The relationship between the decomposition of chlorogenic acid and coffee roasting process

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Chlorogenic acid is formed by dehydration and condensation of quinic acid and caffeic acid by esterification. This is a reversible reaction. In other words, chlorogenic acid can be hydrolyzed into quinic acid and caffeic acid when it comes to water. Because hydrolysis is an endothermic reaction, coffee will decompose after being heated during roasting. 
 but we have to have a concept, because the content of chlorogenic acid in raw beans varies depending on bean species or planting conditions, so no matter how baked, chlorogenic acid is not likely to decompose completely. According to rough statistics, even when baked, only about half of chlorogenic acid will be decomposed. Therefore, beans still have to choose high altitude is the first choice.

The roasting process and the decomposition of chlorogenic acid 
, then we begin to imagine that when roasting coffee, we start to heat the coffee after we put in raw beans. At the initial stage of roasting, the system begins to heat the raw beans, and after heating, the mobility of water molecules increases, and they will begin to gasify. At this time, if the wind is blown, it can accelerate the departure of water molecules, which is commonly known as dehydration reaction. At this stage, there are two major schools. The technique is completely opposite, one is to accelerate the heating of water (beans) completely and to achieve the purpose of dehydration (for example, Nordic is a baking method), the other is to use a small fire and a small throttle to slowly heat it evenly (the traditional steaming dehydration method), these two methods have their own characteristics, but recently, much like the Nordic baking method is more popular. After 

 water is heated, chlorogenic acid will begin to decompose, but in the baking process, water is continuously lost, water is removed quickly, or slowly, more or less will affect its flavor (Mena reaction), but I will only discuss chlorogenic acid here. The relationship between 
 moisture and chlorogenic acid when there is sufficient moisture (high water content of beans, or slow dehydration process before explosion), chlorogenic acid can be fully decomposed into caffeic acid and quinic acid, which is the "decomposition with water" reaction mentioned by Mr. Taguchi in the boutique coffee collection, and there will be sour (quinic acid) and astringent (caffeic acid) in flavor. After an explosion, the water in the coffee bean is lost (in this case, the water that can flow freely in the raw bean). If the bean is continuously heated, it will force the molecules in the chemical structure to dehydrate. Quinic acid will dehydrate to form quinic acid lactone, which is due to the original acid characteristics of the functional group (shuttle machine) of the hydroxyl radical combined with another hydrogen to form water, so it no longer has the characteristics of acid, and will be bitter in the taste. 

 and caffeic acid will be detached (de-CO2) to become vinyl catechol. The ethylene structure of this substance is the most terrible. If it is continuously heated to form polyethylene, it will form the "bad bitter" vinyl catechu polymer described by Taguchi. Look at its phenolic structure, which is also a polymer. This substance is not only bitter, but also astringent, and should be located at the root of the tongue (bitter) and throat (Kaka's). 

 in the case of insufficient water (the water content of beans is low, or the dehydration process before explosion is too fast), when the water in raw beans is insufficient (free water is used up in advance), chlorogenic acid cannot be fully decomposed into caffeic acid and quinic acid, and chlorogenic acid will take the "dehydration reaction" to dehydrate the quinic acid in chlorogenic acid molecules to form chlorogenic acid lactone. According to Taguchi, this is a good bitter taste (sweet in bitterness), and there will be layers of bitterness to sweetness when tasting. The above description of 

 is mainly based on the chemical reaction and structure to analyze the situation of chlorogenic acid. Different methods will lead to different results in the decomposition of chlorogenic acid.

It would be interesting to discuss it in a baking way. Recently, Nordic baking has caused a whirlwind in the coffee industry, and many stores and players have followed suit in pursuit of new methods. Individuals also observe this phenomenon and put forward their own opinions for reference only. 


If someone wants to copy Nordic-style baking, use the front stage of the big fire and the big throttle, and gently roast the entrance flowers with lively acidity, the former stage can still withstand the strong wind and fire because the beans are well hydrated, and then we should be careful of the wind and fire configuration in the middle and the condition of the beans, because once the wind fire slows down, the bean table shrinks because of the loss of water, resulting in the water inside the beans can not get out. Then it is possible to have the first condition (chlorogenic acid hydrolysis reaction). In this way, while tasting the aroma of Nordic coffee, the throat will also get stuck. When I visit some coffee shops, I will find that when the aroma of coffee rushes into the nasal cavity, it usually brings a "card" sensation, otherwise the front edge of the tongue will feel astringent, and the worst thing is that the tongue feels like sandpaper. As a matter of fact, many coffee drinkers in Taiwan regard the existence of astringency as the first priority for tasting coffee. I urge you to pay attention to the problem of chlorogenic acid. "