Development of double network gels based on soy protein isolate and sugar beet pectin induced by thermal treatment and laccase catalysis

•Laccase catalysis and thermal treatment were adopted to establish double-network gel.•The microstructure was improved greatly after the formation of double-network gel.•Double-network gel showed better WHC properties than single network gel.•Double-network gel showed better mechanical properties than single network gel.•The tertiary and secondary structure of SPI changed after covalent cross-linking with SBP. Soy protein isolate (SPI) and sugar beet pectin (SBP) were adopted to fabricate double network (DN) gels via thermal treatment and laccase-catalysis. The concentrations of SBP (0.5%–2.5%, w/w) and SPI (4%–8%, w/w) were evaluated. DN gels showed higher holding water capacity (WHC, above 83%), compared with SBP single gel (75.96%). The presence of SPI improved the mechanical properties of gels significantly. Apparent phase separation could be observed when SPI concentration was 4%. Moreover, interpenetrating networks gradually formed with the increase of SPI concentration. The favorable structural heterogeneity and mechanical integrity derived from these polymers might be mainly responsible for the enhancement of the mechanical properties. The presence of SBP and laccase could improve the β-sheet amounts of SPI and make it form more rigid structure according to the results of circular dichroism (CD) and fluorescence spectra. The excellent performance of DN gels could enable the delivery of various components.