Relationship of Methyl Sulfide and Flavor Score of Milk

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Abstract
Methyl sulfide (Me2S) concentrations and organoleptic analyses of milk from poloxalene-treated and untreated cows fed bromegrass or rye pasture or freshly cut alfalfa were compared. These results were compared with those of the same analyses on composite samples from the University herd during the bromegrass and rye trials and those from 2 cows fed hay and grain during the alfalfa trial. Me2S levels in milk from both treated and untreated cows on bromegrass or rye pasture, as determined by gas-liquid chromatography, were less than 12 ppb. Milk produced from treated and untreated cows fed freshly cut alfalf contained 36 and 31 ppb, respectively. Milk from the University herd during the bromegrass and rye trials had less than 11 ppb and from 2 cows, fed hay and grain during the alfalfa trial, 11 ppb Me2S. Only milk produced on freshly cut alfalfa had above-flavor-threshold levels of 19 ppb. Negative correlations were found between flavor scores and Me2S concentrations. Processing in a commercial vacuum pasteurizer removed 95% of the Me2S and half of the acetone from milk but alcohol concentrations were not affected. Laboratory pasteurization did not affect concentrations of volatile constituents of the milk.