ENHANCEMENT OF THE BIOACTIVE AND NUTRITIONAL PROPERTIES OF SOY PROTEIN CONCENTRATE THROUGH THE USE OF ENZYME TECHNOLOGY

Abstract

Soybean, a protein-rich leguminous oilseed, is often unacceptable due to its taste, appearance, and smell. Enzymatic technologies offer an alternative to conventional chemical procedures for protein modification, allowing for accurate oversight and adjustment of reaction flow to desired nutritional and bioactive properties due to the high sensitivity of protease under mild reaction conditions. Herein, the feasibility of implementing a one- or two-step biotechnological process, triggered by commercial endo- and exo-peptidases, to enhance the nutritional and bioactive characteristics of soy protein concentrates (SPC), was investigated. Two nutritionally valuable fractions, the hydrolysate (liquid stream-fraction) and the ocara (solid stream-fraction), have been separated. The hydrolysates were characterized by examining the crude protein content, protein recovery, and free amino group content. The antioxidant activity was quantified by measuring superoxide radical inhibition, and metal-ion chelation. Commercial peptidases led to different reaction kinetics and protein recovery, resulting in different peptide profiles determined by dead-end ultrafiltration (3, 10, and 30 kDa) and subsequent gel-filtration chromatography using the Toyopearl HW40F resin. Enzymatic hydrolysis seemed to enhance the hydrolyzate's protein content while decreasing the ocara's protein content. The percentage of soluble protein recovered from SPC ranged between 68 and 82%, revealing that Flavourzyme was most suitable to solubilize SPC. The highest yield of hydrolyzed peptide bonds, correlated with higher antioxidant activity, was shown by Alcalase- Flavourzyme (~20%) as well as Neutrase-Flavourzyme (~21.5%), with a tendency to favor Neutrase due to more sensory-acceptable product. Each produced hydrolysate's amino acid content, sulfhydryl groups, and surface hydrophobicity have been examined, and substantial correlations with antioxidant activity have been found. Because the quantity of phytic acid and trypsin inhibitor, the principal anti-nutritional components of SPC, was greatly reduced by enzymatic hydrolysis, the ocara were classified as value-added byproducts. Neutrase- Flavourzyme hydrolyzate's antioxidant activity was attributed to its large proportion of peptide fractions below 3 kDa.