Wheat straw-based carboxymethyl cellulose and glycerol films enriched with polymalate: Characterization and application in grape preservation

The shelf-life of grapes is reduced due to infection by various pathogens and mechanical damage, which consequently limits their availability on the market and results huge economic losses. Active packaging films are expected to overcome this problem. In this study, packaging films (CMC-Gly-PMA) were developed using wheat straw-based carboxymethyl cellulose (2 %), glycerol (30 % w/w of CMC) and polymalate (0.9 %) to prolong the grape shelf-life. With regard to physical properties of films, TS, EB, OP and WVP were 28.4 MPa, 142.1 %, 8.52 mmol/kg and 0.55 × 10^-12 g·m/m²·s·Pa, respectively. The FTIR spectra indicated that the interactions between CMC, glycerol and polymalate within the matrix were primarily physical in film formation process. In addition, the film cross-section showed a compact yet smooth surface. Films had UV barrier performance and positive antibacterial effects on E. coli and S. aureus. From the composting experiment, films decomposed almost entirely on day 21. Besides, during the storage period, the coated grape exhibited a lower decay index, weight loss and respiration rate than the control group, and the coated grape exhibited greater hardness than the control group. It can therefore be concluded that the coating treatment preserved grape quality and extended their shelf-life. The findings suggest that the active film has the potential to serve as an edible and biodegradable material for food packaging, which represents a promising avenue for further research in this field and supports the transition towards a circular economy in the packaging industry.