Margarida I. V. Teixeira^1,2, M. Vitória San Romão^2,3,4, M. Rosário Bronze^*1,2,4, Luís Vilas Boas^2,5

¹ Faculdade de Farmácia da Universidade de Lisboa, Av. das Forças Armadas, 1649-019 Lisboa, Portugal

² Instituto de Tecnologia Química e Biológica, Apartado 127, 2784-505 Oeiras, Portugal

³ Estação Vitivinícola Nacional (INIAP), 2565-191 Dois Portos, Portugal

⁴ Instituto de Biologia Experimental e Tecnológica, Apartado 12, 2781-901, Oeiras, Portugal

⁵ Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

*Corresponding author. Tel: +351214469770; fax: +351214417062, E-mail address: mbronze@itqb.unl.pt

SUMMARY

The “cork taint” is a major problem in wine industry and may caused by the several sources of contamination although wine cork stoppers are usually subject to suspition: 2,4,6-trichloroanisole (TCA) has been frequently associated to this off-flavour. In this work, a consumer panel performed “forced choice” triangular tests in order to measure Odour Detection Thresholds (ODT) and Taste Detection Thresholds (TDT) of TCA in water, hydro-alcoholic solutions (11.5% and 18% ethanol) and white and red wines. A paired preference test was also performed by the panel in order to measure Odour Rejection Threshold (ORT) in white and red wines spiked with TCA. Results obtained show that the ODT and the TDT for TCA were respectively: 0.2 and 0.3 ng/ L in water, 0.9 and 1.7 ng/L in red wine and 1.5 and 1.0 ng/L in white wine. ODT were 4 and 10 ng/L respectively for hydro-alcoholic solutions with 11.5% and 18% ethanol. ORT for white wines was 10.4 ng/L and for red wines 16.0 ng/L. These results suggest that although this group of non trained assessors detected very low concentrations of TCA in wines, they did not reject the wine at these low concentration values.

Key words: TCA; Cork taint; wine; sensory evaluation

RESUMO

2,4,6-Tricloroanisol: avaliação por um painel de consumidores

O denominado “gosto a rolha” é um problema de grande importância para a indústria vitivinícola e constitui um defeito que aparece por contaminação dos vinhos. Esta contaminação é normalmente atribuída à rolha de cortiça e o 2,4,6-tricloroanisol (TCA) é o composto mais frequentemente associado a este “off-flavour”. Neste trabalho, um painel de consumidores efectuou ensaios triangulares de resposta obrigatória, com vista à determinação dos Limiares de Detecção Olfactivos (LDO) e Limiares de Detecção Gustativos (LDG) do TCA em água, soluções hidroalcoólicas (11,5 e 18% etanol) e vinho de mesa branco e tinto. Um ensaio de comparação por pares foi utilizado pelo painel para avaliar o Limiar de rejeição Olfactivo (LRO) em vinhos brancos e vinhos tintos aos quais foi adicionado TCA. Os resultados obtidos mostram que o LDO e LDG em água correspondem respectivamente a 0,2 e 0,3 ng/L, em soluções hidroalcoólicas a 11,5 e 18% o LDO foi de 4 e 10ng/L respectivamente. Nos vinhos tintos o LDO e LDG foi de 0,9 e 1,7 ng/L e nos vinhos brancos foi respectivamente 1,5 e 1,0. O LRO obtido para o vinho branco foi de 10,4ng/L e para o vinho tinto 16,0 ng/L. Os resultados obtidos indicam que, embora este grupo de consumidores tenha detectado a presença de TCA em baixas concentrações nas diferentes amostras testadas, não rejeitaram as amostras de vinho que apresentavam estes teores.

RÉSUMÉ

2,4,6-Tricloroanisol: évaluation par un group de consommateurs

Le «goût de bouchon» est un problème important dans l’industrie vinicole et est provoqué par la contamination des vins. Cette contamination est habituellement attribuée aux bouchons de liège et le 2,4,6-trichloroanisole (TCA) est l’un des composés la plupart du temps associés à ce goût. Dans ce travail, un panel de consommateurs a effectué des essais triangulaires de choisi «forcé» afin de mesurer les seuils de détection d’odeur (SDO) et les seuils de détection de goût (SDG) de TCA en eau, solutions hydroalcooliques (éthanol de 11.5% et de 18%) et vins blancs et rouges. Un épreuve de préférence par paire a été également exécuté par le panneau afin de mesurer le seuil de rejet d’odeur (SRO) en vin blanc et rouge pointu avec TCA. Les résultats obtenues pour les SDO et les SDG pour TCA dans l’eau étaient 0.2 et 0.3 ng/L, respectivement. Dans les solutions hydroalcooliques avec de l’éthanol de 11.5% et de 18% les SDO étaient 4 et 10 ng/L respectivement. En vin rouge les SDO et les SDG étaient 0.9 et 1.7 ng/L et en vin blanc était 1.5 et 1.0 ng/L respectivement. SRO pour le blanc était 10.4 ng/L et pour les vins rouges 16.0 ng/L. Ces résultats suggèrent que bien que ce groupe de consommateurs ait détecté des concentrations très basses de TCA en vins, ils n’aient pas rejeté le vin à ces valeurs basses de concentration.

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