How to roast good coffee beans | How does roasting affect the flavor of coffee?

Coffee roasting is crucial to the flavor of coffee. The purpose of roasting coffee is to get a delicious cup of coffee, and "good roasting" can bring out the personality of the raw beans to the extreme, but what is "good roasting"?

The process of coffee roasting is the process of changing green coffee beans into brown coffee beans. In this evolution, coffee roasting needs to go through five stages: warm-up → dehydration period → Mena reaction period → development period → bean cooling.

Warming up: Preheat the coffee roaster boiler and set the temperature to the temperature at which roasting begins, which is called the bean temperature.

Dehydration period: The so-called "dehydration" does not mean completely removing the water. It generally refers to the roasting process below 170 degrees. Different roasting utensils require different dehydration times, but it is usually best to control it within 5 to 8 minutes, depending on the water content of the beans.

Menard reaction period: Menard reaction, also known as flavor compound, is a series of reactions between reducing sugars and proteins/amino acids in food when heated, which produce brown-black macromolecules.

Development stage: When the color turns to a darker brown and the temperature rises to nearly 185 °C (the value may vary depending on the temperature measurement point), you should pay attention to the upcoming popping sound. The first pop is the reaction of carbon dioxide and water in the green beans expanding due to heating, which is also the key point affecting the flavor. After the beans begin to pop for the first time, they enter the development stage. The Menards reaction has come to an end, and caramelization is accelerating. During the first pop, the water vapor and carbon dioxide in the cells will be discharged in large quantities in a short period of time, causing the bean temperature to drop slightly and the humidity to rise rapidly. After the free water is completely released at the end of the first pop, the humidity will drop again. Many reactions occur in a short period of time, so the air volume and firepower control in the later stage of the Menards reaction have a great impact on the final flavor of the beans.

Bean cooling: Cooling is the final key to coffee roasting. When the beans are roasted to the roasting degree or temperature you choose, they can be cooled.

Coffee roasting has the following purposes:

1. Remove excess moisture from coffee beans.

2. After roasting, the wood structure of the coffee beans will expand and have air holes.

3. Start a continuous process of converting sugar into carbon dioxide gas. This process will not stop immediately after roasting is completed, but will continue until the coffee beans lose their flavor.

4. Some of the sugar in the coffee beans is converted into caramel, and some of the ingredients are converted into fat.

Coffee roasting levels are not limited to light, medium, and dark roasting, but are divided into the following eight levels:

Light Roast

Also called "light roast"

Time to place beans: around the time of the first crack

Flavor: The bean surface is light cinnamon color, with a strong grassy flavor, lacking taste and aroma. It is generally used for experiments and rarely for tasting.

Light Roast/ Cinnamon Roast

Also known as "Cinnamon Baking"

Time to bean: from the first crack to the dense

Flavor: The bean surface is cinnamon-colored, and the grassy smell has been removed. It has a strong acidity and a slight aroma. It is often used to brew American coffee.

Medium Roast

Also known as "micro-baking"

Time to place beans: from the first crack to the end

Flavor: The bean surface is chestnut-colored, with a light, sour and bitter taste.

It has a moderate aroma and retains the original flavor of the coffee beans. It is often used to make American coffee or blended coffee.

Medium dark roast/ High Roast

Also known as "concentrated baking"

Time to place beans: the first burst ends

Flavor: The bean surface is light reddish brown, the taste is refreshing and rich, the sourness and bitterness are balanced without irritation, and it is slightly sweet. The aroma and flavor are good. Blue Mountain and Kilimanjaro coffee are suitable for this roasting degree.

Medium Dark Roast/ City Roast

Also known as "City Baking"

Time to place beans: After the first crack, i.e. between the first and second cracks

Flavor: The bean surface is light brown, the taste is bright and lively, the acidity is light and the sourness is balanced between sourness and bitterness, and it releases the high-quality flavor of the coffee. It is the standard roasting degree and the most popular roasting degree.

Full City Roast

Also known as "Deep City Baking"

Time of bean placement: Second burst

Flavor: The bean surface is brown, with a steady and full taste, a stronger bitterness than sourness, a sweet aftertaste, and a full aroma. It is roasted in Central and South American style and is mostly used for iced coffee and black coffee.

