Counter-current carbon dioxide extraction of fat from soy skim

Abstract

This research aims to investigate the use of counter-current carbon dioxide extraction method as a means to reduce residual fat in soy skim after the enzyme-assisted aqueous extraction of soybeans. Extractions with liquid CO2 at 25°C and 10.34MPa and supercritical CO2 at 50°C and 25.16MPa are compared. The effects of solvent-to-feed ratio (2.5–10), addition of ethanol as a modifier (5% w/w) and introductions of packing in the column are also analyzed. Results show that the highest reduction of fat content is obtained without modifier and with packing in the column at 50°C and 25.16MPa. At these conditions, the total fat content present in soy skim was reduced from 4.4 to 0.7%, with the protein content practically unaffected. ANOVA was applied to determine effects on fat and protein in soy skim, being the addition of packing in the column the most significant one. The fatty acid profile was also analyzed, with C18:2 being the predominant fatty acid present in all the soy skim samples. Gel electrophoresis indicated that supercritical CO2 settings did not affect the polypeptide band patterns; however, higher pressure, temperature, and CO2 flow significantly increased protein solubility in aqueous media (pH 2–10) compared with un-treated samples.