ANTIMUTAGENIC EFFECTS OF CASEIN AND ITS DIGESTION PRODUCTS

The antimutagenic potential of casein was investigated using several m utagens, including some food-related mutagens, and the Salmonella/micr osome and Escherichia coli DNA-repair tests. The effect depended on th e type of mutagen and the incubation time of casein with the mutagens. Casein was very effective against benzo[a]pyrene, N-methylnitrosourea and nitrosated 4-chloroindole, and was less effective towards sodium azide and N-nitroquinoline-1-oxide (NQO). Preincubation increased the antimutagenic potential of casein towards NQO. Heating of casein (up t o 20 min at 130-degrees-C) did not alter its antimutagenic capacity. T he effect of pepsin hydrolysis under simulated gastric conditions on t he antimutagenic capacity of casein was tested with sodium azide and N QO in the Salmonella/microsome test. The peptides formed were separate d by ultrafiltration or by isoelectric precipitation of casein, and we re characterized by HPLC size-exclusion and Kjeldahl analysis. The ant imutagenic potential of casein increased with pepsin hydrolysis; this increase was due to the peptides formed and might be explained by a be tter accessibility of casein peptides for interaction with mutagens. T he antimutagenic potential of pepsin-hydrolysed casein towards sodium azide was observed over the whole dose-response curve.