The Effect of Roasted Sesame Seed Oil on the Color Stability of Paprika Oleoresin
Walter, Polly Anastasia
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Roasted sesame seed oils are known to have high levels of antioxidants, which resist oxidation that causes the oil to go rancid. The antioxidant effect of the oil is due to a combination of the Maillard browning product formed during roasting, tocopherols and the lignans. The tocopherol and lignan levels can also be altered during this roasting process. Numerous roasting methods, such as an oven, microwave and stovetop, were used to optimize the formation of products containing antioxidants. Ideally, the added stability from the roasted seed oil could be transferred to a unstable pigment dissolved in it. Roasted sesame oil was used to inhibit oxidation in carotenoid pigments, commonly used in the food industry. The rancidity of the oil was monitored by measuring the peroxide value of the oil. A high peroxide level is characteristic of an oil that is extremely rancid. By accelerating the degregation of the oil, the oxidative stability is also monitored. These tests are used to monitor the original condition of the oil. Once the oil is blended with a carotenoid pigment, further testing is done to observe the effect of the oil on the color stability. A silica gel TLC plate first spotted with the oil, then dipped into a carotenoid solution and faded in an oven at 200°C demonstrates that the roasted oil increases the color stability. Distinct red spots remain where the plate was spotted, while the rest of the plate was white. However, this was not the result when the medium was changed to flour salt (a blend of flour and salt commonly used in the food industry). The color of dispersion of carotenoid on flour salt was monitored as a function of time in an oven at 65 °C. Roasted sesame oil has a positive effect on the color stability of the dyed salt sample, increasing the 2/3 life (the length oftime for the flour salt to fade to 2/3 of the original color) by 38%. This 2/3 life test measures the effectiveness of the antioxidant. Additives such as ascorbic acid can increase the stability even more. Foods colored with these pigments have a longer shelf, due to a more durable color.