Common sense of coffee roasting

1. Definition of baking

The so-called coffee roasting (coffee roasting) refers to the process that through heating the raw beans, a series of physical and chemical reactions take place inside and outside of the coffee beans, and in this process, the sour, bitter, sweet and other flavors of the coffee are formed, forming mellowness and hue, and transforming the raw beans into dark brown beans.

two。 The importance of baking

Among the factors affecting the taste of a cup of coffee, raw beans account for 60%, roasting accounts for 30%, and extraction accounts for 10%. Good roasting can maximize the personality of raw beans and minimize the occurrence of defective flavors. on the contrary, improper roasting 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.

II. History of baking

As early as the 13th century, Arabs invented to put coffee beans in a pot, heat them and stir-fry them, then grind them into powder, and then brew coffee. The early Arabs liked to bake the beans shallowly and boil them with spices such as cardamom.

Later, this method of stir-frying coffee spread to Syria, Turkey and Egypt, where it is customary to stir-fry coffee black, then grind it into powder, add sugar and boil it in water, then pour it into a small cup without precipitation and drink it with coffee grounds.

After coffee was introduced into Europe in the 18th century, Europeans also used the Turkish style to stir-fry coffee until black.

Later, because of geographical and cultural differences, Europe was divided into shallow baking schools dominated by Nordic, German, British and Scandinavian countries and deep baking schools dominated by southern Europe. The former usually bake the beans to city--full-city, while the latter generally bake them to the same depth as italy,french.

Accordingly, the North American continent, which was later dominated by immigrants from northern Europe, also followed shallow baking, while Latin America, which was dominated by immigrants from southern Europe, was popular in baking.

Until the mid-19th century, most of Europe used iron pots or ovens to bake beans at home, and later invented small roasters that use closed iron buckets instead of iron pans and put them on a fire to manually control, and can bake a few pounds of beans at the same time. Used by some coffee shops.

With the advent of large baking machines in the mid-19th century, large quantities of baked beans became possible. After continuous innovation after the advent of large roasters, electronically controlled precision machines have appeared in the first half of the 20th century, and machines that can continuously bake 5000kg every hour have been developed.

The emergence of large roasters has changed people's own baking habits. Buying packaged baked beans or coffee powder to cook directly at home facilitates the fast-paced life of modern people. By the 1960s, branded beans dominated the market. But there are also problems in mass roasting: ordinary raw beans, in order to maintain excessive shallow baking, lack of freshness caused by the lack of flavor, since the 1980s, a "boutique coffee movement" was launched in the United States. It advocates people to buy boutique raw beans, home baking, drink fresh coffee, pursue quality and taste, and home roasting begins to receive attention. At the same time, the pursuit of coffee quality also forces some big roasters to adopt higher quality beans to ensure the baking quality.

3. The development and evolution of roaster

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

In the 1860s, large roasters began to come out, and the use of blower to cool baked beans in 1867 gave birth to the development and innovation of large roasters.

At the end of the 19th century, the advent of hot air roaster greatly improved the speed and efficiency of coffee roasting, making it possible to produce more in large quantities.

In the 20th century, with the combination of roaster and electronic, it was improved to be more precise, and the fully automatic roaster appeared and had more advanced functions.

Four. common types and main brands of roasters at present

(1) Common types of roasters

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.

Advantages: high thermal efficiency, fast heating, relatively uniform heating of raw beans, easy to control.

Disadvantages: because of the high heating efficiency, 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.

Taste characteristics: the acidity is obvious, the taste is relatively clean and simple, but the taste is not rich enough and lacks depth, and deep baking is easy to produce irritating taste.

2, 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.

Advantages: the baking time is long, so the caramelization reaction is sufficient and the flavor is 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 baking method, which combines the advantages of direct fire and hot air, is the mainstream of commercial baking machines at present. Semi-direct-fire baking is actually similar to direct-fire baking, but because there are no holes in the outer wall of the baking container, the flame will not directly touch the coffee beans. In addition, a ventilation device is added to introduce the hot air from the outside of the baking container into the baking room to improve baking efficiency. Another function of this ventilation device is to suck out the exfoliated silver skin (the film attached to the outer layer of coffee seeds). Prevent the silver skin from burning because of high temperature in the baking room, thus affecting the taste of coffee beans.

Semi-direct fire semi-hot air machine has the advantages and disadvantages of both direct fire type and hot air type, but its heating mode is changed according to the adjustment of hot air and boiler speed. The larger the hot air is, 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.