Conjugated linoleic acid (CLA) rich soy oil (CLARSO) with about 20% CLA has recently been produced by UV photo-isomerization of soy oil linoleic acid using an iodine catalyst, on both a laboratory and pilot plant scale.
Conjugated linoleic acid (CLA) rich soy oil (CLARSO) with about 20% CLA has recently been produced by UV photo-isomerization of soy oil linoleic acid using an iodine catalyst, on both a laboratory and pilot plant scale. It was further adsorption processed with carbon to remove residual iodine. The objective of this study was to compare the oxidative stability of CLARSO obtained by both methods with conventional soy oil. Oil samples of CLARSO and a soy oil control were air-tightly sealed in 100-mL vials, wrapped in aluminum foil and incubated at 60°C. Fatty acid analysis, headspace oxygen, peroxide value and lipid oxidation volatiles were determined in triplicate daily. Oxidation weight studies were conducted at 64°C in triplicate to measure the induction time of oil samples during lipid oxidation. Antioxidant (tocopherols and polyphenolic) and iodine levels were also measured in duplicate before and after photoirradiation. Adsorbed CLARSO produced more hexanal than the control and was overall less oxidatively stable than soy oil. There were minimal amounts of polyphenols throughout with a slight decrease after processing, and no change in the tocopherols content. Addition of tocopherols to oil did not show any improved oil stability. Neutron Activation Analysis showed that over 75% iodine was retained in the oil even after adsorption. Different deodorization techniques were thus employed for effective iodine removal with little success. The reduced oil stability was probably due to residual catalytic iodine radicals which require a more efficient removal of iodine after photoirradiation to enhance CLARSO stability.