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Science

The science of good coffee

Today it's hard to find a city street in Italy that doesn't have at least one coffee bar, serving cappuccino, macchiato, caffé latte and, of course, espresso. But just how hard is it to make a really good coffee?

Along with their food, art and architecture, one of the greatest sources of pride for Italians is their coffee. Many claim that, even if you use the same beans and the same machine to make your coffee outside of Italy, it simply doesn't taste as good.

The espresso machine was, of course, invented in Italy, and Italy still produces the majority of professional coffee machines for bars all over the world. So it may come as a surprise to hear that espresso coffee is actually a post-World War II phenomenon.

Coffee used to be a luxury item. Poorer people would usually drink toasted chicory or barley instead. But after 1945 lifestyles began to change, and the espresso was invented as a way for ordinary Italians to down a quick coffee on their way to work.

This evolved into the now-famous Italian coffee culture of espresso machines, coffee bars, baristas - and, of course, the different forms of the drink itself.

'Coffee lab'

Terzi's coffee bar in central Bologna has a vast selection of beans and roasts from all over the world. It's also got a "coffee lab," where baristas experiment with different methods of making a perfect espresso.

The proprietor, Manuel Terzi, says he's trying to adopt a scientific approach to coffee-making.

Bar owner Manuel Terzi with a cup of coffee in front of his espresso machine in his cafe in Bologna, May 2013 Photo: Dany Mitzman

Manuel Terzi has opened a 'coffee lab' in his cafe in Bologna

"When you go into a coffee shop and ask for an espresso, you can have just this kind of coffee in this kind of coffee machine," he says. "So you have no choices. But maybe it could be interesting to learn what differences you can find, between the same coffee bean prepared with different kinds of coffee machines, or the same machine using different beans."

The various types of coffee machine offer possibilities for brewing coffee in different ways, depending on whether the machine is a classic espresso machine, spring-lever, vibration pump, or cold percolator or siphon.

It really is possible to make coffee using cold water, Terzi insists. Cold percolated coffee takes an entire night to brew, but is supposed to be easier on the stomach.

Variable pressure

Terzi's Bologna bar is a unique combination of café, museum and laboratory. He even possesses an example of the first modern coffee machine for making espresso coffee. "It's called E61 because it was made in 1961," he explains. "It's a great machine."

Like many others, the E61 is spring-operated. This means the coffee is brewed at a controlled but variable pressure: initially high, when the barista pulls the lever to compress the spring, gradually declining as the spring releases. Controlling the pressure is key to creating a good espresso.

Water being boiled on a tiled surface in the Terzi cafe's coffee lab

Terzi experiments with different beans, roasts and coffee machines to discover what makes the perfect espresso

The general assumption is that a small cup of espresso is stronger than a long coffee - but that isn't necessarily the case. "Caffeine can melt very easily in the water, so in the first five or 10 seconds you extract all the caffeine from the coffee," Terzi explains.

"But a short coffee is more easily digested than a longer one, because in the beginning you extract only the good substances from the coffee." After that, he says, if the coffee keeps on brewing, it starts to release other elements as well which are not so desirable.

Similarly, while drinking milk with your coffee can help caffeine to pass through the stomach wall, it's very important that the milk should not be boiled.

"The milk must not be warmed up over 72 degrees (162 degrees Fahrenheit), because in this case the substances can change," Terzi warns. It creates casein tannate, which is very hard to digest. "You cannot sell a cappuccino with milk heated over 72 degrees," he says, disapprovingly. No respectable barista would contemplate such a thing.

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