Canolol oxidative stability

In the literature, canolol is described as an effective antioxidant (Koski et al., 2003 Kuwahara et al., 2004 Vuorela et al., 2005 Wakamatsu et al., 2005). Figure 17.8 shows increased oxidative stability of canola oil accompanied increasing amounts of canolol. Using the Rancimat test at 120°C canolol contents below 200 itg/g in canola oil from roasted seeds resulted in slight decrease of the oxidative stability. In contrast, amounts of canolol higher than 200 g/g improved oxidative stability of the oil dramatically. Wijesundera et al. (2008) also showed an improvement in... 

FIGURE 17.8 Formation of canolol during roasting of canola seeds and its effect on the oxidation stability of the resulting oil in the Rancimat test at 120°C. 

At higher contents of canolol in the oil, a good correlation with the oxidation stability using the Rancimat test was found. If the temperature load was <15 min at 180°C, a decrease in the oxidation stability was observed due to the low formation of canolol. With increasing temperature load, the oxidation stability increased from 4 to 7 h, before the oxidation stability decreased again as a result of a temperature load of more than 45 min at 180°C. At a low temperature load, less canolol is formed so that the temperature is sufficient to impair the oxidation stability of the oil. Only when the content of canolol in the oil from roasted seeds increases does oxidative stability improve. If the temperature load is too high, the impairment of the oil is faster, then the formation of canolol can improve the oxidation stability. 

The effect of canolol on the storage stability was confirmed by storing canola oil at 60°C over 168 h. The parameters used to monitor the oxidative state of the oil were diene absorption as well as the hexanal content. An increase of absorption at 240 nm was found as a resnlt of a shift of the double bond in unsaturated fatty acids during oxidation. Hexanal, a key compound of the oxidation of fats and oil can be used as an indicator to follow the extent of oxidation. 

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