AOAC 905_02

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33.2.25

AOACOfficialMethod905.02

FatinMilk

Roese-GottliebMethodFirstAction1905FinalAction

ReferenceMethod1973

IDF–ISO–AOACMethodCodex-Adopted–AOACMethod*

Prepareasin925.21(see33.2.02)andweigh,tonearestmg,ca10gtestportionintofat-extractionflaskortube.Add1.25mLNH4OH(2mLiftestsampleissour)andmixthoroughly.Add10mLalcoholandmixwell.Add25mLether(allethermustbeper-oxide-free),stopperwithcorkorstopper(syntheticrubber)unaf-fectedbyusualfatsolvents,andshakeveryvigorously1min.Cool,ifnecessary;add25mLpetroleumether(boilingrange30–60°C)andrepeatvigorousshaking.Centrifugeflaskatca600rpmorletitstanduntilupperliquidispracticallyclear.Decantethersolutionintosuitableflaskormetaldish.Washlipandstopperofextractionflaskortubewithmixtureofequalpartsofthe2ethersandaddwashingstoweighingflaskordish.Repeatextractionofliquidre-maininginflaskortubetwice,using15mLofeachsolventeachtimeandaddingH2Oifnecessary,butomittingrinsingwithmixedsol-ventsafterfinalextraction.(Thirdextractionisnotnecessarywithskimmilk.)

Evaporatesolventscompletelyonsteambathattemperaturethatdoesnotcausespatteringorbumping(boilingchipsmaybeadded).Dryfattoconstantweightinovenat102±2°Corvacuumovenat70–75°Cunderpressure<50mmHg(6.7kPa).Weighcooledflaskordish,withoutwipingimmediatelybeforeweighing.Removefatcompletelyfromcontainerwith15–25mLwarmpetroleumether,dry,andweighasbefore.Lossinweight=weightfat.Correctweightfatbyblankdeterminationonreagentsused.Ifblankis>0.5mg,pu-rifyorreplacereagents.Differencebetweenduplicatedetermina-tionsobtainedsimultaneouslybysameanalystshouldbe≤0.03gfat/100gproduct.

References:Z.Nahr.Genussm.9,531(1905).

JAOAC34,237(1951);52,235(1969).Revised:March1996

*AdoptedasaCodexReferenceMethod(TypeII)forgravimetryoffatinmilk.

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