The flavor of coffee depends not only on the variety of coffee, but also on roasting, which is a decisive factor. Basically, the roasting of coffee is a high-temperature coking process that completely changes the substances inside the green beans, producing new compounds that recombine to form aroma and mellow taste. This effect only occurs at high temperatures. If only low temperatures are used, it will not cause decomposition and the coffee beans will not ripen even if they are roasted for a long time.

1、 Baking process

Most people think baking is nothing, just frying raw beans over fire. In fact, roasting is the most difficult step in the process of coffee processing. It is a science and an art, so experienced roasters enjoy a highly respected position in European and American countries. The baking process can be divided into the following three stages:

1. Drying

In the early stages of baking, green beans begin to absorb heat, and the internal moisture gradually evaporates. At this point, the color gradually changes from green to yellow or light brown, and the silver film begins to peel off, revealing a faint grassy scent. The main function of this stage is to remove moisture, which accounts for about half of the roasting time. As water is a good heat conductor, it helps to roast the internal substances of coffee beans. So, although the purpose is to remove moisture, bakers will make good use of the temperature of water and control it properly to prevent it from evaporating too quickly; Usually, it is best to control the water to reach its boiling point and convert to steam within 10 minutes. At this point, the internal substances are fully cooked and the water begins to evaporate, rushing out of the outside of the coffee beans.

2. High-temperature decomposition

When roasted to around 160 degrees Celsius, the moisture inside the beans evaporates into gas and begins to flush out of the outside of the coffee beans. At this point, the interior of the green beans changes from absorbing heat to releasing heat, producing the first cracking sound. After the explosion sound, it will turn into heat absorption again, and the pressure inside the coffee beans is extremely high, reaching up to 25 atmospheres. High temperature and pressure begin to deconstruct existing tissues, forming new compounds that create the taste and aroma of coffee; At around 190 degrees Celsius, the transition between heat absorption and release occurs again. Of course, high-temperature cracking continues to occur, causing coffee beans to turn from brown to dark brown and gradually enter the stage of heavy roasting.

3. Cooling

After roasting, coffee must be cooled immediately to quickly stop the high-temperature cracking process and lock in the flavor. Otherwise, if the high temperature inside the beans continues to act, it will burn off the aromatic substances. There are two methods of cooling: one is air-cooled; One is water-cooled. The air-cooled method requires a large amount of cold air to quickly cool the coffee beans within 3-5 minutes. In the field of professional baking, large baking machines are equipped with a tray, which also has a rotatable push arm; When baking is complete, the beans are automatically fed into the tray, and the fan at the bottom of the tray immediately starts to blow cold air, which is then stirred by the pushing arm to cool the coffee beans. Although the water-cooled speed is slow, it is clean and non polluting, and can better preserve the aroma of coffee, which is adopted by selected coffee operators. The water-cooled method involves spraying a layer of water mist on the surface of coffee beans to rapidly lower the temperature. Due to the importance of the amount of water sprayed, precise calculation and control are required, and it will increase the weight of baked beans. It is generally used for large-scale commercial baking.

2、 Baking degree and characteristics

In terms of baking degree, the deeper the baking degree, the stronger the bitterness; The lighter the degree of baking, the stronger the acidity. The degree of roasting to be chosen depends on the characteristics of the coffee beans themselves. For coffee beans with strong bitterness and light acidity,

Generally, a moderate to light baking degree is chosen.

1. Light Baking

The mildest decoction has no aroma or concentration, and the beans are not yet ripe, with a green flavor of raw beans, which is not suitable for grinding and drinking. Usually used for experimentation.

2. Deep and shallow baking (Cinnamon)

Also known as cinnamon baking, it is a common frying method with a strong sour taste. The color of beans is quite similar to cinnamon, so it is also known as cinnamon baking, which increases the acidity. Beloved to Westerners in the United States.

