How We Fried the Burgers We Studied
One major difficulty in our dose- and exposure-assessment work is that the content of mutagens can vary widely even in the same kind of food product when it is obtained from different suppliers or prepared by different restaurants. Although the relative amounts of the heterocyclic amines are generally consistent among different studies and laboratories, the precise amount of mutagen per gram in a given cooked food can span a tenfold range.
Hamburgers from fast-food restaurants generally have considerably lower levels of mutagens than those prepared at home. This result is probably due to the fact that many fast-food restaurants cook their meat at moderate temperatures on a grill or over open flames for a short time. Because the meat patties are thin, the products are not generally overcooked.
Because food-preparation practices vary, over the years we have attempted to approximate a range of cooking practices that are common in American households. In various experiments, foods were pan fried, oven broiled, baked, boiled, stewed, grilled over coals, or left raw. However, for the studies on red meat reported in this article (see Table 3), we purchased ground beef, sold as containing 15% fat, from a local market. We formed the meat into patties weighing 100 grams (a little less than a quarter of a pound) and fried them on a commercial, electric, stainless-steel griddle for 2 to 10 minutes per side and at surface temperatures of 150, 190, or 230°C. We monitored the griddle surface with a digital probe thermometer. After the meat was cooked, it was homogenized in a blender to produce a uniform sample. Samples were frozen at -4°C until extraction for subsequent testing and analysis.