Z. Bachari Saleh - Department of Food Science and Technology, Faculty of Agriculture and Natural Resources, Science and Research Branch, Islamic Azad University, Tehran, Islamic Republic of Iran.
H. Ezzatpanah - Department of Food Science and Technology, Faculty of Agriculture and Natural Resources, Science and Research Branch, Islamic Azad University, Tehran, Islamic Republic of Iran.
M. Aminafshar - Department of Animal Science, Faculty of Agriculture and Natural Resources, Science and Research Branch, Islamic Azad University, Tehran, Islamic Republic of Iran.
H. Safafar - Technical Manager, Olive Oil Section, Techno Azma Laboratory, Adl Blvd, Poonak Sq., Tehran, Islamic Republic of Iran.

The present study was carried out to investigate the effect of various refining processes’ conditions on conjugated dienes in soybean oil. Conjugated dienes contents of soybean oil were found to undergo reduction in neutralization and bleaching steps while being increased in deodorization. It was observed that alkali refining (neutralization) through ۱۲ and ۱۴ °Bé, bleaching with either acid activated clay or a mixture of acid activated clay plus activated carbon at ۱۱۰˚C along with deodorization at ۲۲۰˚C and at ۴ or ۸ mbar had the highest effect on reduction of conjugated dienes in soybean oil. Conjugated dienes were in good correlation with peroxide value, free fatty acids, Totox value and as well with p-anisidine value in each step. Overall, alkali refining 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.

Conjugated dienoic acid, Edible oil, Oil processing, Peroxide value, p-Anisidine value