| The essential oil of pomelo peel is one of citrus essential oils,which is the most widely applied fragrance around the world.The essential oil has the function of anti-inflammation,digestion,anti-oxidation and antimicrobial.In the study,the extraction technology assisted by pulsed electric fields(PEF)was applied to improve the extraction ratio of essential oil from pomelo peel.At the same time,effects of electric field intensity,pulse number,temperature and time on the extract ratio of the essential oil were explored and the extraction technology was optimized.Subsequently,the composition and aroma profiles of the essential oil extracted by cold pressing(CP),PEF extraction and water distillation(WD)were discussed.Furthermore,antibacterial activity and mechanism were investigated in this study.The main results were as following:1.The main factors affecting extract ratio of essential oil from pomelo peel were electric field intensity,pulse number and temperature.Among them,pulse number had the most significant impact.Based on this,the extraction conditions were optimized using response surface methodology.Optimum conditions were electric field intensity of 2.5 kV/cm,pulse number of 25 and temperature of 68?.Under the optimal conditions,the total flavonoids extraction ratio was 1.37%.2.Composition of the essential oils extracted by three different ways were analyzed through GC-MS.The results showed that there were 61 different kinds of compounds and 18 common compounds.At the same time,there are 39,45 and 33 kinds of compounds in the extraction by CP method,PEF method and WD method,respectively.3.Cluster analysis was done to evaluate the aroma profiles of the essential oil.The results showed that the essential oil extracted by PEF and CP method had similar fragrance with a better sensory like the odour of citrus and fresh pomelo.However,the aroma of the WD extract was different from grapefruit note.It had a woody,floral,oily and overripe odour.4.Based on the investigation of antibacterial activity of the essential oil,the result showed that the essential oil had inhibitory effect on gram-positive bacteria,and the inhibitory effect on gram-negative bacteria was not obvious.Different extraction methods have different antibacterial effects,among which,the anti-bacterial effect of the PEF assisted extraction method is the best,and the distillation method is the worst.It was suggested that different extraction methods have the antibacterial effect by the difference of essential oil composition,while the PEF extract had the best quality.5.The antibacterial mechanism of the essential oil on Staphylococcus aureus was explored in this study.The results showed that the essential oil can change permeability of cellular membrane and destroy cell wall which causing the losses of intracellular materials and the change of cell morphology.Furthermore,as the concentration of the essential oil increased the damage degree of cell enhanced. |
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