Physicochemical studies on sunflower oil blended with cold pressed tiger nut oil during the deep frying process

摘要

Sunflower oils were blended with different levels of cold pressed tiger nut oil. Blended oils were obtained by mixing tiger nut oil with sunflower oil at the volume ratios of 0:100, 10: 90, 20: 80, 30: 70, 40: 60, 50:50 and 100: 0. The effects of deep frying on physico-chemical parameters (Free Fatty Acid (FFA), Peroxide Value (PV), thiobarbituric acid value (TBA), iodine value, Total Polar Compounds (TPC), color and viscosity) were evaluated over 30 hours of the frying process. The total phenolic content of native oils was determined. GLC analysis was performed to illustrate the fatty acid composition of sunflower oil, tiger nut oil and binary mixtures of them as well as their oxidation rates. The pure and blended oils were heated at 180°C ± 5°C, then frozen French fried potatoes were fried every 30 min. Oil samples were taken every 5 h and the entire continuous frying period was 30 h. The results showed that fresh sunflower oil had significantly the highest value of COX (7.25); while tiger nut oil had significantly the lowest (2.24). Mixing sunflower oil with different levels of tiger nut oil led to an increase in its stability against oxidation. The phenolic content of cold pressed tiger nut oil was about 3.3 times as high as that of sunflower oil. The analytical data showed that the lowest deterioration during the frying process occurred in tiger nut oil and the highest in sunflower. The changes in the physico-chemical parameters were controlled and significantly (P < 0.05) decreased when tiger nut /sunflower oil (W/W) proportions were varied between 20/80 to 50/50. The obtained results indicate that mixing sunflower oil with cold pressed tiger nut oil increased the stability and hence improved the quality of sunflower oil during the frying process.