Antioxidant activity assessment in fruit liquors and spirits: methods comparison

Avaliação da atividade antioxidante em licores de frutos e aguardentes: comparação de métodos

¹ Department of Food Science and Technology, Coimbra College of Agriculture, Polytechnic Institute of Coimbra, Bencanta, 3045-601 Coimbra, Portugal
² CERNAS Research Unit, Coimbra College of Agriculture, Polytechnic Institute of Coimbra, Bencanta, 3045-601 Coimbra, Portugal
³ National Institute of Agricultural and Veterinary Research-INIAV, Dois Portos, Quinta da Almoínha, 2565-191 Dois Portos, Portugal
⁴ Institute of Mediterranean Agrarian and Environmental Sciences, University of Évora, Portugal
⁵ Department of Life Sciences, Faculty of Science and Technology, University of Coimbra, Coimbra, Portugal
⁶ Department of Environment, Coimbra College of Agriculture, Polytechnic Institute of Coimbra, Bencanta, 3045-601 Coimbra, Portugal
⁷ Center for Investigation and Agro Environmental and Biological. Technologies (CITAB) – UTAD, Quinta de Prados, Apartado 1013, 5001-801 Vila Real, Portugal

^* corresponding author: Goreti Botelho. Tel. +351 239802940, Fax +351 239802979, E-mail: goreti@esac.pt

Received: 16 May 2014
Accepted: 30 May 2014

Abstract

During the last few years, Portugal has seen an increasing trend in the development of new fruit-based products, such as liquors and spirits. The antioxidant capacity of fruit liquors and spirits, sourced commercially or produced on a pilot-scale, was assessed using two simple spectrophotometric methods: the 2,2’-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays. The major goal of this work was to find which of the two methods is the most suitable and accurate in determining antioxidant capacity for fruit liquors and spirits. In addition, the total phenolic compounds of both kinds of alcoholic beverages were determined by Folin-Ciocalteau method. Despite the widespread use of DPPH assay for distilled drinks, a weak Spearman correlation coefficient (r = 0.023) between ABTS and DPPH methods in spirits were found, as well as, between DPPH values and total phenolic compounds content (r = 0.239). This work highlights the limitations of DPPH assay when used for analysis of samples with very low antioxidant capacity, as distilled spirits.

Resumo

Portugal, nos últimos anos, tem desenvolvido novos produtos à base de frutos, tais como aguardentes e licores. A capacidade antioxidante dos licores de frutos e aguardentes, obtidos comercialmente ou em produções à escala piloto, foi medida usando dois métodos espetrofotométricos: o 2,2′-azino-bis-(3-etilbenzotiazolina-6-ácido sulfónico) (ABTS) e o 1,1-difenil-2-picrilhidrazil (DPPH). O principal objetivo deste trabalho consistiu em determinar qual o método mais fiável na determinação da capacidade antioxidante total das aguardentes e licores. Adicionalmente, o conteúdo total em compostos fenólicos de ambos os tipos de bebidas alcoólicas foi determinado pelo método de Folin-Ciocalteau. Embora o DPPH seja o método mais utilizado neste tipo de análises, no presente trabalho, no entanto, verificou-se que o coeficiente de correlação de Spearman (r=0.023) entre o ABTS e DPPH é baixo, bem como entre os valores de DPPH e o teor de compostos fenólicos totais (r=0.239). Este trabalho destaca assim as limitações do método de DPPH quando usado em amostras com baixa capacidade antioxidante, como é o caso dos licores de frutos e das aguardentes.