Enzymatic pre-treatment defines the water-binding and rheological properties of dynamic ultra-high-pressure homogenised pea hull suspensions

Abstract

Pulse hulls are composed of cell wall polysaccharides and are a concentrated source of dietary fibre. However, the dense microstructure hinders their industrial application, resulting in poor techno-functional properties. To improve their functionality, the cell wall (cellulose, hemicellulose, and pectin) is disrupted by combining enzymatic pre-treatments and microfluidization. This work aims to study the impact of a fixed reduction of the insoluble mass by selective enzymatic pre-treatment of pulse hulls on the composition, microstructure, water binding, and rheological properties of microfluidized suspensions. To that end, enzymatic pre-treatments using cellulase, hemicellulase, pectinase, and their binary and ternary mixtures were conducted to reduce insoluble mass content. The combined treatment improved the water-binding properties, leading to the formation of viscoelastic gels. Microfluidized suspensions enzymatically pre-treated with a binary mixture of cellulase and hemicellulase presented the highest water binding capacity, viscosity, and viscoelasticity. The partial enzymatic degradation of the cellulose-hemicellulose network weakened the interactions between both polysaccharides. It facilitates the disruption of the particles and the release of high molecular weight soluble dietary fibre (HMWSDF), which are gelling substances. On the contrary, an enzymatic pre-treatment using only cellulase increased the content of low molecular weight soluble compounds, resulting in low viscous and viscoelastic suspensions. Thus, the concentration of remaining microfibrillated cellulose and HMWSDF are key parameters controlling the rheological behaviour of the suspensions. This study enhances comprehension regarding pea hulls' molecular and macromolecular modifications, potentially enabling the production of tailor-made pulse hull suspensions.