There are two process methods for extracting edible oil from plants. They are divided into chemical extraction method and physical extraction method.
Physical pressing method: the pressing method has a long history. The process is relatively simple: after the oil is steamed and fried, the oil is mechanically squeezed out from the oil. The ancient pressing method requires heavy manual labor by the operator. And in the squeezed oil residue, the residual oil content is quite high, thus wasting extremely valuable oil resources. Modern pressing method is already an industrialized and automated operation. Cold pressing and hot pressing are also called cooked pressing methods. Cold pressing means that the raw materials are directly fed into the oil press machine to produce oil without roasting or steaming. This method is relatively lighter in color and brighter in color. But the oil yield is low, and the oil taste is not strong and mellow. The cooked oil crops must be dried before pressing, the purpose is to increase the activity and fluidity of the oil molecules, thereby increasing the oil yield and ensuring the fragrant taste of the oil. But it also destroys the chemical composition of the oil, resulting in a darker oil color.
(1) Pressing seeds after heating
Features of hot oil press:
Everyone knows the hot oil press: the oil crops are steamed and then pressed. Usually, the cooked press is used to press cleanly once, without the need for a second time. The oil pressed out by a hot expeller machine smells more mellow.
(2) Pressing seeds without heating
Features of raw press:
Simply put: the raw press does not need to steam and fry the raw materials, and directly put the raw materials into the oil press for pressing. Usually it needs to be pressed 2-3 times before the oil crops can be completely pressed clean. The oil does not smell so mellow, but the raw oil is rich in nutrients, which is very good for the human body, and the raw oil will exude a tangy fragrance during daily cooking.