The ability of a coffee baker and a bean baker.

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Everyone has different opinions about whether coffee is good or not, and this is the wonderful thing about coffee.

Some people say that sour taste is everything to coffee, while others prefer bitter taste, and think that hierarchical taste is called coffee.

Therefore, everyone has a different way of tasting coffee.

The aroma and taste of coffee are produced after roasting. In the process of baking, the moisture of raw coffee beans is slowly released, the weight is reduced, the color deepens, the volume expands, and the aromatic oil is slowly released. In addition, the large amount of chlorogenic acid originally contained in raw beans will gradually disappear with the baking process, releasing good-smelling fruit acid, and its taste varies with the baking time. In the following picture, you can see the change in the shape of coffee beans during roasting.

There are three main influencing factors for a good 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 flavor. and the selection of coffee bean roaster is extremely important.

The ability of a bean baker

To be a competent coffee bean roaster, you should have four abilities.

1. Identification of raw beans: using experience or instruments to judge the quality of raw beans and pick out defects.

2. Coffee roasting: familiar with the function of the machine and can be completely controlled to bake coffee beans of stable quality.

3. Coffee cup test: evaluate and describe the flavor of roasted coffee beans, and find out the advantages and disadvantages caused by roasting.

4. Formula blending: blending a comprehensive coffee with personal characteristics, which meets the business needs.

An excellent bean baker must constantly bake and record in order to overcome the many changes encountered in the roasting process of coffee beans, and at the same time, through the accumulation of cup samples, to achieve a more in-depth and comprehensive understanding of the flavor of coffee beans from different areas. In this way, for the modulation of the comprehensive formula, it can be easily used to convey the flavor to the consumers.

Roasting coffee starts here.

"one pot, two beans, three baking." In this sentence, the factors that affect roasting coffee are pointed out.

Pot refers to the machine used to bake coffee. The stability and controllability of the bean baking machine are related to the replicability of flavor. In other words, the occasional high-quality baking is not worth rejoicing, the good taste must be able to be copied again, maintain a certain level. Therefore, machine manufacturers have made great efforts in this respect. in addition to the increasingly accurate temperature measurement, thanks to the development of science and technology, the new bean dryers in recent years have even been able to adjust the throttle and firepower according to the data set by the computer. trying to minimize the error caused by human operation

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Under the condition that the roaster is stable and controllable, the result can be predicted from the quality of raw beans, and what is put into the machine is what comes out. The water content and texture of raw beans will be affected in the baking process. Fresh raw beans have rich aroma and flavor after being baked at high temperature. if they are stored for too long or in an improper environment, the flavor of raw beans will be lost, and the final result must be far from satisfactory.

Baking skills are put last because the difference between the same raw beans when using the same machine and baking in the right way is the so-called personal baking style. The biggest difference is usually caused by the depth of roasting, which makes the coffee different in acidity, sweetness, bitterness and richness, and the retained flavor and cleanliness are also key.

The principle and process of coffee roasting

We must first understand that raw beans are hard seeds in coffee berries. In addition to crude fiber, they also contain water, chlorogenic acid, protein, alkaloids, caffeine, fats, sugars and other substances. At the same time of baking at high temperature, the above substances will appear chemical changes such as Mena reaction and Stryker degradation, resulting in coffee tannic acid, tobacco acid, aromatic esters, alcohols, carbohydrates and other substances that affect the flavor of coffee.

So, when it comes to roasting coffee beans, we can think of it as a process of rising temperature, but it must be under control. Because of this, the temperature and heating rate during baking are the main reasons for the difference in flavor.

From the actual baking process, we can observe the change in the color of raw beans, from the turquoise when the water content is high, to a whitish yellow after baking at high temperature to remove most of the moisture. As the temperature continues to rise, it gradually yellowes, and when it reaches the temperature at which the Mena reaction occurs, the surface turns brown and deepens gradually. If you continue to heat up, there will be carbonization, coffee beans will become dark black, the surface is still bright with grease, if you do not stop heating, it will eventually catch fire.

In addition to the change in color, the volume of coffee beans will also change. In addition to a small degree of thermal expansion, there will be two bursts at different temperatures, increasing the volume by as much as 60%. As the volume expands, the total weight will also be reduced due to the loss of moisture and the removal of silver skin, and the weight will be reduced by about 12% as the baking is shallow to deep.

