Kosiyanant_2018_J.Oleo.Sci_67_1299

This study used a rice bran oil solid fat fraction (RBOSF) to produce cocoa butter alternatives via interesterification reaction catalyzed by immobilized lipase (Lipozyme RM IM) in hexane. Effects of reaction time (6, 12, and 18 h), temperature (55, 60, and 65 degC), mole ratios of 3 substrates [RBOSF:palm olein:C18:0 donors (1:1:2, 1:2:3, and 1:2:6)] were determined. The substrate system was dissolved in 3 mL of hexane and 10% of lipase was added. Two sources of C18:0 donors, stearic acid (SAd) and ethyl stearate (ESd) were used. Pancreatic lipase - catalyzed sn-2 positional analysis was also performed on both substrates and structured lipids (interesterification products). Structured lipids (SL) were analyzed by gas - liquid chromatography (G40.35LC) for fatty acid composition. Major fatty acids of RBOSF were C18:1, oleic acid (OA, 41.15+/-0.01%), C18:2, linoleic acid (LA, 30.05+/-0.01%) and C16:0, palmitic acid (PA, 22.64+/-0.01%), respectively. A commercial raw cocoa butter (CB) contained C18:0, stearic acid (SA, 33.13+/-0.04%), OA (32.52+/-0.03%), and PA (28.90+/-0.01%), respectively. Fatty acids at sn-2 position of RBOSF were OA (46.52+/-0.63%) and LA (42.98+/-1.1%), while major fatty acid at sn-2 position of CB was OA (85.24+/-1.22%). The RBOSF had low SA (2.40+/-0.01%) compared to CB (33.13+/-0.04%). The content of OA (46.52+/-0.63%) at sn-2 position in RBOSF was half of that found in CB (85.24+/-1.22%). Optimal reaction was 1:2:6 mole ratio of the substrate (RBOSF:PO:SAd), at 65 degC for 12 h. Fatty acid compositions of the SL were 31.72+/-0.99% SA, 30.91+/-0.53% LA, 23.18+/-0.32% OA, and 13.26+/-0.34% PA, respectively. Fatty acids at sn-2 position of the SL were 53.72+/-4.21% OA, 25.11+/-3.69% LA, 14.18+/-1.58% PA, and 6.99+/-0.02% SA, respectively. DSC curves showed the melting point of CB at 20.94 degC, while those of the SL were 14.15 and 40.35 degC, respectively. The melting completion temperature (T(mc)) of CB was 25.5 degC while that of SL was 43.9 degC, respectively.