Background: Transglutaminase (TGase) is a heat-resistant biocatalyst with strong catalytic activity, which functions effectively under moderate temperature and pH conditions, and is used widely in protein cross-linking and recombination. Transglutaminase cross-linking is a novel and specific modification method for black bean protein isolate (BBPI). This article investigates the effect of transglutaminase cross-linking on the structure and emulsification performance of heated BBPI.
Results: Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that heated BBPI with TGase had a higher molecular weight than heated BBPI without TGase, and the protein bands widened with increasing enzyme activity, indicating that TGase cross-linking promoted protein molecule aggregation. A high molecular weight polymer can better stabilize the oil-water interface, preventing the emulsion from layering. Fourier transform infrared (FTIR) spectroscopy showed that the α-helix content decreased from 15.64% to 13.75%, and the β-sheet content increased from 48.13% to 54.08%. The decrease in α-helix content and increase in β-sheet content could make the structure more stable and improve the emulsifying properties of heated BBPI. When TGase was 20 U g-1, the protein emulsification activity index (EAI) reached its highest value of 1.87 m2 g-1, and the emulsification stability index (ESI) value was 0.27 min (P < 0.05); these figures were 0.19 m2 g-1, and 0.07 min higher, respectively, than in the sample without added TGase.
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