Performance of sonic assisted solvent mimicry using water on ginger bioactive compounds extraction

Abstract

The uses of water in subcritical conditions have several drawbacks, which include safety features, increase of production costs and possible degradation of bioactive compounds due to high operating conditions. To overcome these problems, sonic energy and entrainer were used as external interventions in decreasing the dielectric constant of water at milder operating conditions. The extraction efficiencies were compared and related to the solubility curve of ginger bioactive compounds in hot water, which was calculated using conductor-like screening model for real solvents (COSMO-RS). A sonic-assisted water extraction (SAWE) prototype with 1.5 liter capacity was designed and fabricated using a high frequency sonication probe (800kHz, Shinka Industry Co., Japan). The effect of low (28 kHz) and high (800 kHz) frequencies of sonication in the extraction of four major ginger bioactive compounds (6-, 8-, 10-gingerol, and 6-shogaol) were compared. Six parameters were studied, which were mean particle size (MPS, mm), time of extraction (15 to 60 minutes), applied power (40 to 80 Watt), sample to solvent ratio (w/v), temperature of extraction (25 to 45 oC), and the percentage of entrainer (5 to 15 %, v/v). The optimum conditions for the high frequency SAWE prototype were MPS 0.89- 1.77mm, 45 minutes, 40W applied power, 1:30 (w/v) and 45 minutes. The concentration and recovery of 6-gingerol from the high frequency of the SAWE prototype was 2.69 times higher than the low frequency of SAWE at the optimum conditions. The performance of high frequency SAWE was improved with a pump around process with distilled water (13.0681±0.0210mg/g), which was slightly higher than with 10% ethanol as the solvent in the batch system (12.9733±0.3186mg/g) for 6-gingerol extract. It was found that milder operating conditions can be achieved using high frequency SAWE compared to subcritical water extraction (135- 200oC, 0.1 MPa).