Regioselective enzymatic hydrolysis of blackcurrant seed oil in supercritical CO2

Continuous flow hydrolysis of blackcurrant seed oil dissolved in supercritical carbon dioxide (scCO(2)) was catalyzed by immobilized lipase Lipozyme TL IM. HPLC-MS and acid-base titration were used to determine composition of oil and hydrolysis products comprised of tri-, di- and monoglycerides, free fatty acids and glycerol. The oil contained 10 % linolenic and 2 % stearidonic fatty acids (omega-3), 51 % linoleic and 19 % gamma-linolenic fatty acids (omega-6), 12 % oleic acid, 5 % palmitic acid, and 1% stearic acid. Effects of enzyme load (17-500 mg), pressure (15-30 MPa), temperature (30-50 degrees C), and CO2 flow rate (0.2-4 g/min) on the conversion were evaluated. The reaction was reversible and the time to reach steady state was enzyme load-dependent and took up to 200 min. A slight drop of enzyme activity after four experimental runs and total reaction time 17 h was indicated by the decrease of free fatty acid content in the product from 0.72 % to 0.69 %. Due to the regioselectivity of lipase-catalyzed hydrolysis, the omega-3/omega-6 ratio was increased from 17:83 in oil to 23:77 in produced diglycerides.