Effect of Alkali-induced deacetylation of konjac glucomannan on the structure and barrier properties of wheat gluten-based composite films for blueberry preservation

Wheat gluten (WG) has garnered significant attention as a promising candidate for replacing conventional petroleum-based materials due to its biodegradability, good film-forming ability, and gas barrier properties. Nevertheless, the poor mechanical strength and water resistance of WG restricted its potential as a preservation material for fresh produce. In this study, sodium hydroxide served as both a solvent, dissolving WG, and a deacetylation agent, inducing the deacetylation of konjac glucomannan (KGM), thus enabling the preparation of a WG/deacetylated KGM (DKGM) composite film for postharvest fruit preservation. The optimized film showed a 52-fold enhancement in elongation at break (31.4% vs. 0.6% for the pure WG film). The WG/DKGM composite film achieved low oxygen and carbon dioxide transmission rates of 3.62 and 5.87 g/(m 2 ·h), respectively, confirming its excellent gas barrier properties. Evaluation of appearance, firmness, pH, total sugar content, and decay rate demonstrated that the WG/DKGM composite film effectively delayed blueberry ripening and decay. The developed film effectively retarded the softening and spoilage of blueberries, extending their shelf life by over 5 days compared with uncoated blueberries and commercial PE film. Therefore, this novel gas-barrier composite film showed great potential for application in fruit preservation. • Deacetylated konjac glucomannan raises film elongation from 0.6% to 31.4%. • The film showed lower gas transmission (O 2 3.62, CO 2 5.87 g/(m 2 ·h)). • Films extend blueberry life by 5 days, surpassing PE and control.