EFFECTS OF HYDROLYSIS OF MILK GLYCERIDES ON THE ANTIMUTAGENICITY OF AHEXANE EXTRACT OF MILK

Reconstituted nonfat dry milk was treated with different amounts of li pase from Pseudomonas fluorescens. Hexane extracts of treated milks we re dissolved in dimethylsulfoxide and assayed for antimutagenicity usi ng the Ames test (Salmonella typhimurium TA 100) against N-methyl, N'- nitro, N-nitrosoguanidine. Anti-N-methyl, N'-nitro, N-nitrosoguanidine activity increased significantly as the amount of added lipase increa sed. At the highest lipase concentration tested, activity increased 5- fold, suggesting that liberated fatty acids contributed to the increas ed antimutagenicity. The activities of mixtures of pure fatty acids on antimutagenesis were examined using the Ames test. At the lowest conc entrations tested, mixtures of palmitic and stearic acids and mixtures of palmitic and isopalmitic acids exhibited greater activity than did the individual acids. At all doses tested, mixtures of the monoacylgl ycerides of palmitic and stearic acids exhibited the same activity as the individual components. Quantification of fatty acids in milk and y ogurt by gas chromatography indicated a 2 to 20-fold greater content o f free fatty acids in yogurt. The increase in free fatty acids may con tribute to the increase in antimutagenicity of yogurt relative to that of milk.