Incorporation of capric acid in pumpkin seed oil by sn-1,3 regioselective lipase-catalyzed acidolysis

Vanessa Sousa,Vitor Campos,Paula Pires-Cabral,Patrícia Nunes

doi:10.1051/ocl/2018004

Abstract

Structured lipids (SLs) are novel triacylglycerols obtained by changing the native fatty acid (FA) profiles or by the incorporation of a new desired FA in the acylglycerol backbone. These modified fats present important medical and functional properties for food applications. This work aimed to synthetize a MLM-type SL, which consists of triacylglycerols containing a medium-chain FA (M) at sn-1,3 positions and a long-chain FA (L) at sn-2 position, by acidolysis of pumpkin seed oil with capric acid, catalyzed by a commercial lipase preparation from Thermomyces lanuginosa (Lipozyme TL IM). Reactions were performed at 45 °C, in solvent-free media, at 1:2 molar ratio (pumpkin seed oil:capric acid) and a fixed amount of immobilized lipase of 5%, 10%, 15% or 20%. Incorporations of C10:0 increased with time up to 31 h (29.9 ± 0.7 mol-%) when 5% lipase load was used. Significant differences were only observed between the results obtained with 5 and 20% of biocatalyst load. The subsequent experiment was carried out with 5% lipase load, at 45 °C, 1:2 molar ratio and in the presence of n-hexane. The results showed slightly higher incorporation yields in the presence of solvent, namely at 48 h-reaction (34.7 ± 1.0 mol-%). However, since the structured lipids are to be used in food products, together with environmental and economic concerns, solvent-free systems are preferred. In this study, the synthesis of a MLM-type SL from pumpkin seed oil for food uses was well succeeded.

Highlights

IntroductionThe demand for new, healthy and economically viable products has increased considerably
During the last decades, the demand for new, healthy and economically viable products has increased considerably
The peroxide value obtained in this study (19.008 ± 1.710) was higher than the maximum limit of 15 meq O2/kg oil regulated by Codex Stan 210 (1999), which suggests that, at the moment of analysis, the pumpkin seed oil had begun to degrade by oxidation reactions, since the high amount of linoleic acid makes it prone to oxidation

Summary

Introduction

The demand for new, healthy and economically viable products has increased considerably. TAG, containing a medium-chain FA (M) at sn-1 and sn-3 positions, and a long-chain FA (L) at sn-2 position, named as MLM-type TAG, present lower caloric value than conventional fats and oils of the type LLL (Smith et al, 1994; Morales-Medina et al, 2017) The importance of this SL is that it is metabolized differently compared to conventional fats and oils. The sn-1,3 specific lipases have currently been used to catalyze the incorporation of medium chain FAs at the sn-1,3 positions of the TAG molecule, while the central position is preferentially occupied by unsaturated long-chain FAs, namely oleic and linoleic acids (Osborn and Akoh, 2002; Turan et al, 2006; Feltes et al, 2009; Nunes et al, 2011a, b). Interesterification produces a randomly structured medium- long-chain tricylglycerols with low content of MLM compared to acidolysis reaction (Lee et al, 2012)

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