Interesterification of olive oil with a fully hydrogenated fat in a batch reactor using step changes in temperature.

Interesterification of a 60:40 (wt/wt) mixture of olive oil and fully hydrogenated canola oil was carried out in a batch reactor using a commercial immobilized lipase from Thermomyces lanuginose as a biocatalyst. The effects of a stepwise change of temperature on the degree of conversion, the solid fat content (SFC) of the products, and the residual activity of the enzyme were investigated. As a reference condition, an interesterification trial was conducted at a constant temperature of 70 degrees C for 48 h. For trials in which a temperature of 70 degrees C was used for the first 4 h of reaction and a temperature of 60 degrees C was employed for the following 44 h, there were no significant differences (p < 0.05) in the overall degree of conversion relative to the reference condition. Oils interesterified for only 1 or 2 h at 70 degrees C had melting points higher than 60 degrees C, whereas an oil produced by interesterification at 70 degrees C for only 4 h had a melting point of 58 degrees C. There was little difference (p < 0.05) between the SFC profiles of the interesterification products prepared by two different temperature protocols (70 degrees C for 24 h; 70 degrees C for 4 h followed by 60 degrees C for 20 h). Use of the protocol involving a step decrease in temperature significantly decreased catalyst deactivation effects, thereby increasing the residual activity of the immobilized lipase.