Chitosan and oregano essential oil pretreatments preserve quality and extend shelf life of organic strawberries during cold storage

Strawberries are highly perishable fruits, particularly under organic production systems where synthetic preservatives are restricted. This study assessed the efficacy of postharvest pretreatments, including chitosan (CH), oregano essential oil (OEO), their combination (CH+OEO), carbon dioxide (CO₂), ozone (O₃), and distilled water, in preserving physicochemical quality, bioactive compounds, antioxidant capacity, and microbiological safety of organic strawberries stored at 4±0.5°C for 15 days, compared to a nontreated control (NTC). The CH+OEO and CO₂ treatments were most effective in reducing weight loss and maintaining firmness, color, and visual and textural attributes. CH+OEO-treated fruits retained the maximum levels of total phenolics, anthocyanins, and antioxidant activity, whereas CO₂ slowed down ripening and suppressed microbial growth. O₃ treatment, in contrast, accelerated softening and surface damage, limiting its practical use. Pearson’s correlation and principal component analysis highlighted strong relationships among bioactive compounds, antioxidant activity, and microbiological quality, with CH+OEO clustering closest to optimal preservation. These findings indicate that the combination of chitosan and OEO provides a natural, safe, and scalable approach to extending the shelf life and marketability of organic strawberries while maintaining their nutritional and visual-textural attributes.