Effect Of Refining And Storage On Quality Of Rapeseed Oil

Rapeseed oil is one of the main edible oils in our country. It is hopeful to be the dominant edible oil of our people with the extension of low erucic acid rapeseed oil and identity of its nutritive value. The stability and technology control of rapeseed oil are closely wathched in the oil processing.This paper investigates the quality change of low erucic rapeseed oil during its refining and storage.Firstly, this work evaluates rapeseed oil samples from 6 domestic large-scale rapeseed oil refineries as to changes of minor compounds content. The oxidation stability of rapeseed oil showed a significant linear relationship with the minor compounds content,especially the tocopherol content and trans fatty acid content.The acid value,phosphorus content,color and peroxide value of rapeseed oil can meet The National Standard.At the same time,the minor compounds which are conductive to quality,such as tocopherol and sterol, reduce to some extent.The average loss of tocopherol is 23.47% during refining in the 6 domestic large-scale rapeseed oil refineries, and that of sterol is 37.61%.The content of trans fatty acid increases to 3.02% .This shows that rapeseed oil is over refined at present. As a whole, deodorization affect the quality of rapeseed oil most significantly. The deodorization loss of tocopherol is up to 14.43%,that of sterol is up to 15.93%. Therefore, proper deodorization conditions is very important to the rapeseed oil quality.Accordingly, effect of deodorization conditions on the rapeseed oil quality is investigated. Compared with time,the deodorization temperature has a more significant effect on the quality of rapeseed oil. The content of minor compounds vary obviously when the deodorization temperature ranges from 190 oC to 270 oC.Finally, effect of storage conditions on the rapeseed oil quality is investigated. The refining rapeseed oil are stored under 6 conditions:at room temperature in light,at room temperature in natural light,at room temperature in dark place,at room temperature in nitrogen,at room temperature full in container,at low temperature in dark place. The minor compounds which have great change during storage are fatty acid,peroxides and tocopherol.Rapeseed oil can keep good quality under low temperature,at dark place with nitrogen. At the same time ,the result shows that the OSI of rapeseed oil has obvious linear relationship with the content of tocopherol at room temperature in light and in natural light,the linear equations are as follows:Y=2.321 + 0.059X1 - 3.348X2;Y=0.032 +0.097X1.The OSI of rapeseed oil has obvious linear relationship with the content of acid value at room temperature in dark place and in nitrogen, the linear equations are as follows:Y=6.201-13.192X2;Y=5.889-10.255X2.The OSI of rapeseed oil has obvious linear relationship with peroxide value full in container and at low temperature in dark place.,the linear equations are as follows: Y=5.223-0.251X3;Y=5.079-0.138X3.In all equations, X1 represents tocopherol content, X2 represents acid value, X3 represents peroxide value,Y represents OSI.This paper provides the basis of moderate refining and storage of rapeseed oil.