A Full Breakdown of the Latest Rapeseed Oil-Pressing Process
Rapeseed is also called Brassica campestris seed; it is a herbaceous cruciferous crop and one of China's main oil crops and nectar-source crops, and its seeds are one of the main raw materials for oil extraction. It is cultivated throughout China and is divided into two types, winter rapeseed and spring rapeseed. Its planting area accounts for more than 40% of China's total oil crop area, and its output accounts for more than 30% of China's total oil output, ranking first in the world.
Cleaning and Drying the Rapeseed
If the soil, stems and leaves and other debris mixed in with the rapeseed are not removed before it enters the oil press, it will not only affect the quality of the oil and the pressed cake, but will also absorb part of the oil, lowering the oil yield. If sand, stones, metal, hemp rope and other debris are mixed in with the rapeseed, it will cause even more wear to the machine parts, trigger production accidents and affect the process results. Therefore, to ensure smooth production, impurities must be removed as much as possible, and for individual rapeseed fruits with high moisture content, drying is also very necessary in order to make shelling easier.
Heat Treatment
Heat treatment is one of the most important steps in the oil extraction process, including moistening and heating the raw cake, known in production as steaming the cake or roasting the cake; the cake after steaming and roasting is called the cooked cake. Pressing raw cake after heat treatment is called hot pressing, and pressing without heat treatment is called cold pressing. Rapeseed is mainly hot pressed. The quality of the heat treatment has a direct effect on the smooth progress of the entire oil-making process, the level of the oil yield, and the quality of the oil and the pressed cake.
Pressing
The round press bars of the oil press have a sawtooth-shaped curve and a conical surface. When the rapeseed is being pressed, it is pushed and squeezed by the pressing screw, causing the volume of the space between the pressing screw and the inner wall of the press cage to change constantly. At the rear part of the press cage, because round press bars are arranged there, the inner wall of the press cage is sawtooth-shaped; the material cake is alternately pressed and relaxed here, and the structure of the material cake is constantly adjusted and it is evenly turned, so that the material cake from which the oil has not been pressed out, or from which less oil has been pressed out, has more opportunity to be fully pressed.