Biology and biotechnology of modified oils

Hamam, Fayez (2007) Biology and biotechnology of modified oils. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The objectives of this study were three fold and these are described in three parts. In the first part incorporation of long-chain n-3 fatty acids (FA) into three types of high-laurate canola oils was examined. Incorporation of the n-3 FA, namely eicosapentaenoic acid (EPA, C20: 5 n-3), docosapentaenoic acid (DPA, C22: 5 n-3), and docosahexaenoic acid (DHA, C22: 6 n-3) into three types of high-Iaurate canola oils, known as Laurical 15, 25, and 35 with 15, 25, and 35% oleic acid content, respectively, was carried out. -- Production of SL via acidolysis of Laurical 15 with EPA, DPA, and DHA was carried out using five lipases from Candida antarctica, Mucor miehei, Pseudomonas sp., Aspergillus niger, and Candida rugosa. Pseudomonas sp. lipase gave the best incorporation of EPA, DPA, or DHA into Laurical 15. Optimum reaction conditions for EPA incorporation into Laurical 15 were 4% enzyme load, and an oil to EPA mole ratio of 1:3 at 45°C over 36 h. For DPA incorporation into Laurical 15, the optimum conditions were 6% lipase amount, and an oil to DPA mole ratio of 1:2 at 35°C over 48 h. Similarly, incorporation of DHA into Laurical 15 was best achieved at a mole ratio of oil to DHA of 1:3, 10% lipase concentration, at 35°C over 48 h. Lauric acid remained mostly esterified to the sn-1,3 positions while EPA, DPA or DHA was also located mainly in the sn-1,3 positions of the modified oils. The modified oils were more prone to oxidation than their unmodified counterparts, as evidenced by the 2-thiobarbituric acid reactive substances (TBARS) test. -- In another study, response surface methodology (RSM) was employed to obtain a maximum incorporation of EPA or DHA into Laurical 25. Under optimum conditions incorporation of EPA (61.6%) into Laurical 25 was achieved using 4.6% enzyme from Pseudomonas sp. at 39.9°C over 26.2 h. The corresponding maximum incorporation of DHA into Laurical 25 was 37.3% using 4.79% enzyme from Pseudomonas sp., 46.1°C, and 30.1 h. For EPA-modified Laurical 25, lauric acid was present mainly in the sn-1,3 positions while EPA was randomly distributed over the three positions. Similarly, DHA as well as lauric acid were primarily located at the sn-1,3 positions of the modified oil. The unmodified oil remained unchanged during storage for 72 h as indicated by the conjugated diene (CD) values, but EPA- or DHA-modified Laurical 25 SL were oxidized to a much higher level than the original oil. The CD values were higher in DHA-modified than EPA-modified oil. The modified oils also attained considerably higher TBARS values than the original oil over the entire storage period. -- Lipases from Mucor miehei (Lipozyme-IM), Pseudomonas sp. (PS-30), and Candida rugosa (A Y -30) catalyzed optimum incorporation of EPA, DP A, and DHA, into Laurical 35, respectively. The maximum incorporation of EPA (62.2%) into Laurical 35 using RSM was predicted at 4.36% of enzyme load and 43.2°C over 23.9 h. Under optimum conditions (5.41% enzyme; 38.7°C; 33.5 h), incorporation of DPA into Laurical 35 was 50.8%. The corresponding maximum incorporation of DHA (34.1 %) into Laurical 35 was obtained using 5.25% enzyme, at 43.7°C, and over 44.7 h. EPA and DHA were mainly esterified to the sn-1,3 positions of the modified oils while DP A was randomly distributed over the three positions of the TAG molecules. Meanwhile, lauric acid remained primarily esterified to the sn-1 and sn-3 positions of the modified oils. The modified oils were more susceptible to oxidation than the unmodified oil, when considering both CD and TBARS values.

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