Enzymatic Production of Trans-Free Hard Fat Stock from Fractionated Rice Bran Oil, Fully Hydrogenated Soybean Oil, and Conjugated Linoleic Acid

ABSTRACT:  Rice bran oil (RBO) was fractionated into 2 phases, solid (S-RBO) and liquid (L-RBO), using acetone at –18 °C and the weight yield of each S-RBO and L-RBO was 45.5% and 54.5%, respectively. Then, trans -free hard fat was synthesized from trans -free substrate of S-RBO and fully hydrogenated soybean oil (FHSBO) at different molar ratios (S-RBO : FHSBO; 1 : 1, 1 : 1.5, 1 : 2, and 1 : 3) with Lipozyme TL IM lipase (10% of total substrate). Conjugated linoleic acid (CLA, 20% of total substrate) was used as functional fatty acids for the production of trans- free hard fat. After fatty acid analysis, CLA (12.2% to 14.2%) was found on the triacylglycerol (TAG) backbone of the interesterified products along with stearic (37.6% to 49%), palmitic (15% to 17.9%), and oleic acids (13.3% to 19.2%). The interesterified product contained higher level of saturated fatty acid (62.6% to 70.1%) at sn -2 position. Total tocopherols (α-, γ-, and δ-; 1.4 to 2.6 mg/100 g) and phytosterols (campesterol, stigmasterol, and β-sitosterol; 220.5 to 362.7 mg/100 g) were found in the interesterified products. From DSC results, solid fat contents of the interesterified products (S-RBO : FHSBO 1 : 1, 1 : 1.5, 1 : 2, and 1 : 3) at 25 °C were 23.1%, 27%, 30.1%, and 44.9%. The interesterified products consisted mostly of β' form crystal with a small portion of β form. The interesterified product (S-RBO : FHSBO 1 : 1.5) was softer than the physical blend but slightly harder than commercial shortenings as measured by texture analyzer. Thus, trans- free hard fat stock, which may have a potential functionality could be produced with various physical properties.