河工大双语homework.docx

河工大双语homework.docx

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河工大双语homework

Homework（I）

Answerthefollowingquestions:

1.Whatarefatsandoils?

2.Whatarethecompositionoffattymaterials?

3.Whatistheacidvalue（AV）?

4.Whatisperoxidevalue（PV）？

5.Whatissaponificationvalue（SV）

6.Whataretheprincipleandpurposeofdegumming/refining/bleaching/deodorization？

7.Whatarethemainproductsoffatsandoilsinfoodindustry？

Explainthefollowingterms:

（1）Deodorization

（2）Refining

（3）Degumming

（4）Hydrogenation

（5）Bleaching

Thenaturaloilsandfatscannotfulfilltherequirementofmodernfoodmanufacturefortheirlimitedcharacteristic,itisnecessarythatmodifythenaturaloilstoneedthedemandoffoodproduction.Themodificationmethodsofoilsandfatsincludeblending,hydrogenation,fractionation,andinteresterification.

Blendingvegetableoilsbydifferentoriginortheircombinationwithanimalfatsisjustifiedfortechnological,nutritional,andeconomicreasons.IftheFAcompositionsofdifferentvegetableoilsareknown,theycanbecombinedincertainratiostoobtainproductsofimprovedcompositionandbetterfunctionalproperties（e.g.,improvedoxidativestabilityofshiftedmeltingpoint）.

Hydrogenationistheprocessbywhichhydrogenisaddeddirectlytopointsofunsaturationinthefattyacids.Hydrogenationoffatshasdevelopedasaresultoftheneedto（A）convertliquidoilstothesemi-solidformforgreaterutilityincertainfoodusesand（B）increasetheoxidativeandthermalstabilityofthefatoroil.Hydrogenationisanextremelyimportantprocessasfarasourfoodsupplyisconcerned,becausethisprocessingimpartsthedesiredstabilityandotherpropertiestomanyedibleoilproducts.Thelevelofunsaturatedfattyacidspresentinsomeoilssuchassoybeanoilisreducedinorderfortheoilstohavefunctionalpropertiesinmanyfoodapplications.Hydrogenationistheonlypracticalwaytoimparttheseproperties.

Fractionationistheremovalofsolidsbycontrolledcrystallizationandseparationtechniquesinvolvingtheuseofsolventsordryprocessing.Dryfractionationencompassesbothcrystallizationandpressingtechniquesandisthemostwidelypracticedformoffractionation.Itreliesuponthedifferencesinmeltingpointsandtriglyceridesolubilitytoseparatetheoilfractions.Solventfractionationisthetermusedtodescribeaprocessforthecrystallizationofadesiredfractionfromamixtureoftriglyceridesdissolvedinasuitablesolvent.Fractionsmaybeselectivelycrystallizedatdifferenttemperaturesafterwhichthefractionsareseparatedandthesolventremoved.Solventfractionationispracticedcommerciallytoproducehardbutters,specialtyoils,andsomesaladoilsfromawidearrayofedibleoils.

Anotherprocessusedbyoilprocessorspermitsarearrangementoraredistributionofthefattyacidsontheglycerolfragmentofthemolecule.Thisprocess,referredtoasinteresterification,isaccomplishedbycatalyticmethodsatrelativelylowtemperature.Undersomeconditionsthefattyacidsaredistributedinamorerandommannerthantheywerepresentoriginally.Otherconditionspermittherearrangementprocesstodirectthefattyaciddistributiontoanextentthatallowsfurthermodificationofshorteningpropertiestobeobtained.Therearrangementprocessdoesnotchangethedegreeofunsaturationortheisomericstateofthefattyacidsastheytransferintheirentiretyfromonepositiontoanother.

Therearetwomajortypesofoilrefining:

chemicalandphysical.Themajorstepsinvolvedinchemicalrefiningincludedegumming,neutralizing,bleaching,anddeodorizing.Physicalrefiningremovesfreefattyacidsandflavorsbydistillation,tocombinethestepsofneutralizationanddeodorizationintooneoperation.

Degummingisawater-washingprocesstoremovephosphatides.Unlessremoved,phosphatidescanspontaneouslyhydratefrommoistureintheairduringstorageorintheheadspace.Degummingmaybeconductedeitherasaseparateoperationorsimultaneouslywithneutralization.Inthecasesofoilsrichinphosphatides,suchassoybeanandcanolaoil,degummingisusuallyaseparateoperation.Theprocessgenerallyinvolvestreatingthecrudeoilwithalimitedamountofwatertohydratethephosphatidesandmakethemseparablebycentrifugation.Thephosphatidesareoftenrecoveredandfurtherprocessedtoyieldavarietyoflecithinproducts.

AlkaliRefining（Neutralization）generallyisperformedonvegetableoilstoreducethefreefattyacidcontentandtoremoveothergrossimpuritiessuchasphosphatides,proteinaceous,andmucilaginoussubstances.Byfarthemostimportantandwidespreadmethodofrefiningisthetreatmentofthefatoroilwithanalkalisolution.Thisresultsinalargereductionoffreefattyacidsthroughtheirconversionintowater-solublesoaps.Mostphosphatidesandmucilaginoussubstancesaresolubleintheoilonlyinananhydrousformanduponhydrationwiththecausticorotherrefiningsolutionarereadilyseparated.Oilslowinphosphatidecontent（palmandcoconut）maybephysicallyrefined（i.e.,steamstripped）toremovefreefattyacids.Afteralkalirefining,thefatoroiliswater-washedtoremoveresidualsoap.

