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Acetylation AOACOfficial 965.32HydroxylValueofOilsandFatsAcetylation

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AOAC Official 965.32 Hydroxyl Value of Oils and Fats Acetylation First Action 1965 Final Action 1969_AOAC.rar,Acetylation,AOACOfficial,965.32HydroxylValueofOilsandFatsAcetylation

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41.1.12AOAC Official Method 965.32Hydroxyl Value of Oils and FatsAcetylation MethodFirst Action 1965Final Action 1969AOCSAOAC Method(Hydroxyl value is number of mg KOH equivalent to hydroxylcon-tent of 1 g oil or fat. Applicable to fatty oils and derivatives such asfatty alcohols, mono- and diglycerides, and hydroxystearic acid.)A. Reagents(a) Pyridine.Reagent grade, redistiled at 114115C.(b) Acetic anhydride.ACS, fresh.(c) Pyridineaceticanhydridereagent.Mix3volumesreagent(a) with 1 volume (b) just before use.(d) n-Butyl alcohol.Reagent grade. Neutralize with 0.5MKOH to faint pink phenolphthalein end point.(e) Alcoholic potassium hydroxide standard solution.0.5M.(Should be 0.5M so that blank titers do not require refilling of50 mL buret.)B. Determination(Caution:SeeAppendixB,safetynotesonpipetsandaceticanhy-dride.)According to expected hydroxyl value, weigh following amountsof sample into 250 mL standard taper glass-stoppered Erlenmeyersto nearest mg for acetylation:Weigh 9.011.0 g test portion into another flask for acidity deter-mination. (For fatty acids such as hydroxystearic acid, take0.91.1 g.)Pipet5.0mLreagent(c)intoflaskcontainingacetylationsample.For samples with 020 hydroxyl value, add additional 5 mLpyridine. Mix thoroughly by gentle swirling. Pipet 5 mL reagent (c)(and 5 mL pyridine, if used in acetylation) into another flask for re-agent blank. Place flasks on steam bath under standard taper refluxcondenserandheat1h.(Donotusehotplateormantle.)Add10mLH2O through condenser and heat additional 10 min. Let flasks coolwithcondenserattached.Add25mLn-butylalcohol,cahalfthroughcondenser, remove condenser, and use rest to wash down sides offlask. Add 1 mL phenolphthalein and titrate to faint pink end pointwith 0.5M alcoholic KOH.Add 10 mL pyridine, neutralized to phenolphthalein, to test por-tion for acidity determination. Swirl gently to mix, add 1 mLphenolphthalein, and titrate to faint pink end point with 0.5M alco-holic KOH.Hydroxyl value = B + (W V/C) S molarity 56.1/Wwhere V = mL KOH for acidity titration, B = mL KOH for reagentblank,C=gsampleforaciditytitration,S=mLKOHforacetylatedsample, W = g sample used for acetylation.References: Ber. 34, 3354(1901).J. Biol. Chem. 104, 627(1934).Ind. Eng. Chem. Anal. Ed. 17, 394(1945).AOCS Method Cd 1360 (Revised 1993).JAOAC 48, 131, 175(1965). 2000 AOAC INTERNATIONALTable 965.32