Studies on the ripening of stilton cheese: Lipolysis

Abstract

The levels of free fatty acids (FFA) in Stilton cheese showed very slight increases during the first 28 days, but they then increased rapidly up to the end of ripening. Some individual FFA, as mole percentages of total FFA, changed irregularly during ripening. Long-chain FFA were present at higher concentrations than were lower fatty acids. A relatively high level of carbonyl compounds, methyl ketones in particular, were present in Stilton during ripening. A good recovery of methyl ketones was obtained using a method based on reverse-phase high-performance liquid chromatography. The concentration of each methyl ketone did not depend on the level of available fatty acids. While the proportions of C 13 and C 15 ketones were relatively low compared with their precursor C 14 and C 16 fatty acids, the concentrations of C 7 and C 9 ketones were relatively high compared with their precursor C 8 and C 10 fatty acids. With the exception of C 7 and C 9 ketones, which showed consistent and considerable increases up to the end of ripening ( C 7 + C 9 accounted for 60% of total methyl ketones), the relative concentrations of methyl ketones fluctuated during ripening; this is probably the result of interconversions of the methyl ketones and/or their reduction to secondary alcohols.