Salmonella/microsome mutagenicity tests of heat-processed milk samples

Change in mutagenicity in white rice after accelerated and long-term storage

Certain reactions that occur in food during storage, such as nonenzymatic browning and lipid oxidation, form compounds that have been shown to be mutagenic. It is possible that over long storage periods, significant amounts of these products could be formed. Although some research has been published concerning the mutagenicity of foods due to processing or cooking, little research has been done regarding mutagenicity of foods stored for an extended time. The objective of this research was to determine the potential mutagenicity of white rice held in accelerated and long-term storage using the Ames Salmonella/microsome assay. Fresh long-grain white rice was packaged in foil laminate pouches and held at 60 degrees C for 18 wk. Rice stored for > 25 y in an oxygen-free environment at or below room temperature in size number 10 cans was obtained from residential storage. The standard plate-incorporation method was used to evaluate the mutagenic potential of all treatments using Salmonella typhimurium tester strains TA97a, TA98, TA100, and TA102. Samples were plated at 5 dilutions with and without rat liver S9 enzyme. A solvent control was also plated for each strain. Treatments yielding counts at least double the solvent control level were considered mutagenic. Plate counts for all treatments fell well below the required doubling of the solvent control value. White rice held in accelerated and long-term storage appears not to increase in mutagenic compounds as measured by the Ames assay, supporting its use for long-term storage purposes such as emergency preparedness and humanitarian food aid.

Dairy cattle as a bioindicator of exposure to genotoxic substances in a heavily polluted area in northern Bohemia

The exposure of dairy cattle to genotoxic agents in two districts with different levels of environmental pollution was estimated using cytogenetic analysis of bovine peripheral lymphocytes. The Teplice district represented an industrialized area where the air pollution rate is extremely high mainly in the winter, and the Prachatice district--an agricultural area with a relatively low level of pollution. The Ames test was used to examine feed samples for the content of mutagenic substances. Cows in the Teplice district showed a significantly higher count of aberrant cells (4.83 +/- 2.36) than cows in the Prachatice district (3.63 +/- 2.12). The sum of revertants induced by rinsings or extracts of feeds in both of the two test strains (Salmonella typhimurium TA 98 and TA 100) was significantly higher in the district of Teplice than in the district of Prachatice. The percentages of findings with mutagenic responses were 56.3 and 34.8% for the districts of Teplice and Prachatice, respectively. No mutagenic activity was found in milk samples collected in any of the districts. Apparently, the cows kept in the Teplice district were more exposed to genotoxic substances than the cows in the Prachatice district. The major source of this exposure was probably fresh fodder contaminated by industrial emissions.

Nutritional and toxicological aspects of the Maillard browning reaction in foods

The Maillard, or nonenzymatic, browning reaction between carbonyl and amino groups is a common reaction in foods which undergo thermal processing. The Maillard reaction is a desirable consequence of many industrial and domestic processes and is responsible for the attractive flavor and brown color of some cooked foods. An early recognized consequence of the Maillard reaction was the destruction of some essential amino acids, such as lysine. More recently, research interest has focused on the production of toxic and antinutritive compounds. This review examines the nutritional and toxicological consequences of the Maillard reaction in light of the findings of such research. In particular, the effect of Maillard reaction products on the digestion, absorption, and excretion of nutrients is considered. The cytotoxicity, mutagenicity, and immunochemical aspects of selected Maillard reaction products are also examined and suggestions are made for future areas of investigation.