and fats,its chemistry nameis tri-glyceride ， but edible oil always contain other ingredients ， this will take bad effects in colour,odour and storage 。 oil’s refining is in order to take off the impurities conained,the less impurities contained ,the higher oil grader can reach 。 according to the impurities state in oil   impurities can classify to four kinds:suspend impurities 、 gumming soluble impurities 、 oil soluble impurities 、 moisture ； different oilseeds have different impurit content because of different oilseeds breed,producing area,storage conditions But they have the same way to refine