OXIDATIVE SUSCEPTIBILITY OF CATFISH LIPIDS AS AFFECTED BY THE MICROENVIRONMENT OF ASCORBIC ACID
ABSTRACT
The predominant site of lipid oxidation in frozen channel catfish has previously been attributed to both triacylglycerols and phospholipids. This study was designed to delineate the extent to which the microenvironment of ascorbic acid might alter the oxidative susceptibility of lipid classes. Modification in microenvironment was achieved by administering ascorbic acid in two different ways: metabolic absorption of dissolved ascorbate by live catfish, or tumbling of fillets in the presence of an ascorbic acid solution. Fillets from both treatments were subjected to frozen storage (-6C) for up to 6 months and their oxidative stability compared to untreated fillets stored under similar conditions. Oxidative products in vacuum tumbled fillets were generated sooner but at a slower rate than metabolically absorbed fillets suggesting that the oxidative substrate differed. Further characterization of stored fish samples for lipids, tocopherol, and ascorbic acid led to the conclusion that intercellularly distributed ascorbic acid (vacuum tumbled fillets), while capable of regenerating tocopherol and protecting membrane phospholipids, simultaneously accelerated oxidation of the triacylglycerols. Application of ascorbic acid via metabolic absorption, on the other hand, did not lead to an acceleration in triacylglycerol oxidation.