Send Orders of Reprints at bspsaif@emirates.net.ae 22 Combinatorial Chemistry & High Throughput Screening, 2013, 16, 22-31 Assessing and Comparing the Total Antioxidant Capacity of Commercial Beverages: Application to Beers, Wines, Waters and Soft Drinks Using TRAP, TEAC and FRAP Methods Raquel B. Queirós 1,2 , Paula A.R. Tafulo 2 and M. Goreti F. Sales *,1 1 BioMark/ISEP, School of Engineering, Polytechnic Institute, R. Dr. António Bernardino de Almeida, 431, 4200-072 Porto, Portugal 2 INESC Tec (coordinated by INESC Porto) and Faculty of Sciences, University of Porto, Rua do Campo Alegre, 687, 4150-179 Porto, Portugal Abstract: This work measures and tries to compare the Antioxidant Capacity (AC) of 50 commercial beverages of different kinds: 6 wines, 12 beers, 18 soft drinks and 14 flavoured waters. Because there is no reference procedure established for this purpose, three different optical methods were used to analyse these samples: Total Radical trapping Antioxidant Parameter (TRAP), Trolox Equivalent Antioxidant Capacity (TEAC) and Ferric ion Reducing Antioxidant Parameter (FRAP). These methods differ on the chemical background and nature of redox system. The TRAP method involves the transfer of hydrogen atoms while TEAC and FRAP involves electron transfer reactions. The AC was also assessed against three antioxidants of reference, Ascorbic acid (AA), Gallic acid (GA) and 6-hydroxy-2,5,7,8-tetramethyl- 2-carboxylic acid (Trolox). The results obtained were analyzed statistically. Anova one-way tests were applied to all results and suggested that methods and standards exhibited significant statistical differences. The possible effect of sample features in the AC, such as gas, flavours, food colouring, sweeteners, acidity regulators, preservatives, stabilizers, vitamins, juice percentage, alcohol percentage, antioxidants and the colour was also investigated. The AC levels seemed to change with brand, kind of antioxidants added, and kind of flavour, depending on the sample. In general, higher ACs were obtained for FRAP as method, and beer for kind of sample, and the standard expressing the smaller AC values was GA. Keywords: Antioxidant capacity, beer, beverages, FRAP, soft drinks, TEAC, TRAP, water, wine. 1. INTRODUCTION Humans cannot exist without oxygen but oxygen is intrinsically dangerous to their existence. The major production of ATP in the cell is an oxygen dependent process, carried out in the mitochondria via the electron transport chain. It involves the oxidation of energy-rich molecules and the transfer to oxygen (O 2 ) of the redox power in NADH and FADH 2 , produced in several steps. This univalent reduction of oxygen generates reactive intermediates, including the superoxide anion radical, hydrogen peroxide and the extremely reactive hydroxyl radical. These seem to be the main responsible for oxygen toxicity [1-3]. The defense network in vivo against these radicals [4] includes various antioxidants (AOs). Some are proteins and enzymes, while others are small molecules [5]. They may act as (i) preventing antioxidants by suppressing the formation of reactive oxygen and nitrogen species, (ii) scavenging antioxidants by removing active species rapidly before the active species attack biologically essential molecules, and (iii) by repairing damages (de novo antioxidants), clearing the wastes, and reconstituting the lost function [6]. A body *Address correspondence to this author at the BioMark/Instituto Superior de Engenharia do Porto, R. Dr. António Bernardino de Almeida, 431, 4200-072 Porto, Portugal; Tel: +351 228 340 500; Fax: +351 228 321 159; E-mails: goreti.sales@gmail.com, mgf@isep.ipp.pt deficiency in these AOs can lead to oxidative stress and, subsequently to the oxidation of biomolecules [3, 7], accelerating the aging process and contributing to the development of chronic degenerative diseases, including coronary heart disease and cancer [2, 3, 7-10]. Exogenous AOs intake can play a crucial role in body protection against such diseases [11], as suggested by epidemiological data [12]. Foods obtained from plant processing methods constitute an important source of dietary AOs [13-15], with great emphasis for polyphenol compounds [16]. These include daily beverages such as wines, beers, soft-drinks, flavored waters, and juices. Some advantages coming from drinking these have also been highlighted in the literature. Drinking wine moderately may help preventing cardiovascular diseases and some types of cancers [3, 17-21]. This has been associated to the high levels of polyphenols in wines, because they act as free radical-scavenging compounds, participating in the second line defense in vivo [6]. A similar condition was attributed to beer, although with lower levels of polyphenols [22-24]. Drinks derived from fruits and vegetables are also rich in polyphenolic compounds [25-27], although less biologically available than in wines because they are strongly bonded. In addition to their AO activity, dietary AO are thought to have several beneficial activities by behaving as antibacterial and antiviral agents [28]. 1875-5402/13 $58.00+.00 © 2013 Bentham Science Publishers