The Chemistry of Coffee – What you should know

Coffee remains one of the most popular beverages in the world, second only to water and tea, and is still one of the most consumed.

This is due to the effects of the caffeine in coffee, but there are also things you didn’t know about coffee, such as: B. the sensations it creates in the mouth and how it can help in the production of other foods.

What is a coffee infusion?

Coffee infusion is the mixing of ground coffee beans with hot water (in most cases). This triggers a series of complex chemical processes.

One of the most important factors in brewing coffee is the carbon dioxide contained in the coffee beans. When the beans are roasted, the heat from the roaster causes carbon dioxide (CO2) gases to remain in the bean.

After the roasting process, the coffee beans slowly begin to release gases, a process known as “degassing“.

Substances that make the coffee special

In the coffee itself, whether ground or as beans, there are more than 800 chemical compounds, including:

  • Sucrose
  • Cellulose
  • Organic acids
  • Aldehydes
  • Ketones
  • Ester
  • Proteins
  • Trigonelline
  • Lipids
  • Glycosides
  • Minerals


Caffeine is a bitter chemical compound found in over 60 plants around the world and is the world’s most commonly consumed mind-altering chemical. Caffeine is an alkaloid from the xanthine group, which normally has a bitter taste.

Caffeine acts like a psychoactive drug that stimulates the central nervous system.

Chemistry in the aroma of coffee

Basically, it’s a drink made mostly of hot water that’s passed through the ground coffee beans, and there are about 900 chemical compounds found in the aroma alone.

One of the reasons for the popularity of coffee is its attractive and calming aroma. A study by Yoshinori Masou from the National Institute of Advanced Science and Technology in Japan in 2008 showed that just the smell of coffee can be beneficial to health.

By depriving rats of sleep and exposing them to the aroma of coffee, changes in the protein content of brain cells were found to protect against stress-related damage.

The chemicals that give coffee its aroma and flavor are modified as the beans are dried and roasted, with many of these substances being different depending on the variety and type of coffee.

Coffee made from Arabica beans has sweeter notes because it contains more sucrose and also compounds like sotolone and furaneol that give it a caramel flavor.

Robusta beans, on the other hand, have a stronger flavor as they contain more caffeine and also pyrazines, which are responsible for the famous coffee aroma.

The degassing of coffee

The gases in the coffee are ultimately responsible for the aromas in the cup of coffee, so it is important that they are present to the greatest possible extent when the coffee is brewed.

Degassing is slow if the coffee beans have not been ground. It usually takes 8 to 10 days for a coffee bean to release most of the CO2 after roasting.

If you want to speed up the coffee degassing process, you need to grind it. If you grind it, the coffee will be fully degassed in about three days. It is therefore always advisable to grind the coffee just before brewing, otherwise you will not be able to enjoy the full taste of the coffee while brewing.

Degassing coffee is a natural process with no chemicals or anything involved.

When the hot water meets the freshly ground coffee, the remaining CO2 is released and the brewing process begins.

Factors affecting degassing

Degree of roasting

Whether the roast was strong, weak, fast or slow has a major impact on the coffee’s degassing process. Normally, a very dark or intense roast means that the coffee beans can store gases longer. In other words, more gases are retained or absorbed, so it takes longer for degassing to occur completely.


As is often stated on coffee packaging, the warmer the environment around the coffee, the more gases are released from the bean. It is therefore always recommended to store the coffee in a cool, dry environment, away from heat and strong odors.

Origin of the coffee

There are many types and types of coffee, so each type of coffee is different and their gas holding capacity differs from one another.


This is pure chemistry. The drier the environment, the more gas the coffee bean releases. However, one should not attempt to increase the moisture content of the coffee. Storing coffee in colder and wetter environments to better preserve it can lead to mold and fungal growth.

