Abstract
Blends ofcoconut (Cocosnucifera) oil (CO) and sesame (Sesamumindicum) oil (SO) were enzymatically interesrerified using aqueous lipase derived from Thermomyceslanuginosus and the reaction conditions were optimized using Response Surface Methodology (RSM). A three-factor, three-level central composite design (facecentred cube design) was employed to optimize the reaction parameters, namely temperature (45-65°C), time (16-48 h) and mass ratio of oils (CO:SO; 70:30 - 50:50). Lipase, diluted in phosphate buffer (pH 8) was used at 0.2% (v/w) of the substrate. Degree of interesterification (DI), and the ratio of monounsaturated and polyunsaturated fatty acids (MUFA:PUFA) of triacylglycerols (TAGs)were used as response variables. Triacylglycerol (TAG) fractions of the samples were separated using Thin Layer Chromatography (TLC) and the fatty acid composition of TAGs was determined using Gas-Liquid Chromatography (GLC). Thelinear and squared effects of temperature and time were significant (p<0.05) for DI whilethe reaction conditions did not exhibit a significant (p<0.05) effect on MUFA: PUFA ratio. The optimum conditions for enzymatic interesterificationwere45°C (temperature), 40.24 h (time) and 70:30 (weight ratio of CO:SO).Under these optimized conditions, the DI was 28.98% and MUFA:PUFA was 1.50±0.06. According to the response surface regression analysis, the R2 value for DI versus reaction parameters was 91.85% and MUFA:PUFA ratio versus reaction parameters was 61.82%. Therefore it can be concluded that enzymatic interesterification can effectively be applied to develop nutritionally and functionally superior modified oilknown as structured lipids using coconut and sesame oils.
Highlights
Structured lipids are thetriacylglycerols (TAG), re-structured or modified to change the fatty acid composition and/or their positional distribution in the glycerol molecule by chemical or enzymaticinteresterification (Timm-Heinrichet al., 2003)
In 2015, the total area under the coconut cultivation stood approximately at 455,000 hawhile CO production was about 52,790 MT (Central Bank of Sri Lanka, 2016).Controversy appears regarding the nutritional value of CO which is composed of 92% of saturated fatty acids of which more than 50% are medium chain fatty acids (MCFAs) (C8-C12).According to the universally accepted Lipid-Heart Theory, high saturated fats lead to hypercholesterolemia and coronary heart disease
Studies on enzymatic interesterification of CO and SO are scanty while this is the first time an interesterification study was reported in Sri Lanka.This study aimed at optimizing the parameters of enzymatic interesterification of two edible oils available in Sri Lanka such as CO and SO by lipase from T.lanuginosususing Response Surface Methodology (RSM)
Summary
Structured lipids are thetriacylglycerols (TAG), re-structured or modified to change the fatty acid composition and/or their positional distribution in the glycerol molecule by chemical or enzymaticinteresterification (Timm-Heinrichet al., 2003). In 2015, the total area under the coconut cultivation stood approximately at 455,000 hawhile CO production was about 52,790 MT (Central Bank of Sri Lanka, 2016).Controversy appears regarding the nutritional value of CO which is composed of 92% of saturated fatty acids of which more than 50% are medium chain fatty acids (MCFAs) (C8-C12).According to the universally accepted Lipid-Heart Theory, high saturated fats lead to hypercholesterolemia and coronary heart disease. Despite the fact that lauric acid is classified as MCFA, there iscompelling evidence that lauric acidfollows the absorption pattern of bothLCSFAs and MCFAs. the presence of high quantity of lauric acid in the diet may contribute to increase the risk of heart disease (Jandacek, 1994;Amarasiri and Dissanayake, 2006; Dubois, 2007). In this backdrop, replacing some of the SFAs such as lauric acid and LCSFAswith nutritionally important fatty acids such as monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFAs) is beneficial
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