| In recent years,the fresh walnut market has developed rapidly,and the proportion of online sales has risen against the trend.However,fresh walnuts are susceptible to infection with Colletotrichum（Colletotrichum）fungi,which makes the fruit black and rot,and is not resistant to storage.Therefore,it is urgent to treat the pathogenic bacteria that cause anthracnose.Separation and identification lays the foundation for the prevention and control of anthracnose;at present,domestic cold-chain logistics cannot meet the transportation conditions of fresh walnut kernels,and fresh walnut kernels are extremely prone to spoilage during transportation.Therefore,preservation and logistics methods have become the key technical support for the development of fresh walnuts.In this paper,"Liaoning No.1"fresh walnuts and chilled walnut kernels were used as experimental materials to isolate and identify the pathogenic bacteria causing fresh walnut anthracnose.The compound preservative formula with the best storage effect of chilled walnut kernels was screened and simulated.The transportation experiment verifies the storage effect of the compound preservative,hoping to lay the foundation for the research on the prevention and treatment of walnut anthracnose and the e-commerce transportation of chilled walnut kernels.The specific research results are as follows:1.Use Koch’s rule to isolate and purify the pathogenic bacteria on the surface of fresh walnut fruits with typical symptoms of anthracnose,and determine the fungal species by r DNA-ITS sequencing.The results showed that four pathogenic bacteria were isolated from fresh walnut fruits with typical symptoms.One strain may be C.gloeosporioides,two strains may be C.siamense,and one the strain is an anthracis fungus.2.According to GB2760-2014,use response surface methodology to optimize the formula of chilled walnut kernel compound preservative and evaluate the application effect.The results are as follows:Potassium sorbate 323.7 mg·kg-1,Ethyl p-hydroxybenzoate 8.4mg·kg-1,ε-polylysine hydrochloride,ε-PL)202.4 mg·kg-1 compound preservative can effectively inhibit the increase in the total number of colonies,coliforms,and molds of frozen walnut kernels during shelf life;slow down the decomposition of protein,reducing sugar,crude fat and other nutrients The acid value and peroxide value of fats and oils have increased;the activities of CAT,POD,LA,and PPO are well controlled,and the browning of chilled walnut kernels is alleviated;the original flavor is effectively maintained;and the shelf life of chilled walnut kernels is changed from 3 d extended to 7 d.3.Place the chilled walnut kernels treated with the compound preservatives in a sealed foam box with ice packs,and place them in a 38℃constant temperature environment to simulate transportation.The results show that the compound preservative can delay the occurrence of unfavorable changes such as browning and fat oxidation of chilled walnut kernels,and can effectively inhibit the growth of microorganisms:the total number of colonies exceeds the standard time from 24 h to 48 h,and the number of coliforms exceeds the standard time from 36 h was extended to 48 h,and the time for the number of molds to exceed the standard was extended from 48 h to 60 h.It can be seen that the compound preservatives can significantly extend the time of frozen walnut kernels in simulated transportation at 38℃（P<0.01）,thereby providing effective technical support for e-commerce transportation. |
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