PRODUCTION OF SPECIFIC STRUCTURED LIPIDS BY ENZYMATIC INTERESTERIFICATION - OPTIMIZATION OF THE REACTION BY RESPONSE-SURFACE DESIGN

Rapeseed oil and capric acid were interesterified in solvent-free medi a catalyzed by Lipozyme IM from Rhizomucor miehei to produce specific- structured lipids (SSLs). The process was optimized by response surfac e design concerning the effects of acyl migration and the byproducts o f diacylglycerols (DAGs). A five-factor response surface design was us ed to evaluate the influences of five major factors and their relation ships. The five factors were water content (W-c, wt-% based on enzyme used), reaction temperature (T-e, degrees C), enzyme load (E-l, wt-% b ased on substrates), reaction time (T-r, h) and substrate ratio (S-r, rapeseed oil/capric acid, mol/mol), varied at three levels together wi th two star point levels. The net incorporation [Delta(I-f-M-f)], in w hich I-f represents incorporation (1,3-positions) and M-f acyl migrati on (2-position), and the contents of DAGs were analyzed and calculated . All parameters had strong influence on the net incorporation, and th e experimental and predicted values were close. The best fitting quadr atic model was determined by regression and backward elimination. The coefficients of determination (R-2) of the models were 0.971 for net i ncorporation and 0.938 for DAG content. Thus, we conclude that the qua dratic response models adequately expressed the reaction. Based on the models, the reaction was optimized for the maximum net incorporation and minimum DAG content. The reaction and the control of water content or water activity (Aw) was also discussed.