The procedure, however, appears to show considerable promise. These authors described a colorimetric assay that could detect the loss of methionine in proteins due to heat treatment by specifically determining the actual methionine content of the protein before and after heat treatment. The Me2SO was evolved into the headspace above the peptide solution and was then measured using GLC techniques. This procedure was then applied to food proteins that had part of their methionine in the oxidized form, either from H202 treatment or from typical industrial processing procedures. Of the procedures so far described for determining the methionine content of food proteins, those that determine methionine directly on the intact protein, and therefore that eliminate the variable and timeconsuming enzymic hydrolysis step, have a definite advantage.
Oilseeds tend to have a more constant amino acid composition.
Azo dyes cannot therefore be relied on for process control of milk powders. However, the method involves gel filtration and is less convenient than azodye procedures.