食品科學(xué)和技術(shù)英文

FoodScienceandTechnologyByGilsonl10/23/2002DefinitionFoodscience:Scientificstudyoffoodfrom“farmtofork”.Foodtechnology:Useoftheinformationgeneratedbyfoodsciencetoproducesafe,nutritiousandwholesomefood.FOODSCIENCEMultidisciplinary

Engineering

Chemistry/Biochemistry

Microbiology

NutritionFoodsasediblebiochemicals

Touchesonmanyotherareas

Globalizationofworldfoodsupply

MOREPEOPLE,LESSFOODWidespreadfoodshortageswilldevelopoverthenext40yearsasapopulationexplosiongraduallyoutstripsworldfoodsupply.ThefoodsupplyisthemostimmediateconstraintontheEarth’spopulation-carryingcapacity.

Milestones&Projections:

1830:Worldhumanpopulationreaches1billion

1930:2billion

1960:3billion

1975:4billion

1999:6billion[Assuminga64-yearhumanlifeexpectancy,ofallthepeople

bornonearthsinceitscreation,2/3arenowalive.]

2030:9billion

Biggestincreasesareexpectedinsomeofthepoorestareas,suchasAfrica,southernAsia,andSouthAmerica.

HumanpopulationofAfricawilldoublein23years.

PopulationofSouthAmericawilldoublein29years.

PopulationofEuropewilldoublein343years.

Projection:Maximumamountofpeopleearthcansustain=20.7billionFoodScienceAchievements:1900-19991900s:

Vacuumpackaging-removesatmospherefromfoodpackages.Hydrogenation-tokeepunsaturatedfatsfromturningrancid.U.S.&Britishpatentsissuesforkillingbacteriainfoodwithionizingradiation(1905).InU.S.,firstcommercialfreezingoffruitandfish.

1910s:

InU.S.,firstlarge-scalecommercialpastaproduction.1920s:

ClarenceBirdseyedevelopsquick-freezingprocessforfoodsandfirstcommercializesblanchedfrozenvegetables.Foodfortificationbeginsbyfortifyingtablesaltwithiodine(1924).1930s:

Freeze-dryingprocessinventedtopreservefood.VitaminDfirstaddedtomilkthroughultravioletradiation(1933).1940s:Massproductionoffoodusingautomationtakesoff.Concentrated,frozen,anddehydratedfoodsproducedinmassquantitiesforshippingoverseastomilitary.Flourfirstfortifiedwithvitaminsandiron(1940).Asepticprocessingandpackagingisdeveloped,increasingfoodquality,safety,andretentionofnutrients.1950s:

Controlled-atmospherepackaging(CAP)developed(CAPcontrolsO2andCO2inthepackagetolimitrespirationandethyleneproduction,therebydelayingripeningandspoilage).U.S.Armybeginsfoodirradiationprogram(1953).

