Upcycling kimchi cabbage by-products into edible cellulose microfibre-based coatings for extending the shelf life of blueberries

In this study, a novel strategy was developed for upcycling kimchi cabbage by-products (KCBs) into sustainable edible coatings to extend the shelf life of blueberries. High-purity cellulose microfibres (CMFs) were successfully extracted using eco-friendly citric acid-hydrogen peroxide (25 and 30%, w/v) pretreatment and mechanical disintegration. The resulting CMF-2 exhibited a high whiteness index (91.22%), high crystallinity (67.35%), and excellent dispersion stability (zeta-potential of -46.07 mV), rendering it ideal for use in sprayable coatings. Upon increasing the CMF concentration in the films from 0.3 wt% to 1.0 wt%, the ultraviolet-shielding capacity and tensile strength increased significantly, while the water vapour permeability and elongation at break decreased, indicating a denser and more robust film matrix. Higher CMF concentrations (0.7 and 1.0 wt%) led to superior anti-abrasion performance and water-induced self-healing behaviour compared with the 0.3 wt% CMF film. Furthermore, these coatings were completely removed from the blueberries within 3 min by washing with distilled water. After 35 d of storage at 4 °C, the 1.0 wt% CMF-coated blueberries showed a significant reduction in weight loss (4.52%) compared with the control (8.95%). Moreover, they maintained superior quality retention, with a moisture content of 81.21%, titratable acidity of 0.95%, and total anthocyanin content of 106.05 mg/100 g, indicating significantly higher levels than those of the blueberries coated with lower concentrations (i.e., 0.3 wt%). These findings highlight the potential of KCB-derived CMFs as a clean-label preservation technology for highly perishable blueberry fruits, offering environmental benefits through agricultural waste valorisation.