Evaluation of antioxidant activity of red bell pepper extract in soybean oil

Edible oils and fats are an important part of human diet. Oxidation has an adverse effect on the storage of oils in two ways, including reduced shelf life and reduced nutritional value, which is due to the production of undesirable compounds and procarcinogen properties during high heating. There are several ways to prevent the oxidation of oils, one of them is the addition of synthetic antioxidants. Due to the fact that synthetic antioxidants have adverse effects, such as mutagenicity and procarcinogen, on the human body, research on natural antioxidant sources seems to be essential in order to replace synthetic compounds. At present, increasing attention is paid to natural antioxidants and preservatives, including plant extracts. The most important positive feature of natural antioxidants compared to synthetic antioxidants is their safety and high acceptance by consumers.

In this study, ethanolic extract of red bell pepper was extracted by ultrasound. Then the free radical scavenging power of the extracts at concentrations of 100, 200, 400, 800, 1600 ppm was measured by DPPH test. A completely randomized statistical design was used to evaluate the results. Data were analyzed using SAS statistical software and the means were compared using Duncan test at the probability level. Microsoft Excel 2016 software was used to draw the charts.

The results showed that as the concentration of the extract increased from 100 to 1600 ppm, the antioxidant property of the extract also increased. In addition, as the concentration of the extract in soybean oil increased, the free radical scavenging activity of the oil increased significantly. Moreover, there was a statistically significant difference between the concentrations of 100, 200, 400, 800, 1600 with the control sample at 0.01 level. The highest free radical scavenging power was observed at 1600 ppm and the lowest was observed in the control sample; so that at a concentration of 1600 ppm, the antioxidant properties increased.

The results of oil oxidative stability containing different concentrations showed that the sample containing 1600 ppm of red bell pepper extract had a greater effect on reducing the TBA index. Furthermore, it has a greater effect on increasing the oxidative stability index than other concentrations and also compared to the synthetic antioxidant BHT at a concentration of 200 ppm. Due to the presence of phenolic compounds and antioxidant activity in higher concentrations of bell pepper extract and a positive effect on maintaining oil quality, a decrease in oxidation during storage is evident in comparison of the control sample containing no antioxidants and the sample containing synthetic antioxidants. Therefore, The higher antioxidant capacity of 1600 ppm compared to other concentrations during the thermal process can be attributed to the residual amounts of most phenolic compounds in it at 65 ° C and also the high amount of these compounds in the extract.