Study On Antioxidative And Antimicarobial Activity Of Garlic On The Preservation Of Citrus

In this paper,garlic, chitosan and litchi skin as main materials, determinate the method of inhibition zone, test antimicrobial activity of garlic extract,and determinate antibacterial effect against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Aspergillus niger, Rhizopus, Mucor, Penicillium.Then by response surface methodology further optimize inhibition condition of garlic extract against Penicillium. After those tests, use the garlic extract about the antioxidant effects into vitro,the content of experiments include inhibition of lipid peroxidation experiment, clearing DPPH test, scavenging experiment and superoxide radical experiment. Finally,use garlic and garlic with other natural substances in the preservative effect to citrus, and test the corresponding various indicators. The range of determination include weight loss rate, SOD activity, MDA content, Vc content, titratable acidity, mildew rate. The main results are as follows:(1) In the four solvents:ethanol, water, ethyl acetate, petroleum ether, when the garlic in the liquid ratio is higher, the greater the inhibition zone are. After tests find that in 30% ethanol extract the maximum zone of inhibition is biggest,indicating that garlic extracts have obvious inhibition effect. At the same time tested can draw this conclusion:when ethanol concentration is lower,the solvent inhibitory effect is stronger.Under Garlic:30%ethanol=2:1 condition, the maximum inhibition zone is biggest,Aspergillus niger(29.3mm)>Penicillium(24.8mm)>Staphylococcus aureus (23.8mm)>Escherichia coli(22.5mm)>Rhizopus sp.(21.9mm)> Mucor sp. (21.4mm)>Bacillus subtilis (20.9mm).(2)According to the response surface method,the optimization results are as follows:Optimum conditions of ethanol extract of garlic inhibiting Penicillium are hydrolysis temperature 45.02℃, hydrolysis time 35.56min, extraction time 43.18min. Under this condition, the maximum inhibition zone is 28.1554mm.Optimum conditions of water extract of garlic inhibiting Penicillium are hydrolysis temperature 41.04℃, hydrolysis time 54.10min, extraction time 84.39min. Under this condition, the maximum inhibition zone is 8.81mm.Optimum conditions of ethyl acetate extract of garlic inhibiting Penicillium are hydrolysis temperature 41.59℃, hydrolysis time 37.14min, extraction time 40.36min. Under this condition, the maximum inhibition zone is 12.8302mm. The method can better provide for the antibacterial effect of garlic and the theoretical basis for experimental conditions.(3)Inhibition of lipid peroxidation experiment, clearing DPPH test, scavenging experiment and superoxide radical experiment prove that antioxidant properties of garlic extract consistent:30% ethanol> water> ethyl acetate> petroleum ether.Under the condition of garlic:30%ethanol=2:1,the indicators of the antioxidant are the best, but there are also high or low in others, inhibition of lipid oxidation rate (63.2%)> rate of DPPH scavenged(55.5%)>rate of hydroxyl radical scavenged(33.9%)> rate of superoxide radical scavenged(13.2%).(4)From the six measurement indices of weight loss from the citrus,MDA content, SOD content, Vc content, titratable acid content and mildew rate,under the condition of 2% chitosan, garlic:30% ethanol=2:1 and 1.5% chitosan, garlic:alcohol extract of litchi skin=2:1 on citrus,the effect of inhibitory preservation is significant.