Mutagen production during pan-broiling compared with microwave irradiation of beef.

Segments of beef were cooked either by broiling on a hot plate or by irradiation at 2450 MHz in a microwave oven. Extracts of surface layers of the cooked meat were tested for mutagenic activity using Salmonella typhimurium TA98 and TA100 with and without S-9 liver microsomal preparation. The broiled beef extracts with S-9 activation exhibited marked frame-shift mutagenicity, which increased with cooking time. No such activity was detected with beef cooked by microwave irradiation, with exposures ranging from normal to 3 times the normal cooking period.