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Rather partial to a Spanish white

Scientists have showed that NIR spectroscopy can determine a whole load of information about wine, including alcohol content, pH, acidity and chemical composition. As a consequence, NIR spectroscopy has also proved adept at classifying wines by grape variety and wine-producing region, based on characteristic differences in the wines' chemical properties.

Now, analytical chemists at the University of Santiago de Compostela, led by Manuel Vázquez, have gone one better, by showing that NIR spectroscopy can also distinguish between wines made in different zones of a single wine-producing region. That is as long as NIR is combined with a few other optical spectroscopy techniques.

Vázquez and his colleagues focused on white wines made from Albariño grape varieties grown in the Rías Baixas region of Spain. This region is a controlled designation of origin, meaning it is officially recognised to produce food products with unique characteristics; in this instance, that means white wines made from Albariño grapes. The Rías Baixas region is divided into five sub-zones, which possess different landscapes and soils, and so produce slightly different white wines.

Using a combination of ultraviolet (UV), visible (VIS) and NIR spectroscopy, Vázquez and his colleagues analysed 33 wines from four of the sub-zones. They then processed the resultant spectral data using various different multivariate statistical techniques, including linear discriminant analysis (LDA) and soft independent modelling of class analogy (SIMCA), in order to try to classify the wines into the different sub-zones.

As they report in the Australian Journal of Grape and Wine Research, what they found was that wines from different sub-zones were best classified by different combinations of spectral data and statistical technique. So wines from the Condado zone were most accurately classified by applying SIMCA to a combination of UV, VIS and NIR data; wines from the Salnés and Ribeira du Ulla zones were most accurately classified by applying SIMCA to UV and VIS data; and wines from the Rosal zone were most accurately classified by applying LDA to VIS and NIR data.

In addition, the scientists were also able to distinguish all the Rías Baixas wines from white wines produced in other regions of Spain. Vázquez and his colleagues therefore conclude that this combination of UV, VIS and NIR spectroscopy could make an effective technique for authenticating Rías Baxias wines.

Still, not as much fun as simply drinking the wines.

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