How important is coffee bean roasting to beans? What is the definition? Why bake?

How important is coffee bean roasting to beans? What is the definition? Why bake?

So what is the importance of baking? Among the factors that affect the taste of a cup of coffee

Raw beans account for 60%, baking for 30%, and extraction for 10%.

Good baking can maximize the personality of raw beans and minimize the occurrence of defective taste, while improper baking will completely destroy good beans. As the heating, time, and temperature control in the baking process is very difficult to grasp, baking technology is a very complex technology, so the importance of baking is more prominent.

What is baking? What is the definition of baking?

Generally speaking, the so-called coffee bean roasting (coffee roasting) refers to the heating of raw beans to promote a series of physical and chemical reactions inside and outside the coffee beans. When coffee beans are roasted, the volume of coffee beans expands and is 1/3 larger than that of raw beans. How to perfectly show the characteristics and flavor of coffee is the most important key, so how to bake is a technology, but also an art. Because of the different depth of roasting, the coffee beans have different personality and flavor.

And in this process, the formation of sour, bitter, sweet and other flavors of coffee, the formation of mellow and tone, the process of converting raw beans into dark brown beans. There are many ways to bake, and the baking depth of coffee beans

It can be divided into three types: shallow baking, medium baking and deep baking.

The consistent goal is a series of chemical reactions to transfer heat to coffee beans.

In the early days, people generally used iron pots to stir-fry coffee beans. after coffee was introduced into Europe, Europeans used Turkish iron pots to stir-fry beans, and then invented hand-operated rotary roasting, which could bake several pounds of beans at the same time, which was used by some coffee shops.

1860's: large roasters began to come out.

At the end of the 19th century, the advent of hot air roaster greatly improved the speed and efficiency of coffee roasting.

Makes it possible to produce more in large quantities.

20th century: the combination of roaster and electronic, has been improved to be more sophisticated, the emergence of fully automatic roaster

And has more advanced functions.

There are three major difficulties that coffee beans often face when roasting:

one. External environmental impact: air temperature, air pressure, humidity. Etc.

two. Coffee bean characteristics: water content, bean seed, bean quantity. Etc.

three. Types of baking machines: direct fire, semi-direct fire, hot air

1. Hot air type

The hot air type bean dryer uses the blower to absorb the air, and then let the air pass through a heating coil to raise its temperature. Hot air is used as a heating source to bake coffee beans. Hot air can not only provide the temperature needed for baking, but also use the power of airflow to stir coffee beans, killing two birds with one stone.

★ has the advantages of high thermal efficiency, fast heating, uniform heating of raw beans and easy control.

★ disadvantages: because the heating efficiency is high, it is easy to lead to excessive heating, resulting in beans "entrainment", and too high temperature is easy to make the caramelization reaction is not sufficient.

* (meaning of Jiaosheng: not fully cooked)

★ taste characteristics: the acidity is obvious, the taste is clean and simple, but the taste is not rich enough and lacks depth, and

Deep baking is easy to produce a pungent taste.

two。 Direct fire type

As the name implies, the direct fire is to heat the coffee beans directly with a flame. Up to now, the "fire" of direct fire not only includes general flame (including gas furnace fire and charcoal fire), but also includes infrared and electric heating pipe.

Put the raw beans into a perforated drum and heat the beans with the fire of a gas burner.

Advantages: the baking time is long, which makes the caramelization reaction more sufficient and the flavor more rich.

Disadvantages: it is easy to cause uneven baking, and if the heat is not well controlled, it is also easy to scorch coffee beans and form a scorched bitter taste.

3. Semi-direct fire semi-hot air type

The drum is covered with iron plate and hot air is sent from behind the drum so that the beans do not come into direct contact with the baking of the fire.

At present, it is the mainstream of commercial baking machines, similar to direct-fire baking, because there are no holes in the outer wall of the baking container, so the flame

Will not be in direct contact with coffee beans; ventilated equipment, the hot air outside the baking container into the baking room to improve baking efficiency.

"another function of the ventilation equipment is to suck out the exfoliated silver skin (the film attached to the outer layer of the coffee seed) to avoid the silver skin.

The taste is affected by high temperature combustion in the baking room. "

★ has both advantages and disadvantages of direct fire and hot air.

The heating mode is changed according to the adjustment of hot air and boiler speed.

