INTERESTERIFICATION OF BUTTER FAT BY LIPASE FROM RHIZOPUS-NIVEUS IN COSURFACTANT-FREE MICROEMULSION SYSTEM

Buffer fat was interesterified in a cosurfactant-free microemulsion sy stem containing nonionic and ionic surfactants, using commercial lipas e obtained from Rhizopus niveus, at different concentrations of surfac tant mixtures and hydrophilic-lipophilic balance (HLB) values. The res ults indicated that the interesterification yield (IY) of lipase-catal yzed interesterified butter fat reached its maximum in the microemulsi on system prepared with the surfactant mixture of HLB value of 9, foll owed by that of HLB value of 10. In addition, increasing concentration s of surfactant mixtures, from 3 to 6 mM, resulted by an increase in t he IY. The interesterification of butter fat in the microemulsion prep ared with 3 mM of surfactant mixture of HLB value of 10 showed a minim um hydrolytic activity. The results showed that the interesterified se lected triacylglycerol molecules were enriched with the hypocholestero lemic fatty acid C18:1, originally located on sn-1,3 positions, on the ir sn-2 positions; this fatty acid was favorably interchanged with the hypercholesterolemic fatty acid C16:0, originally located on sn-2 pos ition. The results also indicated that the use of 6 mM of surfactant m ixtures increased the acyl exchange reaction toward the long-chain sat urated fatty acid C16:0 an the sn-2 position of triacylglycerol molecu les.