Preparation and characterisation of water dispersible cellulose nanocrystals (CNC) dry powder from potato waste pulp of the potato starch industry: effect of drying method

Abstract

This study introduces a novel and efficient dialysis-free methodology for isolating cellulose nanocrystal (CNC) powder from potato processing byproducts, employing sodium acetate (NaOAc) as a neutralising electrolyte. The NaOAc approach yielded 72.3 ± 2.1 % CNCs, a value competitive with the traditional sulfuric acid hydrolysis yield of 68.5 ± 3.4 %. This method significantly enhanced process efficiency, reducing the purification time by 48 h and decreasing total water consumption by approximately 60 % by eliminating the dialysis step. Sodium acetate effectively screened the negative surface charges of the CNCs, facilitating rapid precipitation governed by DLVO theory. The influence of downstream drying was critically evaluated: spray drying produced CNCs with superior water dispersibility, characterised by a mean redispersed particle size of 68 nm and a uniform morphology, while freeze drying provided CNCs with enhanced thermal stability (onset degradation temperature of 298 °C; peak at 353 °C). Structural analysis confirmed the preservation of cellulose Iβ crystallinity across all samples, with crystallinity indices inversely related to the drying intensity, ranging from 72.8 % (spray-dried) to 78.5 % (oven-dried). The NaOAc-assisted technique presents a scalable and economically viable solution for valorising potato waste into high-value CNCs, with the selection of drying method (spray vs. freeze) being guided by application-specific requirements for either colloidal dispersibility or thermal performance.