The formation of mutagens in the major cooked protein-rich foods in the US diet was
studied in the Ames Salmonella typhimurium test. The nine protein-rich foods most
commonly eaten in the USA--ground beef, beef steak, eggs, pork chops, fried chicken,
pot-roasted beef, ham, roast beef and bacon--were examined for their mutagenicity
towards S. typhimurium TA1538 after normal 'household' cooking (deep frying, griddle/pan
frying, baking/roasting, broiling, stewing, braising or boiling of 100-475 degrees
C). Well-done fried ground beef, beef steak, ham pork chops and bacon showed significant
mutagen formation. For chicken and beef steak high-temperature broiling produced the
most mutagenicity, followed by baking/roasting and frying. Stewing, braising and deep
frying produced little mutagen. Eggs and egg products produced mutagens only after
cooking at high temperatures (the yolk to a greater extent than the white). Commercially
cooked hamburgers showed a wide range of mutagenic activity. We conclude that mutagen
formation following cooking of protein-containing foods is a complex function of food
type, cooking time and cooking temperature. It seems clear that all the major protein-rich
foods if cooked to a well-done state on the griddle (eggs only at temperatures above
225 degrees C) or by broiling will contain mutagens detectable by the Ames/Salmonella
assay. This survey is a step towards determining whether any human health hazard results
from cooking protein-rich foods. Further testing in both short- and long-term genotoxicity
bioassays and carcinogenesis assays are needed before any human risk extrapolations
can be made.