Improvement of the Oxidative Stability of Canola Oil Using Carum copticum fruit extracts as a Natural Antioxidant

Lipids are valuable foods that operate as the medium of heat transfer to the food and susceptible to oxidation on storage and frying processes. Lipid oxidation is one of the major cause of food quality deterioration during storage for vegetable oils, fats and other food systems. The free radical are defined as any chemical species having one or more unpaired electrons is generally responsible for the deterioration and limiting the shelf life of fatty foods. Characteristic changes associated with oxidative deterioration include development of unpleasant tastes and odors as well as changes in color, specific gravity, viscosity and solubility .Moreover, the products of lipid oxidation may be potentially toxic and may lead to adverse effects such as the production of carcinogens, mutagenesis and aging. Autoxidation occurs when molecular oxygen reacts with unsaturated lipids like canola oil. Antioxidants are a group of chemicals affect the process of lipid oxidation at different stages and capable of extending the shelf life of food that contain lipids. In general, food industry have been added and applied the synthetic antioxidants such as BHA (Butylated hydroxyl anisole), BHT (Butylated hydroxyl anisole) and TBHQ (Tert-butyl hydroquinone) during the manufacturing process to retard lipid oxidation and prevent fat oxidative and rancidity. They are used to retard the development of unpleasant flavour caused by the oxidation of unsaturated fatty acids. They retard oxidation of lipids by reacting with free radicals, chelating free catalytic metals and also by acting as oxygen scavengers. However, there is concern about the safety and toxicity of synthetic antioxidants in relation to their metabolism and accumulation in body organs and tissues. Synthetic antioxidants are known among other things to cause impairment of blood clotting, lung damage and to act as tumor promoters. Consumers acceptance of synthetic antioxidants remains negative due to their perceived detrimental effect on human health like carcinogenic effects. Consequently, This has led to an increasing trend and interest in the search for effective natural antioxidant and there has been a tendency towards natural antioxidants and replace of these synthetic antioxidants with natural ones such as phenolic compounds. Finding new resources of vegetal antioxidants in order to use them in food (as an additive or alternative with artificial antioxidants) is an important research subject in the field of food science and technology.Researches on alternative natural products such as aromatic plants extract and essential oil have been extended. Phenolic compounds are defined as substances possessing a benzene ring bearing one or more hydroxyl substituents, including their functional derivatives. There are different sources of phenols such as grapes, olive oil, sorghum, beans, spices and herbs. Aromatic plants are used traditionally in various regions of Iran for their preservation and medicinal properties, in addition to enhancing the aroma and flavor of foods. Aromatic plants components that have antiradical activities were used as natural antioxidant in food and biological products. Carum copticum (C. copticum )is well known and valuable medicinal plant that is used widely in Iranian traditional medicine. In this study C. copticum ,as natural antioxidant, was added to Canola oil for improving its oxidative stability .The aim of this research was to evaluate the antioxidant properties of C. copticum extracts (aqueous and alcoholic),and its antioxidant activity in canola oil In this study, aqueous and alcoholic extract of C. copticum fruit was extracted as a natural antioxidant. In the first stage, the amount of phenolic compounds content in extracts were measured. Then to determine antioxidant power and activity of extracts the two methods was investigated, DPPH◦ free radical scavenging and β-carotene/linoleic acid system. Each extract at three concentrations of 200 ppm ,400ppm and 600ppm added to canola oil and storage in a period of 49 days. BHT were added to Canola oil at 100 and 200ppm. Also their oxidative stability in canola oil was investigated by measuring peroxide and thiobarbituric acid values. The results showed that, C. copticum has good total phenolic content and in β-caroten bleaching assay, by concentration of 2 mg/ml BHT showed the highest inhibition effect (%96 ± 0.09) and followed CE (%76±0.0). In DPPH◦ free radical scavenging and β-carotene/linoleic acid systems, the sequence of the power of antioxidant activity was BHT then CE in concentration of 400 and 600 ppm. In oven test, all extracts inhibited primary and secondary oxidation products of canola oil. Statistical results revealed that CE in concentration of 600 ppm, did not showed significant difference for PV and TBARS comparing with 200 ppm BHT(p>0.05). But CA and CM had lower antioxidant activity in comparision with 200 ppm BHT (p<0.05). Acocording to results, C. copticum is a potent antioxidant for stabilization of canola oil and can be used as a natural antioxidant. It seems that after complementary test because of appropriate antioxidant activity, C. copticum can be used as natural antioxidant in foodstuff, especially in edible oils to improve the oxidative stability of canola oil.