Oil expression characteristics of rapeseed for a small capacity screw press

Oil expression studies were conducted on rapeseed, employing the Mini-40 screw press (oil expeller). With a view to maximize the oil recovery, rapeseed samples were given four pre-treatments viz., (i) moisture conditioning through water sprinkling (ii and iii) tap and hot water (80 °C) soaking for 1 h followed by drying and (iv) direct steaming of raw samples for 5, 10, 15 and 20 min duration. Prepared samples were dried to moisture levels near to 5, 7, 9 and 11% (w.b.) prior to expelling in the screw press, except for steaming. The effects of these pre-treatments were studied on oil recovery, specific energy consumption and the press capacity. The pre-treatment of hot water (80 °C) soaking for an hour followed by drying to a moisture level of 7% (w.b.) gave the maximum oil recovery of about 82% and was found to be the optimum. Though the percent oil recovery was reasonably good, the low effective capacity of the press (2.8 to 4.0 kg/h) and the frequent choking/jamming problems encountered during press operation prevented the possibility of adoption of this press at rural level in India.