Effect of freeze-thaw treatment on the structure and texture of soy protein-dextran conjugate gels crosslinked by transglutaminase

Abstract This study aimed to investigate the effects of freeze-thaw treatment on the structure and texture of transglutaminase crosslinked soy protein isolate gels with glycated modifications. Different mass ratios (1:1, 2:1, 3:1 and 4:1) of a soy protein isolate/dextran mixture (SPI + D) and the structural properties and gel texture of a soy protein isolate-dextran conjugate (SPI-D) were investigated. The results showed that the degree of grafting increased with increasing dextran content and was maximized when SPI:D was 1:1 (16.51%). The SDS-PAGE results showed that the glycation reaction generated glycoprotein. Fluorescence spectroscopy and surface hydrophobicity results confirmed the change in the structure of the soy protein isolate. The SPI-D (2:1) gel exhibited the highest water holding capacity, with values of 90.33%, 68.67%, 60.11% and 58.49% at 0, 1, 3 and 5 freeze-thaw cycles (FTCs), respectively. Scanning electron microscopy results showed that the structure of the SPI-D gel was uniform and more regular after being subjected to FTCs. The hardness and gumminess of all experimental groups increased with the increasing number of FTCs. Glycation could reduce the degree of SPI gel soluble protein reduction during freezing and thawing.