HEAT-TREATMENT ON HEME IRON AND IRON-CONTAINING PROTEINS IN MEAT - IRON-ABSORPTION IN HUMANS FROM DIETS CONTAINING COOKED MEAT FRACTIONS

The present study was undertaken to characterize the effect of heat on iron compounds and iron-containing proteins of rabbit meat. We also s tudied human iron absorption from beef meat precipitates and investiga ted changes in the cysteine content in beef and rabbit meat caused by cooking processes. Supernatant and precipitate fractions were obtained by an extraction procedure that included homogenization and repeated centrifugations. A 50% decrease of soluble iron was produced by cookin g the meat. Cooking also reduced the heme iron content of the meat by 62%. Chromatographic separation of soluble meat extracts showed change s in ferritin, hemoglobin, and myoglobin elution profiles in cooked me at compared with raw meat. Determinations of the cysteine content in r aw or cooked meat samples showed a statistically significant reduction (P < 0.0001) in the cysteine content in cooked samples compared with raw counterparts. Iron absorption studies in humans Seeding the subjec ts with a typical beef-containing diet, which contained 60% of meat ir on as heme iron, showed a 13.5% absorption from heme iron and a 6.3% f rom nonheme iron. The subjects fed with a diet containing beef precipi tate in which only 30% of meat iron was heme iron showed a 7.6% absorp tion from heme iron and 7.5% from nonheme iron. These results show tha t although there are important changes in iron-containing proteins, he me iron, cysteine content, and iron absorption by cooking procedures, the factor present in meat responsible for enhancing nonheme iron abso rption is not affected by heat and is still present in insoluble meat precipitates.