Improvement of thermo-resistance and quality of soybean oil by blending with cold-pressed oils using simplex lattice mixture design

Abstract

Soybean oil is the most consumed oil worldwide due to its cheapness but presented a weak thermo-resistance due to its richness in poly-unsaturated fatty acids. This study aims to improve the thermo-stability of refined soybean oil by blending it with some cold-pressed oils. For this, cold-pressed and soybean oils were firstly characterized (K232, K270, acidity, peroxide value, iodine value, induction time, phenolic contents, and antioxidant activity). Then, binary blends of each cold-pressed oil (30%) with soybean oil (70%) were analyzed before and after heat treatment (170 °C for 10 h/day for 5 days) followed by the application of the simplex lattice mixture design in order to optimize the combination of the three best cold-pressed oils. The changes in fatty acid profiles were assessed by gas chromatography (GC-FID). The results revealed that soybean oil presented the best physicochemical traits, while cold-pressed oils expressed high levels of phenolic contents and antioxidant activities. From the six binary oil blends, soybean oil mixed with lentisk, sesame, or almond oils were selected for their best thermo-stability. The simplex lattice mixture design, applied for these three chosen oils, indicated that the combination of soybean oil (70%) with lentisk and sesame oils (17.7 and 12.3%, respectively) was considered the optimal blend that gives the maximal thermo-stability improvement to soybean oil. GC-FID analysis showed that fatty acids, particularly linoleic and linolenic acids, were more conserved after heat-treatment in optimal oils blend than soybean oil. This study clearly demonstrated that lentisk and sesame oils enhanced the thermo-resistance of soybean oil, and the findings of this study could be used as an integrated model in oil and fat industries.