| Abstract
| - Screening of five commercially available lipases for the incorporation of capric acid (CA) intodocosahexaenoic acid single cell oil (DHASCO) indicated that lipase PS-30 from Pseudomonas sp.was most effective. Of the various reaction parameters examined, namely, the mole ratio of substrates,enzyme amount, time of incubation, reaction temperature, and amount of added water, for CAincorporation into DHASCO, the optimum conditions were a mole ratio of 1:3 (DHASCO/CA) at atemperature of 45 °C, and a reaction time of 24 h in the presence of 4% enzyme and 2% watercontent. Examination of the positional distribution of fatty acids on the glycerol backbone of the modifiedDHASCO with CA showed that CA was present mainly in the sn-1,3 positions of the triacylglycerol(TAG) molecules. Meanwhile, DHA was favorably present in the sn-2 position, but also located inthe sn-1 and sn-3 positions. The oxidative stability of the modified DHASCO in comparison with theoriginal DHASCO, as indicated in the conjugated diene values, showed that the unmodified oilremained relatively unchanged during storage for 72 h, but DHASCO-based structured lipid wasoxidized to a much higher level than the original oil. The modified oil also attained a considerablyhigher thiobarbituric acid reactive substances value than the original oil over the entire storage period.However, when the oil was subjected to the same process steps in the absence of any enzyme,there was no significant difference (p> 0.05) in its oxidative stability when compared with enzymaticallymodified DHASCO. Therefore, removal of antioxidants during the process is primarily responsiblefor the compromised stabilty of the modified oil. Keywords: Acidolysis; lipase; structured lipids; medium-chain fatty acids; capric acid (C10:0);docoshexaenoic acid single cell oil (DHASCO); oxidative stability; conjugated dienes; thiobarbituric acidreactive substances (TBARS); positional distribution
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