Effects of compound coating combined with ultraviolet treatment on quality of cold storage fresh-cut papaya

A compound coating was prepared by chitosan, nisin, natamycin, mint oil, calcium chloride and vanillin. The effects of compound coating combined with ultraviolet treatment on the quality (including color, soluble solid content, water loss, Vitamin C content, titratable acid, counts of moulds, yeasts and bacteria) of storage fresh-cut papaya were investigated. The formula of compound coating and the parameters of ultraviolet treatment were optimized by uniform design experiment. The results showed that the coating and ultraviolet treatment were able to protect the color of the fresh-cut papaya, inhibit browning, maintain high soluble solid content, reduce water loss during storage time and restrain the growth of moulds and yeasts as well as aerobic bacteria. A regression equation reflecting the relationship of the factors and the aerobic bacterial count was built by SAS software. And optimal compound coating formula and ultraviolet treatment parameters were obtained by means of nonlinear programming, which were chitosan 1.0%, nisin 0.10 g/kg, natamycin 14.0 mg/kg, mint oil 1.5 mL/L, calcium chloride 0.6%, vanillin 0.3% and ultraviolet treatment time 22 min, the distance of ultraviolet irradiation ranged from 44 to 66 cm. The shelf life of fresh-cut papaya was at least 6 days by this compound coating and ultraviolet treatment.