No abstract

In this study, high-acid soybean oil, with acid values (Av) ranging from 10 to 50, was enzymatically deacidified for diacylglycerol (DAG) production. The effects of glycerol amounts were studied intensively. The glycerol amount could be calculated theoretically based on the Av of the raw oil (1 mol glycerol with 2 mol oleic acid to form 1 mol DAG, and 1 mol glycerol with 2 mol soybean oil to form 3 mol DAG). A total of 60-62% of DAG could be obtained and the free fatty acid (FFA) content was reduced to 0.36-0.66%. Increased glycerol did not lead to DAG content improvement. However, the glycerol amount based on just the deacidification theoretical calculation (1 mol glycerol with 2 mol oleic acid to form 1 mol DAG) was not feasible to reduce the FFA content. Moreover, Novozym 435 was rather stable in the present reaction procedure, no loss of activity was observed after 10 consecutive uses.

In this study, Candida antarctica lipase B (CALB), Rhizomucor miehei lipase (RML) and Lecitase ® Ultra (LU) were immobilized onto the mesoporous silica SBA-15. The glycerolysis performance of the obtained supported lipases (lipase@SBA-15) in solvent systems was carefully investigated. LU@SBA-15 exhibited good glycerolysis performance in solvent-free system, with diacylglycerols (DAG) content and triacylglycerols (TAG) conversion at 52.4 and 98.6% respectively obtained after 12 h reaction at 60℃. CALB@SBA-15 showed good glycerolysis activity in tert-pentanol and tert-butanol systems, with TAG conversion over 90% obtained. In addition, the present CALB@SBA-15 exhibited selectivity for monoacylglycerols (MAG) production, with glycerol to TAG molar ratio increased to 3:1, MAG content over 80% and TAG conversion over 99% could be obtained from both tert-pentanol and tert-butanol systems. However, RML@SBA-15 showed low glycerolysis activity neither in solvent nor in solvent-free systems. The present results favor the practical enzymatic design for MAG and DAG production.

Four samples of soybean oil refining process—a crude oil, a refined oil, an acid oil, and a deodorizer distillate—representing water contents from 0.02 to 3% were submitted to 16 laboratories for analysis by the Karl Fischer method ISO/TC 34/SC11/N99 recommended by the International Organization for Standardization. The laboratories were asked to perform 2 sets of replicate analyses within 2 weeks. Data population was homogeneous at the 95% confidence level except for the acid oil sample where a sampling problem caused wider than expected variation between laboratories. However, overall results indicated interlaboratory variations of the order of 15% at the 0.3% moisture level, in line with the 10% coefficient of variation suggested by the American Oil Chemists' Society at the 0.5% level. The experience of several participants in practicing the method leads to the recommendation that the draft method be modified to include special care in handling heterogeneous and semisolid or solid samples, use of test sample sizes of 5-25 g, adoption of alternative weighed water standardization, use of chloroform-methanol (1 + 1) or (2 + 1) premixed solvent, and use of reagent dilution for low water samples. The method has been adopted official first action by AOAC.