Supercritical CO2 extraction of allicin from garlic flakes: Screening and kinetic studies

The nutraceutical industry is currently interested in obtaining garlic extracts using mild extraction processes to recover high levels of labile allicin. This work studied oleoresin yield and extraction selectivity for allicin in the supercritical CO2 extraction of freeze-dried aqueous garlic homogenate as a function of sample conditioning and process conditions. Agglomeration phenomena, which is responsible for substrate lumps in packed beds and flow channeling in the bed during extraction, was avoided by lowering sample moisture below 31 g kg(-1) water/substrate, and/or process temperature below 65 degrees C. Oleoresin yield increased slightly with extraction pressure (15-45 MPa) and dramatically with process temperature (35-65 degrees C), but the concentration of allicin in the extract decreased as the temperature increased. Thus, an optimal combination of intermediate temperature and pressure was selected that allowed reasonably large yields (>=-19 g kg(-1) oleoresin/substrate) and extraction selectivities (>= 75 mg kg(-1) allicin/oleoresin). Based on experimental results, a 4 h extraction process at 55 degrees C and 30 MPa using 55 kg kg(-1) CO2/substrate was recommended. Cumulative extraction plots for oleoresin and allicin were successfully adjusted using a linear driving force mass transfer model. (C) 2011 Elsevier Ltd. All rights reserved.