A Scientific Review of Coffee Brewing Methods

Last Updated on January 18, 2021

A Scientific Review of Coffee Brewing Methods

Coffee is one of the most consumed beverages worldwide. There are several methods of preparing coffee beverages, a fact that often leads to heated discussions. What is the correct method of preparing coffee? Which is the ‘authentic’ one?

Many accept only one way of making coffee out of the different methods available. But the truth is that one can make coffee correctly in each of those ways. It is the view of Leonardo Lelli, founder of Torrefazione Caffe Lelli.

His small company produces different types of coffee, all of them exceptionally delicious. It’s not the result of fortune. He has traveled to the countries that are the main coffee producers. He has acquired vast knowledge in the preparation of coffee beverages. But also he has gained expertise in botany, chemistry, and the process to select and roast coffee grains.

Why does coffee have many followers and enthusiasts? It’s definitely because of a very special blend of taste and aroma. The main chemical substance responsible for this characteristic is caffeine. Let’s review the different methods to extract this substance from ground coffee to create different beverages. Insight from Leonardo’s expertise helps to describe more adequately these methods.

Turkish coffee

This method utilizes the finest ground coffee. Each coffee particle has less than 0.1 mm in diameter. Hence, this ground coffee is like dust. This consistency allows extracting caffeine in a short time at normal pressure.

Turkish coffee

For this sake, the temperature used to brew the coffee is higher than the optimal value. But many particles of ground coffee remain in the brewed coffee in this way. Thus, the brewing process goes on until several substances are extracted. Among these substances are aromatic organic compounds. The resulting beverage has a full taste, which is bitter and astringent to some extent. Many consider the use of a traditional copper pot as necessary for superior authenticity.

French press

Even though some coffee enthusiasts regard the beverage prepared with this method as “ersatz coffee, it is quite real. It’s coffee with very specific characteristics, according to Leonardo. To prepare it, the coarsest ground coffee is used. Each particle is approximately 1 mm in diameter. The preparation takes between 4 and 6 minutes. It requires a water temperature of 85-90 °C.

French press

This method is ideal for some coffee varieties such as Arabica from the highlands. The resulting beverage has a rather sweetish taste. A similar method, referred to as Brazilian, is used to prepare degustation drinks for potential buyers. One just needs to put coarse ground coffee in hot water for 5 minutes.

Geyser coffee maker

The beverage prepared with this method is commonly known as Moka Espresso. The geyser coffee maker was invented by Luigi de Ponti and Alfonso Bialetti in 1933. In this case, medium grinding is needed. Each particle of the coffee ground has approximately 0.5 mm in diameter.

Geyser coffee maker

This coffee maker forces boiling water through a container that contains the ground coffee. Since the temperature of the water is 110 °C, steam plays a role in extracting the aromatic compounds. This process is performed at 1.5 bar of pressure. Because of the high temperature, the brewing process takes about 1 minute only. However, the resulting beverage has a full taste, slightly bitter.


Espresso Machine

Espresso is one of the most popular coffee beverages. It requires a machine that forces water at around 80 °C through a container with fine ground coffee. In this case, each coffee particle is approximately 0.3 mm in diameter. The process is done at high pressure, approximately 8-10 bars. The relatively low temperature combined with high pressure ensures the extraction of chemicals from the ground coffee. Besides caffeine and aromatic compounds, the process extracts oils that give an espresso its characteristic long-lasting flavor. Also, the extracted compounds such as carbohydrates, proteins, and carbon dioxide form a consistent foam, which characterizes a well-made espresso.

Coffee cups with froth

Marco Maggiolo, Espresso Production Manager for Phillips Saeco machines at the Gaggio-Montano plant in Italy, identifies 3 points for the best espresso:

  1. Keeping the right temperature maximizes the extraction of the relevant chemical compounds;
  2. The grinding process must be performed such that the particles of the ground coffee are uniform in size; Moreover, the grinding process shouldn’t involve metal, which gives a ‘metallic’ taste to the coffee. Instead, Phillips Saeco machines use ceramic millstones;
  3. The right amount of ground coffee per cup should be 5-7 grams.

The first modern espresso machine was invented in Italy by Achille Gaggia in 1931. It was a manual machine though.

In 1981, Saeco introduced the first fully automatic espresso machine for preparing the beverage at home. The machine grinds roasted coffee beans. Then, a piston is used to compact the ground coffee in the filter. The compactness can be regulated to change the saturation of the beverage to meet personal preferences. Finally, hot water at the optimal temperature is forced through the ground coffee at a pressure of 8-12 bars. Some Phillips Saeco machines moisten the ground coffee with hot water previous to the brewing process. This action enhances the aroma.

Evaluating the quality of the espresso

The quality of the aroma and taste of espresso is quite subjective. However, coffee machine manufacturers need objective assessments to know how users perceive their products. An evaluation method that uses sensory analysis has been developed by the ‘Centro Studi Assaggiatori –Italian tasters’ (Italian Association of Tasters). This evaluation method is based on subjective perceptions as well as psychological and statistical analyses.

Manuela Vialone, a member of the Association, explains how this evaluation works. All the possible aromas and tastes of espresso are listed on a questionnaire. Then, a population sample is polled using this questionnaire. The collected information is processed statistically. The result allows drawing clear conclusions about the performance of the coffee machine. For example, if a majority feels the smell of caramel, one can conclude that the pulp, which has high sugar content, has not been properly removed from the coffee beans.

To meet the personal taste of each machine owner, the machines allow controlling different parameters. The level of roasting and grinding, compactness of the ground coffee, and water pressure can all be adjusted. Also, the machines are equipped with flow sensors to enable the flow of hot water at an optimal time. All these sensors are calibrated to obtain optimal results.

About your guides

Stephen Gardner

Coffee Grinders Advice Staff

(Coffee Grinders Advice is reader-supported. When you buy through links on our site, we may earn an affiliate commission)

Featured Image Source: Pixabay.

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