In addition to the baking temperature and time, we can preliminarily judge the roasting degree of coffee beans by the appearance color, volume change and weight loss ratio. In addition, it can also be detected by Agtron caramelization spectrum analyzer to accurately get the depth of baking degree.

Understand the design principle of coffee roasting machine

Take the bean baking machine made in Taiwan as an example, during the baking process, the functions that can be controlled are gas firepower, exhaust valve, and boiler speed, while the temperature observation values provided are the bean temperature in the furnace and the temperature of the air outlet. There are bean viewing windows and sampling rods to judge the appearance and smell of raw beans.

The rotating boiler is to let the raw beans be heated evenly, and the good baffle design in the boiler makes it more lively and leaping when stirring, so as to avoid point scald. When the rotational speed is slow, the raw bean is in contact with the boiler for a long time; when the rotation is fast, the raw bean is thrown in the hot air for a long time, both of which will affect the flavor. However, the speed of the boiler cannot be adjusted on the baking machines in Germany, Japan and the United States.

In addition to firepower, the distance between the gas fire row and the boiler, called fire distance, is also a difficult problem in machine design. The modification of the Japanese brand bean dryer is to increase the number of gas nozzles, but the problem of uniform heating is also considered when the fire is farther away. The new machine made in Taiwan changes the design of gas nozzles to three rows and double switches, igniting according to the amount of baking, and increasing the flexibility of operation.

Ignition heating, heat energy through conduction, convection, radiation of these three types of coffee beans have a heating effect.

In addition to the full hot air machine is mainly convective heat, we often hear of semi-hot air and direct fire type of these two machines. To put it simply, the wall of the baking room of the direct-fire bean dryer is perforated to allow the radiant heat to act directly on the raw beans. Such a machine can also be equipped with a far-infrared kit to maximize the effectiveness of the radiant heat.

The semi-hot air machine mainly uses conduction heat and convection heat. When the firepower is fixed, the size control of the exhaust valve is the main factor affecting the convection heat.

Steps to actually operate a coffee roaster

Start the machine, light the fire, wait for the temperature of the boiler to rise to a certain degree, turn off the fire and put the coffee into the raw beans.

At this time, the raw beans at room temperature will have heat exchange with the hot boiler, and it can be observed from the instrument that the boiler temperature will drop, and according to the number of raw beans, the time of heat exchange will increase. Until the heat absorption of raw beans is complete, the temperature of the boiler begins to rise, which is called the "temperature recovery point".

Before the raw beans are put in, whether the fire is turned off or not, everyone has different baking habits, but this will affect the temperature recovery point, so we should pay attention to it.

At first, the temperature will rise faster, but with the yellowing of bean color and the decrease of moisture, the temperature rise will gradually slow down and stabilize. If you use a sampling stick to remove raw beans, you can obviously smell the change in taste, from the astringent taste of grass evaporated to the aroma similar to toast or sweet potato, the silver skin will gradually peel off, and the exhaust valve can be opened moderately. Let the silver skin blow out. Before the first burst, the temperature rises slowly, and the raw beans absorb a lot of heat from the hot air, ready to burst.

From the sporadic burst sound, gradually dense, the temperature rises faster, a large number of smoke is discharged, and then it needs to be vented properly through the exhaust valve. It should be noted that excessive exhaust will lead to excessive convective heat and bad flavor.

Continue to heat, after the first burst sound temporarily, the coffee beans are brewing a second burst, the temperature difference between the two is 25 ℃. When the second burst, the smoke intensified, coffee beans gradually turned dark brown, slightly scorched aroma.

Before dropping the beans, start the cooling plate fan and stir to cool the coffee beans in the shortest possible time to keep the flavor good.

How to achieve stable baking

How to achieve stable baking and replicate the most perfect flavor is the biggest task for every bean baker.

First, use the instrument to detect the water content of raw beans, work out the baking plan curve in advance, and record the data of the baking process in detail as the basis for reference and correction.

Second, use the fixed temperature recovery point as the benchmark to keep the heating curve consistent and avoid unnecessary firepower adjustment and correction.

Third, do a good job in the maintenance and cleaning of the bean baking machine, including dust collection buckets, so that the baking conditions are consistent.

Fourth, carefully choose the location of the bean baking machine to minimize environmental factors, and even the number of baking pots in each batch must be controlled in a certain range to avoid too little or too much.

Roasting coffee beans is a very interesting and challenging job, and the pursuit of perfect ultimate flavor is a goal that can never be stopped.

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