Development of a water-resistant salep glucomannan film via chemical modification.

Deacetylation is a chemical modification process (DD, 0-50-100%) that was applied to purified salep glucomannan at different glycerol concentrations (G, 0-5-10%) to decrease its high hydrophilic film behavior and improve its barrier, mechanical and structural characteristics. The solubility and water vapor permeability of films were significantly reduced by deacetylation. The film mechanical parameters were decreased by 50% DD, but 100% DD increased these parameters compared with the unmodified film. The improved interactions between glucomannan chains induced by deacetylation were revealed by FTIR. SEM results indicated that acetyl-free films had a smooth and compact microstructure when treated with glycerol, but 50% DD films showed aggregation at the surface. XRD analysis showed the conformational rearrangement and improvement in the crystallinity of the films due to deacetylation. Deacetylated films possessed higher thermal stability. Overall, deacetylation provides a promising and potential approach to improve salep film performance, which can benefit its applications in the food industry.