Evidence for a Dimethyl Sulfide Precursor in Milk

The dimethyl sulfide (Me~S) content of milk was increased by heating which indicated the presence of a heat labile Me~S precursor compound. A quantitative gas chromatographic method was employed to demonstrate that the precursor remained in the skimmilk fraction. A concentration procedure, involving dialysis and Iyophilization, yielded sufficient compound for characterization. The precursor was identified as an S-methyl-methionine sulfonium salt on the basis of its thin-layer chromatographic mobility and the heat instability of the compound. Heating of samples caused the disappearance o the compound with a subsequent increase in the content of homoserine and Me~S.