Effect of konjac glucomannan with different degrees of deacetylation on the gel behavior of transglutaminase induced soybean protein isolate emulsion gels

Abstract

In this study, the effect of konjac glucomannan (KGM) with different degrees of deacetylation (DD) on the gel properties of transglutaminase induced soybean protein isolate (SPI) emulsion gel was investigated. It was found that the three kinds of KGM increased the breaking force and water holding capacity, enhanced the freeze-thaw stability of the SPI emulsion gel, while KGM with DD of 59% (DKGM1) improved these properties to the largest extent. This was because SPI-DKGM1 had the lowest oil water interfacial tension, resulting in the formation of the most uniform and the smallest oil droplets, which then led to the formation of much denser gel network. Moreover, the hydrophobic interaction and hydrogen bonding between DKGM1 and SPI were the strongest compared with that of other KGM. Besides, FTIR results showed that SPI-DKGM1 emulsion gel had higher β-sheet content, which was conductive to the formation of a stable three-dimensional network structure. However, the combination of SPI and KGM with high DD (DKGM2, DD = 92%) destroyed the gel structure to some extent and resulted in emulsion gel with weakened gel properties compared with that of DKGM1. Therefore, KGM with proper DD was conducive to the formation of more ordered and much denser gel network structure, which then resulted in SPI emulsion gel with the best gel properties.