Abstract:

In this study, the toxicity of mixtures of two food preservatives, imazalil and prochloraz, to major postharvest
pathogens of ‘Jincheng’ orange (Citrus sinensis Osbeck. cv. Jincheng) and their efficacy in preserving the quality of
‘Jincheng’ orange was investigated. The results showed that 333.3 g/L preservative mixture at an imazalil/prochloraz mass
ratio of 1:2 had the highest toxicity to Penicillium italicum Wehmer, Penicillium digitatum Saccardo and Colletotrichum
gloeosporiorides Penz with median effective concentrations (EC50) of 0.473 6, 0.241 9 and 10.121 7 μg/mL, respectively.
The antibacterial activities of 500 g/L imazalil and 250 g/L prochloraz were weaker when used separately. The cotoxicity
coefficients of the mixture for Penicillium italicum Wehmer, Penicillium digitatum Saccardo and Colletotrichum
gloeosporiorides Penz were 273.485 4, 293.900 9 and 207.017 2, respectively, which were all higher than 170, showing
significant synergism. Furthermore, our results demonstrated that this preservative mixture was as effective as 500 g/L
imazalil in preserving ‘Jincheng’ orange after 30 days of storage, both showing a preservation efficiency of 96.15%. The
preservation efficiency of the mixed preservatives was over 90% after 45 days and over 85% after 60 days, which was better
than that of 250 g/L prochloraz alone and 500 g/L imazalil alone. This study has indicated that imazalil plus prochloraz EC
at 333.3 g/L could be the best preservative mixture.

Key words: preservative, mixtures, citrus fruit, pathogens, preservation effect