National

Dr Karl Kruszelnicki's science conundrums – does wine differ according to the glass?

Photo montage: Simon Bosch
Photo montage: Simon Bosch  

We humans have drunk alcohol for thousands of years. This means we've had plenty of time to make many different shapes of glasses from which to drink alcohol. We've got shot, brandy and martini glasses, and even several different types of wine glass.

Some rather recent and neat technology can show alcohol concentrations in the air in real time. These analyses seem to have confirmed at least one claim by wine connoisseurs could well be right – the shape of the wine glass can affect the aroma and flavour.

Dr Kohji Mitsubayashi​ and his colleagues at Tokyo Medical and Dental University developed the technology. It can directly portray, in real time, ethanol vapour escaping from a glass. (There are many alcohols, but the one we commonly drink is called "ethanol".)

They started with a cotton mesh. It was a millimetre thick, had tiny holes about one millimetre across, and measured 80 millimetres by 80 millimetres. They added a whole bunch of very specific chemicals, including one called "luminol". They then part-filled the test glasses with a Japanese red wine. 

As the ethanol rose upwards, it hit the cotton mesh. A bunch of chemical reactions started, and the luminol began to glow. They could "see" the alcohol vapour in the air. By 50 seconds, the light output of the glowing cotton mesh had stabilised. They repeated the experiment with various glasses, and at different temperatures.

The researchers found that ethanol vapour appeared in a very characteristic ring shape. Alcohol concentrations were low towards the centre, but high in a doughnut-shaped ring just inside the rim of the wine glass.

Because the alcohol concentration was lowest in the centre of that glass, that made it the best location to sample the delicate aromas of the wine. The lack of alcohol allowed the aromas to come forth and present themselves. 

The authors wrote: "The shape of the wine glass has a very sophisticated and functional design for tasting and enjoying the aroma of wine". 

On a similar but different theme, the shape of the drinking glass can affect how much you drink. Certainly, over the years, wine connoisseurs have maintained that the same wine can have very different bouquets and finishes depending on the wine's temperature and the shape of the glass in which it is served.

For example, it's been claimed that the tiny bumps on the surface of lead crystal glass can bring forth a multitude of extra fragrances.

The wine scientist Regis Gougeon​, from the University of Burgundy, France, admired the new technique, which enables a very simple and inexpensive, yet graphic, detection of ethanol.

He said: "This work provides an unprecedented image of the claimed impact of glass geometry on the overall complex wine flavour perception, thus validating the search for optimum adequation​ between a glass and a wine." 

This new technique allows better matching of the wine to the glass in which you serve it. But there are two things to note. First, the effect happened at 13 degrees, and only in the wine glasses. The effect vanished at 17 degrees. It was most present in a pinot noir wine glass (about 70 millimetres across, at the mouth).

Second, in accordance with all known ethics committee requirements, no wine was wasted in this study ...

This is an edited extract from Dr Karl's Short Back & Science by Dr Karl Kruszelnicki, Macmillan Australia, RRP $32.99.