Oils and fats contain trace amounts of wax fat, which will increase the cloud point of the oil, reduce the transparency and digestion and absorption rate of the oil, and worsen the smell and palatability, thereby reducing the edible quality, nutritional value and industrial value of the oil. In addition, Wax is an important industrial raw material and can be used to make wax paper, waterproofing agent, gloss agent, etc. Removing and extracting wax from oils and fats can not only improve the quality, nutritional value and oil-containing food of edible oils, but also improve the industrial utilization value of oils and comprehensively utilize vegetable oils and wax sources.

There are many methods of dewaxing: conventional method, solvent method, surfactant method, combined degumming, deacidification method, etc. In addition, there are also coagulant method, urea method, electrostatic method, etc. Although the auxiliary means used in various methods are different, the basic principles belong to the category of freezing crystallization and then separation. That is, based on the melting point difference between wax and grease and the property that the solubility (or decomposition degree) of wax in grease becomes smaller as the temperature decreases, crystallized wax (or a mixture of wax and crystallizer) is precipitated by cooling, and is separated by filtration or centrifugation. Achieve the purpose of oil-wax separation.

The presence of acyl groups in wax molecules makes wax slightly polar, so wax is a lipophilic compound with a weak hydrophilic group. When the temperature is higher than 40°C, the polarity of wax is weak and it dissolves in oil. As the temperature decreases, the mobility of wax molecules in oil decreases, and the polarity of the ester bonds in wax molecules increases, especially below 30°C. When the temperature continues, the wax crystallizes out and forms a relatively stable colloid system. As the low temperature continues, the wax crystals condense into larger grains, and the density increases to form a suspension. It can be seen that the interfacial tension between oil and wax changes with the Changes with temperature changes. There is an inverse relationship between the interfacial tension and the viscosity, which is the theoretical basis why the dewaxing process must be carried out at a lower temperature.