Ohmic heating treatment for Gac aril oil extraction: Effects on extraction efficiency, physical properties and some bioactive compounds

The effects of ohmic heating on Gac aril oil extraction in comparison with conventional heating were studied. The experiments were conducted using three extraction stages with the selected ratio of Gac aril powder to n-hexane (solvent) and time for each stage of 1:7 (7 h), 1:6 (6 h) and 1:5 (5 h), respectively. The aims were to (1) study the possibility of applying ohmic method in Gac aril oil extraction and (2) compare between oil extraction using ohmic and conventional treatments. It appeared that the electrical conductivities of fresh Gac aril, Gac aril powder with water and Gac aril powder with hexane ranged between 0.54 and 1.16, 0.50-1.46 and 0.18-031 S.m(-1) respectively. The extraction efficiency, color characteristics and the contents of beta-carotene and lycopene of Gac aril oil were enhanced by extraction with ohmic method. Three extraction stages with ohmic heating treatment at 50 degrees C in all stages resulted in the highest extraction efficiency (81.40%). The SEM micrographs proved that the cell wall of the Gac aril powder after extraction with ohmic heating was more ruptured than that of conventional heating. Physical properties of Gac aril powder and residues collected from different extraction methods were diverse due to their dissimilar compositions and structures. (C) 2017 Elsevier Ltd. All rights reserved.