Application of Mulberry (Morus nigra) Anthocyanin Extract Combined with Carboxymethyl Chitosan for Postharvest Preservation of Strawberry (Fragaria x ananassa)

Strawberries are highly susceptible to postharvest deterioration, including softening, decay, and nutrient loss, which severely limits their shelf life and commercial value. This study developed and evaluated a natural composite coating combining mulberry anthocyanin extract from Morus nigra fruits and carboxymethyl chitosan to extend the postharvest life of strawberries. The coating was rationally designed based on complementary functions: carboxymethyl chitosan acts as a semi-permeable barrier reducing water loss and microbial infestation, while mulberry anthocyanin provides antioxidant activity to mitigate oxidative stress-induced senescence. The anthocyanin extract contained cyanidin-3-glucoside (32.9%) and cyanidin-3-rutinoside (29.7%) as major components and exhibited good radical scavenging activity. Strawberries were treated with the composite coating, carboxymethyl chitosan alone, potassium sorbate, or left untreated, and then stored at 25 °C for five days. The composite coating treatment was most effective, significantly reducing weight loss, maintaining firmness, inhibiting browning, and lowering malondialdehyde accumulation compared to other treatments. These findings demonstrate that the mulberry anthocyanin-carboxymethyl chitosan composite coating is a promising natural strategy for strawberry preservation.