Dried water-redispersible bacterial nanocellulose with sorbitol as capping agent

Abstract

In view of the economic and technical limitations associated with diluted aqueous suspensions of cellulose nanofibrils, in the present contribution sorbitol was assayed as capping agent in the drying of bacterial nanocellulose (BNC) for the first time. The effect of different sorbitol:BNC mass ratios (1:1, 3:1 and 5:1), drying strategies (freeze-drying versus oven-drying), and redispersion methods (high-speed homogenization and mechanical stirring) on the water redispersibility of dried BNC was studied. Sedimentation, specific surface area and rheology assays all demonstrated the suitability of sorbitol for significantly limiting irreversible hydrogen bonding between adjacent cellulose nanofibrils during dehydration, leading to redispersed BNC suspensions with characteristics similar to those of never-dried ones. In the case of freeze-dried samples, results showed that the lowest sorbitol:BNC mass ratio assayed (i.e., 1:1) was enough to prevent irreversible hydrogen bonding between adjacent cellulose fibrils, whereas for oven-dried BNC samples full redispersion was achieved by mechanical stirring when sorbitol:BNC mass ratios of at least 3:1 were used. The feasibility of easily removing sorbitol from the dried product upon redispersion was also verified.