The oil refining process includes important processes such as degumming, deacidification, decolorization and deodorization of fats and oils, which are commonly known as the four deodorization processes. Among them, the deodorization of fats and oils is the process of removing odorous substances in fats and oils. Gross oil by degumming, deacidification, decolorization, there are still some bad odors in the oil, such as vegetable oil soap flavor, white earth flavor, etc., these bad odors will have a bad impact on the sensory quality of edible oil. The substances that cause bad odor are mainly low molecular aldehydes, ketones and some free fatty acids and their oxides. These odor substances have low boiling points and affect the flavor, odor, color and stability of fats and oils.

        Deodorization of fats and oils is the use of fats and oils in the odor and triglyceride volatility of the difference between the high temperature, high vacuum conditions with the help of water vapor distillation to remove the odor of the material process, in the liquid - gas mass transfer process, through the vapor - liquid contact, so that the steam is saturated by the volatile odor of the material to escape from the oil, to achieve the purpose of removing the odor of the material in the edible oils. Deodorization is not only to remove the odor substances in the oil, but also to improve the smoke point in the process, improve the flavor of edible oil, and also remove the undesirable substances, including peroxides and decomposition products, protein volatile decomposition products, small molecular weight aromatic hydrocarbons, and residual pesticides (e.g., ddt), etc., and in addition to destroying a part of the pigmentation of the oil, thus improving the quality of the oil.

        Factors affecting the effect of deodorization of fats and oils in addition to the deodorization tower itself, there are mainly the following aspects: feed flow, deodorization time, deodorization temperature, deodorization of the vacuum and the direct steam intake.

        To give a common and easy to understand example, can be deodorized grease is understood as clothes to be dried, the feed flow is understood as the number of pieces of clothing, the odor in the grease is understood as the water contained in the clothes, deodorization steam is understood as the wind, the deodorization temperature is understood as the ambient temperature of the drying of clothes. The fewer the clothes to be dried, the thinner the clothes are spread out in the limited space, the higher the ambient temperature, the higher the wind speed, the faster the water in the clothes is removed, and the shorter the drying time of the clothes. Translated into the deodorization process is that the smaller the feed flow, the higher the deodorization temperature, the more direct vapor flux, the faster the removal of odor substances in the grease, the shorter the deodorization time.

        When drying clothes, the number of pieces is too small, the drying space is wasted; the ambient temperature is too high, the clothes are easy to be scalded; the wind speed is too fast, the clothes are easy to be blown away by the wind. Similarly, if the flow rate of deodorization is too small, the capacity of the equipment will be greatly reduced, and it will also affect the deodorization time; if the temperature of deodorization is too high, the oil will be easy to oxidize, decompose and polymerize and other undesirable reactions, which will cause excessive loss of micro-nutrients, increase the harmful substances such as trans fatty acid, 3-chloropropanol ester and glycidyl ester, and the color will be deepened, which will reduce the nutritional value and quality of the oil; if the direct steam is too large, the oil will have the following advantages may be taken away with the odor substance, thus reducing the yield of deodorization.

        The main functions of deodorization vacuum here are as follows: ① avoid the contact of oil and grease with oxygen under high temperature, prevent the oxidation, decomposition and polymerization of oil and grease, especially the oxidation and decomposition of unsaturated fatty acid; ② reduce the boiling point of deodorized distillate, so that it can be quickly removed under lower temperature; ③ reduce the deodorization temperature, avoid the isomerization of fatty acid and the decomposition and polymerization of oil and grease, and thus control the trans fatty acid, 3-chloropropanol, 3-chloropropanol, 3-chloroethylene ester, and other fatty acids, and the polymerization of fatty acid. (iii) Reduce the deodorization temperature to avoid isomerization of fatty acids and decomposition and polymerization of fats and oils, so as to control the production of harmful substances such as trans fatty acids, 3-chloropropanol esters and glycidyl esters, etc.; (iv) Reduce the deodorization temperature to avoid the destruction of micro-nutrients in fats and oils at high temperatures.