8-4 |
Protein oxidation in foods: Mechanisms and implications |
H. J. ANDERSEN, Dept. of Animal Products Quality, Danish Insitute of Agricultural Science, Research Center Foulum, PO Box 50, Tjele, DK-8830, Denmark and H. Ostdal, Department of Animal Product Quality, Danish Institute of Agricultural Sciences, Research Centre Foulum, PO Box 50, Tjele, DK-8830, Denmark. It has long been recognized that oxidation in foods is a major problem during storage which results in deterioration of food quality. The majority of research performed previously in relation to oxidative processes and their implications for food quality has focused on lipid oxidation. This may seem logical, as lipid oxidation results in the development of rancidity (unpleasant tastes and odors), color changes and potential formation of toxic compounds. Consequently, the mechanisms by which lipids react with molecular oxygen (autoxidation) have been studied in detail. In contrast the analogous reactions by which proteins, prominent biomolecules in most foods, undergo oxidation are more poorly characterized; this is despite the fact that protein oxidation is known to proceed simultaneously with lipid oxidation in most foods. Proteins highly influence the physical characteristics of foods and so oxidative changes of these biomolecules may have a significant effect on food integrity. Physical and chemical changes in oxidized proteins include amino acid destruction, decrease in protein solubility due to polymerization, loss of enzyme activity, formation of amino acid derivatives including reactive carbonyls and changes in protein digestibility. Moreover, oxidative changes may give rise to altered water-binding capacity and hydration of the protein and can also lead to the formation of protein-lipid complexes. Most of these oxidative changes have been correlated with loss in food quality, however, during the past 5-10 years increasing evidence has shown that protein oxidation may actually improve textural properties of foods. This implies that controlled protein oxidation could be employed either to improve the textural properties of foods or in the development of modified proteins for use as food ingredients. This presentation will give an overview of the mechanisms involved in the initiation of protein oxidation, the reactivity of protein radials towards other biomolecules and the formation and degradation of protein hydroperoxides. The implications of these findings in relation to protein oxidation in foods will be discussed.
Session 8, Oxidation in heterogenous foods and biological tissues: Impact on food quality and health
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