Why do green coffee beans have to be roasted to taste good?

Most people who have been drinking coffee for a long time may have a question: Why does coffee have to be roasted before it can be used for drinking? Can't it be eaten raw like peanuts? Maybe some people think that coffee beans are like the picture below, but in fact, they are coffee fruits.

After the coffee fruit is peeled and the pectin is removed, the remaining two core particles (the variant round beans are single grains) are the coffee beans. As shown in the picture.

When its moisture content is processed to only about 12%, it is what we often call green coffee beans, which can be used for storage and roasting. In fact, green coffee beans are hard. If you must eat them raw, you must be prepared to break your teeth. Secondly, green coffee beans themselves only have a "raw taste" like raw soybeans, and do not have other special coffee aromas. They also have a raw taste when you put them in your mouth, and they are not delicious.

Because of this, coffee roasting becomes a very important part. During the whole roasting process, the coffee beans will expand, and their color, taste, smell and density will change. High temperature and dry environment can accelerate Maillard reaction and other chemical reactions, so that the unique aroma of cooked coffee can be obtained, which is why roasting is necessary.

What is Mena Reaction ?

In 1912, French chemist Maillard discovered that when glycine and glucose are mixed and heated, a brown substance is formed. Later, people found that this type of reaction not only affects the color of food, but also plays an important role in its flavor, and this reaction is called nonenzymatic browning. The Maillard reaction can produce aromas and colors that people need or don't need. For example, the reaction of leucine and glucose at high temperature can produce a pleasant bread aroma. This Maillard reaction is also known as a necessary process in coffee roasting.

The key reaction for the flavor and color of fermented roasted coffee is the Maillard reaction. At temperatures of 150-200°C, carbonyl groups (from sugars) and amino groups in proteins react to form aroma and flavor compounds. Hundreds of coffee flavor compounds are formed by Maillard chemistry, including the potent coffee aroma flavor compound, 2-furfurylthiol. The Maillard reaction gives coffee a better flavor.

What is caramelization ?

Coffee roasting not only has a Mena reaction process, but also a caramelization reaction process. When the roasting furnace temperature reaches 170-200°C, the sugar in the coffee begins to caramelize, turning the sugar brown and releasing aromatic and acidic compounds.

Of course, we don’t need to delve into the specific chemical reactions in coffee roasting, as those are only used by scientists for experiments. It is enough for us to know that it can make the flavor, acidity, and aftertaste of coffee better. After all, our ultimate goal is to drink more delicious coffee.

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