A study of the rates of the competitive nitrosations of pyrrolidine, p‐cresol and L‐cysteine hydrochloride

The competitive nitrosations of pyrrolidine, p‐cresol and L‐cysteine hydrochloride were studied in aqueous solution. The reactions were studied at pH values 3.0, 5.0 and 5.5 and at temperatures 20, 37 and 120°C, conditions which simulate those found in meat during processing, storage, cooking and gastric digestion. The formation of N‐nitrosopyrrolidine was observed only in the reactions carried out at 120°C, subject to a detection limit of 0.2 parts/106. At this temperature the effect of L‐cysteine hydrochloride alone and in combination with p‐cresol is to enhance the rate of N‐nitrosopyrrolidine formation at pH 5.0 but to inhibit it at pH 3.0. In reactions at 20 and 37°C, where N‐nitrosopyrrolidine was not detected, the rate of C‐nitrosation of p‐cresol to give o‐nitro‐p‐cresol is inhibited in the presence of L‐cysteine hydrochloride at pH values 3.0, 5.0 and 5.5.