Impacts of salicylic acid, chitosan, and salicyloyl chitosan on quality preservation and microbial load reduction in strawberry fruits during cold storage

The effects of salicylic acid (SA), chitosan (CS), and salicyloyl chitosan (SCS) treatments on quality and microbial load of strawberry fruits cv. Parous were investigated during storage at 4°C. Fruit decay and microbial load were alleviated by the SCS treatment more compared to the SA and CS treatments alone, although there was no significant difference among the two concentrations of SCS (0.15% and 0.3%). Furthermore, SCS-treated fruits had significantly higher antioxidant activity, phenolic content, and antocyanins than those treated with SA and CS. The results also showed that, SCS treatment maintained better firmness, soluble solid contents, titratable acidity, and L-ascorbic acid contents and inhibited the increase in weight loss, fruit decay, and microbial populations of strawberries stored at 4°C for 15 days. Our findings suggested that SCS has great potential of fruit preservation as an edible coating material for strawberries. Novelty impact statement This is the first report which has demonstrated a synergistic effect between SA and CS when they used together as an edible film to preserve the quality and prevent decay of strawberry fruit during cold storage. On the other hand, strawberry fruit treated with salicylic acid conjugated to chitosan has not only alleviated microbial load even more but also has positive impact on fruit storability as well as nutritional value, which was the novelty of the present work. Also, due to lack of attaching ability of SA to fruits surface, its protective effects are not sustained, but CS exhibits superior adhesive attribute, so that modification in chemical structure of CS by introducing SA into the polymer backbone may render excellent microbial activity.