Argan Oil as a Rich Source of Linoleic Fatty Acid for Dietetic Structured Lipids Production

Argan oil is rich in long-chain unsaturated fatty acids (FA), mostly oleic and linoleic, and natural antioxidants. This study addresses the production of low-calorie structured lipids by acidolysis reaction, in a solvent-free system, between caprylic (C8:0; system I) or capric (C10:0; system II) acids and argan oil, used as triacylglycerol (TAG) source. Three commercial immobilized lipases were tested: Novozym^® 435, Lipozyme^® TL IM, and Lipozyme^® RM IM. Higher incorporation degree (ID) was achieved when C10:0 was used as acyl donor, for all the lipases tested. Lipozyme^® RM IM yielded the highest ID for both systems (28.9 ± 0.05 mol.% C10:0, and 11.4 ± 2.2 mol.% C8:0), being the only catalyst able to incorporate C8:0 under the reaction conditions for biocatalyst screening (molar ratio 2:1 FA/TAG and 55 °C). The optimal conditions for Lipozyme^® RM IM in system II were found by response surface methodology (66 °C; molar ratio FA/TAG of 4:1), enabling to reach an ID of 40.9 mol.% of C10:0. Operational stability of Lipozyme^® RM IM in system II was also evaluated under optimal conditions, after eight consecutive 24 h-batches, with biocatalyst rehydration between cycles. The biocatalyst presented a half-life time of 103 h.

Potential use of avocado oil on structured lipids MLM-type production catalysed by commercial immobilised lipases

Structured Lipids are generally constituents of functional foods. Growing demands for SL are based on a fuller understanding of nutritional requirements, lipid metabolism, and improved methods to produce them. Specifically, this work was aimed to add value to avocado oil by producing dietary triacylglycerols (TAG) containing medium-chain fatty acids (M) at positions sn-1,3 and long-chain fatty acids (L) at position sn-2. These MLM-type structured lipids (SL) were produced by interesterification of caprylic acid (CA) (C8:0) and avocado oil (content of C18:1). The regiospecific sn-1,3 commercial lipases Lipozyme RM IM and TL IM were used as biocatalysts to probe the potential of avocado oil to produce SL. Reactions were performed at 30–50°C for 24 h in solvent-free media with a substrate molar ratio of 1∶2 (TAG:CA) and 4–10% w/w enzyme content. The lowest incorporation of CA (1.1% mol) resulted from Lipozyme RM IM that was incubated at 50°C. The maximum incorporation of CA into sn-1,3 positions of TAG was 29.2% mol. This result was obtained at 30°C with 10% w/w Lipozyme TL IM, which is the highest values obtained in solvent-free medium until now for structured lipids of low-calories. This strategy opens a new market to added value products based on avocado oil.

Fatty acid selectivity of lipases during acidolysis reaction between triolein and saturated fatty acids varying from caproic to behenic acids

The chain length selectivity of three immobilized lipases, namely, Lipozyme TL IM from Thermomyces lanoginosus, Lipozyme RM IM from Rhizomucor miehei, and Novozym 435 from Candida antarctica, was determined in acidolysis performed in hexane using the homologous series of even carbon number, saturated fatty acids (SFAs) of 6-22 carbons. Triolein with individual SFAs or a mixture of equimolar quantities of SFAs was used as the substrate. The effects of operating variables including the mole ratio of fatty acid to triolein, temperature, enzyme dosage, and time on incorporation were also investigated. Incorporation abilities of the enzymes tested were found to be significantly different for most of FAs at the experimental conditions evaluated. Lipases acted weakly on SFAs of which the carbon chain length was shorter than eight carbon atoms and higher than 18 carbon atoms. Lipases showed a bell-shaped distribution in incorporation vs chain length plot with a maximum around C12-C16. Among the experimental parameters tested, the effect of the substrate mole ratio was greater than those of the others, and the highest incorporation was observed for C12 (36.98%), C14 (37.63%), and C16 (38.66%) at a 4:1 substrate mole ratio with Lipozyme TL IM. Lipases caused significantly different levels of acyl migration from sn-1,3 to sn-2 positions.