Enzymatic hydrolysis as a tool for enhancing antioxidant capacity and sensory qualities of soy proteins

Introduction: Soy proteins are widely used in several food products in the forms of soy flour, soy protein concentrate (SPC) and soy protein isolate (SPI) to improve water and fat binding ability and improve nutritional content. Recent research efforts in this field continue to look at novel functional properties of soy proteins through physical, chemical or enzymatic modifications [1]. Although it has been demonstrated that the enzymatic hydrolysis of SPI is a suitable route to improve its antioxidant properties, there is a general lack of knowledge about the potential for beneficial effects of protease hydrolysis on soy products other than SPI, such as soy flour or SPC. The aim of this study was to investigate the antioxidant activities, and color of spray-dried hydrolysates of SPC obtained with several proteases. Materials and methods: A commercial SPC (protein content 71.24%) was a gift from the SOJAPROTEIN, Bečej. The proteases used were: alcalase® 2.4L, neutrase® 0.8L, papain, everlase 16.0 L (Sigma) and umamizyme (Amano Enzyme Inc). The antioxidant activity was tested by using several methods: DPPH, ABTS, and linoleic acid emulsion system [2]. Results: Process parameters like substrate concentration, E/S ratio, temperature, and DH have been optimized for each selected enzyme or their combination. The five proteolytic enzymes used for hydrolysis of SPC led to different reaction kinetics resulting also in different peptide profiles determined by gel filtration chromatography using Sephadex G-50. Conclusions: The alcalase hydrolysate seemed to be the most effective antioxidant determined by DPPH, ABTS, and linoleic acid emulsion system assays. The enzymatic hydrolysis in all cases resulted in an increase in the antioxidant activity of hydrolysate and all hydrolysates showed significantly changed color compared to SPC.