Modified properties of a glycated and cross-linked soy protein isolate by transglutaminase and an oligochitosan of 5 kDa

BACKGROUNDSoy protein is an important protein ingredient for the food industry; however, its properties can be improved by enzymatic and chemical modifications. This study applied a new enzymatic glycation and cross-linking to modify soy protein isolate (SPI), using an oligochitosan of 5 kDa and transglutaminase. Properties of the obtained glycated and cross-linked SPI (GC-SPI) were unknown and thus assessed. RESULTSGC-SPI contained glucosamine of 13.6gkg(-1) protein, but less reactable & bond;NH2 than SPI (0.42 vs. 0.50molkg(-1) protein). Infrared spectra and circular dichroism results showed that GC-SPI other than SPI and cross-linked SPI had more & bond;OH in molecules, and was more disordered in secondary structure. In comparison with SPI, GC-SPI showed enhanced water-binding capacity, could form aggregates with enlarged hydrodynamic radius (180.2 vs. 82.9nm) and negative zeta-potential (-31.2 vs. -27.7 mV) in dispersion, but exhibited lower thermal stability (e.g. greater mass loss) upon heating at a temperature above 288 degrees C. GC-SPI also had lower in vitro proteolytic digestibility than SPI due to the protein cross-linking. CONCLUSIONOligochitosan of 5 kDa and transglutaminase can be used to glycate and cross-link SPI. This approach is applicable to generate potential protein ingredient with good hydration and dispersive stabilisation. (c) 2016 Society of Chemical Industry