Investigation on the frying stability of canola oil as affected by bene kernel oil and its unsaponifiable matters fraction using colour chanes measured by the method of image processing

The changes in color (L, a, b and total colour difference, TCD) of canola oil (CAO) as affected by bene kernel oil (BKO, 0.05-0.4%) and its unsaponifiable matters (USM, 100 ppm) fraction during 48 h frying process at 180 ºC was compared with tert-butylhydroquinone (TBHQ, 100ppm) by the method of image processing. The BKO, TBHQ or USM were significantly capable of lowering the darkness (lowering L value), redness (increasing a value), yellowness (increasing b value), TCD, and total polar compounds (TPC) content of the CAO during the frying process. The effeciency of samples containing100 ppm USM and 0.1% BKO was the same as or much better than that of 100 ppm TBHQ. There was a strong correlation (R2=0.965) between the TPC content and TCD of the oils studied. Assuming that the maximum level of TPC content permitted in frying oils is 24%, the TCD of the oils studied should be ≤ 20.98.