576. The volatile compounds associated with oxidized flavour in skim milk

Abstract

Using chromatographic techniques, a number of compounds was isolated from the steam distillates of skim milk containing oxidized (cardboard) flavour. The following compounds were definitely identified: acetone, acetaldehyde, n –hexanal, crotonaldehyde, and the C 5 to C 11 2-unsaturated aldehydes. Presumptive evidence for the presence of several 2,4-diunsaturated aldehydes of medium chain length was obtained also. Acetaldehyde and acetone were also isolated from normal skim milk; these two compounds appear to play no part in the defect. 2-Enals, in particular the C 8 and C 9 , were considered to be the principal flavour-determining compounds. In milk at dilutions of 1 part in 10 7 to 10 9 they impart an oxidized type of flavour resembling that known as cardboard. Evidence was obtained that 2,4-dienals were also present and they produced a similar flavour. It may further be deduced that cardboard flavour in milk is caused by the preferential oxidation of di- and polyunsaturated fatty acids.