Gel-like emulsions stabilized by tyrosinase-crosslinked potato and zein proteins

The increasing preference of vegetarian and vegan diets has led to the development of new and diverse food formulations based on plant proteins with high nutritive value. Industrial side-products such as functional potato proteins and non-functional corn zein fractions are promising sources of protein in food application. This study demonstrates for the first time the functionalization of zein in concentrated oil-in-water emulsions. Emulsions comprising 40% oil were fabricated using enzymatic crosslinking of potato protein (PP) solubilized in the aqueous phase and zein solubilized in the oil phase. Emulsions were characterized by their droplet size distribution, rheological behavior, creaming resistance, texture profile analysis and microstructure. The present study demonstrated that TyrBm (tyrosinase from Bacillus megaterium) plays a crucial role in the gel-like structure formation of zein-PP stabilized emulsions. The TyrBm-crosslinked emulsion was stable over a month without noticeable separation, compared to the non-crosslinked emulsion. Crosslinked zein-PP emulsions presented 10-fold larger particle size in the form of covalent aggregates, 2-fold increase in hardness, 3-log higher storage modulus, 40-fold higher viscosity and were devoid of sedimentation in comparison with the non-crosslinked control. The increase in stability is attributed to the formation of covalent bonds between potato low molecular weight proteins and α-zein fractions, as observed by SDS-PAGE analysis. Zein fractions and PP complement each other in their amino acid composition. TyrBm-crosslinking assisted in the formation of a novel texture, potentially leading to a wide variety of non-meat foods such as cheeses, creams, meat replacements, spreads, mousses, and dressings.