Insights into transglutaminase on structural and rheological properties of gels from adzuki bean protein pretreated by electric fields

The demand for protein is increasing as the global population continues to grow. The plant protein has been favored and plant-based food has become a research hotspot for healthy diet, environmental protection, animal ethics and other issues. Adzuki bean protein (ABP) is a quality source with complete amino acids, abundant essential amino acids and beanless flavour. ABP is rich in glutamine and lysine which are good substrates for transaminase (TGase) induced gelation. The pulsed electric field (PEF), alternating current EF (ACEF), direct current EF (DCEF) were applied to pretreat ABP aiming at improving the efficacy of TGase induced crosslinking. The results showed that the TGase decreased the free amino amount significantly and increased the molecular weight of ABP. The EF pretreatments significantly influenced the secondary and tertiary structures of ABP with a decrease in β-sheets, increase in random coils, β-turns, and α-helices, also decrease in fluorescence intensity with blueshift. The content of disulfide bond increased with the decrease of free sulfhydryl groups. The ionic bonds decreased and hydrophobic actions surpassed significantly hydrogen bonds. The hydrophobicity increased. The electric field intensity corresponded to variation of microstructure, texture and rheological behaviour of the ABP gel according to the type of the EF.