Enhancing rheological and textural properties of pea protein-collagen gels via transglutaminase crosslinking

Plant-based proteins are gaining attention in the food industry as a healthier and more sustainable alternative to animal proteins due to health concerns, growing global population, water scarcity and climate change. However, controlling their structural and textural characteristics is still a challenge. Combining plant-based proteins with other substances is an effective method for modifying their gelation and textural properties. An enzymatic crosslinking agent, transglutaminase (TG), was herein employed to enhance the gel strength of a mixture consisting of pea protein isolate (PPI) (50 mg/mL) and collagen (3 mg/mL). Rheological oscillatory time sweep analysis showed an enhancement in gel strength of the PPI and collagen gel compared to PPI alone, and even more so after treatment with the cross-linking enzyme. Scanning electron microscopy imaging provided evidence for the formation of gel networks and crosslinks when the protein mixture was treated with low concentrations (2.5 U/mL) of TG, whereas high TG loading (18 U/mL) caused protein phase separation. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis analysis also showed formation of higher molecular weight bands after TG crosslinking. Particle sizes of the PPI and collagen mixture after TG treatment were larger than without TG. In addition, sodium chloride (150 mM) addition significantly improved the gel strength of PPI collagen gels crosslinked by TG. In conclusion, TG with or without salt can be utilized to enhance the strength of PPI and low concentration collagen gels.