Extraction and Properties of Soy Protein from Heat-denatured Soy Meal Using Enzyme-Assisted Subcritical Water Treatment
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Abstract:
The extraction process to obtain soy protein isolate (SPI) was optimized from heat-denatured soy meal (TDSM) by using enzyme-assisted subcritical water treatment. The physicochemical properties, structural properties, and antioxidant activity of SPI were investigated. The results showed that with the addition of β-glucosidase to TDSM, the isoflavone in glucoside form in TDSM was converted to the aglycone form, which showed higher biological activity. Subcritical water treatment increased the water solubilities of SPI and soybean isoflavone and strengthened the hydrophobic interactions between them, thus producing a form of aglycone-enriched SPI. While soybean cellulose was partially hydrolyzed into reducing sugar by β-glucosidase, high temperature and high humidity provided by the subcritical water treatment caused protein unfolding. Consequently, the surface hydrophobicity significantly increased, leading to the formation of soluble protein aggregates and causing the Maillard reaction. Enrichment of the isoflavone in the aglycone form in TDSM and the formation of grafting products may enhanced the DPPH and ABTS free-radical scavenging activities of the protein.
