“…It was considered of value in the present study, therefore, to find some substance in fish tissue that could be utilized in a critical experiment to evaluate the approach to spoilage indices proposed here. Cystine was chosen for study since the S-S bonds joining peptide chains are quite labile and since results from chemical studies have indicated that hydrogen sulfide (1, 26,27) and sulfhydryl-containing compounds (3, 18,25) increase in fishery products undergoing spoilage.…”