Revealed: The four-step guide to help you brew the perfect cup of tea
Published 23/03/2016 | 12:10
Leaving the tap to run before filling the kettle could be the key to making a perfect brew, as UCL researchers’ reveal the chemistry of tea making.
Ireland is a nation of tea lovers, with 76 per cent drinking at least one cup every day.
And for generations the best method has been debated, from the type of tea to use, to how long to brew it, and if – or when – to add the milk.
George Orwell famously stated in his 11-point essay, A Nice Cup of Tea, in 1946, that the milk debate was “one of the most controversial points of all” and said that “in every family in Britain there are probably two schools of thought on the subject”.
Although he said the milk-first school brought forward some "fairly strong arguments", he maintained that putting the tea in first allowed the maker to regulate the amount of milk. And so his mind was set.
But by using scientific analysis, Professor Mark Miodownik, a materials scientist at UCL, says the chemistry behind making a good cup of tea is all you need to know.
According to Professor Miodownik, the first step is to use loose tea leaves as opposed to a tea bag.
"When adding hot water to loose tea leaves, convection currents swirl them around, allowing the fragrant flavours to diffuse," he told the BBC Radio 4 Today.
But if those leaves are tightly packed into a teabag they are unable to move freely and some of the flavours that dissolve from the leaves do not make it into the water.
Professor Mildownik says using loose leaves means the tea is given the best chance to release its flavours.
However, 96 per cent of tea in Britain is made using the arguably more convenient option of a bag. Professor Mildownik says in this case, it is important to ensure there is lots of space inside the bag.
The second step is to use filtered or soft water. The waxy layer that sometimes floats on top of a cup of tea is technically called ‘tea scum’ and the culprit is hard water.
"Hard water contains much more calcium than soft water and this binds to the plant extracts in the tea leaves to form scum. So if you live in a hard water area, make sure you filter your water before putting the kettle on," Professor Miodownik said.
Experts have also suggested letting the tap run before filling the kettle first thing in the morning.
Particularly in houses with old pipe systems, the water has spent all night sitting in the pipes, and reacting with the material.
The third step is to uses boiling water for black tea, but not for green.
Black tea and green tea are both made from the same plant but what makes them different are the ways the leaves are processed.
Black tea leaves are crushed so the chemicals inside them get exposed to the air, altering the bitter-tasting compounds, such as tannins, into more floral and fruity flavours.
The tea leaves that become green teas remain more intact and less of the tannins get oxidised. Tannins dissolve in water at 80 degrees centigrade, meaning that black tea needs boiling water to bring out its characteristic flavours, but for green tea, a much lower temperature is needed.
The final step is to be patient and let it brew.
According to Professor Miodownik, the evidence on brewing time varies, but researchers are sure that British people do not let their tea brew for long enough.
Professor Miodownik said: “There are more than 30,000 chemicals in tea, all of which need time to emerge. So, while most people wait for well under two minutes, studies show we should be brewing for at least two and even up to eight minutes."
The Royal Society of Chemistry published a study said that milk should go into the mug before the hot water. It argues that when milk is poured into hot tea the high temperature affects its taste. As droplets of milk fall through the tea, their proteins degrade as they are heated above 75 degrees.
However the Institute of Physics said it was all to do with the cup. Tea was supposed to be drunk out of high quality, fine porcelain, and so pouring milk in before the tea was a necessity – it stopped the cup from cracking.
However UCL stand firm on the view that due to 91 per cent of tea drinkers using a mug, as opposed to a cup, milk should be poured in last, so as not to interfere with the brewing process.