ABSTRACTRacemization of amino acids and crosslinking appear to be at least partly responsible for decreased quality of alkali‐treated proteins. Cystine is thought to be one source of the dehydroalanine residue of lysinoalanine. Thus, the lower quality of alkali‐treated soy protein may also be due to cystine destruction. Results demonstrated that severe alkaline treatment reduced total sulfur amino acid bioavailability by 71, the histidine bioavailability by 80. It was concluded that the decrease in sulfur amino acid bioavailability was the result of decreased efficiency of utilization rather than cystine destruction, since the magnitude of the decrease was similar to that observed for histidine, an amino acid not chemically altered by alkaline treatm
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