DETERMINATION AND MUTAGENIC ASSESSMENT OF MAILLARD BROWNING PRODUCTS IN THE REACTION WITH NITRITE (AMES TEST, AMINO ACID, HETEROCYCLIC COMPOUNDS)
The Ames mutagenicity assay was employed to investigate the mutagenic substances from Maillard browning products with nitrite. Ten different kinds of amino acid-glucose browning products were prepared and tested for mutagenicity before and after nitrosation. No mutagenicity was observed in the methylene chloride extracts of any browning products tested before nitrosation. However, mutagenicity was found in most of the browning products after nitrosation. Among the nitrite-treated browning products, lysine-glucose and phenylalanine showed the greatest mutagenic activity. In Amadori compound system, the nitrite-treated fructose-L-tryptophan showed a clear dose-responsive mutagenicity, while the nitrite-treated fructose-L-phenylalanine showed no mutagenicity. The effects of reaction conditions on the mutagenicity of lysine-glucose browning product with nitrite were studied. The mutagenic activity of this sample was related to the browning reaction intensity of the reaction mixture. Optimal pH for the formation of mutagen was found to be pH 3. Also, mutagenicity was dependent on nitrosation time and nitrite level. Several antioxidants showed effective inhibition of mutagen formation. Two apparent nitrosamines were revealed in nitrite-treated lysine-glucose by TLC. The mutagenicity resulting from different treatments of casein-glucose mixture was evaluated. The ether extracts of both nitrite-treated casein-glucose mixture and nitrite-treated 60-day browned casein-glucose gave mutagenic response, however, the casein-glucose mixture, 60-day browned casein-glucose, and nitrite-treated casein did not. In addition, it was determined that the total lysine and available lysine in these samples were drastically reduced. In both cases the reductions were greatest with combination of nitrosation and the Maillard reaction. Three 2-substituted pyrroles of the Maillard browning products, 2-acetylpyrrole, pyrrole-2-carboxaldehyde, and pyrrole-2-carboxylic acid, were reacted with nitrite in pH 3 at 50(DEGREES)C for 24 hr. The DCM extracts of the 2-acetylpyrrole-nitrite reaction mixture showed significant mutagenicity, but not in the case of other two compounds. It indicated that a functional group play an important role in the mutagenicity of these nitrite-treated 2-substituted pyrroles. Two fractions, separated by TLC, with mutagenic response were found in the reaction products of 2-acetylpyrrole with nitrite. The main mutagen was proposed as a C-nitro pyrrole dimer based on spectral characteristics using UV, IR, MS, and NMR.
"DETERMINATION AND MUTAGENIC ASSESSMENT OF MAILLARD BROWNING PRODUCTS IN THE REACTION WITH NITRITE (AMES TEST, AMINO ACID, HETEROCYCLIC COMPOUNDS)"
Dissertations and Master's Theses (Campus Access).