Control and comparison of the antioxidant capacity of beers

The purpose of the present work is to determine the antioxidant capacity (AC) of 27 commercial beers. The AC indicates the degree of protection of a certain organism against oxidative damage provoked by reactive oxygen and nitrogen species. Assays were carried out by the following methods: (i) total radical trapping antioxidant parameter (TRAP); (ii) trolox equivalent antioxidant capacity (TEAC); (iii) trolox equivalent antioxidant capacity (DPPH); (iv) ferric-ion reducing antioxidant parameter (FRAP); (v) cupric reducing antioxidant capacity (CUPRAC); (vi) oxygen radical absorbance capacity (ORAC). Ascorbic acid (AA), gallic acid (GA) and trolox (TR) were used as standards. All beers showed antioxidant power, but a wide range of ACs was observed. The effect of several factors upon these differences was studied. Statistical differences were found between ACs of beers of different colours. ORAC method provided always higher experimental ACs, of significant statistical differences to other assays

Capacidade antioxidante de cervejas comerciais

Mestrado em Engenharia QuímicaO estudo da capacidade antioxidante (CA) de cervejas consistiu na determinação e avaliação da CA de cervejas comerciais, disponíveis no mercado nacional. A CA indica o grau de protecção conferido ao organismo relativamente a danos oxidativos radicalares envolvidos em processos degenerativos. A CA foi determinada pelos métodos (i) Total radical trapping antioxidant parameter (TRAP); (ii) Trolox equivalent antioxidant capacity (TEAC); (iii) Trolox equivalent antioxidant capacity (DPPH); (iv) Ferric ion reducing antioxidant parameter (FRAP); (v) Cupric reducing antioxidant capacity (CUPRAC); (vi) Oxygen radical absorbance capacity (ORAC). Estes métodos são ópticos e baseiam-se na inibição de radicais livres em solução. Os valores de CA foram calculados relativamente aos compostos ácido ascórbico (AA), ácido gálico (AG) e o trolox (TR). No sentido de esclarecer o efeito de alguns factores na CA das várias amostras de cerveja procedeu-se à análise estatística dos resultados com base no teste ANOVA (analysis of variance). Os factores considerados neste estudo foram: método de análise, composto padrão, marca comercial, tipo, origem, corantes, aromas, antioxidantes, edulcorantes, teor de álcool, cor, sumo e outros aditivos. O teste ANOVA sugeriu a existência de diferenças estatisticamente significativas entre as marcas nos métodos FRAP (para o padrão AG) e no método ORAC. Relativamente ao teor de álcool, somente o método ORAC, para os padrões AG e TR, sugeriu existirem dois subgrupos diferentes. Todos os métodos indicaram diferenças estatisticamente significativas entre os vários grupos de cores da cerveja. No estudo relativo ao efeito do método verificou-se que, para todos os padrões, o método ORAC apresentou diferenças estatisticamente significativas dos restantes, tendo valores de CA muito superiores aos dos restantes métodos usados. No efeito dos padrões concluiu-se que, para todos os métodos, existiam diferenças estatisticamente significativas entre os vários padrões. No método TRAP e CUPRAC todos os padrões se comportaram de forma distinta, nos métodos TEAC e FRAP o padrão AG apresentou CA inferiores aos restantes, pertencendo a um subgrupo diferente. O método DPPH sugeriu que o AG produzia valores de CA superiores aos dos demais padrões. O método ORAC registou um comportamento semelhante, mas para o padrão TR.The antioxidant capacity (CA) of beers was studied by means of its determination and evaluation in commercial beers, available in national market. The CA indicates the degree of protection of a certain organism against the radical oxidative damage, correlated to degenerative diseases. The CA was determinate several methods, such as (i) Total radical trapping antioxidant parameter (TRAP); (ii) Trolox equivalent antioxidant capacity (TEAC); (iii) Trolox equivalent antioxidant capacity (DPPH); (iv) Ferric ion reducing antioxidant parameter (FRAP); (v) Cupric reducing antioxidant capacity (CUPRAC); (vi) Oxygen radical absorbance capacity (ORAC). These are optical methods based in the inhibition of free radicals in aqueous solution. Ascorbic acid (AA), Gallic acid (AG) and Trolox (TR) were used as standards. The effect of some factors upon the observed CA was studied by ANOVA statistical analyses (analysis of variance). Method, standard, commercial brand, kind of fermentation (ale or lager), origin, colorants, flavors, antioxidants, sweeteners, alcohol, color, juice and other additives, were the factors under evaluation. The ANOVA test suggested statistical differences between commercial brands for FRAP (for the standard AG) and ORAC methods. With regard to alcohol level, only ORAC method (standards AG e TR) suggested significant statistical differences between the observed groups. All methods pointed out statistical differences within the different color groups of beers. Evaluation of the effect of method upon CA indicated that ORAC provided higher experimental CA values, of significant statistical differences to other methods. With regard to the effect of standards the observed results depend on the experimental method. TRAP and CUPRAC point out statistical differences within all standards. TEAC and FRAP suggested lower CA for AG. On the contrary, DPPH produced higher CA for AG standard. ORAC method showed statistical differences and higher CA when TR was used as standard

Assessing and comparing the total antioxidant capacity of commercial beverages: application to beers, wines, waters and soft drinks using TRAP, TEAC and FRAP methods.

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

Rapid determination of tartaric acid in wines

A flow-spectrophotometric method is proposed for the routine determination of tartaric acid in wines. The reaction between tartaric acid and vanadate in acetic media is carried out in flowing conditions and the subsequent colored complex is monitored at 475 nm. The stability of the complex and the corresponding formation constant are presented. The effect of wavelength and pH was evaluated by batch experiments. The selected conditions were transposed to a flowinjection analytical system. Optimization of several flow parameters such as reactor lengths, flow-rate and injection volume was carried out. Using optimized conditions, a linear behavior was observed up to 1000 µg mL-1 tartaric acid, with a molar extinction coefficient of 450 L mg-1 cm-1 and ± 1 % repeatability. Sample throughput was 25 samples per hour. The flow-spectrophotometric method was satisfactorily applied to the quantification of tartaric acid (TA) in wines from different sources. Its accuracy was confirmed by statistical comparison to the conventional Rebelein procedure and to a certified analytical method carried out in a routine laboratory

Fiber Optic-Based Refractive Index Sensing at INESC Porto

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