Some Factors Affecting Free Fatty Acid Distribution in Lipase-Hydrolyzed Milk Fat

Abstract

A gas chromatographic study of the methyl esters of free fatty acids revealed that the relative concentration of free fatty acids hydrolyzed by milk lipase from milk fat at pH 7.0 and pH 8.6 was affected by milk fat substrate concentration, incubation temperature, and inhibitors.Eighteen methyl esters were separated and 11 were identified. Generally, the unidentified esters were present in higher concentrations in the free fatty acid mixture following lipolysis than in the saponified substrate fat.At both pH 7.0 and 8.6, the substrate concentration was inversely related to the relative concentration of the free short-chain fatty acids (C-6 to C-12).The pH had a slight effect on the relative concentration of free fatty acids resulting from lipase action. Short-chain acids were in greater concentration when the assay was at pH 8.6 than at 7.0, whereas concentrations of several of unknown acids displayed an opposite pH relationship.In comparison to the control, ferric chloride was found to have no effect on the relative concentration of free fatty acid methyl esters at pH 7.0, but caused a marked increase in the relative concentration of both known and unidentified long-chain esters at pH 8.6. Changes in distribution of free fatty acids caused by the presence of cupric chloride and diisopropyl fluorophosphate (DFP) during lipolysis did not exceed 10% of the control.The relative concentration of the short-chain fatty acid methyl esters was found to increase and that of the long-chain methyl esters to decrease when the temperature of lipolysis was changed from 37 to 4C at pH 8.6.