation-developmentofoff-flavor.-reactwithproteinandresultinextensivecross-linking.b.Non-enzymaticbrowning、、、、、、、、、、、、、、、、、、、、、、、、、、、-oneofthemajordeteriorativechemicalreactionsoccursduringstorageofdriedandconcentratedfoods.-leadstoformationofinsolublebrownpolymers(mw>1000).c.Colorchange-changeinstructureorcontentofchlorophyll,hempigment,anthocyanins,carotenoids.d.Flavorchanges-flavorhasevolvedtoausagethatimpliesandoverallintegratedperceptionofthecontributingsensesofsmellandtasteatthetimeoffoodconsumption.thepermeabilityofpackagingmaterialsisofimportanceinretainingdesirablevolatilecomponentswithinpackage,orinpermittingundesirablecomponentstopermeatethroughpackagefromtheambientTo.NutritionalQualityfourmajorfactorswhichimpactonnutrientdegradationandcanbecontrolledtovaryingextentsbypackagingareLight,O2concentration,ToandAw

C.Physicalchangesphysicalpropertiesincludegeometrical(size,shape,volume,densityandsurfaceareaasrelatedtohomogeneousfoodunits,aswellasgeometricaltexturalcharacteristicssuchasreferringtoparticlesizeandshape;referringtoparticleshapeandorientation),thermal,optical,mechanical,rheological,electrical,andhydrodynamicproperties-forfoodscontainingsolidcarbohydrates,thelargesteffectinphysicalpropertiesresultsfromsorptionofwater,especiallyfortherecrystallizationofamorphouscarbohydrate,e.g.inboiledsweetsleadingtostickinessandgraining,inmilkpowdersleadingtocakingandlumpiness案例MethodsSurimiSurimipasteHeat-inducedgel1.Defrosting(half-thawed).2.GrindingwithNaCl,additives,chilleddistillwater,etc.3.Stuffingintoa35mmdiameterfoldedPVDCtubecasing,ca.100geachsample.Incubatedatacertaintemperatureforadefinitetime,including:*One-stepheating(<60Csuwarigel;>60Ckamabokogel)*Two-stepheating(cookingat85C/30minafterone-stepsetting)Measureindices:

breakingforce(g),breakingstrain(mm),whiteness,foldingtest,compositionanalysis,andSDS,etc.

GelationcurveofwalleyepollacksurimibyheatingtemperatureandheatingtimeHeatingtemperature

V-valleytypesurimi

SilvercarpBig-headcarpChinesesnake-headBluntsnoutbream

Plateautypesurimi

TilapiaGrasscarpMudcarpCommoncarpCalculationofgelationrate:

WhereT1/2isthetime(sec.)requiredforreachingthehalf-maximalbreakingforce.

K=1/(T1/2),s-1KD=(lnG0-lnGt)·1/t,s-1WheretheG0andGtwerethebreakingforcebeforeandafterheatingfortsecond.Calculationofgeldisintegrationrate:T1/2(1500sec)160g(0.5Fmax)ABCArrheniusequation:K=K0exp(-Ea/RT)85706050