Changes in the roasting process of coffee beans changes occurred before and after roasting

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Volatile and non-volatile compounds

You may have heard that volatile and non-volatile compounds are produced during baking. Generally speaking, volatile compounds are aroma and non-volatile compounds are flavors. But what kind of substances are these?

Volatile compounds are organic chemicals with high vapor pressure at room temperature, many of which are formed in the degradation reaction or in the development stage of baking. When the volatile compounds escape, we will smell the unique aroma of this coffee, including:

Aldehydes: bring fruit aroma, green aroma. Furan: helps caramel smell pyrazine: has the smell of dirt.

Sulfur compounds: including 2-furfuryl mercaptan. Some of these compounds are often described as having the aroma of "roasted coffee", but some substances are unpleasant when smelled independently. For example, methanethiol smells like rotten vegetables.

Guaiacol: with the smell of smoke and spices. Carbon dioxide is a volatile substance that does not affect the aroma, but does affect the thickness of alcohols.

Non-volatile compounds are usually stable at room temperature, which means they do not evaporate. These parts of the compounds will change during the baking process, while the rest will remain stable throughout the baking process, and non-volatile compounds will help to produce flavor.

Caffeine, for example, may bring some bitterness. Caffeine occurs naturally in coffee and remains unchanged during roasting. Other non-volatile compounds, including sucrose that provides sweetness, oils that provide alcohol thickness and taste, and protein melanin, which produce color and alcohol thickness, are non-volatile compounds.

The role of acid

Acids play an important role in producing flavor. Baking can degrade some acids and produce other acids.

For example, citric acid and tartaric acid, which produce sour and sweet flavors, decompose during baking. So roasting for a long time or overheated will greatly reduce the sweetness of the final coffee.

Coffee contains a lot of chlorogenic acid, which can be broken down into caffeic acid and quinic acid when roasted. Chlorogenic acid and quinic acid are both thought to form bitterness and astringency.

Coffee roasting includes many chemical changes that help develop into the flavor, aroma and alcohol thickness of the coffee cup. Many reactions are sensitive to temperature changes and the length of heating. Therefore, small changes in baking technology will have a far-reaching impact on flavor characteristics.

Understanding what happens during baking and why these changes occur will help you make wiser choices. If you have an idea of how these compounds are produced during baking, you can better understand what went wrong with your baked batch, or use this information correctly to make the next pot more successful.