Abstract
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.
Highlights
Deep-fat frying is one of the oldest and most popular food preparation methods (Garayo and Moreira, 2002)
Various methods to improve the oxidative stability of soybean oil have been developed and studied, for example, partial hydrogenation, fatty acid modification and blending with more saturated or monosaturated oils to reduce the amount of polyunsaturated fatty acids (Cuesta et al, 1993; Hunter and Applewhite, 1991; Su and White, 2004)
The main objective of the present study was to evaluate the effects of the fatty acid compositions of tiger nut oil, sunflower oil and binary mixtures of them on the changes in physicochemical parameters during the deep frying process by assessing the Free Fatty Acids (FFA), Peroxide Value (PV), thiobarbituric acid value (TBA value), iodine value, Total Polar Compounds (TPC), as well as the color and viscosity of the oils
Summary
Deep-fat frying is one of the oldest and most popular food preparation methods (Garayo and Moreira, 2002). These reactions in the deep-fat frying process depend on factors such as replacement with fresh oil, frying conditions, original quality of the frying oil, food materials, type of fryer, type and concentration of antioxidants and oxygen concentration (SánchezMuniz et al, 1992) Other factors such as frying temperature, quantity of frying, initial content of free fatty acids, polyvalent metals, type of food material, design and maintenance of fryer, light, use of filters and unsaturated fatty acid content of the oil affect the oxidative stability and overall quality of the oil during the frying process (Melton et al, 1994; Paul and Mittal, 1996; Farag and El-Anany, 2006; El-Anany and Ali, 2008). The oils can be blended even to derive a protective advantage due to the presence of specific ingredients that offer protection against oxidation to improve frying recyclability (Toliwal et al, 2005)
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