Colorimetry in Port wines

Resumen

This paper sets out to establish a methodology for measuring the colour of Port wines that complies with both the EU Regulation and the Office Internationale de la Vigne et du Vin (OIV) guidelines using the simplest possible approach. Fifty six Port wines of various types have been utilized, namely Brancos, Aloirados, Tintos and Retintos. In order to determine the influence of the spectral interval on the results, the colour coordinates have been calculated using spectral measurements every 1, 5 and 10 nm. The colour differences between them were lower than 0.5 CIELAB units and, therefore the use of a spectral interval of 10 nm is sufficient, as the CIE recommends. Absorbance spectra were recorded with 2, 5 and 10 nm pathlength cells to test the validity of Beer's law for Port Wines. In general, they comply quite well with that law, but some precision problems arise in the measurements, in relation to the pathlength of the cell. We conclude that the best measurements are obtained with 2 mm pathlength cells for Tintos and Retintos Port wines, and with 10 mm pathlength cells for Aloirados and Brancos Port wines.