The larger the hot air, the faster the speed is, the closer it is to the hot air type; on the contrary, the closer it is to the direct fire type.

Roasting degree of coffee beans

When studying the roasting degree of coffee beans, the roasting degree can be judged by sound, color and aroma.

Its color is from light soil yellow to dark brown, the aroma is from light and elegant, and the sound is twice burst sound.

Take the heat-resistant raw bean as an example, the first explosion began at about 7 points and lasted for about 2 minutes, and its low voice indicated the beginning.

After pyrolysis, starch conversion to caramel, water evaporation and exhaust, the second explosion occurs at about 12 minutes, and the sound is violent and sharp, indicating that the cell fiber is broken and the deeper the baking is.

Reactions and changes that occur during baking:

One explosion and two explosions

1. Dry

When the raw bean is heated, the water vapor in the raw bean will evaporate, and at about 135 ℃, the raw bean will turn white from green.

two。 dehydration

As the heating goes on, the raw bean changes from green to light yellow, and when the temperature reaches about 160℃-175℃, it will give off baking.

The aroma of the grain is continuously heated, and the beans turn light brown.

3. An explosion

After the dehydration of about 190 ℃-205 ℃ is completed, the cell wall is ruptured due to internal thermal expansion to form an "explosion".

At this time, a series of thermal decomposition reactions take place inside the beans, and the appearance of the beans is about 40% to 60% larger than that of the original beans. The color of beans can also be clearly detected, from light yellow to khaki, to darker and darker brown.

The compounds in the beans are hydrolyzed to produce water-soluble polysaccharides. When the reaction continues, these polysaccharides will begin

Caramelization reaction, which brings the sweetness and brown color of coffee beans, is also the main reason for the aroma of coffee. When the others

Carbohydrates continue to decompose and become volatile acids. Among them, chlorogenic acid, the key factor affecting the taste of coffee, is coffee.

The main reason for astringency and thickening is that it decreases with the degree of baking and is inversely proportional to the baking speed. Therefore, if the baking speed is too fast, it is easy to make the coffee astringent.

4. Second explosion

As the heating goes on, the beans become more fragile because they have been dehydrated, and the pressure in the cells continues to rise.

About 225℃-230℃, enter the "second explosion", when the wood structure inside the bean splits, which will occur more violently.

React and give off a lot of heat. With the end of the second explosion, the raw beans have basically turned black, and the beans have swelled to

The original 1.5 times, the surface oil, the weight reduced to 12% Murray 20% or so.

If you continue baking so that the process goes beyond the second baking, the initial caramelization and starch will begin to carbonize and present

And the coke characteristics of deep baking.

5. Stop it

Usually the baking ends about one minute after the end of the second explosion, when the temperature reaches 240℃-245℃, then it will be a deeper French or Italian baking. Continuous heating when the temperature exceeds 230 degrees may cause the coffee beans to ignite spontaneously.

Stop baking with a lot of cold air or water. The effect of water will come faster than air. But if you stop it with water,

Baking, water is the key point, must be a moderate amount, so as not to cause the beans to absorb water.

The timing of subdividing the popping sound:

Burst loudness table-01

Roasting degree of Coffee and timing of Bean drop

The sour ingredients in raw coffee beans are citric acid, malic acid, quinic acid, phosphoric acid and so on, but this is not the sour taste we feel when we drink coffee. The sour taste we taste mainly comes from the acid produced in the baking process.

The well-known roasting degree of coffee is mainly divided into the following four degrees:

1. Shallow baking 2. Medium baking 3. Deep baking

High acidity → low acidity (bitter)

Each degree can be subdivided into two, a total of 8 stages.

Baking degree-01

The sour taste of coffee can also be defined by technology, that is, the so-called PH value (pH value)!

The lightly roasted breakfast coffee → PH is between 4.5 and 4.7.

The medium and deep baked (Full City) → PH is about 55.5.

Deep baking (Dark Roast) → PH above 5.5

These factors have a direct and indirect relative relationship to the roasting of coffee beans, and if we deal with them carefully, we can make proper use of the various conditions of interest and achieve expectations. Therefore, it is not enough to know the roasting mechanism and know the roasting process. People use all kinds of coffee roasters on the market, and opinions vary from family to family on their effectiveness. Why?. It is caused by the fact that they do not know enough about the construction and operation principle of the baking mechanism they use.