Physicochemical, morphological, and rheological properties of cellulose nanofibrils produced via ultra-high-pressure homogenization

Cellulose nanofibrils (CNFs) possess desirable properties, including low density, high tensile strength, large surface area, and high biodegradability, making them valuable for broad industrial applications. High-pressure homogenization is the most common processing method to produce CNFs. This study reports on the impact of ultra-high-pressure homogenization (UHPH) on the structural and technofunctional properties of CNFs, including their Pickering o/w emulsion stabilizing performance. Microcrystalline cellulose suspensions (0.5 % w/w) were processed at pressures ranging from 500 to 3500 bar for up to 25 passes. According to our findings, the size (fiber length and width) of the CNFs was reduced with pressure increase. The highest colloidal stability of cellulose suspensions was observed at ≥ 2500 bar for at least 5 passes. The viscosity of cellulose suspensions increased progressively with the severity of the UHPH. Dynamic rheological characterization of the cellulose suspensions processed for 25 cycles revealed a true gel-like behavior within the linear viscoelastic regime and a strain stiffening effect at large strains (> 10 %). The lipid droplet polydispersity and creaming index of Pickering emulsions were minimized using the 3500 bar processed CNFs. In conclusion, UHPH is an efficient method to induce the nanofibrillation of cellulose, and improve its techno-functionality.