Specific distribution of short-chain fatty acids in molecular distillates of bovine milk fat.

Triglycerides with a total of 34-44 acyl carbon atoms have previously been shown to account for nearly 50% of bovine milk fat. About 80% of this material was isolated by molecular distillation and a representative fraction of these glycerides was subjected to a stereospecific analysis. Of the 29 moles % of C(4)-C(8) fatty acids present in the analyzed fraction, at least 95% were specifically attached to the glycerol molecule in the position corresponding to carbon 3 of sn-glycerol 3-(dihydrogen phosphate) (L-alpha-glycerophosphate). The distribution of the other fatty acids (C(10) or greater) did not show such marked specificity for either the 1- or the 2-position. The data support the hypothesis that the short-chain fatty acids are esterified with long-chain diglycerides, or are substituted in glycerophosphatide intermediates, during the final step in the biosynthesis of milk fat triglycerides.