Quantification of Antioxidants in Channel Catfish during Frozen Storage

Levels of ascorbic acid, α- and γ-tocopherol, glutathione, and volatile aldehydes were monitored over 6 months in frozen minced and intact fillets of channel catfish. For both samples, decline of glutathione occurred at a faster rate than that of ascorbic acid which in turn was faster than decline of α-tocopherol. Loss of α-tocopherol and formation of volatile aldehydes in mince were either similar or slightly less than in intact fillets throughout storage. γ-Tocopherol levels increased significantly during initial stages of storage and then declined for both mince and intact fillets. Ascorbic acid and glutathione levels in mince, on the other hand, decreased faster than levels in intact fillets during early stages of storage. It is conjectured that any enhancement of oxidation which might have been generated through tissue disruption is balanced either by enhancement of ascorbic acid or glutathione's antioxidant activity or by enhancement of some other unmeasured antioxidant system such as phospholipase. The possibility also exists that tissue levels of ascorbic acid and glutathione are insufficient to have a noticeable effect on the oxidation of lipids. Keywords: Tocopherol; glutathione; ascorbic acid; lipid oxidation; mince