Evaluation of the Antioxidative Effects of Black Tea Extracts

Subject Areas : Microbiology

Z. Nazari ¹ ( دانش آموخته کارشناسی ارشد علوم و صنایع غذایی، واحد علوم و تحقیقات، دانشگاه آزاد اسلامی، تهران، ایران )
M. Gharachorloo ² ( دانشیار گروه علوم و صنایع غذایی، دانشکده علوم و مهندسی صنایع غذایی، واحد علوم و تحقیقات، دانشگاه آزاد اسلامی، تهران، ایران )
A. H. Elhamirad ³ ( استادیار گروه علوم و صنایع غذایی، واحد سبزوار، دانشگاه آزاد اسلامی، سبزوار، ایران )

Received: 2016-11-16 Accepted : 2016-11-16 Published : 2016-12-21

Keywords: antioxidant, Edible Oil, Tea Extract, Tannic Acid,

Abstract :

Introduction: Oxidative rancidity is one of the important reactions in oils and fats. Tea contains some effective antioxidants namely tannin and catechins. In this research project the antioxidative activities of tea extract in comparison with tannic acid has been investigated.  Materials and Methods: This study was carried out in order to compare the effects of three different extraction methods consisted of methanolic extraction, agarwal method and extraction with hot water. In order to investigate the antioxidant activities, three concentrations of tannic acid (0.01%, 0.05% and 0.1%) and tea extract (0.1%, 0.5% and 1%) were added to four types of oils with different fatty acid unsaturation and composition (sunflower, canola, olive oils and tallow) separately. The induction period was measured by Rancimat at 120ºC and peroxide values were determined after 24 hours of heating intervals at 105ºC for six consecutive days.  Results: According to the results, the highest extraction yield belonged to the hot water extraction method. The results showed that different concentrations of tea extract had antioxidative property. In sunflower and canola oils, 0.5% tea extract and 0.1% tannic acid and in tallow and olive oils, 1% tea extract and 0.1% tannic acid showed the highest activity to increase the induction period and to prevent the increase of peroxide values of oils. Olive oil containing natural antioxidants and tallow that is deficient in natural antioxidants showed increased induction periods as the concentrations of the extract were increased.  Conclusion: Tannic acid and tea extract exhibited antioxidant activities by increasing the induction periods of oils and fats while preventing the increase of peroxide values. 

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