Gelation profile of laccase-crosslinked Bambara groundnut (Vigna subterranea) protein isolate

Enzymatic crosslinking has gained attention in improving plant protein heat-induced gels, which are composed of weak network structures. The aim of the study was to investigate the effect of laccase crosslinking on the rheological and microstructural properties of heat-induced Bambara groundnut protein gels. The rheological properties of laccase-modified Bambara groundnut protein isolate (BPI1) gel formed in situ were investigated. Changes in viscoelastic properties were monitored during heating and cooling ramps and gel structure finger-prints were analyzed by frequency sweep. Laccase addition induced an initial protein structure breakdown (G ''>G ') at an enzyme dose-dependent (1-3 U/g) before gel formation and stabilization. Gel point temperatures were significantly decreased from 85 degrees C to 29 degrees C (similar to 3 folds) with increasing laccase activity (0 to 3 U/g protein, respectively). For laccase crosslinked gels, G ' was substantially greater than G (>1 log) with no dependency on angular frequency, which suggests the formation of relatively well-structured gels. The highest gel strength (tan delta of 0.09, G* of 555.51 kPa & An of 468.04 kPa) was recorded at a laccase activity of 2 U/g protein and the gels formed at this activity appeared homogeneous with compact lath sheet-like structure. The crosslinking effects of laccase were corroborated by the decrease in thiol and phenolic contents as well as the crosslinking of amino acids in model reactions. Overall, the use of laccase improved gel properties and significantly altered the gelation profile of BPI. Laccase-modified Bambara groundnut protein gels have potential to be used in food texture improvement and development of new food products. For instance, they can be used in plant-based milk products such as yoghurt and cheese.

Automated summary

The study investigates the effect of laccase crosslinking on the rheological and microstructural properties of heat-induced Bambara groundnut protein gels. The study finds that laccase addition can break down protein structure and significantly decrease the gel point temperatures. Laccase-crosslinked gels demonstrate good structural stability and high gel strength, showing potential for food texture improvement and development of new food products.