Document Type : Research Article
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Abstract
Introduction: Lipid oxidation is a major cause of food quality deterioration during storage of oils, fats and other fat-containing foods. Oxidation of lipids results in changes that may affect the nutritional quality, wholesomeness, colour, flavour and texture of food. 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. The process involves a free radical chain reaction that is most frequently initiated by exposure of unsaturated lipids to light, heat, ionizing radiation, metal ions or metalloprotein catalysts. Free radicals are defined as any chemical species having one or more unpaired electrons. Antioxidants are a group of chemicals capable of extending the shelf life of food that contain lipids. 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. Currently the food industry uses synthetic antioxidants such as BHA, BHT and TBHQ to retard lipid oxidation. 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. As a result of this, consumers have a preference for natural ingredients and there is a growing interest in the potential use of antioxidants from natural sources. Phenolic extracts from herbs and spices, cereals and legumes have been reported to effectively retard lipid oxidation in oils and fatty foods. As a result of concern for the safety of synthetic antioxidants, there is a growing interest in the potential use of phenolic extracts from plant sources as antioxidants in lipids. The potential use of phenolic extracts from different plant sources such as sorghum, herbs and spices have been studied extensively. Extracts of spices such as rosemary and sage are now available commercially for use as natural antioxidants. 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. Phenols have many favourable effects on human health. They decrease the risk of heart diseases by inhibiting the oxidation of low-density lipoproteins (LDL). A large range of low and high molecular weight phenols exhibiting antioxidant properties have been studied and proposed to be used as antioxidants against lipid oxidation. This is particularly true for those phenolics with multiple hydroxyl groups that are generally the most efficient for preventing lipid oxidation. Phenolic compounds are also known to possess antibacterial, antiviral, antimutagenic and anticarcinogenic properties. Generally the efficacy of phenolic compounds as antioxidants depends on a number of factors such as the number of hydroxyl groups bonded to the aromatic ring, the site of bonding, mutual position of hydroxyls in the aromatic ring and their ability to act as hydrogen or electron donating agents and free radical scavengers. All polyphenols are capable of scavenging singlet oxygen and alkyl radical through electron donating properties, thus generating a relatively stable phenoxyl radical. The goals of this study were to investigate the effect of incorporation of different apple cultivars’ phenolicextracts onformation of primary oxidation products in buttercomparing tosome of thesynthetic antioxidants such as BHA and BHT
Material and methods: Different apple cultivars from different places of West Azerbaijan province had been collected and their total phenol content, flavonids and antioxidant properties were measured according to Folin-Ciocalteu, Colorimetry and Diphenylpicrylhydrazyl (DPPH) methods respectively. The measurement of peroxide value and thiobarbituric acid of local butter oil samples consisting of different concentrations of extract and synthetic antioxidants was performed as well.
Discussion & Results: In conclusion, this investigation demonstrates that apple is a rich source of phenolic compounds and antioxidant capacity.Fuji and Sheikh Ahmad cultivars showed the maximum and minimum content of total phenol content, flavonoids and antioxidant activity which are 2940.24 and 1350.22 microgram equivalent gallic acid/ gram of dry extract; 2530.32 and 1200.74 microgram equivalent quercetin/ gram of dry extract and 91.87 and 32%. The maximum and minimum amount of peroxide value and thiobarbituric acid was reported for control and 400 ppm apple extract samples respectively. The results of this study showed that "Fuji" cultivar contained the highest antioxidant activity.The Fuji apple extract are able to reducethe formation of hydroperoxides in butter oil during storage at 6ooC. The phenolic extracts from Fuji apple to be more effective than BHA in stabilising butter oil at 60ºC. Apple phenolic extracts inhibited oxidation of butter oil. Theextracts were able to retard oxidation because of the ability of phenolic compounds toscavenge and stabilise lipid radicals by donating hydrogen atoms.Also the concentration of the extract was an effective factor in the inhibition of oxidation; that is, as we increased the concentration, the inhibition of oxidation also increased.
Conclusion:: Due to their ability to act as reducing agents, phenolic compounds in apple phenolic extracts from Fujivarieties can be used as antioxidants in butter oil toretard formation of primary oxidation products, specifically hydroperoxides.
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