There are two process methods for extracting edible oil from plants, the chemical oil extraction method and the physical oil extraction method, or what we usually call the leaching method (chemical) and the pressing method (physical pressing method: the pressing method has a long history and its process is relatively simple: the oil is steamed and fried and then the oil is squeezed out of the oil by mechanical means. The ancient pressing method requires heavy physical labor for the operator. The residual oil content of the squeezed oil residue (oil cake) is quite high, thus wasting the extremely valuable oil resources. Modern pressing method has been industrialized and automated operation, but the problem of high residual oil content in the oil residue is also distinguished from the pre-treatment of raw materials for pressing there are cold pressing method and hot pressing method, also called cooked pressing method. Cold pressing is the raw materials are not baked or steamed directly into the oil press to squeeze out the oil, this method of oil is relatively light in color, brighter colors, but the oil yield is low, and the oil does not taste thick and tangy. And cooked pressing to put the oil crop in the press before baking thousand, the purpose is to reduce the moisture of raw materials, increase the activity and mobility of oil molecules, so as to improve the oil yield, to ensure that the oil taste fragrant. However, it also destroys the chemical tissue composition of the oil, resulting in a darker and blacker oilseed pressing process with the following basic processes: 1.
1. conventional production process: raw material - steaming and frying - pressing a machine to press the gross oil
2. special oil production process: oil seeds - frying seeds - pressing - filtering - aroma oil
3. special oil production process: oil seeds - whole seeds cold pressing - over loose - cold pressing oil oil is squeezed out of the oil process: when the oil into the oil press chamber, with the rotation of the chamber, the pressure increases. The seeds are squeezed tightly as the oil is extruded, and the direct contact between the particles of the squeeze material generates mutual pressure and causes plastic deformation of the seeds, especially at the rupture of the oil film and the bonding of one. In this way, after being extruded and fried, the pressed material is not a loose body, but a plastic body, called oil cake. When pressing, due to the dual effect of temperature and pressure, the protein will continue to degenerate, and then affect the plasticity of the pressed material, in short, the appropriate degree of protein denaturation to ensure the best pressed oil results.