The changes in colour (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 C was compared with tert-butylhydroquinone (TBHQ, 100 ppm) 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 efficiency of samples containing 100 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 theTPCcontent 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.

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