Oxidations involving the heme complex in raw meat

Abstract

In raw meat systems one is concerned with both lipid and pigment oxidations. Heme pigments catalyze oxidation of tissue lipids causing a stale or rancid odor and flavor. Free radicals from lipid oxidation can oxidize and decompose the red ferrous hemes. This results in the brown colored meat commonly rejected by the consumer. This paper reports three approaches taken to study means of reducing these nonmicrobial oxidative changes: (1) enzymatic reduction of metmyoglobin to maintain ferrous pigments; (2) inhibition of lipid and pigment oxidation and decomposition by means of an antioxidant and reducing agent; (3) the use of model systems to study the kinetics of lipid and heme oxidations. While a biological metmyoglobin reducing system has been found to exist in post mortem suscles, its practical significance in relation to retention of meat color and odor is not fully understood. Anaerobic conditions are usually necessary to achieve complete reduction. The common phenolic antioxidants, butylated hydroxyanisole (BHA) and propyl gallate, along with ascorbic acid will protect meat color and odor for up to eight days according to both chemical analyses and sensory evaluations. Such meat can be packaged aerobically. Surface pigments will remain as the bright red oxymyoglobin familiar to the consumer rather than the purple reduced myoglobin of anaerobically packaged meat.

The peroxide-heme ratio may be an important factor in determining rate of oxidation of both pigment and lipid. Maintenance of a high proportion of heme to lipid appears to prevent catalysis of lipid oxidation. The importance of this in relation to actual storage life of meat has not been explored.