Lipase redistribution in cows' milk during induced lipolysis II. Activation by milk pH adjustment

Abstract

SummaryCold-stored milk lipolysis was enhanced from 5- to 50-fold when milk pH was adjusted to 7–8 with NaOH, while it was greatly decreased or stopped by an adjustment to pH 6–5·5 with citric acid. Small adjustments in pH (≤ 0·5 pH unit) also affected lipolysis, but the pH of native milk was not related to spontaneous lipolysis. The binding of lipoprotein lipase to cream was a pH-dependent process with an optimum near pH 7·0. Activity of the cream lipase on cold-stored milk fat continuously increased from pH 6·6 to pH 8·5. The activating effect of heparin on cold-stored milk lipolysis reached a maximum at pH 7·0–8·0 and a minimum in native milk, while addition of blood serum gave an opposite response.