3. Shallow moderate baking (Media)

The color deepens, making it easy to extract the original flavor of coffee beans, with a mellow and sour taste that is delicious. Mainly used for mixing coffee.

4. Moderate baking (High)

The taste of coffee is stronger and the acidity becomes lighter, which is the typical roasting method for coffee beans. It has a neutral sour taste and a bitter taste, suitable for coffee such as Blue Mountain and Girlimazaro. Beloved by Japanese and Nordic people.

5. Deep moderate baking (City)

Also known as city baking, it has a stronger bitterness than sourness, almost no sourness, and a unique aroma. Coffee suitable for Colombia and Brazil, loved by New Yorkers.

6. Normal baking (Full City)

Also known as city wide roasting, suitable for brewing iced coffee. No sour taste, mainly bitter taste, the bitterness will be aggravated, but high-quality beans will have a sweet taste. Used for iced coffee, favored by people from Central and South America.

7. French Baking

The French style baking method has a slightly black color, strong bitterness, and oil leakage, deepening bitterness and concentration. Coffee brewed with a steam booster.

8. Deep Baking (Italian)

Also known as Italian style baking, the deepest degree of baking, the beans are dark and transparent, with oil seeping out from the surface and a strong bitter taste. At this stage, the coffee beans have already undergone severe carbonization, making it difficult to distinguish the taste of one type of coffee bean from another. Used for Italian style steam pressurized coffee.

3、 Baking characteristics from around the world

Cities around the world have their own preferences for frying and baking.

In Tokyo, slightly deep moderate baking is more popular, but gradually there is also a tendency towards deep baking. In the West, deep baking has been popular since ancient times. New York, as its name suggests, generally prefers urban roasting, but due to the diverse ethnicities living in the city, it sells coffee beans of varying degrees of roasting, with a wide range of variations. Vienna prefers deep baking. The French prefer the French style of baking; Italians often use Italian style baking techniques.

However, in recent years, Italian roasting (the most commonly used deep frying roasting method in Brazil and Italy) has been widely used by Europeans and Americans, with various changes, and coffee brewed with steam pressure is still loved by people. Deep roasting Ethiopian coffee beans would be a waste. Because it would lose the unique characteristics of this coffee. Baking Yaoco and Kona coffee beans in black is also not good, as it will lose the classical flavor you pursued when purchasing them.

When some coffee beans are roasted black, they will develop new and interesting qualities. Mexican coffee beans produce an interesting sweetness when roasted in black. Guatemalan Antigua coffee beans tend to retain their sour and fruity flavors when deeply roasted, which can be challenging for other types of coffee. Sumatran coffee beans are usually plump in granules, but have lower than moderate acidity. When roasted deeper, they lose their acidity and easily turn into a sugar paste. Overall, the darker the baking, the lower the quality. Deeper roasting means that most of the flavor of the coffee beans will be lost.

4、 Baking coffee beans at home

The most difficult activity related to coffee is baking coffee beans at home. When preparing high-quality coffee, the freshness of the coffee beans is crucial.

The easiest way is to bake coffee beans in the oven. The biggest advantage of doing this is that it can regulate the temperature and prevent the smell of roasted coffee from permeating your home. Heat the oven to 230 degrees Celsius beforehand. Remember to maintain air circulation between the coffee beans and not spread them too thick. After baking for about 10 minutes, observe the color change. Pay attention to the crackling sound of coffee beans and constantly check the color. When the color of the coffee beans is only slightly lighter than you want, take them out of the oven and cool them down. The residual heat will continue to heat the coffee beans for 2-4 minutes.

Home baking stoves can also be used, but the best ones are traditional pan or popcorn models. Use a handle to operate the two vertical metal plates inside the machine, which can rotate the coffee beans during baking. This can be purchased at second-hand shops or good kitchenware stores, where you can also buy affordable oven thermometers. After the coffee is roasted, take them out of the grill and place them in a heat-resistant bowl. Place the bowl by the window or outdoors.