Effect of Refining Process and Use of Natural Antioxidants on Soybean Oil

Soybean (Glycine max L. Merril.) is an annual plant of Asian origin, adapted to temperate climates. This plant is a member of the family Fabaceae, subfamily Papilionoideae, tribe Phaseoleae, genus Glycine and subgenus Soja (Hymowitz, 2004). One of the most important agronomic characteristics of soybean is that it can take nitrogen from the air and fix it to be used as nutrient by the plant. The symbiotic relationship between the soybean plant and its modulation by bacterium (Rhixobium japonicum) is responsible for the conversion of atmospheric nitrogen into plant-available nitrogen. This also makes to soybean a good rotational plant for use with high nitrogen-consuming crops. Another important benefit of this nitrogen fixation is that it helps to keep the production cost of soybeans relatively low compared to other crops that competing for the same land area (Erickson, 1995). Among the factors that allow the soybean to be a dominant crop could be mentioned some of the most important agronomic traits: good profits for producers and processors, as well as the possibility of obtaining high-protein quality meal, which are used as ingredient in food animal. These characteristics have allowed the soybean oil is consumed more than other vegetable oils. Soybean is the most important crop in the world because of its high quality protein and edible oil products. World production of oilseeds during 2009-2010 was 403.58 million metric tons (tons), from which 60% corresponded to soybean, 13.74% to rapeseed, 10.23% to cottonseed, 8.30% to peanut and 7.87% to sunflower (Soya & Oilseed Bluebook, 2010). Others factors that have contributed to soybean worldwide importance are the high demand of meal and oil. The main consumer of these meals is the agricultural sector. World production of vegetable meals during 2009-2010 was 237 million tons; soybean meal represented 67%, rapeseed 13.6% and cotton 6.2% (Soya & Oilseed Bluebook, 2010). Oil is a byproduct of meals production, which has a great demand. In this situation of soybean oil domain in fat total supplies, is extremely important to take advantage of its nutritional properties, such as its high content of polyunsaturated fatty acids essential for humans(n-6 and n-3), and their contents of tocopherols (vitamin E) (Emken, 1995).