Lipid and haemoprotein oxidation in meat emulsions

Emulsions of refined additive-free lard, egg albumin and water were designed to study the effect of haemoproteins, iron salts and sodium chloride on lipid oxidation. It was found that ferric haematin pigments (metmyoglobin, methaemoglobin and heat denatured myoglobin and haemoglobin) were all catalysts of lipid oxidation whereas the oxy and carboxy derivatives were not effective. Emulsions prepared using meat of high and low metmyoglobin contents supported these findings. At the levels present in meat products, both ferrous and ferric salts were only very weak catalysts of the lipid oxidation compared with the ferric haematin complexes. Sodium chloride (1·5%) also possessed little or no pro-oxidant activity in these systems. Emulsions prepared from fresh meat and fats from various sources and of different histories indicated that although, in model systems, peroxidising lipids can catalyse the oxidation of myoglobin, in meat and meat-based emulsions the effect is of minimal importance.