Wine discrimination: Chemometric distinction

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  • Published: Sep 15, 2014
  • Author: David Bradley
  • Channels: Chemometrics & Informatics
thumbnail image: Wine discrimination: Chemometric distinction

Grapely distinction

A useful approach for the differentiation of wines according to geographical origin based on global volatile patterns Photo by David Bradley

The analysis of gas chromatography and quadrupole mass spectrometry data obtained after solid-phase extraction of wine samples can be carried out by using partial least squares discriminant analysis. The approach can successfully discriminate between wines based on geographical origin as well as wine type and vintage and has proven itself with wine from the Azores, the Canary Islands and Madeira.

Rosa Perestrelo, Catarina Silva and José Câmara of the Centro de Química da Madeira, Campus Universitário da Penteada, in Funchal, Portugal, investigated 34 monovarietal wines (white, red and fortified) from the three wine grape-growing regions and exploited the what they refer to as the high throughput extraction efficiency of their solid-phase extraction procedure with the separation and identification ability of the PLS technique. Fundamentally, their testing notes suggest that the wines of Madeira can be clearly distinguished from those originating in the Azores or the Canaries.

Whisky lactone is go, go!

The team identified approximately 120 volatile compounds distributed in nine chemical groups, including higher alcohols, ethyl esters, fatty acids, terpenoids, carbonyl compounds, furanic compounds, volatile phenols, lactones, and sulfur compounds, were identified. Specifically, their analysis revealed that wines from Madeira wines are characterized chemically by the presence of various organic compounds: 2-ethylhexan-1-ol, 3,5,5-trimethylhexan-1-ol, ethyl 2-methylbutanoate, ethyl dl-2-hydroxycaproate, decanoic acid, 3-methylbutanoic acid, and (E)-whisky lactone. By contrast wines from the other two regions derive their particular bouquet from primarily 3-ethoxypropan-1-ol, 1-octen-3-ol, (Z)-3-hexenyl butanoate, 4-(methylthio)-1-butanol, ethyl 3-hydroxybutanoate, isoamyl lactate, 4-methylphenol, gamma-octalactone and 4-(methylthio)-1-butanol.

Wine authenticity control, with particular regard to grape varieties and geographical region is a critical part of sustaining an important part of the global economy given the popularity and relative high value of wines. There is also the introduction of regional law regarding the identification of products from particular areas under European law that must be complied with in marketing and selling wine, and indeed many other food and drink products. Analytical control can also help wine makers improve their products by allowing them to refine its characteristics based on additional chemical information not available through conventional taste tests.

Aromatic distinction

Wine aroma, often referred to as its bouquet, is a major factor in determining the quality of a wine and is affected by grape variety, terroir (climate, soil type), geographical location, and the wine-making, vinification, processes (fermentation and ageing) and the character of the containers in which it is made, says the team. Many compounds present in wine derive directly from the grapes themselves, others such as higher alcohols, fatty acids and ethyl esters are produced during fermentation. The aging process leads to yet others including volatile phenols, furans, lactones and oak-derived-vanillic compounds from wooden casks.

Earlier studies have demonstrated that it is possible to discriminate wine based on geography using the chemical profile of the product, with gas chromatography and mass spectrometry the most common analytical tools used. However, chemometric methods using the latest computational tools can improve on essentially manual analysis of the data, in particular, partial least squares- discriminant analysis (PLS-DA), a multivariate classification technique based on PLS, the regression extension of principal component analysis (PCA), holds great potential for distinguishing between the chemical profiles of wine, the team suggests.

The success of the team's novel approach yields information that could be crucial to guarantee wine authenticity and prevent fraud even to the point of distinguishing between wine from regions that are not too distant geographically and fall under neighbouring jurisdictions.

Related Links

J Sep Sci, 2014, 37, 1974-1981: "A useful approach for the differentiation of wines according to geographical origin based on global volatile patterns"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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