Theterm“bleaching”referstotheprocessforremovingcolorproducingsubstancesandforfurtherpurifyingthefatoroil.Normally,bleachingisaccomplishedaftertheoilhasbeenrefined.Theusualmethodofbleachingisbyadsorptionofthecolorproducingsubstancesonanadsorbentmaterial.Acid-activatedbleachingearthorclay,sometimescalledbentonite,istheadsorbentmaterialthathasbeenusedmostextensively.Thissubstanceconsistsprimarilyofhydratedaluminumsilicate.Anhydroussilicagelandactivatedcarbonalsoareusedasbleachingadsorbentstoalimitedextent.Thepurposeofdeodorizationofoilsandfatsisremovingtraceconstituentsthatgiverisetoundesirableflavors,colorsandodorsinfatsandoils.Thedeodorizationprocessissimplyaremovaloftherelativelyvolatilecomponentsfromthefatoroilusingavacuumsteamdistillation.Thisisfeasiblebecauseofthegreatdifferencesinvolatilitybetweenthesubstancesthatgiveflavors,colorsandodorstofatsandoilsandthetriglycerides.Normallythisprocessisaccomplishedafterrefiningandbleaching.Deodorizationdoesnothaveanysignificanteffectuponthefattyacidcompositionofmostfatsoroils.Inthecaseofvegetableoils,sufficienttocopherolsremaininthefinishedoilsafterdeodorizationtoprovidestability.

Time,temperature,andmoisturecontentarecriticalfactorsincontrollingtheheatdenaturationofsoyproteins.Heat-denaturedproteinsareinsoluble.Twotermsusuallyencounteredintheliteraturetodescribeinsolubilityarenitrogensolubilityindex（NSI）andproteindispersibilityindex（PDI）.NSIrepresentsthepercentageoftotalnitrogeninthesamplethatissoluble,andPDIrepresentsthepercentageoftotalproteinthatissoluble.

Thegenerallyaccepteddefinitionofsoybeanproteinconcentrateisaproducthavingaproteincontentof70%（N¡Á6.25）onamoisturefreebasis.Fourgeneralizedprocessesareusedtomanufacturesoybeanproteinconcentrate.Threeofthesearepresentlyusedtoproducecommerciallyavailablesoybeanproteinconcentrate.Theprincipalobjectiveforeachprocessistoimmobilizethemajorproteincomponentandextractthenonproteincomponent.Theextractablecomponentsconsistofsolublecarbohydrates,principallyraffinoseandstachyose,salts,solubleproteins,andotherminorsolubleconstituents.Soybeanproteinconcentratesgenerallyhavebeeterflavor,improvedfunctionality,andreducedflatulenceascomparedtothefeedstock.Eachprocesshasitsadvantagesanddisadvantages.Thesewillbediscussed.Commontoeachprocessistheneedtohaveproperequipmentdesignandoperatingconditions,whichwillminimizethebacterialpopulationofthefinishedsoybeanproteinconcentrate.Thepossiblemanufacturingprocessesforsoybeanproteinconcentratedifferinthemannerinwhichtheproteinsareimmobilizedandhowthecarbohydratesandsaltsaresolubilizedandremoved.

Isolatedsoyproteinsarehigh-qualityproteinfoodingredientswhichareusedtomakequalityfoodsthathavehighconsumeracceptance.Isolatedsoyproteinsarethemajorproteinfractionsofsoybeansobtainedinhighpurityfromhigh-qualitydehulledsoybeansbyprocessesthatremovethenonproteincomponents.Bydefinition,isolatedsoyproteinsmustcontainnotlessthan90%dry-basisprotein（Nitrogen¡Á6.25）.Thus,theyarethemosthighlypurifiedformofcommercialsoyproteiningredients.Isolatedsoyproteinsareblandintaste,nearlywhiteincolor,andhaveotherfunctionalattributesthatallowtheiruseinawidevarietyoffoodappllicatios.

Typicalchemicalcomponentsofisolatedsoyproteinsonadrybasisareatleast90%（N×6.25）protein,4.5%ash,0.5%ether-extractablefat,and0.3%carbohydrate.（Otherminorcomponentsareacidhydrolyzablefats,phytate,andtraceamountsofsmallorganiccompounds.）

Byfarthelargestportionofthesoybeanmealandcakeproductionisusedasaproteinsourceinanimalfeed.Thedifferenttypesofsoybeanmealsarecharacterizedmainlybytheirproteincontentandtheextentofheattreatmentappliedintheirproductiontoinactivateanti-nutritionalfactors.

（1）Ifthesoybeansareextractedwithoutdehulling,orifthehullsareaddedbackafterextraction,themealwillcontainabout44%protein.Mealsproducedfromdehulledbeanscontainsapproximately50%protein.

Defattedsoybeanflours,intendedforhumanconsumption,areessentiallysoybeanmealwhichhasbeengroundtotheappropriatemeshsize.Thestartingmaterialisdehulledbeansandstrictsa