Soy proteins are widely applied in food products, due to their high nutritive value and ability to improve texture. Nevertheless, there is constant need for biocatalytic reactions that can modulate food functionality. This work is aimed at improving the functionality of soy proteins in order to facilitate their diverse applications in foods. To this end, we utilized a tyrosinase from Bacillus megaterium (TyrBm) isolated and characterized in our lab. We investigated the impact of TyrBm cross-linking on emulsions and gels formed from soy glycinin. Findings show that high-molecular weight fractions of glycinin were formed after incubation with TyrBm as demonstrated by SDS-PAGE. Native and crosslinked proteins were used to fabricate emulsions using high-pressure homogenization. Those were studied for their physical stability, particle size, viscosity and structure. Results elucidate that improved physical stability can be achieved when crosslinking is performed after homogenization. Particle size increased indicating the formation of flocs, formed by covalent bond between the peptides. This was in contrary to the decrease in creaming velocity and was explained by the rise in the emulsion viscosity as a result of the crosslinking reaction. Fluorescence microscopy revealed local gel-like structures formed by TyrBm activity. By introducing the enzymatic crosslinking to the protein network we can achieve a cold-set gelation process. The novel cold-set process can enable the encapsulation and delivery of sensitive substances as oils, flavor and aroma molecules.
