SIGNIFICANCE OF THE REACTION OF NITRITE WITH TRYPTOPHAN

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Abstract
The reaction of sodium nitrite with tryptophan was studied spectrophotometrically; the N‐nitroso reaction product had an absorption peak at 330 nm and the absorption maximum of tryptophan was shifted from 277 nm to 266 nm. In model systems, where sodium nitrite was 10 mM and tryptophan was 1.0 mM, the reaction proceeded rapidly at pH 4.0 and very slowly at pH 5.5 or higher. Experiments with acetyltryptophan and dipeptides showed that if the primary amino group of tryptophan was blocked, then nitrosation of the indole nitrogen was promoted. Tryptophan was formed when the N‐nitroso reaction product was subjected to gel filtration in the absence of nitrite. If the concentration of reactants and pH are compared for model systems favorable for formation of nitrosotryptophan and for cured meats, it is apparent that the environment for nitrosation of tryptophan is unfavorable in most cured meats.