Friday 24 November 2017

Bean counters: maths behind the perfect cup of coffee

Scientists are working hard to discover how to make the best brew, writes William Lee

William Lee

Like many people, my day starts with a cup of coffee. This is thanks to an Ethiopian goatherd in the ninth century who noticed the stimulating effect the berries of an otherwise unremarkable bush had on his goats, and tried them for himself. The seeds of that bush are now used to prepare the complex and delicious drink we call coffee.

To become coffee, the seeds are treated by roasting, grinding and brewing. The most expensive coffee beans are collected after they have passed through the digestive system of a type of cat.

Brewing coffee is a delicate business, the optimum cup of coffee (of about 0.2 litres) is made with 12.5 grammes of ground coffee, of which only 2.5 grammes go into the coffee. If you stray too far from the ideal recipe the coffee will taste dreadful. For instance, if you dissolve about three grammes, the coffee will have a bitter taste. Many coffee afficionados prepare their coffee with weighing scales, a thermometer and a stopwatch.

It is therefore no wonder that some people prefer to use instant coffee. Instant coffee is made by taking brewed coffee and removing all the water. The best instant coffee is made by freeze drying, which is carried out at such low pressures that liquid water cannot exist and ice turns directly to steam in a process called sublimation. Freeze drying is widely used in the food and drink industry and also in the preparation of many medicines.

My colleagues and I at MACSI (Mathematics Applications Consortium for Science and Industry) are deeply interested in both the brewing of coffee and freeze drying. We are developing mathematical models of coffee brewing to optimise the design of coffee machines, making it easier for millions of sleepy people to enjoy a perfect cup of morning coffee. We are also working with the pharmaceutical industry to develop mathematical and statistical tools to improve the efficiency of industrial freeze driers.

When you next enjoy a cup of coffee, spare a thought for the mathematicians and statisticians who are working hard to improve it.

Dr William Lee, lecturer, Department of Maths and Statistics, University of Limerick

Irish Independent

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