One question worries many coffee drinkers: Which brewing method gets as many of the good ingredients as possible out of the bean? Not that this question has often been discussed by sommeliers, scientists and other coffee experts … But I came across a particularly well-made overview in the 2013 specialist journal European Food Research and Technology.
The scientists led by Professor Chahan Yeretzian from the University of Applied Sciences in Zurich examined nine different methods – from the Nespresso capsule to the French press. In each brew, the classics caffeine and chlorogenic acids, as well as some other interesting parameters, were measured . For this purpose, beans of the provenance “Guatemala Antigua LA CEIBA” or Nespresso capsules of the “Arpeggio” variety were used for all coffee samples.
The question: Which method brings a lot or less caffeine and chlorogenic acid into the cup?
Man versus machine
First of all: with the exception of the Nespresso capsule, the study mainly allows a comparison between fully automatic coffee machines, semi-automatic machines and non-automatic brewing variants. As for the latter: a mocha pot that is placed on the home stove, as well as a filter machine, a French press and a ceramic filter, the so-called Karlsbad jug. Of course, other ingredients profiles than Guatemalan coffee could also be measured, but here it depends on the differences between the individual forms of preparation.
Personally, I like to make a coffee in a mocha pot at home, while fully and semi-automatic machines tend to be used at work. But what can a machine demonstrably do better than the do-it-yourself variants? For example espresso. It only takes a little brewing water, but a lot of pressure. The result is a concentrated coffee. This is simply not possible by hand. Most fully and semi-automatic machines can also prepare the lungo variant.
Short or long?
Both espresso and lungo from the same machine were also examined in the study mentioned. For this purpose, extraction was carried out with 120 mL instead of 30 mL water. Four times the amount of water for the same amount of coffee powder also means a lower concentration of ingredients. More on that later. The only semi-automatic machine in the study, the Nespresso machine, also brewed with 30 mL, but used only 5.5 grams of coffee, while the fully automatic machines used around 8 grams of freshly ground coffee. The mocha pot took 7.5 grams to 110 mL. In the French press and Karlsberger jug, 27.5 grams were used for half a liter of water and the filter machine was used with 100 grams of coffee powder for 1.8 liters.
Of course, the coffee beans were freshly ground every time, even if there was no grinder, as was the case with the fully automatic machines. The best possible comparability was therefore given.
All coffees are sour in the same way
The “acidity” is an important criterion for the taste quality of a coffee. It is just as often misinterpreted. Let’s get to the bottom of this. From a chemical point of view, acids are nothing more than molecules that can give off a hydrogen ion, chemically speaking an H +. In this form, H + is perceived as sour in taste. Even water, the well-known H2O, can therefore act as an acid if it gives off one of the Hs. This is always the case when water is mixed with basic liquids.
It is then available as H + and OH-. OH-, on the other hand, is basic, you can’t taste it, but it can in turn neutralize acidic liquids. Pure water is neither acid nor basic and therefore ideally suited for diluting and neutralizing. What happens now when making coffee? A small amount of ground coffee is boiled with lots of water.
In coffee, chlorogenic acid and its breakdown products from the roasting process also contain acids, but due to the large amount of water they are neutralized so much that in the end almost every brewed coffee in the world has a pH value of 5.5 to 6, easily so sour. If you compare this with fruit juices, this is nothing, they don’t taste very sour due to the fructose they contain, but they can also have a pH value of 3. For comparison: the human stomach has a pH value of 1-2, which roughly corresponds to that of concentrated hydrochloric acid.
So back to our experiment. The acid content of the coffee beans was, however, quite different between the different coffees. The acidity of the espressos from fully and semi-automatic machines was a good 2.5 times higher than in the hand-made infusions or filter coffee. The same was also true for other ingredients, such as caffeine.
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It’s all about the variety … and the dose
The study shows that all shop talk about machines and methods for brewing coffee is above all one thing: myths.
The results of the study initially indicate significantly higher levels of caffeine and chlorogenic acid in the coffees of the fully and semi-automatic machines, but the amount of coffee powder per milliliter used for the espresso variant is three to four times higher. So it’s no wonder that the concentration of ingredients is simply higher. On the other hand, it is very interesting that the Lungo variants produced with the fully and semi-automatic machines were roughly on a par with the manual methods and the filter coffee.
Of course that makes sense. Because, as already indicated, the ingredient profile can also be affected without major technology by the coffee variety, and this is especially true for caffeine and just the question of choice of Robusta (higher caffeine content) or Arabica (lower caffeine content) concerns . As far as chlorogenic acid and its breakdown products are concerned, these can still be influenced during the roasting process, but less so by the brewing variant. In the end, the most important thing is the amount of coffee powder used per milliliter of brewing water.
So it remains a question of taste : For espresso you definitely need a fully or semi-automatic machine and you get a concentrated coffee. But if you can do without espresso, a well-roasted coffee variety of your choice will also help you with simpler methods – and, of course, cheaper if you take into account the acquisition and maintenance costs.