Manat Chaijan

pp. 47 - 53

Abstract

Lipid oxidation and myoglobin oxidation in muscle foods occur in a concurrent manner and each process appears to enhance the other. During oxidation of oxymyoglobin, both superoxide anion and hydrogen peroxide are produced and further react with iron to produce hydroxyl radical. The hydroxyl radical has the ability to penetrate into the hydrophobic lipid region and hence facilitates lipid oxidation. The prooxidant effect of oxymyoglobin on lipid oxidation is concentrationdependent. At equimolar concentrations, oxymyoglobin shows higher prooxidative activity towards lipid than metmyoglobin. However, the catalytic activity of metmyoglobin is promoted by hydrogen peroxide. The reaction between hydrogen
peroxide and metmyoglobin results in the formation of two active hypervalent myoglobin species, perferrylmyoglobin and ferrylmyoglobin, which are responsible for lipid oxidation. Additionally, lipid oxidation results in a wide range of aldehyde products, which are reported to induce the oxidation of oxymyoglobin. Metmyoglobin formation is generally greater in the presence of unsaturated aldehydes than their saturated counterparts of equivalent carbon chain length. In addition, increasing
chain length of aldehydes, from hexenal through nonenal, results in the increased metmyoglobin formation. Moreover, aldehydes alter myoglobin redox stability by increasing oxymyoglobin oxidation, decreasing the metmyoglobin reduction via enzymatic process, and enhance the prooxidant activity of metmyoglobin. Therefore, the oxidation of both lipid and myoglobin directly affect the quality and acceptability of muscle foods and the lowering of such a phenomenon can enhance the shelf-life stability of those foods.