Study On Fresh-Keeping Effect Of Fruits And Vegetables By Staranise And Other Plant Extract

Chemical fungicides used for fresh-keeping fruits and vegetables in long-term have harmfulness to human body.Effective antimicrobial constituents was extracted from natural plant by steam distillation, ethanol-ultrasound-assisted extraction and other methods in this paper. Plant extracts with the best antimicrobial activity was discovered through the research of antimicrobial test, which was combined with chitosan as a natural vegetation fresh-keeping coating liquid with the function of antimicrobial activity. Finally, the application of the fresh-keeping coating liquid in the storage of fruit was studied, so as to take place of chemical fungicides which was used in longterm and large scale.In this paper,10kinds of natural plant extract with effective antimicrobial activity was extracted by steam distillation,ethanol-ultrasound-assisted extraction and other methods, which include star anise, oregano, thyme, Galangal, Litsea son, Artemsia argyi, lotus leaf, Zong Ye, mint and pepper.Three kinds of plant extract including tar anise, oregano and thyme were analyzed by gas chromatography-mass spectrometry (GC-MS). The results show that:The main chemical components of star anise extract by steam distillation and ultrasound-assisted extraction methods was anethole;thymol and carvacrol are the main chemical components of oregano and thyme extract.The antimicrobial activity of above-mentioned plant extracts to five ive kinds of micro-organisms resulting in ruits and vegetables rot was studied in this paaper, including Alternaria, Penicillium, Pythium, E. coli and Staphylococcus aureus. The diameter of inhibition zone of plant extracts were determined by the method of filter paper dispersion method, and their effective in vitro antimicrobial time were also researched.The minimum inhibitory concentration (MIC) and minimum bactericidal concentration.(MBC) were determined by the2-fold diluent method. The results show that:The inhibition zone diameter of star anise and oregano extract are larger than the other plants extract, and the effective antimicrobial avtitity of oregano extract last longer than star anise.The Oregano extract’s minimum inhibitory concentration (MIC) of Alternaria, Penicillium, Pythium, E. coli, and Staphylococcus aureus were1.56μl/ml,0.78μl/ml,0.78μl/ml,1.56μl/ml,1.56μl/ml. Oregano extract shows the best antimicrobial activity in the selected10kinds of plants, which is followed by star anise extract.A series of concentrations of fresh-keeping fluid were prepared with star anise and oregano extracts combined with chitosan solution, which were applied to fresh-keep sweet cherries, grapes at room temperature (23-27℃).The results show that:0.1%of the star anise extract with1%chitosan can effectively inhibit the decay of sweet cherry, maintain its appearance quality, and extended its shelf life by3days.0.16%oregano extract with1%chitosan coating treatment can effectively inhibit the rot of grape during storage process, and maintain its rigidity soluble solids, titratable acid and vitamin C content, and its appearance quality and taste are better than the control, and shelf life was extended by3days.As to the compound fresh-keeping fluid with oregano and star anise extract,0.08%oregano extract,0.08%star anise extract with1%chitosan also have a good fresh-keeping effect on grape, the appearance quality of grape were maintained, whose fresh-keeping effect on grap is not as good as0.16%oregano extract.