The oil contains a small amount of wax, which can raise the cloud point，reduce the transparency and digestion rate of oil, and make the taste and palatability worse, thus reducing the edible quality, nutritional value and industrial use value of oil. On the other hand, wax is an important industrial raw material and can be used for wax paper, water repellent, gloss agent and the other. Therefore, the removal or extraction of wax from the oil can achieve the purpose of improving the quality of the edible oil and the comprehensive utilization of the vegetable oil wax source.

Separation is essentially divided into two parts: crystallization and solid-liquid separation.

The crystallization process of oils and fats can be divided into three stages:

(1) supersaturation of oils and fats or rapid cooling after melting, which makes the high melting point begin to segregate sufficiently;

(2) slow cooling and slow stirring (135/min) promote the formation of crystalline nuclei;

(3) continue cooling to the target temperature, so that the crystals increase (also known as the crystallization stage), and then to be separated. The main conditions for crystallization are as follows:

(1) crystallization temperature. The temperature is required to be lower than the setting point of the solid grease.

(2) Cooling rate. Each kind of grease has its specific freezing crystallization curve.

(3) Mixing speed. Generally controlled at 10-13r/min.

At present, dry separation is basically used in most country, so the separation method is mainly completed by pressure filtration. The wax components in different vegetable oils are different, and the content of straight chain alcohols in waxes in various vegetable oils is different.