Research Of Naural Fresh-keeping Agents For Fruits

In this paper,pathogens were separated from affected parts of five kinds of postharvest fruits (apples,pears,oranges,grapes and jujube ). After purificated,the pathogens were transferred back to fruits in order to measure the pathogenicity . Accordingly, 3 kinds of predominat pathogenic bacteriums were identified:Alternariaalternata, Monilinia fructicola and Penicillium expansum. And these three bacteriums were using for next study.Thirty species of Chinese herbal medicines were extracted with 80% ethanol and the rough extracts were tested for their antimicrobial activity on the predominat pathogenic bacteriums by hole-dosing method. Results showed that four species, Coptis, Clove, Cassia, giant knotweed rhizome have better antimicrobial effect and wider antibacterial spectrum.The four species'ethanol extracts have showed strong inhibitory effects in mycelial growth inhibition test and inhibitory area test on spore germination of Penicillium expansum, and the inhibition rate were all above 85%. HL-the ethanol extracts of Coptis showed the best inhibitory effect on pathogenic bacteriums in the middle inhibitory concentration(MIC) test. Four matching liquors were generated by the above four extractions with the ratio of 1:1:1. Inhibitory effects of extractions and matching liquors were made by means of MIC, the tests showed the matching liquor, FPI was the best matching liquor,which has the strongest inhibitory effect on any pathogenic bacteriums in the study. The preliminary studies of the physical and chemical properties of HL and FPI were performed.The result showed that matching liquor FPI has better effects than HL in the testing items of illumination , temperature , time lengths for preservation and the activity maintenance time lengths. And the best pH values of the two extractions were both 6.0. The optimum temperature of HL in the activity was lower than 60℃.The illumination has no significant differences on the inhibitory effects of the two extracts.Optimization of their ultrasonic wave extraction conditions were studied by the single factor and orthogonal tests. The best concentration of alcohol, distill time and distill temperature were as followed,Clove:70%,10 min,30℃;Cassia:70%,20 min,20℃;Coptis:80%,20 min ,30℃.The preservative experiment results of Coptis extract HL and matching liquor FPI on pear, and jujube showed that two extracts have really significant fresh-keeping effects.Compared to the control testing, two extracts could reduce loss of water and remain nutritional ingredient of the fruits. And the matching liquor FPI has better keeping-fresh effect than ethanol extracts of Coptis (HL).