Extensive work has been done on the functional and chemical aspects of protein cross-linking using enzymes such a transglutaminases and peroxidases in food manufacturing. However, there is a constant need for novel enzymes that offer new pathways for effective and specific bio-catalysis of reactions that can modulate the functionality of food ingredients.
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, for its polyphenol oxidase activity forming o-diphenols and o-quinones (1, 2). The present study investigated the impact of TyrBm on cross-linking glycinin and β-conglycinin, thereby modulating their gelation and emulsifying properties.
Findings show that high-molecular weight fractions of glycinin were formed in the presence of a low molecular weight phenolic reagent as demonstrated by SDS-PAGE analyses, dynamic light scattering and static light scattering. Gelation data revealed that cross-linked glycinin heat-induced gels were firmer, as discovered using a texture analyzer, and had a better water capacity compared to the untreated glycinin gel. In terms of emulsification properties, proteins and cross linked proteins were used to fabricate emulsions using high pressure homogenization (20kPsi). These were studied for their physical stability using accelerated stability tests performed on an analytical centrifuge (LUMisizer, LUM GmbH). Space- and time-resolved transmission extinction profiles were recorded at 500g over periods exceeding 5h. This data was used to elucidate that a lower creaming velocity can be achieved when using enzymatically-treated glycinin as an emulsifier.
Prof. Ayelet Fishman afishman@tx.technion.ac.il
References:
1. Sendovski, M., Kanteev, R., Shuster Ben-Yosef, V., Adir, N., and Fishman, A. (2011) First structures of Bacillus megaterium tyrosinase reveal plasticity in copper binding. J. Mol. Biol. 405:227-237.
2. Goldfeder, M., Egozi, M., Shuster Ben-Yosef, V., Adir, N. and Fishman, A. (2013) Changes in tyrosinase specificity by ionic liquids and SDS. Appl. Microbiol. Biotechnol. 97:1953-1961.
