Application and Dietary Exposure Assessment of Pyrimethanil and Thiophanate-methyl in Postharvest Storage and Preservation of Litchi Fruit

This study investigated the effects of different dilution concentrations of azoxystrobin and thiophanate-methyl on the preservation of postharvest litchi fruit at ambient temperature. By analyzing the physiological indicators of litchi fruit during storage, the optimal fungicide formulation was selected, verified, and dietary exposure assessed thus the preservation method of extending shelf life for litchi at ambient temperature was obtained. The results showed that the litchi fruit treated with a 1600-fold dilution of 25% azoxystrobin (M1600), or a 1600-fold dilution of 25% azoxystrobin mixed with a 700-fold dilution of 70% thiophanate-methyl (M1600+J700) significantly inhibited the respiratory rate of litchi fruit, decreased the relative conductivity of pericarp and decay rate of litchi fruit (P<0.05), as well as inhibited the decrease of TSS and V_C content in pulp at 25 ℃, and better maintained the sensory quality and edible value of litchi fruit. Two preservative formulation had comparable effects on the preservation of litchi, while the M1600 was superior in inhibiting the pericarp browning. According to the residual detection of fungicides and dietary exposure assessment, it was found that the risk quotient value of azoxystrobin in the whole litchi fruit treated with M1600 alone was far less than 1, which could achieve preservation, safety, as well as reduce economic cost. This study provides a technical reference for the postharvest storage and preservation techniques for litchi or other non-respiratory climacteric fruit.