Detecting the formation of products of radiolysis of tryptophan in foods rich in protein and irradiated with γ rays

N-formyl kynurenine (NFK), OIA and the four hydroxytryptophan isomers (4-, 5-, 6- and 7-OH-TRP) were found as the major radiolysis products in γ-ray irradiated solutions containing tryptophan, in tripeptides and lysozyme. Their identification was achieved by enzymatic hydrolysis with pronase E under mild conditions (40 C, 30-60 min), applying electrochemical methods and RP-HPLC and uv fluroscence methods. Highly significant dissimilarity of results was shown for all the radiolysis products found in the specimens irradiated with 1.3 or 5 kGy and in non-irradiated samples. For release of the radiolysis products from protein-rich foods (egg white, white chicken meat, North Sea shrimps), a two-stage enzymatic hydrolytic process was developed, using proteinase K and carboxypeptidase A for egg white and chicken meat, and proteinase K and pronase E for the shrimps. The four OH-TRP isomers could be detected and quantified in all specimens. The contents varied from 0.02 to 1.97 mg/kg of proteine. Significant deviation of results between irradiated and non-irradiated specimens of egg white and chicken meat could be detected as from an applied dose of 3 kGy. In the shrimps, deviations were evident only at applied doses of 5 kGy. (orig./CB)