Abstract: In this study, tray type deodorizer was modified by external heating strategy to achieve two-stage deodorization. In this deodorization process, decolorized soybean oil was heated by double-helix heater to the optimal temperature of 170 ℃. After the oil entered the upper section of tray type column, primary gas stripping was carried out. Then, the oil was again transferred to double-helix heater where the residual pressure was set at 2 Torr and heated to 248 ℃ before distillation in the bottom section of tray type column. Steam amount in the upper section of tray type column represented 1% of total oil weight and in the bottom section 2%, and the total deodorization time was set at 45 min. As a result, oil retention time in deodorizer was largely shortened and the trans-fatty acids content in soybean oil was only 1.15%. Therefore, two-stage deodorizer reveals pollution-free and energy-saving properties.

Key words: soybean oil, two-stage deodorization, residual pressure, trans-fatty acids