Heat stability of the oils from current canola cultivars in Iran

In this research, heat stability of the oils from the current canola cultivars in Iran (Okapi, Hyola 401, Zarfam, and Talayeh) was compared in terms of the resistance to the conjugated diene hydroperoxides production during the heating process at 180 ºC. The stability test results were analyzed based on the polyene index, peroxide value, acid value, and total tocopherol and phenolic compounds. The highest original conjugated diene value (CDV) belonged to the oils from the Zarfam (8.18) and Okapi (7.73) cultivars in Khorasan Razavi province and the Hyola cultivar (7.78) in Golestan province, and the lowest ones belonged to the oils from the Zarfam (5.38) and Talayeh (5.85) cultivars in Tehran and Fars provinces, respectively. The CDVs exponentially increased during the heating process. The oil from the Okapi cultivar totally had the highest heat resistance to the conjugated diene hydroperoxides production. After 4 h of the heating process, the CDV of the oil from the Zarfam-Khorasan Razavi cultivar varied more severely, but finally at the end of the heating process, showed a similar status to the oil from the Okapi cultivar. Heat stability of the oil from the Zarfam-Tehran cultivar was relatively lower than that of the Zarfam-Khorasan Razavi cultivar. The oil from the Hyola-Golestan cultivar had a moderate heat stability among the canola oils studied, and then the oil from the Hyola-Mazandaran cultivar. After 4 h of the heating process, the oil from the Talayeh-Fars cultivar had a similar quality to the oil from the Zarfam-Khorasan Razavi cultivar but its quality decreased more severely than that of the other non-Talayeh cultivars at the end of the heating process. Finally, the oil from the Talayeh-Khorasan Razavi cultivar had the lowest heat stability after 8 h of the heating process. Assuming the same original quality for the canola oils studied, heat stability was in the order of the Zarfam-Khorasan Razavi > Okapi-Khorasan Razavi > Hyola-Golestan > Zarfam-Tehran > Hyola-Mazandaran > Talayeh-Fars = Talayeh-Khorasan Razavi.