Saline as solvent and ethanol-based purification process for the extraction of proteins and isoflavones from wet okara

Abstract

Okara, the solid byproduct of water-soluble soybean extract production, is a potential source of proteins and isoflavones. This study investigated different experimental configurations for extracting these compounds from wet okara, including lipid removal with ethanol at different stages of the recovery process, sequential crosscurrent extraction, and using a saline MgCl₂ solution as the solvent. Three washes with a 60:40 ethanol:water (w/w) solution after isoelectric precipitation significantly increased protein content by reducing lipid content (60 %). The crosscurrent approach using 0.05 M MgCl₂ yielded okara proteinaceous material with 248 µg/g daidzein and 236 µg/g genistein, along with a 3 % increase in protein content, attributed to enhanced extraction of 7S globulins. These configurations notably affected the functional properties of the protein materials. Overall, this research provides detailed insights into the composition and properties of proteins extracted from wet okara, facilitating their specialized application in food products.

Keywords: Alcoholic precipitation; Crosscurrent extraction; Daidzein; Functional properties; Genistein; Plant proteins.