Mahshid Shamloofar; Zahra Ghiasvand; Elham Payandan
Abstract
Introduction: Free radicals may cause lots of diseases in humans and oxidative degradation of lipids is a major factor limiting the shelf life of foods. The free radical reaction of lipid peroxidation is generally responsible for the deterioration of lipid-containing foods. Use of antioxidants during ...
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Introduction: Free radicals may cause lots of diseases in humans and oxidative degradation of lipids is a major factor limiting the shelf life of foods. The free radical reaction of lipid peroxidation is generally responsible for the deterioration of lipid-containing foods. Use of antioxidants during the manufacturing process can minimize the extent of lipid peroxidation. Phenolic antioxidant compounds can prevent the destructive effect of free radicals and their resulting mutation. Sunflower oil is widely used in nutrition as a source of essential linoleic (9-cis, 12-cis-octadecadienoic) acid. The present study explored the chemical constitution and antioxidant activity of Fleawort (Plantago ovate) extract and the effect of these natural antioxidants on sunflower oil. It is well known that edible oils used as cooking medium at high temperatures in the presence of oxygen are subject to therm-oxidation, polymerization, and hydrolysis, and the resulting decomposition products not only produce undesirable off-flavors, but can also decrease the nutritional quality of the fried product.
Material and methods: The present study was carried out in refined sunflower oil, free of additives, supplemented by pure concentration levels of normal and encapsulated extract of Fleawort (i.e., 200, 500, 700 and 1000 ppm) and one level of BHT (200) ppm .The doses of Fleawort extract were chosen in agreement with previous studies that have proved that the inhibitory effect on lipid oxidation increased with the antioxidant concentration In this research the phenolic content of the ethanol extract of Fleawort was determined by Folin–Ciocalteu method. The antioxidant activity of this extract was evaluated using DPPH• and ABTS methods. Furthermore, the oven tests including peroxide and thiobarbituric acid values were done at 65º C in sunflower oil.
Results and discussion: The results showed that different concentrations of this extract were effective in retarding the oil oxidation at 65ºC. Among the treatments, the 1000 ppm Concentration of encapsulated extract has higher antioxidant activity than other treatments during storage time. Based on the evaluation results of phenolic compounds in Plantago ovata extract, the amount of phenolic compounds of this extract will be increased according to the concentration of the extract. Although this index was the highest in treatment of EN 1000, there was no significant difference between the ordinary and encapsulated treatments (p>0/05). According to DPPH Evaluation Test for determining the antioxidant capacity of the samples, the highest amount of DPPH was seen in treatment of EN 1000 (p0/05). Also, based on the Restoration Power Test, treatment of EN 1000 had the most meaningful restoration power and in all concentrations of the extract and treatment showed the most meaningful restoration power (p< 0/05) . Treatments with concentration of 1000 ml/l had the maximum total antioxidant capacity and this treatment showed higher total antioxidant capacity compared to BHT treatment and numerically the total antioxidant capacity of all treatments of BHT was allocated to the treatments with concentration of 200 to 500 ml/l of fleawort extract. Peroxide value was used as indicators for the primary oxidation of sunflower oil. Hydroperoxides are the primary products of lipid oxidation. They are odorless and colorless, but are labile species that can undergo both enzymatic and non-enzymatic degradation to produce a complex array of secondary products. Determination of peroxides can be used as oxidation index for the early stages of lipid oxidation During the test time, both normal and encapsulated 1000 treatments had lower peroxide value through incubation time compared to all other treatments and 1000 EN treatment showed the lowest meaningful level of peroxide value (p
