Effects of the Deodorization Temperature upon the Quality of Soybean Oil

Abstract

Soybean oil, after undergoing the refining, bleaching and deodorization, generally develops objectionable flavours and also tends to increase colour during storage. These phenomena, commonly termed “flavour reversion” and “colour reversion”, are very undesirable when soybean oil is used for preparing salad oil. Several methods have been known to improve the colour-stability of soybean oil. In this paper, effects of the deodorization temperature (240, 270 and 295°C) upon the colour reversion and other properties of soybean oil were studied with the following results.
1. Increase in deodorization temperature causes a progressive decrease in tocopherol content and a higher colour-stability of deodorized oil, but it is attended with a progressive lowering of iodine value. As the deodorization temperature becomes higher, the linoleic and linolenic acid content of deodorized oil decreases, while the conjugated diene content increases.
2. Increase in deodorization temperature lowers the A.O.M. stability of deodorized oil. The A.O.M. stability is, however, fairly improved by adding citric acid to the deodorized oil.
3. The formation of trans-acid becomes more marked as the deodorization temperature becomes higher.