Preparation of cinnamaldehyde nanoemulsion by response surface method and its preservation effect on Newhall navel oranges
[Objective]This paper attempts to make cinnamaldehyde,the active ingredient of water-insoluble plant essential oil,into a nanoemulsion and explore the application of cinnamaldehyde nanoemulsions(CI)in the post-harvest preservation of Newhall navel oranges.[Method]In order to achieve the preparation of CI by vortexed way with low energy input,the response surface method was used to optimize the formulation of CI using the cinnamaldehyde content in the nanoemulsions and the inhibitory activity of CI against Penicillium digitatum as the response values.After the application of nanoemulsions was validated by the stability tests,the experiment on the control effects of nanoemulsions against green mold on post-harvest Newhall navel orange fruit was conducted to determine the cinnamaldehyde concentrations of the nanoemulsion used for the induction resistance-disease test and the post-harvest Newhall navel orange preservation test.The surface of Newhall navel oranges was evenly spread with CI,and water-treated navel oranges were used as a control to determine the rot rate,weight loss rate,respiratory intensity,peel color,total sugar content,total soluble solids,titratable acid and vitamin C of navel oranges during storage to investigate the fresh-keeping effect of CI on postharvest Newhall navel oranges.[Result]With the optimization analysis of response surface method and the evaluation of nano-emulsion stability-related indexes,the mass percentage formulation of CI was determined as 20.0%Tween80,10.4%RH40,1.4 mass ratio of emulsifier to co-emulsifier and 16.0%cinnamaldehyde.The average oil droplet size of the CI was(118.3±2.52)nm,the polydispersity coefficient of the system was(0.266±0.047).The stability of dilution,(0±2)℃low temperature storage stability and(54±2)℃hot storage stability met the standard.The antifungal activity of CI to P.digitatum was not affected by low temperature and heat storage.With the increase of cinnamaldehyde concentration,the control effect of CI on the green mold disease of Newhall navel orange was significantly improved,hence it was determined that the concentration of cinnamaldehyde of in the postharvest fruit resistance disease test induced by the nanoemulsion was 1.0%,and the concentration of cinnamaldehyde in the storage and fresh-keeping test was 1.25%.The activities of POD,PPO and PAL in the fruits of Newhall navel orange treated with 1.0%CI were significantly higher than those in the control group with 1.17,1.25 and 2.06 folds respectively.The content of MDA in the control group was 1.36 times higher than that in the control group,and the difference reached a significant level.1.25%CI treatment significantly reduced the decay rate,weight loss rate and respiratory intensity of Newhall navel oranges,and significantly improved index values of color consistency index,total sugar content,titratable acid,vitamin C and total soluble solids of Newhall navel oranges during storage.[Conclusion]A stable and effective cinnamaldehyde nanoemulsion was prepared by low energy input method.1.0%CI could effectively induce the fruit resistance to green mold,while 1.25%CI could improve the storage and preservation effect of postharvest Newhall navel orange fruit.The results of the study may provide new ideas and methods for ecological prevention and control of green mold in postharvest Newhall navel oranges.
cinnamaldehydenanoemulsionresponse surface methodpostharvest Newhall navel orangestorage and preservation
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