Production of acylglycerols containing high proportions of docosapentaenoic acid from seal blubber oil and their oxidative stability

Yu, Zhongshui (2002) Production of acylglycerols containing high proportions of docosapentaenoic acid from seal blubber oil and their oxidative stability. Masters thesis, Memorial University of Newfoundland.

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Abstract

The objective of this study was to concentrate polyunsaturated fatty acids (PUFA) from seal blubber oil and to investigate the use of lipases as catalysts for synthesizing acylglycerols from glycerol and polyunsaturated fatty acid concentrates. Additionally, the study of the oxidative stability of acylglycerols synthesized by lipases was intended. Urea complexation was used to concentrate polyunsaturated fatty acids from seal blubber oil. The concentration of docosapentaenoic acid in final products reached as high as 24%. Enzymatic synthesis of acyglycerols directly from glycerol and fatty acid concentrates in organic solvents was studied. Three lipases (Lipase SP435 from Candida Antactica, lipase IM60 from Mucor miehei, lipase PS30 from Pseudomonas sp.) were used as biocatalysts for esterification. Lipase SP435 from Candida Antarctica showed the highest activity for esterification. Effects of reaction parameters, namely temperature, time course and mole ratio of glycerol to fatty acids were followed with all three lipases. The optimal reaction time was 24 h at 30 °C and the mole ratio of glycerol to fatty acid was 14 for lipase SP435. The maximum degree of acylglycerol synthesis exceeded 90%. The effect of time course and mole ratio of glycerol to fatty acids on acylglycerols distribution was also determined. The proportion of monoacylglycerols in samples was low and remained almost constant as the reaction proceeded. However, the proportion of diacylglycerol was increased rapidly in a short time period and then decreased gradually to some extent, depending on the lipase, and then plateaued. The proportion of triacylglycerol was increased gradually to some extent depending on the lipase, than it was maintained constant. The effect of mole ratio of glycerol to fatty acids on the acylglycerols distribution was studied. The higher mole ratio of glycerol to fatty acids, the higher was the proportion of monoacylglycerols and the lower the proportion of triacylglycerols. The oxidative stability of different samples was tested under Schaal- oven conditions. Progression of oxidation was monitored by determination of conjugated dienes (CD), propanal content and TBARS (thiobarbituric acid reactive substances) values. In this study, three samples were used - original seal blubber oil, and concentrate of fatty acid esters and triacylglycerols synthesized by lipase SP435. The results demonstrated that the oxidative stability of synthesized acylglycerols was superior to that of the fatty acid esters. At the beginning, the CD and TBARS values of the three samples were similar. However, fatty acid esters gave rise to higher CD and TBARS values compared to the other two samples as oxidation reaction proceeded.

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