Abstract The protective role of water injection on oil quality was studied in deep fat frying conditions. Oil stability indices included acid value (AV), malondialde- hyde (MDA), p-anisidine, and conjugated dienes (CDs). Water was continuously injected at flow rates of 0.1 to 1.0 and 0.1 to 0.5 mL/min/L into corn and canola oil, respectively. Frying was conducted at 170