Microbial Transglutaminase Cross-Linking Enhances the Textural and Rheological Properties of the Surimi-like Gels Made from Alkali-Extracted Protein Isolate from Catfish Byproducts and the Role of Disulfide Bonds in Gelling

Authors: ZHANG, YAM - Mississippi State University; CHANG, SAM - Mississippi State University

Submitted to: Journal of Functional Foods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2023
Publication Date: 5/17/2023
Citation: Zhang, Y., Chang, S. 2023. Microbial Transglutaminase Cross-Linking Enhances the Textural and Rheological Properties of the Surimi-like Gels Made from Alkali-Extracted Protein Isolate from Catfish Byproducts and the Role of Disulfide Bonds in Gelling. Journal of Functional Foods. 12(10):2029. https://doi.org/10.3390/foods12102029.
DOI: https://doi.org/10.3390/foods12102029

Interpretive Summary: Gels made from catfish byproduct protein isolate tend to be brittle and lack elasticity. Adding varying levels of microbial transglutaminase (MTGase) improved texture significantly, but higher levels didn't enhance it further. Compared to gels from fillet mince, protein isolate gels still lacked cohesiveness. While a setting step benefited fillet mince gels, it worsened protein isolate gels due to protease-induced protein degradation. Protein isolate gels showed higher solubility in reducing solutions, indicating the importance of disulfide bonds in gelation. The distinct properties of fillet mince and protein isolate were due to differences in protein composition and structure. MTGase inhibited proteolysis but didn't fully address protein isolate's susceptibility to it during gelation. Future research should explore additional enzyme inhibitory agents to improve gel texture alongside MTGase.

Technical Abstract: The texture of surimi-like gels made from the protein isolate extracted from catfish byproducts has been proven to be brittle and lack elasticity. To address this issue, varying levels of microbial transglutaminase (MTGase) from 0.1 to 0.6 units/g were applied. MTGase had little effect on the color profile of gels. When MTGase at 0.5 units/g was employed, hardness, cohesiveness, springiness, chewiness, resilience, fracturablity, and deformation were increased by 218, 55, 12, 451, 115, 446, and 71%, respectively. A further increase in added MTGase did not lead to any textural improvement. In comparison to the gels made from fillet mince, the gels made from protein isolate were still lower in cohesiveness. Due to the activated endogenous transglutaminase, a setting step enhanced the textural properties of gels made from fillet mince. However, because of the endogenous proteases-induced protein degradation, the setting step led to a texture deterioration of the gels made from protein isolate. Gels made from protein isolate showed 23–55% higher solubility in reducing solution than in non-reducing solution, suggesting the vital role of disulfide bonds in the gelation process. Due to the different protein composition and conformation, fillet mince and protein isolate exhibited distinct rheological properties. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed the highly denatured protein isolate was susceptible to proteolysis and prone to disulfide formation during the gelation process. It also revealed that MTGase had an inhibitory effect on the proteolysis induced by endogenous enzymes. In view of the susceptibility of the protein isolate to proteolysis during gelation, future research should consider including other enzyme inhibitory agents in the presence of MTGase to improve the gel texture.