Watson&Crickdiscoverthedouble-helixstructureofDNA,layingthefoundationforunderstandinggeneticsanddevelopingrecombinantDNAtechnology1960s:Firstcommercialplantforfreeze-dryingfoodopens(1960-forcoffee).Computercontrolinprocessingplantsfirstintroduced.FDAapprovesirradiationtodisinfestwheatandwheatflour(1963),toinhibitsproutinginpotatoes(1964),andtoextendtheshelflifeofpotatoes(1965).Asepticcanningadoptedbyfoodmanufacturers.1970s:HazardAnalysisCriticalControlPoint(HACCP)systemjointlydevelopedbyNASA,PillsburyCo.,andtheU.S.ArmyNatickLaboratories.RecombinantDNAtechnologydeveloped(1973).1980s:Modified-atmospherepackaging(MAP)introducedtoincreaseshelflifeandprotectthemfromspoilage,oxidation,dehydration,weightloss,andfreezerburn.FDAapprovesirradiationtocontrolTrichinellaspiralisinpork(1985),todisinfestand/ordelayripeninginsomefreshfruitsandvegetables(1986),andtocontrolmicroorganismsinspicesandherbs(1986).1990s:HACCPbecomeswidelyadoptedbyfoodmanufacturerslargelyduetoregulationsbyFDAandUSDA.FDAapprovesuseofirradiationtocontrolharmfulbacteriainfreshandfrozenpoultry(1990)andredmeats(1997).Pasteurizationprocessforshelleggsbyohmicheating(usingelectricity).Flashpasteurizationprocessoffreshjuicescommerciallyappliedleadingtonot-from-concentratecitrusjuices.Orangejuicefortifiedwithcalcium.High-pressureprocessedguacamolecomestoU.S.market(1998).Steampasteurizationandvacuumingofbeefcarcassesintroducedtoreducemicrobialhazards.Recombinantenzyme,chymosin,replacesrennetinmostcheesemanufacture.Firstfoodfromatransgenicplant(atomatowithdelayedripening)comestomarket(1994).Activepackagingsystemsintroducedthatinteractwithpackagecontentsorthepackage’sinternalatmospherearedevelopedtoenhanceproductfreshnessUNITOPERATIONSMaterialshandling-Harvestingandtransportationwhilemaintainingproductqualitytoandintheprocessingplant.Lowtemperaturestoragetomaintainperishableproduceappearanceandvitamincontent.Volumerestrictionsdueto““fieldheat””producedbyfruits&vegetables.Careofhandlinglivestockandfragileproductssuchaseggs.Safetyissuesfromstaticelectricitybuildupignitingsugardustorfineflourtransferwhileavoidinghumiditybuildupandcakingofproduct.Properhandlingofspicestoretaindesirablearomacompounds.Cleaning-oftenrequiredforthesimpleremovalofdirtanddebris.A.Brushes,high-velocityair,steam,water,vacuum,magneticattractionofmetalcontaminants,mechanicalseparation,filtration,etc.B.Watertreatment:Insoftdrinks,watershouldbelowininorganicsalts,sincetheseminimizecarbondioxidesolubilityandpromoteexcessiveescapeofgasbubbles;oftenthisrequiresadditionaltreatmentprocessessuchasmicrofiltrationanddeaeration.C.CleaningoffoodequipmentsurfacesModeratelyalkalineandneutraldetergentsfindwideapplicationinfoodindustryastheyremovesoilandotherdepositsyetarenoncorrosivetofood-contactsurfaces.Manytypesandcombinationsofdetergentsused.SeparatingSolidfromasolid(e.g.,shellingnuts;lyepeelerforpeaches)Solidfromaliquid(e.g.,filtration;centrifugation;crystallizationofsugarcrystalsfromsugarcanejuice)Liquidfromasolid(e.g.,extractingjuicefromafruit;pressingoilfrompeanutsandsoybeans)Liquidfromaliquid(e.g.,centrifugingoilfromwater)Removingagasfromaliquidorsolid(e.g.,pullingavacuum)A.Handsortingandgradingstillverycommon(e.g.,fruits&vegetables),butlaborcostsarehigh.B.Electronicphotocellequipmentusedtodetectandrejectoff-colorproducts(e.g.,potatochips,peanuts,eggs);ultrasonicsalsousedtoscreeninternaltissueofwholefruitsandvegetables.DisintegratingA.Breakdownoflargefoodparticlesintosmallerparticles.Examples:Cutting,grinding,pulping,homogenizing.Somecuttingnowdonewithhigh-pressurewaterjetsandlaserbeams.B.Disintegrationofteninvolvesheatbuild-upduetofrictionandsomeproductsrequirecooling(e.g.,meatstoavoidproteindenaturationandcoffeetoavoidburnedflavors).Grindingoffrozenmeatisdonetoavoidthis.Oradditionofdryicethatdissipatesascarbondioxide.C.HomogenizationPumpingA.Oneofthemostcommonoperationsinthefoodindustry(bothliquidsandsolidssuspendedinliquids)B.Manykindsofpumps-pumpselecteddependsuponnatureoffoodtobemoved.Rotarygearpumpshaveclosetolerancesamongmovingparts,chunk-typefoodswouldbereducedtopurees,andsometimesthisistheintent,sothepumpservestwopurposes.Asingle-screwpump(withlargeclearances)bestformovingfoodwithlargepieceswithoutdisintegration(e.g.,cornkernels,grapes,smallshrimp).C.Itisessentialthatallfoodpumpscanbeeasilydisassembledforthoroughcleaning(stainlesssteelisthemostcommonmaterialusedtomakepumpsforthefoodindustry).MixingA.Again,verycommonoperationinthefoodindustry;canbesolid-solid,liquid-liquid,solid-liquid,gas-liquid,etc.B.Manyare““kitchen-style”mixers,justbigger.

