EFFECT OF RICE BRAN PELLETING AND PELLETS CHARACTERISTICS ON THE EFFICIENCY OF OIL EXTRACTION

A study was carried out to  test and evaluate the effect ofrice bran pelleting using a single face extruder on the extraction efficiency of rice bran oil. Four different various screw speeds 30, 50, 70, and 90 rpm, three different die hole diameters 6, 8 and 10 mm and four different various  pelliting lengths 1, 2, 3 and 4 cm were examined and evaluated. The results show that, moisture content of pellets decreased at all levels of screw speed and die hole diameter. At screw speed of 30 rpm the moisture content decreased from an initial moisture content of 11.9 % (w.b.)  to 6.22, 6.43 and 6.71 % (w.b.) with die hole diameters of 6, 8 and 10 mm, respectively. At all levels of screw speed and die hole diameter the bulk density of pellets ( 0.29 g/cm³ ) increased  by one and half times of raw bran bulk density  and ranged from 0.43 to 0.59 g/cm³. Penetration rate increased by increasing pellets length and diameter and ranged from 37.44 to 38.96 cm/min. Oil retention ratio decreased by increasing pellets length, while increasing pellets diameter tended  to increase oil retention ratio. Residual oil % increased with increasing length and diameter of pellets. Oil extraction efficiency decreased with increasing pellets length and diameter and it was  ranged from 84.6% at 4 cm length and 10 mm diameter of pellets to 95.5% at 1 cm length and 6 mm diameter of pellets.