Kinetics of the Enzymatic Development of Pyruvic Acid and Odor in Frozen Onions Treated with Cysteine C‐S Lyase

SUMMARY— Extracts of commercially frozen onion, although possessing considerable peroxidase and catalase activity, were devoid of strong flavor and of L‐cysteine sulfoxide lyase activity, the enzyme considered to be responsible for the development of onion flavor. These extracts, having been shown to retain the precursor(s) to such flavor, were selected as model in situ substrates for a study of the kinetics of odor production catalyzed by the L‐cysteine C‐S lyase of Albizzia lophanta seed endosperm. The results suggest that both odor and pyruvic acid may be produced via the same enzyme but that the odor is formed after the formation of pyruvic acid. From the data it has been calculated that the odor threshold value of some of the enzymatically produced odor‐bearing constituents in onions may be less than one part per billion.