TGase-induced crosslinking of mulberry leaf protein particles as stabilizer of high-internal-phase Pickering emulsions: characterization and stability.

Abstract

Background: Mulberry leaf protein (MLP) is a high-quality protein with significant nutritional value and functional properties. Enzymatic modification of proteins can enhance their functional properties by using proteases to covalently crosslink or hydrolyze proteins. This study investigates the potential of transglutaminase (TGase)-induced crosslinked MLP as an emulsifier in the formation of high-internal-phase Pickering emulsions.

Results: Crosslinked MLP samples were prepared with TGase concentrations ranging from 0 to 25 U g^-1. High-internal-phase Pickering emulsions (80% v/v) were formed at pH 8, with a crosslinking temperature of 50 °C, a TGase concentration of 20 U g^-1 and an optimal crosslinking time of 60 min. As the enzyme concentration increased, the content of exposed sulfhydryl groups progressively increased, while the total free sulfhydryl content remained relatively stable. After varying crosslinking durations, both total free and exposed sulfhydryl group contents initially increased before declining. Additionally, the content of free amino groups in MLP gradually decreased with higher enzyme dosages and longer crosslinking times. The surface hydrophobicity of crosslinked MLP increased initially, followed by a decrease, reflecting changes in the spatial structure of MLP. SDS-PAGE analysis confirmed the formation of polymer masses after TGase-catalyzed crosslinking. Under optimal crosslinking conditions, the high-internal-phase Pickering emulsion prepared with TGase-induced crosslinked MLP exhibited a relatively uniform droplet distribution.

Conclusion: TGase-induced crosslinking enhances both the emulsifying activity and stability of MLP emulsions. © 2025 Society of Chemical Industry.