ORIGINAL PAPER Paula Andrade ? Rosa Seabra ? Margarida Ferreira Federico Ferreres ? Cristina Garcõ Âa-Viguera Analysis of non-coloured phenolics in port wines by capillary zone electrophoresis Influence of grape variety and ageing Received: 1 August 1997 AbstractmDifferent experimental varietal port wines were analysed in order to determine differences in the concentra- tions of phenolic compounds between some commonly used grapes varieties (Touriga Francesa, Touriga Nacional, Tinta Roriz and Tinta Barroca). Although all samples had the same qualitative pattern of non-coloured phenolic compounds, Touriga varieties contained more than twice the concentration of these compounds compared to the Tinta varieties. A preliminary study of the effect of ageing on these compounds revealed an overall increase in those components associated with the bitter or astringent char- acteristics of food and beverages (tyrosol, gallic acid and catechin). Key wordsmNon-coloured phenolics ? Port wines ? CZE ? Grape variety ? ageing Introduction Traditionally, port wines are produced from blends using a limited variety of grape cultivars. Tinta Roriz, Touriga Nacional and Touriga Francesa have long been considered the most important varieties for making port wines. Also, Tinta Barroca is frequently added in order to improve the characteristics of the wine colour. Port wines made using these varieties have been used in studies of their contents of anthocyanins [1±3], amino acids, organic acids and sugar [4, 5]. Data concerning non-coloured port wine phenols have only recently been published [6]. These phenols make an important contribu- tion to the sensory quality of port wines. They contribute to the characteristic astringent taste [7] and to the wine colour, as a result of condensation reactions with the anthocyanins during maturation [8]. HPLC has been the technique of choice for analysing these compounds, but capillary electrophoresis (CE) has also been used for the analysis of plant secondary metabo- lites because of the high-resolution of separation achieved [9]. Several applications of this technique to the analysis of phenolic compounds in food and plants have been publish- ed in recent years [10±13]. Comparisons of CE and HPLC for analysis of phenolic compounds in wines, grape seeds and other fruits have also been published [14±16]. CE was chosen for this study, since it gives good separation of cis- and trans-isomers, better peak shapes and is quicker than HPLC [14]. Following previous studies, the aim of the present work was to contribute to data on the composition and concen- tration of non-coloured phenols in port wine which, upon maturation, could produce wines with different sensory properties. In order to fulfil this objective the different non-coloured phenol patterns of several varietal young port wines were studied. Also, other standard blended ports have been analysed, as a preliminary study, to determine the influence of ageing on the phenolic compounds. Materials and methods Wine samples. Ports were produced under standard conditions from several Vitis vinifera cultivars, to permit comparisons between grape cultivars or different years (all prepared by the same manufacturer in Vila Nova de Gaia, Portugal). Four experimental varietal port wines grapes (cv Tinta Roriz, Tinta Barroca, Touriga Francesa and Touriga Nacional) were harvested in the same quinta located in the Douro region of Northern Portugal (late September 1995). Wines were bottled and stored in a dark temperature-controlled room at 15 °C until analysis (June 1996). Three further samples were produced by traditional vinification using a standard mixture of grape varieties known to produce a wine of This work was conducted at the Laboratorio Fitoquõ Âmica, Departa- mento Ciencia y Tecnologõ Âa Alimentos, CEBAS-CSIC, Murcia, Spain F. Ferreres ? C. Garcõ Âa-Viguera ( ) Laboratorio Fitoquõ Âmica, Departamento Ciencia y Tecnologõ Âa de Alimentos, CEBAS-CSIC, Apartado Correos 4195, E-30080, Murcia, Spain P. Andrade ? R. Seabra ? M. Ferreira CEQUP/Faculdade de Farma Âcia, Universidade do Porto, R. Anibal Cunha 164, P-4050 Porto, Portugal Z Lebensm Unters Forsch A (1998) 206: 161 ± 164 Ó Springer-Verlag 1998