Mutagenic Analysis as a Means of Detecting Carcinogens in Foods ¹

The Ames test is a valuable screening procedure for environmental carcinogens which are believed to be responsible for a large part of the cancer incidence in the U.S. Mutagens originally detected in bacterial nutrient containing "beef extract" have now been detected in commercial beef extract and in commercial foods containing beef extract. The mutagens did not occur in uncooked beef tissue or in beef stock. The mutagens were formed when beef stock was extensively boiled to produce beef extract. The same mutagens (as evidenced by their chromatographic behavior) were found when ground beef hamburgers are cooked at temperatures in excess of 150-200 C. Well-done hamburgers cooked on an electric frying pan or hot plate, or an electric hamburger cooker (cooking temperatures 190-300 C) contained the mutagens. Hamburgers cooked under the heating element of an electric broiler, or in a microwave oven (but not on the "browning tray") contained no significant mutagenic activity. Mutagen content increased with cooking time, and was concentrated in the outer surface of the cooked hamburgers. These results need to be interpreted in terms of the known relationships between mutagenic activity toward Salmonella and carcinogenic activity toward laboratory animals and between the latter and the risk of cancer in people. The results show that the mutagens which have been found in beef extract and in cooked hamburgers represent a possible risk of cancer of unknown magnitude to people who ingest them. The results also show how the nutritional benefits of hamburgers can be enjoyed without incurring this risk, by a suitable choice of cooking methods.