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Implementação do Sistema CIELab na Avaliação Colorimétrica de Vinhos Brancos e Vinhos Rosados
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A cor é uma das características mais influentes na opinião que o consumidor tece acerca de um vinho.
A medição da cor de um vinho utilizando o sistema CIELab foi aprovada pela Organização Internacional da Vinha e do Vinho (OIV) em 2006. O espaço de cor CIELab baseia-se numa representação cartesiana de 3 eixos ortogonais: L*, a* e b*. Este sistema permite avaliar e expressar a cor de forma exata e universal.
Após o estudo dos parâmetros de precisão e robustez, procedeu-se à validação da metodologia a implementar para a avaliação colorimétrica dos vinhos. Neste processo, concluiu-se que o método é robusto sendo capaz de apresentar resultados consistentes mesmo quando sujeito a pequenas alterações das condições experimentais. Foram também estabelecidos os limites de repetibilidade e reprodutibilidade para cada uma das coordenadas de cor obtidas na análise.
Recorrendo a uma avaliação visual das cores feita por um painel de enólogos da Sogrape Vinhos S.A., foi possível verificar se os limites de especificação numéricos definidos para cada produto correspondiam às cores visualmente consideradas como aceites. Com base no resultado deste teste, procedeu-se à restruturação de alguns dos limites de especificação implementados.
Aplicando o sistema CIELab à avaliação colorimétrica dos vinhos em estudo, foram criados limites para cada uma das coordenadas de cor L*, a* e b*, tendo por base os valores obtidos para as amostras visualmente consideradas como aceites. De forma a complementar esta especificação, foi criado um limite de valores correspondentes à diferença colorimétrica (ΔE) máxima permitida para cada produto, passando este a ser o fator chave na aceitação/rejeição da cor de um vinho.
Colour is one of the most influential characteristics in the opinion created by the consumer when buying a certain wine. The measurement of wine colour using the CIELab system becomes the implemented method by the International Organization of Vine and Wine in 2006. The CIELab color space is based on the cartesian representation of 3 orthogonal axes: L*, a* and b*. This system allows an exact and universal evaluation and expression of the colour. After studying precision and robustness parameters, this methodology was validated. In this study, it was concluded that the method is robust, being able to present consistent results even when subjected to small changes in experimental conditions. Repeatability and reproducibility limits were also established for each of the colour coordinates obtained during the analysis. Through a visual colour evaluation made by a panel of winemakers from Sogrape Vinhos S.A., it was possible to verify whether the numerical specification limits defined for each product corresponded to the colours visually considered as accepted. Based on the results of this test, some of the specification limits implemented were restructured. Applying the CIELab system to the colorimetric evaluation of the wines that are being studied, limits were created for each of the colour coordinates L*, a* and b*, based on the colour values obtained for the visually accepted samples. In order to complement this specification, a limit of values corresponding to the maximum colorimetric difference (ΔE) allowed for each product was created, which became the key factor in the acceptance/rejection of a wine colour.
Colour is one of the most influential characteristics in the opinion created by the consumer when buying a certain wine. The measurement of wine colour using the CIELab system becomes the implemented method by the International Organization of Vine and Wine in 2006. The CIELab color space is based on the cartesian representation of 3 orthogonal axes: L*, a* and b*. This system allows an exact and universal evaluation and expression of the colour. After studying precision and robustness parameters, this methodology was validated. In this study, it was concluded that the method is robust, being able to present consistent results even when subjected to small changes in experimental conditions. Repeatability and reproducibility limits were also established for each of the colour coordinates obtained during the analysis. Through a visual colour evaluation made by a panel of winemakers from Sogrape Vinhos S.A., it was possible to verify whether the numerical specification limits defined for each product corresponded to the colours visually considered as accepted. Based on the results of this test, some of the specification limits implemented were restructured. Applying the CIELab system to the colorimetric evaluation of the wines that are being studied, limits were created for each of the colour coordinates L*, a* and b*, based on the colour values obtained for the visually accepted samples. In order to complement this specification, a limit of values corresponding to the maximum colorimetric difference (ΔE) allowed for each product was created, which became the key factor in the acceptance/rejection of a wine colour.
Descrição
Palavras-chave
CIELab Implementação Limites de Especificação de Cor Validação do Método Vinho