Coffee, chemistry and botany

Coffee farmers must ensure that their coffee trees are in the best possible condition. Even small changes can have a significant impact on your yield. Coffee plants require special attention to reach their full potential. They need sunlight and water.

Most coffee is grown between the Tropic of Capricorn (or Tropic of Cancer), in an area of the world commonly known as the Coffee Belt. Coffee thrives in areas with high levels of sunshine and heavy rainfall.

The quality of the soil is also important for the health and development of the coffee trees. Farmers go to great lengths to ensure their soils are rich and contain enough nutrients.

Coffee is resilient, but farmers prefer higher elevations to get the most out of their coffee trees. Elevated farms offer two main advantages. First, coffee trees grow more slowly at higher elevations due to the harsher conditions.

The second point is that if the ripening process takes longer, the coffee cherries have more time to absorb nutrients and develop complex sugars, resulting in a tastier coffee bean.

Coffee chemistry

Coffee roasting

Coffee roasting is a complex process that has many nuances and subtleties. The first challenge with coffee is to heat the green coffee beans enough to start certain chemical reactions without getting so hot that “pyrolysis” occurs.

Pyrolysis is a chemical process that takes place when a material is heated above a temperature threshold called the “decomposition temperature”.

Pyrolysis is the first step in combustion, which is the charring of wood. However, the coffee roasters ensure that the coffee bean is not completely pyrolyzed or even burned.

To do this, they must also know the Maillard reactions responsible for browning and caramelizing foods.

The Maillard reaction starts at around 150°C and when roasting coffee beans reaches this temperature, this reaction can have a major impact on the flavor of the coffee bean.

Shorter reactions result in coffee beans with more sweetness and acidity, while longer reactions get a malty character.

Color of coffee

This is one of the most influential factors in coffee selection as it is related to the chemical composition of the product and the degree of development or change. Depending on the storage conditions, the color may change due to the physico-chemical action of the water.

This affects the enzymatic activity of the bean and changes the permeability of the cell membrane through the action of hydrolytic and oxidative enzymes that change the color, according to the article “Coffee technology ” by chemical engineer Campo Elías Riaño Luna.

Water in coffee processing

The water used to brew coffee plays an important role. Water you use to brew coffee can change both the taste and texture of the coffee. The taste of coffee is affected by the minerals it contains.

This can happen through the cup of coffee or indirectly through all processes of coffee production and extraction.

How to prepare the perfect coffee using the rules of chemistry

First of all, achieving the perfect or ideal coffee brew is not easy, as there are factors that must be controlled to achieve the expected result. Including the temperature of the infusion, the water and the amount to be used, the size of the coffee beans and their freshness.

Water for coffee

The articles mention that in chemistry there is a term for water hardness that describes the concentration of other compounds and the amount of those compounds in the water.

Soft water

Soft water has very low levels of calcium and bicarbonate ions found in rivers, glaciers, underground rivers and lakes. When this type of water is used, the coffee will have a very high acidity level, which means the coffee will taste a little more bitter than normal.

Hard water

Hard water has a high content of calcium and bicarbonate, so the coffee is not bitter at all, but tastes like a neutral drink. Usually this type of water is found in underground caverns or caves.

It is recommended to use water that can be bottled or filtered to prepare the coffee.

Grind coffee

At this step, the type of grinding depends on each individual’s preference. A coarse grind gives the coffee a more delicate aroma, a fine grind gives it a strong and intense aroma.

When preparing it, it should be noted that the ratio of a spoonful of coffee, about 6 to 8 grams, should be used per cup of water.

As for brewing time, if the coffee is ground finer it should take longer for the water to absorb it, if it’s ground coarser it will take less time. The most important thing is that the water is kept at a temperature below 90 °C and does not reach the boiling point.

Type of coffee to use

For this step, it is advisable to choose a bean that does not have a high degree of roast. It is recommended to use a medium roast bean to retain all of its flavors and a more balanced flavor. But as always, that’s a matter of taste or preference.