The flavor of soybean products, particularly of the hydrosoluble extract (soymilk), is one of the main problems to its acceptance by western people. The compounds responsible for this flavor are secondary products of the oxidation of the fatty acids catalysed by a group of isoenzymes called lipoxygenases, which are activated when soybeans are wet. During soybean soaking, in the traditional process of soymilk production, cells of the cotiledons are broken due to swelling caused by the fast absorption of water, allowing the contact enzyme-substrate. The objective of this study was to extract and to analyse by spectrophotometric absorption at 232 nm the soybean lipid fraction after soaking in different temperatures and freeze-drying. It was observed that the highest the soaking water temperature, the lowest was the oxidation found in the soybean lipids. Results varied from 3.40 [(g/100ml)cm]-1 (dry soybeans) to 5.88 [(g/100ml)cm]-1 (soybeans soaked for 8 h at 22°C). The method adopted allowed the detection of different levels of oxidation for different soaking temperatures.
Soybean milk; soaking; lipid fraction; thermal inactivation; lipoxygenase
