| Citrus postharvest penicilliosis is one of the common diseases and is the main cause of fruit rot. It brings great economic loss to citrus industry. At present commonly used chemical fungicide can cause significant damage to human body and can also cause the rise of drug resistance among fruit. Therefore, the antisepsis method which is efficient and safe is now the research focus at home and abroad.We aimed to develop a compound organic acid coating agent for citrus postharvest antisepsis by the organic acid advantage of the safety and economy. The results are as follows.(1)Through the single factor experiment we got the concentration of the 6 kinds of organic acid for inhibiting the growth of Penicllium italicum, and screened 4 kinds of the organic acids including lactic acid, acetic acid, propionic acid calcium and ascorbic acid among them which can significantly inhibit the growth of P. italicum. We obtained the formulation of the compound organic acids agent by the orthogonal test and some related proof test, which is as follows:1% calcium propionate,0.15% acetic acid,0.15% lactic acid and 1% ascorbic acid.(2) Through the preliminary study of the bacteriostatic ability of composite organic acid, it was showed that the compound organic acid agent can inhibit the spore germination of P. italicum. The 100% concentration of the agent can completely prevent the P. italicum spore from germinating and the spore germination rate was only 5% by 75% the concentration of the agent when it was cultivated 24 hours in the PDA liquid medium containing the agent. The penicillium hyphae became slender, and appeared rupture. The conidium stems were fewer, and the amount of conidium less by the 50% concentration than normal. It was indicated that the compound organic acid agent had wide antimicrobial properties. It had the abilities of inhibiting the growth of all the tested strains, especially the plant pathogenic fungi by the way of the inhibiting growth of different kinds of bacteria, yeast and plant pathogenic fungi.(3) The concentrations of compound organic acid agent were adjusted, and the adhesive was added to the agent by the citrus experiment. Through the method of the orthogonal design, according to the index of the decay rate and the weightlessness rate, the optimal formula of the compound organic acid coating agent, named OAC-1, was as follows:3% calcium propionate,0.5% acetic acid,0.75% lactic acid,2%ascorbic acid, and 1% CMC.(4) It was showed that OAC-1 can obviously reduce the decay rate and the weightlessness rate of the two kinds of citrus fruit, delay the decline of the contents of soluble solids, Vc, titratable acid and total sugar in the process of storage, inhibit the respiratory intensity of the fruit, reduce the consumption of respiratory substrates and the accumulation of MDA, comparing with the most common pesticide (amide 1000 times diluent and 200 ppm2,4-D) and water by the postharvest fresh-keeping of Xinyu orange and Nan fung tangerine. OAC-1 can also reduce the enzyme activity of SOD, PPO, POD and PAL of the fruits, delay the arrival of the activity and the fruit senescence. The pesticide had also the properties of delaying the senescence and prevnting corrosion of the fruit, but the indexes were lower than OAC-1. The results indicated that the OAC-1 had significant properties of the corrosion protection and maintaining the quality of postharvest citrus. |
PDF Full Text Request