Effect of ohmic heating on the extraction of biocompounds from aqueous and ethanolic suspensions of Pavlova gyrans

Abstract

Electric field technology has been highlighted as a promising strategy in the permeabilization of cell membranes and the corresponding bioactive release. In this work, aqueous and ethanolic suspensions of Pavlova gyrans were subjected to moderate electric fields (MEF) to promote rapid heating due to Ohmic Heating (OH) effect. Two approaches were tested: i) OH assisted extraction in a temperature range between 25 ºC and 85 ºC, and ii) OH pretreatment at 25 ºC and 55 ºC followed by solvent extraction. OH treatment at 55 ºC (performed in less than 10 s) in aqueous suspensions promoted a marked increase in the release of organic matter (2.1-fold), chlorophyll a (41.1-fold) and total carotenoids (56.6-fold) when compared to the freeze-thaw cycles (FTC ≈ 3 hours). OH-pretreated biomass subjected to a two-step passive extraction improved the release of proteins and chlorophylls over incubation (p < 0.05) when compared to untreated biomass. This procedure increased 2.2-, 3.9- and 31.9-fold the content of organic matter, protein and chlorophyll a, respectively, in comparison to the FTC procedure. This work presented the OH effect as a promising strategy for enhanced disruption and release of intracellular microalgae compounds.