Evaluation of total polyphenols in selected foods by fast blue BB method and relationship of polyphenols content to total antioxidant activity

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Evaluation of total polyphenols in selected foods by fast blue BB method and relationship of polyphenols content to total antioxidant activity

 

Author: Leung, Yuen Kan Ivy
Title: Evaluation of total polyphenols in selected foods by fast blue BB method and relationship of polyphenols content to total antioxidant activity
Degree: M.Sc.
Year: 2013
Subject: Polyphenols -- Physiological effect.
Antioxidants.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Health Technology and Informatics
Pages: xviii, 161 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2637246
URI: http://theses.lib.polyu.edu.hk/handle/200/7071
Abstract: There is strong epidemiological evidence suggesting that a diet rich in fruit and vegetables may lower the risk of various chronic diseases. Fruits and vegetables contain various health-promoting factors such as fibre, polyphenols, flavonoids, vitamins and minerals. Many of these nutrients such as vitamin C, vitamin E and polyphenols have antioxidizing ability which may prevent or oppose oxidative damage, leading to the hypothesis that the beneficial effects of fruits and vegetables are related to the antioxidant content of these plant-based foods. Since these nutrients can also be found in various beverages such as fruit juices, red wine, tea and coffee, drinking beverages may be effective in term of reducing the risk of chronic diseases. Besides, polyphenols are considered as powerful antioxidants in vitro, which are even more potent that vitamin C, vitamin E and carotenoids in terms of antioxidizing power. Therefore, polyphenols in foods and/or beverages are subject of increasing scientific interest because of their potential benefit on human health.
The Folin-Ciocalteu (FC) method is the most common assay for measuring total phenolics in foods and beverages, which is simple and fast. However, it is well known that it can be interfered with various substances such as reducing sugars, ascorbic acid, ferrous ions, etc. Therefore, there is a need for a simple, rapid and direct detection method for measuring polyphenols in foods and beverages, which is more specific than the FC method. Recently, a Fast Blue BB (FBBB) method has been developed for measuring total polyphenols. Therefore, this study aims to further optimize and evaluate this new method, and compare the results in selected beverages with the well established, but non-specific FC method. Furthermore, the total antioxidant activity of selected beverages is analyzed by the well established ferric reducing/antioxidant power (FRAP) assay for comparing the total polyphenols content measured by the optimized FBBB method and the FC method. The optimized FBBB method is a simple and inexpensive method, which uses 20% Na₂CO₃ as alkalinizing agent and measures absorbance at 350nm after 30 minutes of incubation time at room temperature. The optimized FBBB method exhibited good linear regression correlation (R²=0.9947) with gallic acid calibration standards, low detection limit (0.02M gallic acid), good within-run (CV=3.3%) and between-run (CV=4%) precision, and acceptable recoveries (62.5 - 83.1%) for the total polyphenols content in selected beverages. More importantly, the optimized FBBB method did not interfered with the interfering substances of the FC method, which were commonly found in commercial beverages, such as ascorbic acid, sucrose, fructose and glucose. When comparing the optimized FBBB method with the FC method, although they gave significantly different results (p=0.0068), the ranking of measured value of the optimized FBBB method was significantly correlated with the FC method (r=0.918, p<0.001). Besides, the total polyphenols content measured by the optimized FBBB method was significantly correlated with the total antioxidant activity measured by the FRAP assay (r=0.902, p<0.001). Therefore, the optimized FBBB method might be the preferred method for measuring total polyphenols content in beverages.

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