Mostcommonusedtomixsolidsintoliquidstodissolvethemisapropeller-typeagitatorwithinastainlesssteelvat.C.Mixingusuallyinvolvesthegenerationofheatandinfoodsitisoftendesirabletominimizethistemperaturerisebysomeformofcooling.D.Somemixingrequireshighrpm

Example:Mixer/beaterfoundinicecreamfreezerstoincorporateairintoicecreammixtoproducedesiredvolumeincrease(overrun)requiredtoattaindesiredtextureHeatexchangingA.Reasonstoheat:CookPasteurizePreservation(e.g.,blanching)Driveoffmoisture(evaporate)DevelopflavorsInactivatenaturaltoxicsubstances(soybeanmeal)B.Needtocontrolapplicationofheat(oftennecessarytoheatandrapidlycooltheproduct)Rapidheatingandcoolingoftenrequiremaximumcontactofthefoodwiththeheating/coolingsource(e.g.,heatexchangersinthepasteurizationofmilk).Steam-jacketedstainlesssteelkettleortankoftenusedforheatingliquidfoods(mixingpropellerusuallyincludedtopreventscorchingandevendistributionoftemperature).Canning-usingaretort(pressurecooker)Roasting-circulatinghotairC.CoolingAgain,aheatexchangercanbeused,butwithcoldwaterpumpedthroughtheunit.Commercialblastfreezersreach-26CLiquidnitrogen:-196CEvaporation-toconcentratefoods2-to3-foldA.Toremovewater,torecoverdesirablefoodvolatiles,andtoremoveundesirablevolatiles.B.Canbesolar(raisins),heatedkettle(waterfromasugarsyrup).C.Verycommonintheindustry:Vacuumevaporation-reducedpressureallowsliquidstoboilatlowertemperatures(thelowertemperaturecauseslessdamagetofoodquality).Drying-totakefoodstoneartotaldryness(often2to3%water)ExamplesDriedmilkprocessedbyspraydrying(atomizedliquidmixedwithheatedair);liquidfoodsareeasiesttodry.Mashedpotatoesandtomatopureeprocessedbydrumdrying(drumheatedfromwithin,appliedlayeroffoodflashesoffitsmoistureoncontactwithheateddrum,andthinfilmoffoodscrapedoffdrumwithlongknives).Peasanddicedonionsdriedbymovingthroughalongtunneloven(subjectofoverheatingandshrinkage),butapreferredmethodis,vacuumfreeze-drying(usedforcoffee),foodfrozen,dehydratedundervacuumfromthefrozenstate.Forming-foodsmadeintospecificshapes(e.g.,fishsticks)Applicationofpressurewithinanappropriateform.Rangeofpressuresused,variesconsiderablydependentupontheproduct.Forexample:Extrusion{Breakfastcereals-Extrusioncooking}Formulateddoughormashisextrudedunderhighpressurewithheat.Packaging(foodcontainers)Toprotectfoodfrommicrobialcontamination,physicaldirt,insectinvasion,light,moisturepickuporloss,flavorpickuporloss,andphysicalabuse(damage).Containersincludemetalcans,glassandplasticbottles,paperandpaperboard,plasticandmetallicfilms,andcombinationsofthese.Packagingisautomated.NewprocessesToincreasetherangeofoptionswithineachunitoperation,toimprovequalityorincreaseefficiency.Examplesinclude:supercriticalfluidextraction,ohmicheating,andhighhydrostaticpressureprocessing.QUALITYFACTORSINFOODSAppearancefactorsTexturalfactorsFlavorfactorsAdditionalqualityfactorsAppearancefactorsA.SizeandshapeSize:Easilymeasured(e.g.,fruitsandvegetablescanbesizedaccordingtotheopeningstheycanpassthrough;thebasisforautomatedseparatingandgradingmachines).Shape:Someofthemostdifficultfoodengineeringproblemsarethedesigningofequipmenttopackodd-shapedfoodpieces.B.ColorandglossFoodcolor:Helpsdeterminequality,ripenessandspoilage.Colorandtransparency/cloudiness:Canbemeasuredwithaspectrophotometer(measureslighttransmissionthroughaliquid).Solidsandliquids:Reflectedcolorcanbemeasuredbycomparisonwithdefinedcoloredchips.Huntercolorimeter:Colormeasurementbydivisionintothreecomponents-value,hueandchroma.Value-lightnessordarknessofthecolor.Hue-predominatewavelengthreflected(whichdetermineswhattheperceivedcoloris).Chroma-intensitystrengthofthecolor.Instrumentsavailabletomeasureshineorgloss.C.Consistency-viscosity;manytypesofviscometerstomeasureconsistency.BostwickConsistometer-timeittakesforfoodtoflowdownaninclinedtrough.TexturalfactorsA.Foodqualitieswefeel.B.Foodtexturecanbemeasuredbyresistancetoforce.Squeezing(compression).Shear(forceappliedsothatonepartofthefoodslidespasttheother).Cutting.Tensilestrength(pullingapart).C.Texturechanges-donotremainconstantinafood.ChangeinwatercontentplaysamajorroleFlavorfactorsA.Combinationofbothtasteandsmellandlargelysubjectiveandthereforedifficulttomeasure,verycomplex.Widedivergenceofopinion.B.Colorandtextureinfluenceflavor.Webecomeeducatedastoexpectcertaincolorswithcertainflavors.Greaterintensityofcolorassociatedwithgreaterflavor;samewithgreaterviscositytoperceptionofgreaterflavor.C.Salt,sugarandacidcanbemeasuredusinginstrumentation.D.TastepanelsAnalyticalinstrumentscanbeused,butthehuman“testanimal”isstillthebest.Useofgroupsofpeoplepreferredoveranindividualopinion,asdifferencesofopiniontendtoaverageout.1.Peopleinvolvedintastepanels.Trainedpeopleforspecificproducts(e.g.,butterandcheese).Consumerpreferencegroups-panelsnotspecificallytrainedbutprovideinsightastowhatconsumersprefer.Highlytrainedpeoplewithheightenedtastesensitivityandknowledgeofwhattorecognizeasattributesanddefects2.

