Barista training knowledge introduction to the types of coffee roasting utensils

Coffee is popular mainly because of the aroma formed after roasting and the taste when drinking. Coffee beans themselves do not have any special taste, roasting will be a thorough transformation and reorganization of the substances inside the beans, forming a new structure, thus bringing out the flavor of coffee, and coffee roasting is also a coffee knowledge that baristas need to understand.

Baking tools-baking machine, divided into 3 categories: direct fire, semi-hot air direct fire and hot air. The last two are mainstream.

Direct fire: the earliest baking tool used by humans. Disadvantages: slow heat conduction rate of iron; long baking time; waste of hot air; raw beans contact the drum wall for too long, easy to be burnt, resulting in bitter taste and burnt taste; debris in and out of the barrel attached to the surface of coffee beans will turn the flavor turbid.

Semi-hot air direct-fire type: 1870~1920 German van Guban improved and manufactured. In 1907, Germany's Perfect baking machine began to apply this concept, using gas heating and a fan to bring half of the hot air into the drum and half to the outer heating drum. So far, Germany's Probat drum baking machine is famous all over the world. In addition, Idaho's Dirick Company pioneered the use of gas-activated infrared heat sources in 1987 to make temperature control more precise and became the first brand in North America.

Semi-hot air direct fire type, direct heating of the drum with fire source, while bringing hot air into the drum to increase heating speed, but also blowing away debris, so producing balanced clean coffee beans.

Hot air type, pioneering in the 20th century, roasts coffee beans with hot air to improve roasting efficiency. Thermo Roaster, a large hot-air roaster, manufactured in 1934 by the Burns Company of the United States.

Fluid-bed roaster, which blows green beans up and down with hot air. In 1976, American Michael. Schwitz designed the fluidized bed roaster. Famous Australian coffee expert Ion. Berstein also designed and built fluidized bed roasters. When using this roaster, the coffee beans fall after being blown to a high point, and are roasted again by hot air, so that the coffee beans can be roasted evenly. However, the lack of metal drum smoldering, some people think that one less flavor.

Coffee roasting is a process of pyrolysis that completely changes the substances inside the green beans, creating new compounds that recombine to form aromas and alcohol. This effect only occurs at high temperatures.

In fact, roasting is the most difficult step in coffee processing, and it is both a science and an art. The baking process is divided into approximately 3 stages:

Dehydration. In the early stages of baking, green beans begin to absorb heat, and the water inside gradually evaporates. At this time, the color gradually changed from cyan to yellow or light brown, silver skin began to fall off, you can smell the faint smell of grass. The main function of this stage is to remove moisture, which accounts for about half of the baking time. Since water is a good heat conductor, it helps roast the internal substances of coffee beans. So, although the goal is to remove water, the baker will use the temperature of the water well and control it so that it does not evaporate too quickly.

High temperature decomposition, roasting to about 160 degrees, the water in the beans will evaporate into gas, began to exclude the outside of the coffee beans. At this time, the inside of the raw beans from heat absorption to heat, the first burst sound. After the first crack, it will turn to heat absorption, at this time, the internal pressure of coffee beans is extremely high, up to 25 atmospheres. The heat and pressure begin to break down existing tissues, forming new compounds that give coffee its taste and flavor. At about 190 degrees, the conversion between heat absorption and heat emission occurs again. Of course, pyrolysis continues to occur, and the beans change from brown to dark brown and gradually enter the stage of heavy roasting.

Cool. Coffee should be cooled immediately after roasting to quickly stop pyrolysis and lock in flavor. Otherwise, the high temperature in the beans will continue to take place and will burn off the aromatic substances. There are two cooling methods, one is air-cooled and the other is water-cooled. Air-cooled coffee is slow, but clean and pollution-free, and can retain the aroma of coffee. It is used for fine coffee. Water-cooled coffee beans are sprayed with a layer of water mist on the surface of the coffee beans, causing the temperature to drop rapidly, requiring precise calculation, and increasing the weight of the roasted coffee beans, which is generally used for commercial coffee roasting.

Crack sound, raw beans from heat absorption to heat, internal substances discharged from the body, will form a clear sound. The first time was louder, crisp and scattered, and the second time was softer, detailed and concentrated. Because of the high correlation between cracking sound and temperature, it can fully represent the baking temperature, which is an important basis for bakers to judge baking degree.