Wine Stats

With the holidays fast approaching, many of us are looking forward to drinking a glass or two of Champagne and other sparkling wines.  After all, these are perfect celebratory drinks – but what does physics have to say about how they might best be served?

1. Gently Pour into an Inclined Glass

The traditional way of pouring Champagne and sparkling wines is into an upright glass, which produces a frothy head. Sommeliers may love the drama that this produces, but a great deal of CO₂ is lost in the process. This is bad news because such a dramatic loss of dissolved CO₂ will (1) result in a glass which is less vivacious and (2) contain lesser amounts of volatile organic compounds (VOCs) which are carried in bubbles.

Research by Gérard Liger-Belair and colleagues at the Université de Reims has shown that by pouring into an inclined glass – much as one would pour a beer – the wine can contain up to twice as much dissolved CO₂.  And that means a longer-lasting bubble stream and more intense aromas.

2. Use Flutes Not Coupes

Coupes are the traditional glass of choice for serving Champagne and sparkling wine, but they are to be avoided, even those that are modelled on Kate Moss’s left breast.  There are two main reasons for this.  In a coupe, the sparkling wine will have a much greater surface area in contact with the air, compared to a flute.  Since much CO₂ is lost by diffusion at this interface the flute will naturally retain CO₂ for longer.

Secondly, the differing shape of coupes and flutes result in differing patterns of convection and surface bubble burst.  These bubbles are not merely aesthetic but carry with them volatile organic compounds which are a characteristic of that particular sparkling wine. With a flute the vortex zone covers the entire width of the glass and VOCs are contained within a relatively small volume. By contrast with a coupe, the vortex zone covers only about half of the wine surface.  This results in a doughnut shape adjacent to the rim with far fewer bubbles and VOCs.

3. Serve Chilled but not Cold

The temperature of sparkling wine affects its viscosity and the rate at which CO₂ molecules are able to diffuse.  This means that the cooler the sparkling wine the longer it will retain its dissolved CO₂.  Just as a rapid loss producing a frothy head is undesireable, so also is too slow a loss.  The latter with a sparse flow of bubbles, is aesthetically less apealing and also has a reduced flow of VOCs.  Experience of tasters suggests that 8°-10°C is a good temperature at which to serve the majority of Champages and sparkling wines.

References

Beaumont, F et al. (2013) Temperature Dependence of Ascending Bubble-Driven Flow Patterns Found in Champagne Glasses as Determined Through Numerical Modelling.  Advances in Mechanical Engineering, 10pp

Liger-Belair, G. (2013) Uncorked: The Science of Champagne. 216 pp

Liger-Belair, G. et al. (2010) On the Losses of Dissolved CO₂ during Champagne Serving. J. Agric. Food Chem. v 58, p. 8768–8775

Liger-Belair, G et al. (2012) Monitoring Gaseous CO₂ and Ethanol above Champagne Glasses: Flute versus Coupe, and the Role of Temperature. PLoS one

Beaujolais is one of the world’s most famous wine regions. Best known today for Beaujolais Nouveau, the region has been in crisis since 2000 as low prices, coupled with dropping demand, have forced many wine farmers out of business.  With the region seeking to reinvent itself, this 7 page free downloadable PDF, Beaujolais in Figures summarizes the readily available data to help explain the Beaujolais story.

Winestats would like to thank the staff of Inter Beaujolais for providing data used in this study

As wine consumers, we are often being urged by the trade to increase the amount of money we spend on a bottle of wine.  The argument, goes something like this.  Better wines require superior grapes, more careful vinification and perhaps longer ageing.  Since each of these factors incurs additional expenditure, better wines will inevitably be more expensive.  So if you want a better bottle of wine this holiday, well, simply open your wallet a little wider.

Score vs Price Plot for Soave (Sept, 2012)

Of course, such an analysis is way too simplistic as there are many factors which determine the price of a bottle of wine.  Larger producers may experience economies of scale and have larger marketing budgets.  Smaller producers may argue that they have a boutique offering with rareity value.  As consumers’ tastes change, retailers may have to scramble their prices so as to keep demand in balance with supply.

Similarly, it is very difficult – some would say impossible – to objectively assess wine quality. Not that this has stopped the majority of wine critics.  Although many of them will claim that it is important for consumers to read their tasting notes, most of them post-Parker feel obliged to attach a numerical rating. Retailers love scores as they move markets.  Consumers have been warned about the unreliability of wine scores, but nevertheless continue to make use of them in their buying decisions.

Score vs Price Plot for Albarino (Aug, 2012)

Score vs Price Plot for Brunello 2007 (Aug, 2012)

Given the complexity of factors which determine wine price and the difficulties of objectively scoring wines, we might expect there to be little relation between wine prices and scores.  So is this the case?

Decanter magazine, in their print edition, publish regular reviews of particular wines with quality assessments by respected wine experts.   Each expert includes their numerical assessment of quality for each individual wine, which the magazine averages and then assigns to a quality band.

Plots of average score against price for three wine types (Soave, Albarino and Brunello di Montalcino 2007) show that there is a very low correlation between average Decanter wine scores and price.  Indeed in the case of Soave the correlation is slightly negative.  Wine purchasing will remain a complex decision process.