Chitosan derived nano-selenium based coatings for postharvest safety of cherry tomato

Chitosan (CTS) exhibits notable moisturizing and film-forming capabilities, whereas nano selenium (SeNPs) demonstrates antioxidant and antibacterial properties. In the present study, a CTS/Se film-forming agent was prepared by dissolving CTS, glycerol, and SeNPs in 1% (v/v) glacial acetic acid through heating and ultrasonic treatment. The results revealed that SeNPs fused with CTS via intermolecular forces, thereby enhancing the tensile strength of the CTS film. The water contact angle of the CTS film increased with an increase in SeNPs concentration. The thermal stability and water retention properties of CTS/Se were superior than CTS. In a storage experiment, the content of soluble solids in tomatoes coated with CTS/Se was higher than that in tomatoes coated with CTS and the control. The CTS/Se coating inhibited gas exchange both inside and outside the film, leading to increased activities of antioxidant enzymes. This reduced the oxidation of vitamin C in the tomatoes and decreased the content of malondialdehyde. The CTS/Se film inhibited the growth of bacteria on the tomato surface and mitigated the decline of aldehyde, alcohol and ketone aroma compounds. Consequently, the CTS/Se coating alleviated the softening, aging and rotting of tomatoes. Feeding experiments conducted on mice verified the food safety of the CTS/Se.