Chemistry Changes During Coffee Roasting

Do you know what chemical changes let the coffee beans convert to a charming coffee with a rich and aroma when coffee roasting?

In another article, we have known the structure of the coffee beans plays an important role, making the roasting process have physical changes. This article shows us the chemical changes that will occur when roasting, including how the flavor is developed.

Main chemical reaction

Coffee beans heating will trigger hundreds of different chemical reactions, and roasting will degrade some compounds, alter other compounds, and produce new compounds.

You may listen to some people say that when the organic matter is heated to its decomposition temperature, the volatile compound is produced, and a solid residue containing a large number of carbonization or coke is left. We avoid causing coffee beans to overheat to cause carbonization during the coffee roasting process, but they have experienced chemical changes associated with pyrolysis, including caramelized and volatile compounds.

The following is the chemical change mainly brought by roasting:

Maillard reaction

This reaction occurs at about 150 °C. At this time, the coffee beans are still heat-inspiration and continue to heat the roasting process. The heat causes the reaction between the carbohydrates and amino acids of the beans, resulting in a change in color, taste, and nutrient components.

The color change is mainly because of the production of melanins. These large substances are not just letting coffee beans into brown and will affect the taste of the coffee and alcohol thickness.

The temperature and time of this stage may have a big impact on the final flavor.

The coffee that takes a long time in the Maillard reaction will increase its viscosity. The shorter Maillard response will have more sweetness and acid because if the Maillard is too long, fruit acid and will The acid to convert into sweetness will be destroyed.

When the Goucher experiment roasting technique also contains the length and strength of the Maillard reaction and records what the changes will bring to the final flavor.

Degradation reaction

This procedure depends on the Maillard reaction. The amino acid and the molecule of the carbonyl group reaction produce a compound such as an aldehyde and a ketone. Dried beans do not necessarily understand what these compounds are, and it is important to recognize that this reaction is indispensable for producing aromatic and flavor.

Caramelization of carbohydrates

When heating to approximately 170 ° C, heat will make many complex carbohydrates, which can be decomposed into sugar molecules that can be dissolved in water, representing the last rushing coffee sweetness increases. This reaction will continue until the roasting process ends, which also helps sweet in coffee, such as caramel and almond flavor.

Volatile and involatile compound

You may listen to people that produce volatility and non-volatile compounds when they say roasting. Generally, volatile compounds are aroma, and non-volatile compounds are flavor. But what are these substances?

The volatile compound is an organic chemical substance with a high vapor pressure at room temperature. Many of which are formed in the degradation reaction or the development phase of the roasting. When the volatile compound is dissipated, we will smell the aroma of this coffee, including:

  • Aldehyde: Bringing fruit, green aroma.
  • Furan: contribute to caramel odor
  • Pyrazine: has an earthy smell.
  • The sulfur-containing compound includes 2-Furfuryl mercaptan. Some of these compounds are often described as a fragrance with "roasting coffee", but some substances are not happy when independent. For example, methyl thiol smells like rotten vegetables.
  • Guaiacol: It has a smoky, spicy aroma.
  • Carbon dioxide is a volatile substance that does not affect the aroma but does affect the fullness.

Non-volatile compounds are usually stable at room temperature. That is, they don't evaporate. The compounds of these parts have changed during the roasting process, while the remaining compounds remain stable throughout the roasting process, and the non-volatile compound helps produce flavor.

For example, caffeine may bring some bitter tastes. Caffeine is naturally present in coffee and remains unchanged during roasting. Other non-volatile compounds include sucrose providing sweetness, providing alcohol thickness and greases of grease, color, and alcohol thickness, which are non-volatile compounds.

The role of acid

The acid has a large role in producing flavor, and roasting can degrade some acids and produce other acids.

For example, citric acid and tartaric acid that produces frozen and sweetness are decomposed during roasting. Therefore, long or overheated roasting will significantly reduce the sweetness of the final coffee.

Coffee contains many chlorogenic acids, broken down into caffeic acid and quinic acid during roasting. The chlorogenic acid and Quinic acid have been considered to form bitter taste and astringency.

Coffee roasting includes many chemical changes to help develop flavors, aroma, and alcohol thickness in coffee cups. Many reactions are sensitive to temperature changes and heating length. Therefore, small changes in roasting techniques will have a profound impact on flavor characteristics.

Understanding what happened during roasting and the causes of these changes helps you make more sensible choices. If you have a concept of these compounds in the roasting process, you can better understand what questions you have roasted or use this information correctly to make the next pot more successful.