Study on the Degradation of Oil During Frying of Sel-Roti by Oil Dilution Method

Rice flour of course, medium and fine particle sizes (30:50:20) was blended with sugar, ghee and water followed by kneading to get batter of optimum consistency. After ageing the batter for 1 h, it was poured manually in a ring shape into oil maintained at 210°C. Each sel-roti was fried for about 45 s and turned upside down for uniform cooking. Frying was conducted in 1 h daily cycle to represent common daily frying practices, with batter mixed before each batch to ensure uniformity and aeration. The frying process was repeated for five consecutive days and the oil lost during frying was replenished by fresh oil each day to maintain constant volume of frying oil. The oil samples collected after each frying cycle were stored in refrigerator until analysis. Total polar compounds (TPC), para-anisidine value (p‑AV), acid value (AV), peroxide value (PV), TOTOX value and iodine value (IV) were analyzed. The values for TPC, p‑AV, AV, PV and TOTOX increased significantly (p˂0.05) with repeated frying, reflecting the accumulation of primary and secondary oxidation products. However, IV decreased progressively with frying time which could be attributed to a loss of unsaturation due to oxidative and thermal degradation. Major quality parameters showed strong positive correlations that further supported the progression of oil degradation. Almost all parameters were within safety limits throughout the study period, however, the continuous oil degradation signified potential risks associated with repeated oil use. Oil replenishment retarded oil degradation but could not completely prevent it. The findings emphasize the significance of regular monitoring of oil quality and recommend limiting repeated use of frying oil to ensure food safety and maintain nutritional quality.