Immobilized thermophilic lipases for the interesterification of soybean oil

Abstract

Vegetable oils are a major source of healthy dietary lipids. However, the physicochemical properties of vegetable oils are varied, which affects their application in foods. Interesterification is a method often used to modify the physicochemical characteristics of oils and fats. Enzymatic interesterification is a process that uses enzymes to exchange the acyl groups among triacylglycerols (TAG); an immobilized lipase is one such enzyme that can be used for interesterification. This study immobilized lipases from two strains of thermophilic bacteria (Geobacillus stearothermophilus (GS) and Anoxybacillus flavithermus (AF)) onto silica beads. These immobilized lipases were used to interesterify soybean oil (SBO) with palmitic acid (PA) to change the physicochemical properties of the oil. High-performance liquid chromatography (HPLC) was used to determine the TAG composition and free fatty acids (FFA) after interesterification. The melting point was measured using differential scanning calorimetry (DSC). Optimum reaction conditions were observed at 70°C, and 24 hrs for all reaction ratios of SBO to PA (1:0.1, 1:0.25, and 1:0.5 (v/v)). The PA significantly decreased after 24 hrs at all reaction ratios, and the TAG concentration was significantly different after interesterification. FFA concentration changed after SBO interesterification, and the melting points of the samples increased from 4°C to 40°C. The results suggest that both immobilized lipases have suitable properties for oil interesterification and industrial applications.