Variation in the form of iron in beef and lamb meat and losses of iron during cooking and storage

Iron levels were lower in semitendinosus muscle of beef and lamb than in longissimus or triceps brachii muscles, and were lower for muscles of male than female lambs, but were similar for muscles from bulls, heifers and mature cows. Soluble proportions of haem iron were higher for beef than lamb (66% vs. 56% of total iron, P < 0.0001), and percentages, as insoluble haem iron or insoluble and soluble non-haem iron, were lower in beef. For beef semitendinosus muscle, increases in cooking time and temperature led to losses of soluble iron and haem iron, with increases in insoluble and non-haem forms of iron, and also in the level of iron in the cooking juice. Losses of iron in drip from a free meat sample or a sample on a pad were over 90% soluble haem iron and were greater following freezing and thawing due mainly to higher volumes of drip.