Differential scanning calorimetry analysis of structured acyglycerols obtained from caprylic acid and omega-3 concentrates of rainbow trout (Oncorhynchus mykiss) belly oil

Abstract

The thermal behaviour of structured acylglycerols prepared by lipase-mediated esterification of caprylic acid and omega-3 PUFA concentrates from rainbow trout (Oncorhynchus mykiss) belly oil by differential scanning calorimetry (DSC) was studied. The basic objective of the work was to determine the effect of process variables such as caprylic acid/omega-3 PUFA ratio, reaction temperature, reaction time, pressure during carbon-dioxide supercritical extraction and glycerol content in the structured acylglycerols. For it, changes occurring in parameters such as melting profile, melting range, melting onset, enthalpy and melting peak were analysed. A central composite design 25-1 + star of five factors including 28 runs and based on response surface methodology (RSM) was employed for analysing the esterification mediated by immobilized-1,3-specific lipase (Lipozyme TL IM) obtained from Thermomyces lanuginosus under supercritical carbon dioxide conditions. The melting curve was obtained from the program temperature from -80 to 60°C at 2°C/ min. Belly oil used as control showed a melting peak of -7.30°C with an enthalpy value of 123.2 J/g; meantime, melting point of omega-3-PUFA concentrate was -49.47°C, being its enthalpy score 18.7 J/g. The thermal conditions of structured acylglycerols showed to be significantly affected by all esterification process variables. Structured acylglycerols showing the highest properties were obtained when applying a low temperature and a high pressurization value, which led to a melting peak of -36.67°C and to an enthalpy value of 54.1 J/g