|M.Sc Student||Davidesko Ilil|
|Subject||Enzyme Mediated Crosslinked Zein for Food Applications|
|Department||Department of Biotechnology and Food Engineering||Supervisor||Professor Ayelet Fishman|
|Full Thesis text|
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, along with pea and chickpea proteins are promising sources of protein in food applications. The main goal of this research was to improve the functionality of zein, a by-product of the starch industry, by enzyme-mediated covalent crosslinking, and to enable its usage in food applications. 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) or pea protein 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 demonstrates that TyrBm (tyrosinase from Bacillus megaterium) plays a crucial role in the gel-like structure formation of zein-PP or zein-pea protein 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 a 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. TyrBm-crosslinked zein-pea protein stabilized emulsions showed a 2.3-fold larger droplet size. Additionally, the presence of TyrBm led to better stability, increased viscosity and paste like structure compared to zein-pea protein emulsion without TyrBm. Zein and PP or pea protein complement each other in their amino acid composition and thus provide complete nutritional value to consumers. TyrBm-crosslinking assisted in the formation of a novel texture, potentially leading to a wide variety of non-meat foods such as cheese replacements, creams, meat substitutes, spreads, mousses, and dressings.