Improved frying stability of canola oil blended with palm olein and virgin olive oils as affected by bene kernel oil and its unsaponifiable matter

<jats:sec><jats:label /><jats:p>Bene kernel oil and its unsaponifiable matter fraction, which have been known to be very effective natural sources of antioxidative compounds, were used to improve the frying stability of canola oil blended with palm olein and virgin olive oils (75:15:10) at 180°C. The powerful synthetic antioxidant <jats:italic>tert</jats:italic>‐butylhydroquinone (TBHQ, 100 mg/kg) was employed for the comparative purposes. Frying stability of the oil samples was measured based on the variations of conjugated diene value, carbonyl value, total polar compounds content, thermo‐oxidative and hydrolytic components, and the content of total tocopherols. In the presence of bene kernel oil and its unsaponifiable matter fraction the conjugated diene (194–224 vs. 244%) and carbonyl values decreased significantly (183–265 vs. 358%). Furthermore, the antioxidative additives showed more inhibitory effect on thermo‐oxidative reactions than hydrolytic ones during the frying process. The best frying performance was obtained by using 1000 mg/kg of bene kernel oil and 100 mg/kg of the unsaponifiable matter fraction of bene kernel oil and TBHQ.</jats:p><jats:p><jats:bold>Practical applications:</jats:bold> The frying stability of the canola oil increased in the presence of with palm olein and virgin olive oils. Furthermore, canola oil blended with palm olein and virgin olive oils (75:15:10) containing the Bene kernel oil, unsaponifiable matter fraction of bene kernel oil, and <jats:italic>tert</jats:italic>‐butylhydroquinone (TBHQ) showed much more considerable frying stability, indicating their antioxidative activities. It was interesting to find that there was no marked difference between the effect of 1000 mg/kg Bene kernel oil, 100 mg/kg unsaponifiable matter fraction of bene kernel oil, and 100 mg/kg TBHQ.</jats:p><jats:p><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/ejlt201400344-gra-0001.png" xlink:title="ejlt201400344-gra-0001" /></jats:p><jats:p>Among the different groups of thermo‐oxidative polar components, the contents of the triglyceride dimers (TGD), and triglyceride polymers (TGP) should be considered carefully, as feeding trials showed that they were fairly well absorbed and presented toxic or other biological effects. Therefore, a number of European countries, for example, Belgium and the Czech Republic, has legislated a 10% maximal TGDP (TGD + TGP) content as a criterion for evaluating used frying oils. The TGDP content of the canola oil and their blends during the frying process at 180°C showed linear increases (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> > 0.98) from 3.17–4.3 to 64.23–156.5 mg/g at the end of the frying process. Considering the cutoff point of 10% TGDP, Fig shows the maximum time that the CAOs could be used for frying. These critical times for the CAO and their blends were significantly different and calculated to be 29.2–54.80 h. It was interesting to find that there was no marked difference between the effect of 100 mg/kg UFB and 100 mg/kg TBHQ (54.04 and 54.74).</jats:p></jats:sec>