Miao Fu1, Xin-Huai Zhao1,2. 1. Key Laboratory of Dairy Science, Ministry of Education, Northeast Agricultural University, 150030, Harbin, PR China. 2. Synergetic Innovation Center of Food Safety and Nutrition, Northeast Agricultural University, 150030, Harbin, PR China.
Abstract
BACKGROUND: Soy 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. RESULTS: GC-SPI contained glucosamine of 13.6 g kg-1 protein, but less reactable &bond;NH2 than SPI (0.42 vs. 0.50 mol kg-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. 82.9 nm) 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 °C. GC-SPI also had lower in vitro proteolytic digestibility than SPI due to the protein cross-linking. CONCLUSION: Oligochitosan 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.
BACKGROUND: Soy 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. RESULTS: GC-SPI contained glucosamine of 13.6 g kg-1 protein, but less reactable &bond;NH2 than SPI (0.42 vs. 0.50 mol kg-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. 82.9 nm) 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 °C. GC-SPI also had lower in vitro proteolytic digestibility than SPI due to the protein cross-linking. CONCLUSION:Oligochitosan 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.