Effect of microbial transglutaminase crosslinking time on the structural, physicochemical and gelling properties of black soldier fly larvae protein: a texturization strategy for sustainable alternative proteins

Abstract

Growing population pressures and envionmental concerns over conventional proteins have driven interest in sustainable alternatives such as black soldier fly larvae (BSFL) for texturized insect-based foods. However, the utilization of BSFL protein in food applications is limited and requires an understanding of its structural and functional properties, as well as the effects of processing conditions. This study investigates the effect of microbial transglutaminase (MTG)-catalysed crosslinking on the structural, physicochemical and gelling properties of BSFL protein. BSFL protein dispersions were subjected to different incubation times, ranging from 0.5 h to 24 h to achieve varying degrees of crosslinking. The results showed a consistent increase in the crosslinking degree with incubation time, with the highest level attained after 24 h. The progressive crosslinking of BSFL protein increased particle size but a smaller-sized population emerged after prolonged incubation for 20 h and 24 h. SDS-PAGE showed that 0.5 h to 24 h of MTG treatment resulted in the formation of high molecular weight aggregates (>250 kDa). Progressive reduction in sulfhydryl content and surface hydrophobicity with increasing incubation time indicates that MTG-induced crosslinking caused burial of sulfhydryl groups and hydrophobic residues within the protein network. FTIR analysis revealed that MTG-treated samples exhibit higher β-sheet content, suggesting structural reorganisation towards a more ordered conformation upon MTG-induced crosslinking. Functionally, MTG incubation time for 20 h yielded a BSFL protein network with the highest gel strength and water holding capacity. Extended incubation for 24 h started to compromise the gel strength and WHC. Overall, this study highlights the time-dependent nature of MTG-induced structural modifications and the gelling mechanism. It is important for laying the groundwork for manipulating the gelling properties of BSFL protein and the development of texturized BSFL protein-based insect-based foods, which could advance the utilisation of BSFL protein as a sustainable alternative protein.