Boutique coffee beans | what is the reaction when coffee is roasted? why the coffee is rich in flavor

Do you know what happens when you bake coffee? What changes have taken place to turn mung beans into our favorite delicious, fragrant coffee beans?

In the first part of this two-part series, we studied how the anatomical structure of coffee beans played an important role and outlined the physical changes that took place during roasting. Now, let's take a look at some chemical changes, including how flavor and aroma develop.

Main chemical reaction

The heat of introducing coffee beans into the roaster can trigger hundreds of different chemical reactions. Roasting will degrade some compounds, change others, and produce new compounds.

You may hear people mention a chemical process called pyrolysis. This is a volatile compound produced when an organic material is heated above its decomposition temperature, leaving a solid residue containing large amounts of carbon or carbon. In coffee roasting, we avoid heating coffee beans and causing coke, but they undergo chemical changes related to pyrolysis, including the caramelization of sugar and the production of volatile compounds.

Here are the main chemical reactions that affect your coffee every day.

Maillard reaction

This process begins at about 150 °C / 302 °F, when the beans still absorb heat and continue in the exothermic part of the baking. Calories cause a reaction between carbohydrates and amino acids in legumes. This can lead to changes in color, flavor and nutrients.

The change in color is attributed to the production of melanin. These macromolecules not only make beans brown, but also help taste and body.

Subtle changes in temperature and time length in Maillard reaction may have a significant impact on the final appearance of coffee.

It is reported that the viscosity of coffee that takes longer in Maillard reaction increases. The shorter the duration of Maillard, the higher the sense of sweetness and acidity. Part of the reason is that if coffee stays in Maillard reaction for too long, it destroys the acid that produces fruity and sweetness.

When the roaster tests the roasting curve, it includes changing the length and strength of Maillard reaction and recording its effect on the roasting curve.

Stryker degeneration

This process depends on the Merard reaction. Amino acids react with carbonyl molecules to form aldehydes and ketones. As roasters, we do not need to know exactly what these compounds are-it is important to recognize that this reaction is essential for compounds that produce aroma and flavor.

Caramelization reaction

At about 170 °C / 338 °F, heat causes a large number of complex carbohydrates to break down into smaller sugar molecules that are soluble in water. This means that the sweetness of the finished product will be improved. The reaction lasts until the end of the baking and also contributes to the sweetness in the aroma of coffee, such as caramel and almonds.

Volatile and non-volatile compounds

You may hear information about volatile and non-volatile compounds in roasted coffee. Usually, volatile compounds are responsible for aroma, and some non-volatile compounds are responsible for aroma. But what are they?

Volatile compounds are organic chemicals with high vapor pressure at room temperature. Many of them are formed by the degradation of Strecker in the development stage of baking. When fragrant volatile compounds come out, we feel the typical smell of coffee. These include:

Aldehyde, increase fruit flavor, green aroma.

Furan produces the smell of caramel

Pyrazines, which smell like dirt.

Sulfur compounds, including 2-furfuryl mercaptan. Some of them have aromas commonly referred to as "roasted coffee", while others do not have an isolated smell. For example, methanethiol smells like rotten cabbage.

Guaiacol, with a smoky, spicy hue.

Carbon dioxide is a volatile compound that does not increase aroma, but affects the human body.

Nonvolatile compounds are only substances that are stable at room temperature. In other words, they don't evaporate. Some of these compounds change during the baking process, while others remain stable throughout the process. Many non-volatile compounds contribute to flavor and flavor.

Examples include caffeine, which produces some bitterness. Caffeine occurs naturally in coffee and remains the same during roasting. Other non-volatile compounds include sucrose, which provides sweetness, and lipids, which provide body and taste. Melanin, which produces color and body, is also a non-volatile compound.

The role of acid

Acids play an important role in producing aromas and are sensitive to heat. Baking degrades some acids and produces other acids.

For example, citric acid and tartaric acid, which produce fruity and sweetness, are broken down during baking, so long or overheated baking can greatly reduce the sweetness of the final flavor.

Coffee contains a lot of chlorogenic acid, which breaks down into caffeic acid and quinic acid when roasted. Both chlorogenic acid and quinic acid are thought to provide bitterness and astringency.

Coffee roasting includes many chemical changes that contribute to the taste, aroma and body of the final cup. Many of these reactions are sensitive to changes in temperature and time of exposure to heat. As a result, small changes in baking technology can have a profound impact on the profile.

Understanding what happens during baking and why these changes occur can help you make wiser choices. If you outline how to create and change compounds during this process, you can better understand what went wrong or correct in the batch and use this information to improve the next one.