Roles of four enzyme crosslinks on structural, thermal and gel properties of potato proteins

To form effectively the three-dimensional network structure of potato protein, transglutaminase, laccase, tyrosinase or peroxidase was used to catalyse the covalent crosslinking of protein, respectively, and the structural, crystalline, thermal and gel properties of enzyme-treated proteins were compared. The results indicated that compared to native protein, random coil remarkably reduced by over 50% and beta-sheet content, antiparallel beta-sheet and beta-turn increased by over 30%, 65% and 45%, respectively. The relative crystallinities increased from 7.5 to 8.6-11.8% after enzyme treatments. Enzyme-treated proteins had the higher thermal degradation temperatures (326.91-336.68 degrees C) and residue quantity (26.05-28.75%), and lower weight loss (68.43-70.13%) than native protein (322.32 degrees C, 71.72% and 21.80%). Transglutaminase- and peroxidase-treated protein gels displayed the more homogeneous three-dimensional networks with the larger pore sizes, whereas laccase- and tyrosinase-treated protein gels exhibited the less homogeneous networks with the smaller pore sizes. Similarly, the first two protein gels had higher storage modulus and stronger gel strength, whereas the latter two protein gels had lower storage modulus and weaker gel strength. The outcome may offer a significative insight on the theoretical basis to purposefully change structural, thermal and gel properties of potato protein in exploring novel potato staple foods with high qualifies.