Effect Of Refining On Soybean Oil Quality

This work evaluates SBO samples from 26 domestic large-scale soybean oil refineries as to changes of indices (tocopherol, trans fatty acid, oxidative stability, etc) during refining and studies changes of SBO quality during refining especially in deodorization.Analysis of conventional indices indicated that: 1) each process has a significant influence on color, but deodorization plays a decisive role in colorant removal, reducing R by 3.2; 2) alkali refining and deodorization has significant effects on FFA removal, and deodorization reduces FFA content to the minimum.Under existing refining conditions, the average tocopherol content in deodorization oil from 26 refineries is 106.87mg/100g with a total refining loss of 15.6% including a deodorization loss of 12.5%, which account for 80.1%. Deodorization was the key step causing significant tocopherol losses. During deodorization stage, small amounts of linoleic acid was isomerized to produce an average TFA content of 1.47%. Deodorization oil exhibited an average AOM value of 13.41h, and the whole refining process did not significantly reduce the oxidation stability of oils.Studied effect of deodorizing conditions and equipment on SBO quality, show that, soft colum has better performance than plate tower as to reducing tocopehrol loss, and controlling TFA generation; but both types of deodorizer show similar effects on raising the AOM value of SBO under normal conditions. In addition to temperature and time, the usage of stirring steam and operating pressure are also key factors influencing minor compounds contents.Among 26 refineries, 15.4% of Plants, its deodorization conditions are considered as appropriate, which tocopherol deodorizer loss not exceed 10%, and TFA generation less than 1.01%, and oxidative stability of bleached SBO increased more than 22%. About 11.5% of Plants, its deodorization conditions are harsh, resulting in excessive oil refining. Tocopherol deodorizer loss of part Plants is up to 22.9%, TFA content increases 3.21%.Results from SBO refining simulation showed that, with deodorization conditions (temperature and time) intensified, tocopherol and TFA content showed remarkable changes. Stirring steam and vacuum may be key factors that affect tocopherol and TFA content in oil. Various characteristics of SBO was found to affect its oxidative stability in the following order: TFA contents > acid value > tocopherol contents > peroxide value > color.