The effect of cross-linking degrees on physicochemical properties of surimi gel as affected by MTGase.

BACKGROUND The transglutaminase-induced cross-linking reaction could enhance the textural properties of surimi gels. However, when the cross-linking degree exceeded a certain range, surimi gels became brittle, giving the gel a special mouthfeel. Little information was found about the brittleness of surimi gel and its forming mechanism. The present study aimed to investigate the effects of cross-links on physicochemical properties of surimi gel and to analyze the reason for the texture variation of surimi gels regulated by cross-links. RESULTS When the cross-linking degree was lower than about 30%, the surimi gel could not be fractured and the surimi gel was mushy. When the cross-linking degree was around 40% to 55%, surimi gels without MTGase presented an elastic texture, while surimi gels with MTGase displayed a tough texture. When the cross-linking degrees were 64.1% and 76.5%, surimi gels were brittle. The water holding capacity decreased with the increase of cross-linking degrees and the cross-links released some combined water to free water. With the increase of cross-links, the pore equivalent diameter and the fractal dimension decreased first and then increased. When the cross-linking degree exceeded approximately 50%, the hydrophobic interaction increased, consistent with the exposure of hydrophobic residues and the decrease of the water gap between proteins. CONCLUSION The changes of gel texture were related to micro-network structure, water status, and microenvironment of proteins. It was demonstrated that the texture of slowly heated surimi-based products could be regulated by controlling the TGase-induced cross-links. This article is protected by copyright. All rights reserved.