Enzymatic esterification of olive-pomace oil

ABSTRACT ENZYMATIC ESTERIFICATION OF OLIVE-POMACE OIL ÇİFTÇİ, Ozan Nazım M.Sc. in Food Engineering Supervisor: Assoc. Prof. Dr. Sibel FADILO?LU July 2003 In this study, enzymatic esterification of free fatty acids of olive-pomace oil with glycerol was carried out in microaqueous conditions by using immobilized Candida antarctica lipase. The effects of reaction time, molecular sieve, enzyme concentration and reaction temperature on free fatty acid content, and the effect of glycerol amount on the change in glyceride composition of olive-pomace oil were investigated. The initial acidity of the olive-pomace oil (32 %) reduced to 2.36 % in the presence of 750 mg of molecular sieve in the reaction mixture. It was observed that the effectiveness of esterification reactions was related to the amount of molecular sieve present. As the amount of molecular sieve increased, the conversion of free fatty acids also increased at a defined time. In the absence of molecular sieve, the esterification reaction forced to reverse reaction that was the hydrolysis. The greater conversion of free fatty acids into glycerides was observed at an enzyme concentration of 27.2 mg/mL within 60 min. FFA content decreased sharply with increasing reaction time at all temperatures, and it was sharper at higher temperatures. FFA content reached into the equilibrium in almost 120 min at 60°C. However, the time to reach into the equilibrium was around 300 min at 40 and 50°C. ANOVA showed that the effects of temperature on free fatty acid content were significant (p<0.05). Results obtained from non-linear regression analysis indicated that reaction order was 1.3 for free fatty acid reduction in the olive-pomace oil. Calculated activation energy for free fatty acid reduction was 32.89 kJ mol "'. In order to investigate the effect of glycerol content, esterification reactions were carried out in the absence and in the presence (glycerol to FFA molar ratio of 1/3 and IV1/6) of glycerol. In the absence of glycerol, FFA concentration decreased from 32 to 21 % while triacylglycerol concentration increased from 33 to 40 % by the end of 8 hours of reaction time. The most significant decrease in FFA and increase in triacylglycerols was observed at the limiting concentration of glycerol (glycerol to FFA molar ratio of 1/3). The free fatty acid concentration decreased to a value of 2.5 % and triacylglycerol concentration increased up to 78 %. The change in both FFA and triacylglycerol concentrations was found to be significant (p<0.05) statistically. Keywords: Enzymatic esterification, lipase, olive-pomace oil.