Discarding time evaluation of canola oil based on oxidation indexes during potato deep frying

Repeated uses of frying oil may cause oil deterioration due to subsequent hydrolysis and oxidation reactions. Oxidation products will expose the consumer health to serious dangers. In this project discarding time of canola oil during 40 hours potato frying in different conditions (temperatures 150, 165 and 180 0C, concentration 0, 50 and 100 ppm antioxidant TBHQ) was evaluated based on oxidation tests. Oil stability was determined by measuring acidic value (AV), peroxide value (PV), conjugated diene value (CDV), carbonyl value (CV) and total polar compounds (TPC). The results showed that after 34.1, >40 and 22.9 hours frying the PV, CV and TPC of canola oil respectively was maximum (based on national and international standards at temperature 150 0C). Increasing the temperature up to 180 0C, the rejection time based on these indexes decreased to 28.9, 35.4 and 16.4 hours, respectively. CDV of free antioxidant canola oil increased 592.1 % after 40 hours frying. It was 706.5 and 738.1 % for canola oil containing 50 and 100 ppm, respectively. Also, there was no significant difference between concentrations from 50 to 100 ppm in discarding time development.