What is crude oil:The unrefined animal and vegetable oils obtained by pressing and leaching are called crude oil.Its main ingredient is a mixture of various triglycerides,commonly known as neutral oil.Impurities in crude oil:after chemical and physical refining,impurities in crude oil can be reduced to a certain standard to obtain qualified oil products.The main impurities in the crude oil are as follows:
(1).Suspended impurities:solid impurities such as silt and cake residue
(2).Colloidal impurities:mainly phospholipids
(3).Oil-soluble impurities:mainly free fatty acid(FFA),pigment,etc
The steps of refining crude oil by refined refining equipment are as follows:
(1).The presence of suspended impurities,colloidal impurities and water will be conducive to microbial activities and make oil hydrolysis rancidity.
(2).The presence of phospholipids will make the appearance of grease cloudy and dull.There's a lot of foam when you're cooking.
(3).Grease contain FFA too high,will make fat smell thick,poor flavor,some FFA will smoke when cooking.
(4).Bad pigments make the grease darker or even darker.So in order to get consumers to accept the product,must be refined to the crude oil.The operation of refining equipment usually consists of dewaxing,easterning and stripping.The latter separation process is based on the melting point difference between triglycerides to separate out the components with relatively high melting point and purify them separately.In addition,dewaxing and easternization in the process belong to the special situation in the separation.Refining dewaxing is the removal of high melting point waxes from liquid oils.The waxes in vegetable oils are contained in seed coats,shells and germs of vegetable oils,and the content of waxes varies with different vegetable oils and with different processing methods.It has a very low solubility in oils and a high melting point(78-82 degrees),so it cannot be absorbed by the human body and is difficult to be created.The content of wax in vegetable oil is very low except rice bran oil.Therefore,in daily production,the dewaxing of rice bran oil needs to be treated separately,and other vegetable oil is generally removed together through the process of winter dewaxing.As for winterization,it refers to the removal of high melting point triglycerides(mainly saturated esters)from liquid oils such as cottonseed oil.The aim is to produce high quality edible oil(the so-called first grade oil in China).In essence,the separation is divided into crystallization and solid-liquid separation.
The process of oil crystallization is generally divided into three stages,namely:
(1)Make the oil or grease cool down quickly after melting to form a supersaturated state,so that the high melting point begins to be fully isolated;
(2)Slow cooling and slow stirring(135/min)promoted the formation of crystal nucleus;
(3)Continue to cool to the target temperature to increase the crystal(also known as the trophic stage),and then to be separated.The main conditions for crystal formation:(1)crystallization temperature.The temperature is required to be lower than the freezing point of the solid lipid.
(2)Stirring speed.Generally controlled at 10-13r/min.
(3)Cooling rate.Each type of oil has its own frozen crystallization curve.In the country now mostly still use the dry method separation to produce,so the method of separation is also mainly by pressure filtration,the wax composition contained in different vegetable oil also has differences,the content of linear alcohol composed of wax in all kinds of vegetable oil is different.
Henan Jinzheng Grain and Oil Machinery Technology Co. LTD
|Contact person: Manager Wang|
|E-mail: 1519228 @qq.com|
Address: Henan University of Technology
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