The science behind Christmas cocktails

At this time of year, many of us turn to ethanol-based refreshments — even Father Christmas is partial to a small tipple after descending each chimney.

But what you may not realise is that there is a lot of science involved in the development of beers, wines and spirits.

Alcohol is a mixture of ethanol, water and flavourings — for example, juniper berries give gin its distinctive flavour.

Chemists help to develop new products, optimise the manufacture of existing drinks and undertake routine analysis to ensure standards are maintained.

Ethanol is a natural product of the process of fermentation, yet it can then be converted into a vast array of drinks as a result of chemical combinations and reactions.

The amount of ethanol in a product varies from around five per cent, for beers, to 40 per cent for spirits such as whisky and vodka.

And one of the most fascinating areas in which the science behind the spirits plays a crucial role is the world of cocktails.

James Bond is notorious for ordering a vodka martini shaken, not stirred — but is there a scientific explanation for this?

A recent report suggests there is, based on a theory by researchers at the University of Aberdeen.

Methods to produce vodka have significantly changed over the last 50 years, from the fermentation of potatoes to the modern method using grains.

Vodka made using potatoes tends to contain more oil, which leaves an unpleasant, oily taste in the mouth unless the oil is dispersed.

This dispersion cannot be achieved by simply stirring the vodka, but can be achieved by vigorously shaking the drink. So to avoid the unpleasant sensation it must be shaken, not stirred.

If your cocktail requires ice then there is also the issue of temperature. Many drinks that are best served chilled require the solution to be mixed with ice to reduce the temperature of the liquid.

But this is a tricky issue as it is best to achieve a good ice-liquid mix which should drop the temperature below zero degrees centigrade — but at the same time not allow the ice to melt and dilute the drink.

Scientists have investigated the optimum number of bartender “shakes” to achieve a good mix with no dilution and found the answer to be 20.

Based on this research it can be said the perfect scientific vodka martini requires vermouth, vodka, ice and 20 shakes precisely.

Another famous drink is the controversial French spirit known as absinthe with many renowned admirers including Wilde and Van Gogh, who some claim were inspired to write and paint from the effects of the drink.

One of the key features of the spirit is the distinctive green colour, extracted during manufacture from herbs and mainly the well-known chemical chlorophyll, found in plants.

Scientists still disagree whether the alleged hallucinogenic properties of this spirit are from some of the chemicals it contains, known as terpenes, or the excessively high levels of ethanol in the product. In either case, many people do say that after drinking absinthe they experience unusual effects which is why it has been banned on and off in many countries over the years, although interestingly never in Spain, Portugal or England. The science behind alcohol has helped create a variety of products with different strengths and flavours to suit different people.

It may not always be necessary to be aware of the chemistry behind the product to enjoy it but it can be very interesting.

Whatever form of ethanol-based product you choose to drink this Christmas, don’t forget to leave some by the fire on Christmas Eve for you-know-who. Merry Christmas!




Dr Laura Waters works in the Division of Pharmacy & Pharmaceutical Sciences, University of Huddersfield