French Roast

Also known as "French baking"

Time of planting beans: from the intensive second crack to the end of the second crack

Flavor: The bean surface is dark brown with black, with a strong and intense taste, strong bitterness, light sourness that is almost imperceptible, and rich chocolate and smoky aroma. It is most popular in France, where it is mostly used to make Café au Lait and Viennese coffee.

Extra Dark Roast/ Italian Roast

Also known as "Italian baking"

Time to put beans: from the end of the second crack to the time when the beans turn black and oil is produced

Flavor: The bean surface is black and shiny. Before the coffee bean fibers are carbonized, the taste is strong and complex, with a strong bitterness and a strong roasted and caramelized aroma. It is mainly popular in Italy and is mostly used to make Italian espresso.

What is a “good roast”? How to roast good coffee beans?

1. Preheat the roaster fully to ensure that the temperature is consistent. Performing a sufficient preheating cycle at the beginning of production is one of the key points to pay attention to in roaster operation.

2. The beans absorb heat during the entire roasting process, and only the first and second crackles release heat. It is best not to increase the roasting temperature during these two stages, otherwise the beans will easily become spicy.

3. After the roasted beans are put into the oven, they must be cooled immediately. The faster the better. This will lock in the flavor of the beans and prevent it from being lost.

4. A stronger roasted flavor does not mean a thicker coffee.

During the roasting process, people who don’t have a deep understanding of coffee roasting may think that the stronger the roasting flavor, the higher the consistency of the coffee. In fact, the two are not proportional. The consistency can be made rich and thick, largely because the Mena reaction is done well during the roasting process. This is one of the keys to "good roasting" and can fully develop the compounds in the coffee, such as sugars and lipids. The sweeter the coffee, the more prominent the consistency; on the contrary, the stronger the roasting flavor, the more bitter it will be. If the roasting is not done properly, the overall flavor of the coffee will be unbalanced, and it will only taste like a roasted flavor, and the taste may not be improved.

Of course, French roasting is not just about extending the roasting time, other factors must also be considered. The roaster raises the temperature of the raw beans when they are put into the oven, so that the sugar in the coffee beans can be retained in the early stage, leaving it for the later stage to develop the "Menard reaction" and caramelization reaction to be richer. Extending the roasting time can make the dehydration part better, completely removing the bitter taste of insufficient dehydration, and the sweetness of the beans will be clearer and more prominent.

5. The best roasting time is 12 to 15 minutes for the best flavor. The roasting time below Italian roasting is longer. European and American quick roasting or Japanese slow roasting also has its own characteristics and flavor.

Since baking is about heating something, the size and shape of the object being heated will of course affect the result of the heating.

The first is the volume and surface area of ​​the coffee beans. The larger the volume of the beans, the larger the surface area of ​​each bean. However, assuming that the density of the two beans is the same, the total surface area of ​​the smaller bean under the same weight will be larger than the total surface area of ​​the same weight but with a larger volume and surface area of ​​each bean. The more surface area, the more heat can be absorbed in the same time, and the easier it is for heat to enter the bean core. In the same time, more heat needs to be provided for the beans to absorb heat.

Furthermore, during the roasting process, the temperature of the coffee beans is lower at the core and higher at the surface, and the temperature at the ends of the beans is higher than in the middle. Our experience in roasting tells us that large beans such as Pacamara, Elephant Beans, and Gesha are more likely to produce a black focus at the tip when roasting than beans with smaller particles such as Ethiopian beans.

Long and thin beans are more likely to produce black spots than round beans. Such black spots are caused by too much heat accumulated at both ends of the coffee beans, which cannot be transferred to the bean core in time, resulting in the appearance of burnt black spots. Large beans will accumulate more heat on the bean surface, but it also takes more time for the heat to transfer from the bean surface to the bean core.

Generally speaking, the darker the roasting degree, the less regional flavor the beans themselves will have. At the same time, its taste will become heavier. Therefore, roasters will selectively choose the roasting degree according to the quality of the raw beans and the production method. If you get a good quality bean with a floral, fresh fruity and sour flavor, then choosing a light to medium roast can well preserve its high-quality regional flavor. But if you get a raw bean of poor quality, improperly stored, out-of-season beans. Because the longer the coffee beans are stored, the flavor will slowly dissipate in a bad storage environment. At this time, you can speed up the roasting rhythm, extend the caramelization time, and appropriately deepen the roasting degree to show its taste.

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