Methods of brewing coffee: a scientific view

Posted on Jan 12, 2021      150

Many people are convinced that there is only one correct way to brew coffee. But opinions differ which is the correct method. “There are actually many ways to make coffee correctly,” Leonardo Lelli explains to Popular Mechanics. In 1998, Leonardo founded Torrefazione Caffe Lelli, a small company that produces the most gourmet types of coffee. In that time he has had time to travel to all the major coffee growing countries and become a true expert in botany, chemistry, tasting, bean selection and roasting. And, of course, preparing this famous drink.

The most important component of coffee is caffeine (its formula is shown in the picture), but people love this drink above all for the unique combination of taste and aroma.

Turkish coffee

This method needs the finest coffee beans ground to “dust” (less than 0,1 mm) in order to extract all the substances in a few minutes and to get the fullest taste of the drink at normal pressure. The temperature during the brewing process is higher than optimal, and in the brewed coffee many tiny particles remain, so the process of extraction of different compounds, including phenolic ones, does not stop after serving. The taste of the coffee evolves, changing and taking on a slightly bitter and astringent hint. Brewing in a copper still is the most traditional way of making coffee, so some consider it the most authentic.

The first fully automatic household espresso machine, the Superautomatica, was introduced by Saeco in 1981. Roasted coffee beans go into the mill, after grinding it is tamped in the filter with a special piston. Pressing can be varied, changing the intensity of the drink depending on the owner’s preferences and the type of coffee. Water heated to a desired temperature in the boiler is pumped through the ground coffee at 8-12 bars, allowing for maximum extraction of the substances that give the espresso its characteristic taste and aroma. For flavor enhancement, certain Philips Saeco models pre-ground coffee is saturated with boiling water before brewing.

French Press

Many coffee drinkers consider this drink an “ersatz”. “It’s quite real coffee,” Leonardo explains, “but it has its own specifics. It needs the coarsest grind - about 1 mm, and the water temperature should be 85-90 ° C. You brew it for four to six minutes. Exactly this way is best suited for some sorts, particularly for the high-mountain Arabicas, because the beverage is neither bitter nor sour, but even sweet. By the way, a similar method, the so-called Brazilian method, is used by purchasers when tasting coffee varieties: coarsely ground roasted coffee is poured over with boiling water for five minutes.”

Geyser coffee makers

This method (called Moka Espresso in English) was invented in 1933 by two Italian inventors, Luigi de Ponti and Alfonso Bialetti. In their coffee maker, boiling water is pressed through a cup with ground coffee by the action of steam. The geyser requires a medium grind (0.5 mm), while the extraction of flavour-enhancing substances takes place at about 1.5 bars and 110 °C. Despite the shorter brewing time (about 1 minute), the temperature is higher than optimal, giving a very full coffee flavor with a slight bitterness.


The first espresso machine - albeit manual - was invented in 1931 by Italian Achille Gaggio. During espresso making, water of about 80 °C is pressed through a vessel with relatively finely (0.3 mm) ground coffee at 8-10 bar. The combination of low temperature and high pressure results in maximum extraction of substances, including oils, which give coffee its characteristic “long-lasting” taste. Another characteristic detail, unique to espresso coffee, is the steady crema, a mixture of carbohydrates, proteins, and phenolic compounds, whipped up by the carbon dioxide bubbles that saturate the ground coffee (which are produced during roasting).

“The key to a proper espresso,” explains Marco Maggiolo, production manager of Philips Saeco espresso machines at the Italian factory in Gaggio Montano, “is three points. First, very precise temperature control will maximize the extraction of all the right substances. Second, precision grinding, that is particle size distribution. When grinding, it is important to avoid “metallic” aftertaste, which is why our machines use ceramic millstones. And third, the correct amount of coffee - 5-7 grams per serving.

To allow the owner of the machine to achieve the taste of the beverage according to his own preferences and to use varieties with different roast degrees, it is possible to vary pressing of ground coffee during the brewing process, grinding, and the water pressure. Our espresso machines are equipped with a flowmeter, to allow a certain amount of water to flow through the coffee. All sensors and components of each machine are not only checked on the conveyor belt but also calibrated to achieve minimal variation and optimal results.