Environmentfortastepanels.Isolationoftasterstoavoidinfluencebyobservingothertasters.Tastersunabletoseehowfoodwaspreparedorwhatits‘‘identity’’is.3.

Hedonicscale(forqualityfactors)Rangefrom‘‘dislikeextremelytoneutraltolikeextremely’.4.

ApproachPreferencetest:Choosingonesampleoveranother;samplesarecodedsothatsourceoridentityoffoodsampleisunknowntotaster.Mostcommonisthetriangletest(apreferencetest):Selectingthesamplethatdiffersfromtwoothers(totalof3samples).Usuallynomorethan5samplestestedatonesitting;senseoftastebecomesdulled.Statisticalanalysisofresultsisusuallyemployed.5.

Inadditiontoflavor,tastepanelsjudgetexture,color,packaging,samplearrangement,etc.AdditionalqualityfactorsA.

NutritionalqualityChemicalorinstrumentalanalysesforspecificnutrient;however,oftenanimalfeedingtestsmustbeused,especiallyforqualityofproteinsources(biologicalvalue).B.

SanitaryqualityAnalysisforbacteria,yeasts,moldsandinsectfragments.X-raystodetectphysicalcontaminants(e.g.,glasschips,stones,metalfragments).C.

Keepingquality(storagestability)Measuredunderstorageandhandlingconditionstomatchconditionsencounteredinnormaldistribution.Normalstoragetestsmaytakeayear;extremeconditionsmaybeusedtospeedthingsup.FOODDETERIORATIONANDITSCONTROLFooddeteriorationincludesdeclinesinorganolepticdesirability/aestheticappeal,nutritionalvalue,andsafety(i.e.,productquality);occursunderthebestofconditions.Factorsadverselyaffectingfoodchangesintemperature(heatandcold),lightandotherradiation,

oxygen,

changesinmoisturecontent(waterlossoruptake),detrimentalenzymesofthefood,microorganismsandmacroorganisms,industrialcontaminants(e.g.,packagingmaterials)andcloseproximityofotherfoods,andtime.Someofthemostimportantadvancesinfoodtechnologyhaveoccurredasaresultofwar.NicolasAppert-

developedthetechnologyofcanning(1809)asaresultofprizemoneyofferedbyNapoleonforpreservationoffoodfortheFrencharmyandnavy.Shelf-lifeanddatingoffoodsA.

Definitionofshelf-life:Thetimeittakesforaproducttodeterioratetoanunacceptablelevel(whatisunacceptableissometimesamatterofopinion).B.

Abetterdefinition:Lengthoftimeaproductremainssalable.

Itiscommonforafoodmanufacturertodefineaminimumacceptablequality(MAQ)foraproduct.Actuallengthofshelf-lifedependentonProcessingmethod,Packaging,Storageconditions.Datingsystem1.

Differentcodedates:Dateofmanufacture(packdate),Datetheproductwasdisplayed(displaydate),Datebywhichtheproductshouldbesold(sellbydate),Lastdateofmaximalquality(usebydate),Datebeyondwhichtheproductisnolongeracceptable(usebydateorexpirationdate).2.Useofthesecodedatesrequiresaneedtopredictandmonitorshelf-life.Modelsforpredictingshelf-lifeareparticularlyusefulfornewproductswithoutadistributionhistory.V.MajorcausesoffooddeteriorationA.Microorganisms(bacteria,yeastsandmolds)B.InsectsandrodentsC.Heatandcold-cancausedeteriorationoffoodifnotcontrolled.D.MoistureanddrynessE.OxygenF.LightG.TimeA.Microorganisms(bacteria,yeastsandmolds)Moretypesofmicroorganismscanspoilfoodthancausefoodbornedisease.Sourcesofthesemicroorganisms:soil,water,air,fooditself,humans,foodequipmentenvironment.Healthylivingtissue(internally)isusuallysterile,hencethepresenceofspoilageorganismsismostlytheresultofcontamination.Bacterialendosporesaremostdifficulttoinactivate.Heatandmoisturewillincreasegrowthandactivitiesofmicroorganisms.Moldsascomparedtobacteriacangenerallygrowat:lowerpH(moreacidconditions),lowermoisturecontents(dryerconditions),highersaltconcentrations,andlowertemperatures(inrefrigeratedfoods).Moldsusuallyonlyaproblemwithspoilage,notsafety,butAspergillusflavusandAspergillusparasiticusproduceaflatoxinswhicharepotenthepatocarcinogens.Moldsrequireoxygenforgrowth.B.InsectsandrodentsInsectsdestroy5to10%ofU.S.graincropannually(inotherpartsoftheworlditcanreach50%);insectsdamagecropssothatspoilagemicroorganismsaremoreofaproblem.Rodentsbothconsumeandcontaminatefood;controliscriticalsincemiceandratscanreproduceveryquickly;rodentscanspreaddiseaseFoodenzymesEnzymesinherentinfoodcontinuetofunctionafterdeathofanimalorplant;someenzymaticactivitiescanbeacceleratedfollowingdeath.Canbecontrolledbyrefrigerationorblanching.C.Heatandcold-cancausedeteriorationoffoodifnotcontrolledExcessiveheatdenaturesproteins,breaksemulsions,driesoutfoods,anddestroysvitamins.Uncontrolledcoldwilldamagefruits&vegetablesifallowedtofreezeresultingindiscoloration,andtexturechanges;freezingmilkwillbreakitsemulsionandcaseinwillcurdle;bananas,lemons,squashandtomatoesaresubjectto““chillinjury”at<10C.D.Moisture