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Squeezing is to separate oil directly from the oil by physical pressure. The edible oil squeezing process is mainly a physical change. However, in the squeezing process of edible oil, due to the influence of moisture and temperature changes, certain biochemical changes will also occur, such as protein denaturation, enzyme damage and inhibition, and oil oxidation.

The edible oil squeezing process is an oil squeezing process that uses mechanical force to squeeze the fat from the oil. The edible oil squeezing process can be divided into one-time squeezing and pre-squeezing with leaching and extracting oil by pressing the depth of the squeezed oil and the pressure on the squeezed material during squeezing. Compared with other oil-making processes, the edible oil pressing process has the advantages of simple process, less supporting equipment, strong adaptability to oil varieties, flexible production, good oil quality, light color and pure flavor. However, the residual oil content of the cake after pressing is high, the power consumption is large, and the parts are easy to wear. The edible oil pressing process can be used to extract oil from seeds or nuts such as cocoa beans, coconuts, peanuts, palm kernels, soybeans, and rapeseeds.

The basic principle of edible oil pressing process:

Most of the pre-treated preforms are in a condensed state, and most of these agglomerated oils are present in the pores of the gel bundles of the cells, and external force is used to squeeze them out. During the squeezing process of edible oil, pressure, viscosity and oil cake forming are the three elements of oil production by the squeezing method. Pressure and viscosity are the main power and possible conditions that determine the squeezing and oil discharge, and the forming of the oil cake is the necessary condition to determine the squeezing and oil discharge.

According to whether the material is heat-treated before pressing, the edible oil pressing process can be divided into a hot pressing oil process and a cold pressing oil process.

Hot pressing is to squeeze the seeds of oil crops after roasting, with special fragrance, darker color and higher yield. There are less residues in the product and it is easy to store. The cold-pressed seeds are not roasted, so the smell is poor, but the color is good. There is no solvent residue in both pressing methods. Hot pressing is an oil pressing process of steaming and frying in hot state and pressing with skin. At first, the raw materials are fried in a pot, and then the oil is squeezed through the pressing equipment. The advantage of the hot oil pressing process is that the oil fragrant oil yield is high, and the remaining residual oil is low.

Compared with the hot oil pressing process, the cold pressing oil process strives to avoid overheating and excessive chemical treatment of the oil, so that the quality of the refined oil and cakes will be correspondingly accelerated, such as the taste and appearance of the oil, and maintain The pure natural characteristics of the oil can avoid harmful substances when processing the oil at high temperature, and retain the physiologically active substances in the oil as much as possible, such as vitamin E, r-linolenic acid, etc. The meal protein after the oil processing can also be more fully utilized. The oil obtained by cold pressing contains only a small amount of phosphorus and free fatty acids, and has good quality characteristics such as light color, exceptionally soft taste, and delicate smell.