FACTORS AFFECTING ON RICE BRAN OIL EXTRACTION USING HYDRULIC PRESS UNIT

Abstract

A study was carried out to test and evaluate the effect of bran heat stabilization, steaming process, applied pressure, and pressing time on the extraction efficiency of rice bran oil using a 32 ton hydraulic press unit. Four steaming periods (20, 25, 30, and 35 min), six applied pressures (150, 175, 200, 225, 250 and 275 bar), and four holding times (10, 15, 20 and 25 min) were tested and evaluated. The bran samples were divided into two groups, the first group was left without stabilization (raw bran) while the second group was stabilized by heat treatment at heating surface temperature of 95 oC and exposure time of 10 minutes (stabilized bran) as recommended by (Hendawy 2003). The results showed that, at all levels of applied pressure the moisture content of bran samples (raw and stabilized) increased with the increase of steaming time and it was also gradually increased with the increase of holding time up to 20 minutes and starts to decrease again at the holding time of 25 min. Meanwhile, the percentage of extracted oil increased with the increase of steaming period, the applied pressure and the holding time.The extracted oil percentage of the steamed raw bran ranged from 31.1 to 46.98 % in comparison with 11.87 to 26.94 % for the un-steamed samples. While, it ranged from 23.94 to 38.19 % for the stabilized steamed bran in comparison with 7.63 to 24.03 % for the stabilized un-steamed samples. On the other hand, heat stabilization of the bran samples prior to steaming process causes a slight reduction in percentage of the extracted oil in comparison with the raw bran. On the same time, it has showed a reduction in the percentage of free fatty acids which in turn keep the extracted oil more stable during the storage process.