Inhibitory Effect Of Essential Oil Of Melaleuca Alternifolia On Three Pathogenic Bacteria And Freshness Preservation Of Giant Grapes

Kyoho grape,as the best fresh grape,is widely planted in most areas of North China,South-East China and South China.Because it is easily damaged and invaded by pathogenic fungus,Kyoho grape has caused many storage problems.Tea essential oil,an extract of fresh branches and leaves of Melaleuca alternifolia,is a natural antibacterial agent with strong activity,which is expected to play a role in the storage and preservation of Kyoho grape.Therefore,the main pathogenic fungus of fresh Kyoho grape were isolated and identified,and the inhibitory effect of Melaleuca alternifolia essential oil and its characteristic components on the main pathogenic fungus of Kyoho grape was analyzed.Two preservation temperatures,low temperature(4℃)and room temperature(25℃),were designed to study the effects of Melaleuca alternifolia essential oil preservative,chitosan preservative and Melaleuca alternifolia essential oil-chitosan compound preservative on the preservation effect and quality of Kyoho grape,so as to provide new ideas and methods for storage and preservation of Kyoho grape.The main results were as follows:(1)The main pathogenic fungus of fresh vegetable Kyoho grape are Penicillium notatum,Aspergillus niger and Botrytis cinerea;Under the same concentration of essential oil,the inhibitory effect of Melaleuca alternifolia essential oil on main pathogenic fungus of Kyoho grape had no significant difference at different temperatures(P>0.05).At the same temperature,the inhibitory effect of Melaleuca alternifolia essential oil on main pathogenic fungus of Kyoho grape was significantly different among different concentrations(P<0.05).Moreover,there was a good logarithmic relationship between the antibacterial activity and concentration of Melaleuca alternifolia essential oil against Penicillium,Aspergillus niger and Botrytis cinerea,and the fitting equations were:y=9.0808ln(x)+22.436,y=10.235ln(x)+6.4654,y=9.5795ln(x)+12.256,respectively.(2)The main components of Melaleuca alternifolia essential oil include:1,8-cineole,4-terpene alcohol,α-terpineol,etc.The mass fractions were:29.0%～33.0%,28.0%～30.0%%,8.0～9.0%,8-cineole combined with 4-terpene alcohol 1:1 significantly improved the inhibitory effect on Penicillium(p<0.05),while on Aspergillus niger and Botrytis cinerea There was no significant difference between the inhibitory effect of fungus and the essential oil control group(p>0.05).The diameter of the inhibition zone of essential oils against the three grape rot fungus was not significantly affected by the treatment temperature,which indicated that the essential oil of Melaleuca alternifolia had good antibacterial stability at 4℃～100℃.(3)Storage temperature(4℃,25℃)had significant effects on 11 indexes of Kyoho grape preservation(p<0.05).At the end of the experiment,4℃ was compared with 25℃,The decay rate,dropping rate,weight loss rate,browning rate,respiration rate,titratable acid content,polyphenyl ether content,malondialdehyde content of Kyoho grape decreased by 27.52%,22.84%,12.26%,8.56%,3.6%,4.3%,59.48%,14.97%and 49.42%respectively.4℃ is more effective for the preservation of grape.(4)At the end of the experiment,the analysis of 11 fresh-keeping indexes of Kyoho grape showed that the fresh-keeping effect of Melaleuca alternifolia essential oil-chitosan compound fresh-keeping agent(TTO-CCS)was significantly better than that of Melaleuca alternifolia essential oil or chitosan film(P<0.05);In addition,using a single preservative,Melaleuca alternifolia essential oil preservative has a better effect on Kyoho grape.Conclusion:The inhibition effect of the essential oil of Melaleuca alternifolia on the proliferation of the main pathogenic bacteria of grapes was significant with the increase of the concentration,and the inhibition concentrations of Penicillium,Aspergillus niger and Staphylococcus griseus were>0.56mg/mL,>4.5mg/mL and>1.125mg/mL,respectively;while the combination of the essential oil of Melaleuca alternifolia only had the inhibition effect on Penicillium.The freshness preservation agent prepared from the essential oil of Melaleuca alternifolia had a significant effect on the preservation of grapes at room temperature(25℃)or low temperature(4℃),and the freshness preservation effect was better when combined.