Studies On Extraction Process, Membrane Concen-tration Of Onion Flavonoid And Its Application

Onion is a traditional medicinal and edible plant, containing rich flavonoid compounds, the unique chemical structure of which has many important physiological and biochemical effects on animal cell.It also has a variety of effects in health, prevention and treatment of disease. China is one of the most important producting and exporting countriers in the world, but due to technical level and diet restrictions oioin can not always be use legitimately, resulting in a huge waste of resources. So it is important to carry out the deep processing and comprehensive utilization of onion.This research produce onions beverages by enzyme hydrolysis, water extraction, preparation and concentration through membrane, deployment. The main research include detection of the onion flavonoids through spectrophotometric?optimizating the process parameters of enzyme hydrolysis and water extraction?picking of membranes and their operation conditions, the influence of various factors on the flavor and stability of the beverage?antioxidant capacity of onion beverage. The main conclusions are as follows:1. The method of detecting flavonoids in onion: take a sample solution, adding 0.1 mol/L of AlCl3 solution and KH2PO4-NaOH solution(pH=5.5), add water to the mark and stand for 30 min. Measuring the absorbance of the sample at 400 nm with the sample solution without adding AlCl3 solution.Compare with standard curve of quercetin samples and calculate the concentration of the flavonoids in the sample.2. The best process parameters in water extraction of flavonoids:Pretreat the onion, add with four times the amount of water and cellulase with mass fraction of 2% after pulverized.The extraction continue for 2h in the conditions of 50?and pH value of 4.5. Then add water to eight times the raw material, adjust the temperature to 55? and the pH to 6.5, then extract for 2h. Flavonoids content in the water extraction was 1.453mg/g.3. The purification and concentration are done through the ultrafiltration and nanofiltration membrane in the experiment. The material of ultrafiltration membrane is polyether sulfone with the MWCO of 50000 D.And the material of nanofiltration membrane ultrafiltration membrane is polyvinylidene fluoride with the MWCO of 800 D. The operating parameters of two membranes are determined.The final enrichment factor is 6.41 and the flavonoid content in the concentrated liquid is 9.88 mg/g.4. Determining the ratio of the components in onion beverage, the content of ?-cyclodextrin is 8g/L and the content of guar gum is 0.32%. Uniformity and stability of the product is very good and no precipitation and stratification appears after a high-pressure homogenization with the pressure of 20 MPa. Antioxidant capacity of onion beverage is also determinated, the FRAP value of which is(4.07±0.16) mmol/L, and scavenging rate to hydroxyl radical can reach 22.3% when the concentration of beverage is 0.08mg/ml.