Enzymatic modification of triglycerides in conventional and surfactant-free microemulsions and in olive oil

Abstract

Modification of the acylglycerol profile by interesterification of triacyglycerols (TAGs) can improve certain properties of food products. TAGs enriched in palmitic acid (PA) at the sn-2 position and in unsaturated fatty acids at the sn-1,3 position of the glycerol backbone are an important source of nutrients and energy for humans. In the present study, commercially available lipases have been used for the enzymatic interesterification of TAGs to form lipids containing PA and oleic acid (OA). Lipases A and B from Candida antarctica (CaL A and CaL B) and Thermomyces lanuginosus lipase (TLL) were tested in different environments from organic solvents to non-conventional systems such as w/o microemulsions (in the absence and presence of surfactants) and olive oil. The effects of reaction temperature, substrate molar ratio, and external energy were investigated. AOT microemulsions offered an excellent microenvironment for the interesterification reaction, while lecithin microemulsion affected TLL specificity. Surfactant-free microemulsions were also tested in terms of optimization of production process, however lower reaction yields were obtained. For the commercial immobilized CaL B, the ratio PA:triolein affected the reaction yield with the 2:1 ratio showing promising results in organic solvent environment. The main purpose of the present study was to elucidate the appropriate conditions for the enzymatic modification of olive oil. Several factors were tested such as substrates’ ratio, enzyme’s concentration, reaction temperature and external energy input. Overall, the ideal conditions for the formulation of the desired TAGs included the use of 50 mM free PA as substrate, 3 mg of immobilized CaL B/mL of olive oil while the reaction temperature was set at 40 °C and the duration was 72 h.