Changes in the forms of iron and in concentrations of taurine, carnosine, coenzyme Q10, and creatine in beef longissimus muscle with cooking and simulated stomach and duodenal digestion

Longissimus muscle samples from 31 Angus-cross heifers finished on either a high-concentrate feedlot diet or pasture were used to evaluate the effects of cooking (71 °C) on the concentration and forms of iron in the meat, and also on concentrations of the bioactive compounds taurine, carnosine, coenzyme Q10, creatine and creatinine. For a sub-sample of 15 the effects of pepsin and pancreatin digestion were assessed. For iron, cooking resulted in some overall loss together with a major change from soluble haem and non-haem iron to the insoluble forms, but solubility was regained to a significant extent following digestion. Total haem iron percentage, however, decreased at each step from an initial 88% to a final 61% of total iron. For the bioactive compounds, cooking led to a reduction in taurine, carnosine, coenzyme Q10, and creatine. The effects of digestion on the bioactive compounds varied. No clear differences were shown in the way in which beef from pasture-finished and feedlot-finished cattle responded to cooking and digestion.