The Effect of Refining Process on the Conjugated Di enes in Soybean Oil

Abstract

The present study was carried out to investigate t he effect of various refining processes’ conditions on conjugated dienes in soybe an oil. Conjugated dienes contents of soybean oil were found to undergo reduction in neut ralization and bleaching steps while being increased in deodorization. It was observed t hat alkali refining (neutralization) through 12 and 14 °Bé, bleaching with either acid ac tivated clay or a mixture of acid activated clay plus activated carbon at 110 ̊C along with deodorization at 220 ̊C and at 4 or 8 mbar had the highest effect on reduction of co njugated dienes in soybean oil. Conjugated dienes were in good correlation with per oxide value, free fatty acids, Totox value and as well with p -anisidine value in each step. Overall, alkali refi ning proved to be the most effective step in reduction of conjugated dienes, free fatty acids and oxidative stability index. Peroxide value, p -anisidine and Totox values changed during refining and got significantly decreased in deodorization. Keywords: Conjugated dienoic acid, Edible oil, Oil processing , Peroxide value, p -Anisidine value.