ABSTRACT
Refined expeller-pressed (RCanO-I and RCanO-II) and expeller-pressed and solvent-extracted blended (RCanO-III and RCanO-IV) canola oils were compared to determine the effect of processing (extraction) practice on the frying life of canola oil. Samples were from the 2016/2017 and 2017/2018 production seasons and were used to fry potato chips for 36 to 48 cycles. Frying life was assessed by the total polar compounds, retention of tocopherols, antioxidant activity, and other quality indices. RCanO-II exhibited significantly, the longest frying life as compared with the other three oils and this correlated with tocopherol retention and antioxidant activity (p < 0.05). The extraction practice influenced the frying life of canola oil, but this was dependent on other processing practices employed by the individual processors. Variations in initial oil quality dictated the rates of chemical reactions occurring in the oils during frying and influenced oil stability.
ABSTRACT
@#<p style="text-align: justify;"><strong>BACKGROUND:</strong> Cooking oils used for long periods of frying are subject to oil deterioration. Total polar compounds (TPC) is the general parameter used to quantify oil deterioration wherein the maximum allowable TPC of cooking oil is 25%. The time it takes to reach 25% TPC was defined as the frying life of oil.</p><p style="text-align: justify;"><strong>OBJECTIVES:</strong> This study was undertaken to determine the effect of oil type and frying temperature on frying life.</p><p style="text-align: justify;"><strong>METHODS:</strong> The frying lives of coconut, canola, and palm oil as well as the oils heated at 150ºC, 170ºC, and 190ºC were determined. Spectrophotometric analysis was performed and TPC values were calculated from absorbance using the equation: y = -2.7865x2 + 23.782x + 1.0309.</p><p style="text-align: justify;"><strong>RESULTS AND DISCUSSIONS:</strong> The mean frying lives were 20.24h, 10.80h, and 13.49h for coconut, canola, and palm oil, respectively. Regardless of oil types, the mean frying lives were 16.23h, 11.93h, and 13.82h at the following frying temperatures namely; 150ºC, 170ºC, and 190ºC , respectively. Two-way ANOVA showed a significant difference in the frying lives of the three oil types and those of the three frying temperatures.</p><p style="text-align: justify;"><strong>CONCLUSION:</strong> Coconut oil had a longer mean frying life than both palm and canola oil. In terms of frying temperature, the longest mean frying life was observed in the oils heated at 150ºC, followed by the oils heated at 190ºC. There was a significant interaction between oil type and frying temperature observed in the study.</p>
