Studies On Extraction And Analysis Of Essential Oil And Fresh-keeping Effect

Onion is a medical and edible plant. It is an important flavoring that commandsuniversal applicationas seasonings and flavorings in the food industry with thedevelopment of snacks and prepared foods Furthermore, onion is used in folk therapybecause of its biologically active sulphur compounds. In recent years, the general publichas exhibited increased awareness of health-promoting functional foods.The goal of this work was to determine the optimal conditions of extraction forproducing onion essential oil with the highest yield. Essential analysis and the activity oninhibiting enzymatic browning of vegetables during storage was evaluated with theinhibiting mechanism discussed.1 Two extractions methods were studied.According to experiment, the optimistic combination of extraction rate for SD isenzymatic temerature 40℃,enzymatic time 180min,distillation time 180min。The optimal parameters of MAE-SDE for onion essential oil were obtained for thefirst time. According to orthogonal experiment, the optimistic combination of extractionrate for ME-SDE is:microwave power 616w, distillation time 2.5h, material to water ratio1:40The methods of quantity-determination and quality-determination of onion essentialoil with GC/MS were established. GC-MS was applied to the determination of chemicalcomponents in onion essential oil. 14 surfur-containing compounds,were found in onionessential oil.Onion extract was prepared by extracting onion with PBS, and the effects of theextract on potato polyphenol oxidase and fresh-cut potato were investigated. Thepolyphenol oxidase of potato was inhibited by onion extract, and the inhibitory effect ofonion extract toward potato polyphenol oxidase was increased with the heated extract.The inhibitory effect of the extract was increased with increasing heating temperatureand time. The effect of onion extract on fresh-cut potato polyphenol oxidase activity, a~*and rigidity during ripening of potato when stored at room temperaturefor 7 days wasinvestigated. Onion extract can prevent browning of potato. Lotus root was treated with intermixture of 0.2%,0.4%,0.6%onion essentialoil,showed that 0.6 % onion essential oil effectively reduced browning index of lotus rootepidermis.Onion essential oil(0.04%) is as active as BHA(0.04%). Storage temperature has anobvious effect on antioxidative activity of onion extracts.In higher temperature, lipidsoxidation velocity is faster and onion extracts are unstable, which results in higher lipidsperoxides value. But in lower temperature, these advert conditions are avoided. Therefore,peanut oil added onion extracts should be stored in lower temperature.The antioxidativeactivity of Onion essential oil(0.04%) and citric acid (0.02%) were used in peanut oil arebetter than Onion essential oil(0.04%) and vitamin C(0.02%)By analysis of its antioxidative mechanism,onion essential oil was the mainantioxidant,on one hand,it had the good ability to reduce oxides,and on the other hand,ithad the good ability to ability to extinguish free radicals.