Substrates emulsification process to improve lipase-catalyzed sardine oil glycerolysis in different systems. Evaluation of lipid oxidation of the reaction products

•Emulsified substrates improve the initial rate in solvent-free glycerolysis.•The use of SC-CO2 presents no kinetic advantages in glycerolysis reaction.•Hydroperoxides are adsorbed on the lipase support.•Sorption of hydroperoxide is favored at high reaction temperatures.

Mono- and diacylglycerols rich in omega-3 have a great interest due to their good bioavailability and oxidation stability compared with other kind of omega-3 concentrates. The main drawback in mono- and diacylglycerols production by glycerolysis is the immiscibility of the substrates, oil and glycerol. To improve mass transfer rates, avoiding the use of organic solvents, emulsification of both reactants as reverse micelles (glycerol-in-oil) was carried out previous to lipase-catalyzed sardine oil glycerolysis. Substrate emulsification yielded higher reaction rates compared to kinetics with no previous emulsification, but still lower than in organic solvents. To avoid the use of organic solvent, SC-CO2 was used as reaction medium but no kinetic advantages were demonstrated in the pressure range from 15 to 25 MPa. By increasing temperature, from 40 to 90 °C, reaction rates increased both in a solvent-free system and in SC-CO2 medium. It was also found that an increase in temperature does not lead to an increase in the final oxidation status of the reaction products. This behavior was due to the adsorption capacity of the Lipozyme 435 support, giving lower oxidation status at the highest temperature, 80-90 °C.

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