The interesterification of natural fats can improve certain physical and nutraceutical properties by modification of their acylglycerol profile. The aim of this study was the production of structured lipids by lipase-catalyzed interesterification of blends of palm stearin (PS), palm kernel oil (PK), and olive oil (OO), to be incorporated in margarines. Interesterification activity was evaluated by the decrease of the solid fat content at 35°C (SFC35°C) of the blends. The best interesterification conditions, found by response surface methodology (RSM), catalyzed by “Lipozyme® TL IM” or “Lipozyme® RM IM,” were 65°C and a blend of 45% w/w of PS, 30% w/w of PK, and 25% w/w of OO. Under these conditions, after 2 h of batch interesterification, the product had a SFC35°C of 3.0%. The reaction was implemented in a continuous packed-bed bioreactor, under optimized conditions, for 226 h (“Lipozyme® TL IM”) or 188 h (“Lipozyme® RM IM”), at a residence time of 7 min. The inactivation profile of both biocatalysts followed the first-order deactivation model: half-lives of 88 h (“Lipozyme® TL IM”) and 60 h (“Lipozyme® RM IM”) were estimated, respectively. Free fatty acid content of continuous interesterified blends (c.a. 1% w/w) was lower than that of batch-interesterified blends (c.a. 4–5% w/w).
Practical applications: The obtained structured lipids, with low SFC35°C, are adequate for the production of trans-free table margarines. Using sn-1,3 specific lipases as catalysts, the original fatty acids at sn-2 position will be maintained with nutritional benefits. PS and PK are fats used as trans-free sources of solid fat, for the margarine industry, which are not very sensitive to oxidation. PK, a lauric fat, imparts a fast crystallization rate and confers plasticity to the final products. The incorporation of OO will enrich the blends with natural antioxidants and oleic acid at sn-2 position in acylglycerols. The development of response surface models, describing both final SFC values of interesterified blends and SFC decrease, will allow predicting results for novel proportions of fats and oils and/or a novel combination composition-temperature. The implementation of the interesterification in continuous reactors promotes a faster reaction and lower acidity of interesterified blends, with benefits in terms of product separation and purification.