Thermal and crystal characteristics of enzymatically interesterified fats of fatty acid-balanced oil and fully hydrogenated soybean oil in supercritical CO2 system

Blends of fatty acid-balanced oil that was prepared by the aqueous enzymatic extraction, and with fully hydrogenated soybean oil in different weight ratios from 30:70 to 80:20 (wt%) were interesterified using Lipozyme RM IM in a supercritical CO₂ system. The optimal immobilized enzyme dosage, pressure, substrate ratio, temperature, and time were 6% (w/w) of initial substrates, 8 MPa, blend ratio with 60:40 (wt%) of fatty acid-balanced oil and fully hydrogenated soybean oil, a temperature of 70°C, and reaction time of 2 h, respectively. It was observed that at the optimal conditions, under supercritical CO₂ conditions, the reaction time of the interesterification was shorter than that of conventional enzymatic interesterification. The slip melting point, solid fat content, fatty acid composition, differential scanning calorimetry, polymorphic form and crystal morphology of the enzymatically interesterified fats were evaluated. The results indicated that the interesterified fats showed desirable physical properties with lower slip melting point and solid fat content, suitable crystal form (β′ polymorph), and without trans-fatty acid for possible use as a shortening and margarine stock.