The role of non-haem proteins in meat haemoprotein digestion

The influence of additional protein on the in vitro digestion of haem compounds was investigated. When either (59)Fe-labelled haemoglobin in blood or unlabelled purified haemoglobin were digested in vitro, the formation of low molecular weight (< 10,000), dialysable, iron degradation products was very limited (<18% of the total iron) and consisted mostly of haematin compounds. The presence of additional protein, in the form of bovine serum albumen or gelatin, greatly increased the formation of low molecular weight (<10,000) degradation products; the increase being proportional to the concentration and type of added protein. In these systems approximately two-thirds of the low molecular weight iron compounds were non-haematin in character. However, the digestion of aqueous muscle extracts resulted in the greatest formation of low molecular weight (<10,000) iron degradation products (>70% of the total iron), nearly all of which were non-haematin compounds. A hypothesis is presented explaining how haemoprotein degradation occurs in meat and related systems during normal physiological digestion.