Onion Functional Components And Their Applications

Although onion is planted broadly in our country, the functions of onion have not been explored extensively, except as food raw material. The onion has various medical treatment and health care functions, such as prevent the cardiovascular disease is one of the most important of them. The study of functional composition of onion and application as sanitarian drink or other food will meet the increasing need of people towards the natural function food now days.Besides the recognized sulphide, onion have also plenty of flavonoid compounds The studies of the functions of onion is limited to the extraction of flavonoid and sulphide and the power of lowering cholesterol as whole. In this paper, flavonoid and sulphide are extracted by different methods and analysised by HPLC and colorimetry. The content of functional components changes depending on the parts of onion and also the varieties of onion. Three kinds of flavonoid compounds include quercetin, quercitrin and vitexin have been identified from the extraction mixture. The manufacturing processes of onion beverage and onion vinegar are also studied. The stability including anti-oxidize and anti-fatigue ability of this onion containing beverage are determined. This paper provides valuable fundamental data and theoretical basis for the further study on the application of onion on health care. The results are listed as below:1. The extraction and determination of flavonoid compoundsFour extraction methods were employed in this research; they are pectic enzyme hydrolysis extraction, water immersion extraction , ethanol extraction and supercritical extraction. The content of total flavonoid in onion is determined by HPLC and colorimetry methods. The results indicate that the optimum condition for the enzyme hydrolysis were 0.250‰ of enzyme dosage with 2hrs extraction; the optimum condition for water immersion extraction were at 70℃ with 6∶1 (w/w) of water/onion ratio and extraction time 6hrs, the optimum condition of the ethanol extraction were refluxing in 80% ethanol for 4h.The best method of extracting flavonoid compounds from onion is ethanol extraction which give the most complete extraction. The...