Studies on the Degradation Mechanisms of Proteins and Their Derivatives in the Foods

Cysteine mercaptals and mercaptoles were prepared by the reactions of l-cystine with formaldehyde, acetaldehyde, n-butyraldehyde, benzaldehyde, furfural, pyruvic acid and levulinic acid in 6 n hydrochloric or sulfuric acid. Hydrogen sulfide released from cysteine mercaptals and mercaptoles in heated aqueous solutions (oil bath: 120°C) was determined. Although a small amount of hydrogen sulfide was liberated from l-cystine on one hour heating, its amount increased suddenly after three hours. Among these compounds l-cystine mercaptal of furfural was most unstable and a large amount of hydrogen sulfide was produced.