(浙大食化考研)ppt课件

IntroductiontoFoodChemistry,1,WhatisFoodChemistry,amajoraspectoffoodSciencedealswiththecompositionandpropertiesoffoodandthechemicalchangesthatundergoesduringhandling（处理），processing（加工），andstorage,2,Foodchemistryisintimatelyrelatedtochemistry，biochemistry，physiologicalchemistry，botany，zoology，andmolecularbiologyItwassupposedthattheattendingstudentshaveatleasttakenchemistry，biochemistry,3,RelationshipofFoodChemistrywithOtherScience,foodscienceasciencethatdealswiththephysical，Chemical，andbiologicalpropertiesoffoodsastheyrelatetostability，cost，quality，processing，safety，nutritivevalue，wholesomeness，andconvenienceFoodscienceisaninterdisciplinarysubjectinvolvingprimarilymicrobiology，chemistry,biology,andengineering.,4,InterestsofFoodChemists,theprimaryinterestsofbiologicalscientistsincludereproduction,growth,andchangesthatbiologicalsubstancesundergounderenvironmentalconditionsthatarecompatibleormarginallycompatiblewithlifeFoodchemistsareconcernedprimarilywithbiologicalsubstancesthataredeadordying(post-harvestphysiologyofplantsandpostmortem（死后的）physiologyofmuscle)andthechangestheyundergowhenexposedtoawiderangeofenvironmentalconditions,5,Syllabus(课程提纲）,!UNIT1:Chemistryofwaterinfoods!UNIT2:Chemistryoffoodcarbohydrate!UNIT3:Chemistryoffoodlipid!UNIT4:Chemistryoffoodprotein,6,!UNIT5:Enzymes!UNIT6:ChemistryoffoodPigmentsandcolorants!UNIT7:Chemistryoffoodflavors!UNIT8:Chemistryoffoodadditives,7,Approachtothestudyoffoodchemistry,itisdesirabletoestablishananalyticalapproachtothechemistryoffoodformulation（配方），processing，andstoragestability，sothatfactsderivedfromthestudyofonefoodormodelsystemcanenhanceourunderstandingofotherproductsTherearefourcomponentstothisapproach：,8,(a)determiningthosepropertiesthatareimportantcharacteristicsofsafe，high-qualityfoods.(b)determiningthosechemicalandbiochemcalreactionsthathaveimportantinfluencesonlossofqualityandorwholesomenessoffoods.(c)integratingthefirsttwopointstounderstandhowthekeychemicalandbiochemicalreactionsinfluencequalityandsafety，and(d)applyingthisunderstandingtosolveproblemsencounteredduringformulation，processing，andstorageoffood,9,10,Safetyisthefirstrequisiteofanyfood:afoodmustbefreeofanyharmfulchemicalormicrobialcontaminantatthetimeofitsconsumptionFortheoperationalpurposesthisdefinitiontakesinamoreappliedformsThechangesthatcanoccurtothetexture,flavor,andcolorarereadilyevidenttotheconsumer,alsocalledchangesofsensoryproperties;Ofthoseinvolvingnutritivevalveandsafetyarenotevident,11,Inthecanningindustry，“commercial”sterility（无菌）asappliedtolow-acidfoodmeanstheabsenceofviablesporesofClostridiumbotulinum(肉毒杆菌）Inaproductsuchaspeanutbutter，operationalsafetycanberegardedprimarilyastheabsenceofaflatoxins(黄曲霉毒素）-carcinogenicsubstancesproducedbycertainspeciesofmolds,12,13,Integrationoftheinformationonreactionsandalterationscanleadtoanunderstandingofthecauseoffooddeteriorationdeteriorationoffoodisusuallycausedbyseveraldifferentprimaryeventsfollowedbysecondaryevents(Seethefollowingtable),14,15,Thesequenceintheabovetablecanbeappliedintwodirections,Primarycausativeevents,Secondaryevents,Attributeschanges,determinethecause(s)ofanobservedqualitychangebyconsideringallinvolvedeventsandthenisolatingthekeyprimaryevents.,designaparticularprimary,associatedsecondaryevents,andgetthedesirablequalityattributes.,16,SolveproblembyanalyzingandontrollingtheImportantVariables(factors),Productfactors:FoodcomponentsOxygencontentpHWateractivityTgandWg(Tgglasstransitiontemp.Wg-productwatercontentatTg,Environmentalfacters:Temperature,TimeCompositionoftheairExposuretolightContaminationChemical,physical,biologicaltreatmentsPhysicalabuse,17,TemperatureisperhapsthemostimportantofthesevariablesbecauseofitsbroadinfluenceonalltypesofchemicalreactionsTime:duringprocessing,oneisofteninterestedinthetimeittakestoinactivateaparticularpopulationofmicroorganismsorinhowlongittakesforareactiontoproceedtoaspecifiedextentpH:influencestheratesofmanychemicalandenzymaticreactions,18,Compositionoftheproductisimportantsincethisdeterminesthereactantsavailableforchemicaltransformationwateractivity:stronglyinfluencetherateofenzyme-catalyzedreaction,lipidoxidation,nonenzymicbrowning,sucrosehydrolysis,chlorophylldegradation,anthocyanindegradation,andothers.,19,Glasstransitiontemperature(Tg)offoodandthecorrespondingwatercontent(Wg)ofthefoodatTgarecausativelyrelatedtoratesofdiffusion-limitedeventsinfoodsuchasfrozenanddriedfoodsInfabricatedfoods，thecompositioncanbecontrolledbyaddingapprovedchemicals,suchasacidulants，chelatingagents，flavors，orantioxidants，orbyremovingundesirablereactants，Forexample，removingglucosefromdehydratedeggalbumen,20,AtmosphereisimportantmainlyWithrespecttorelativehumidityandoxygencontent，althoughethyleneandC02arealsoimportantduringstorageoflivingplantfoodsLightcanbedetrimental，anditisappropriatetopackagetheproductsinlight-imperviousmaterial,21,References,OwenR.Fennema:FoodChemistry,ThirdEdition,MarcelDekker,1996JohnM.deMan:PrincipleofFoodChemistry,ThirdEdition,AnAspenPublication,1999DannisD.Miller:FoodChemistryALaboratoryManual,JohnWilley&Sons,Inc.1998冯凤琴，叶立扬：食品化学，化学工业出版社，2005,22,Grading,Finalexam50%Experiments30%(behavior14%,