How to control the change of coffee beans during roasting?
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There are many changes in coffee beans during the roasting process. Constantly changing, reactive substances create a distinctive aroma and taste. However, this process can cause many errors and defects. How to control that? Let’s find out with 43 Factory Coffee Roaster!
Changes in coffee beans during roasting
According to Paul Golding – Roasting Team Leader at Paradox Roasters, coffee beans will have significant changes from the time they are put into the roaster to when they are prepared.
The chemical reaction inside the seeds creates an attractive taste
Every chemical change and reaction time contributes to the flavor. First, the seeds lose moisture due to pyrolysis, creating volatile compounds. Next, the reaction is the Maillard reaction – the reaction between acids and sugars. This process begins at about 150°C (302°F) while the beans are still absorbing heat by the endothermic method and continues in the exothermic part of the roasting process. Heat causes a reaction between carbohydrates and amino acids in beans. This causes changes in color, flavor and nutritional content. Small changes in the temperature and duration of the Maillard reaction also have a big impact on the final character of the coffee. A shorter Maillard time can produce a greater perception of sweetness and acidity. Besides, depending on the degree of Strecker decomposition in the Maillardization stage, the generation of aldehydes and ketones through amino acids that react with carbony group molecules makes coffee flavor and aroma different.
At a temperature of about 170°C (338°F) the beans will caramelize. Large, complex carbohydrates break down into smaller water-soluble sugar molecules. Not only does this give the beans their brown color, but it also contributes to a delicious and rich flavor or flavors like caramel and almond.
Beans can be “dull” during coffee roasting
Coffee is a fruit, so it contains a multitude of different organic acids. Acids play an important role in flavor but are very sensitive to heat. Roasting can degrade some acids and produce others. Roasting for a long time or too hot, the acids that create fruit flavors and sweetness will be destroyed, making the coffee taste dull and lose its inherent sweet and sour taste. For example, chlorogenic acid will break down into caffeic and quinic acids, giving coffee a bitter and astringent taste. In addition, if the caramelization process is prolonged, the sugar molecules can be changed by heat to create solid residues containing a lot of carbon or charcoal, causing an undesirable burning and burning taste.
Controlling the change of coffee beans during roasting
During the roasting process, batches of coffee often fail due to improper heating of the roaster and improper temperature adjustment. To achieve consistent quality coffee, roasters need to identify all the variables at play so that they can be controlled and standardized. Although temperature probes can quickly read accurate charging temperatures, they cannot calculate the thermal energy of the entire roaster. Hasty start-ups will cause a lower than expected heat loss as the beans are loaded, causing the coffee to need heat compensation or to prolong the overall roasting time. This will change the entire roasting profile altering the flavor of the beans. Instead of a hasty roasting start, a roaster can heat the drum above its charging temperature, then leave it empty several times before first loading. Many experts recommend that the device be idling above charging temperature for 15 to 20 minutes before dropping to charging temperature.
Besides adjusting the charging temperature correctly, it is also important to ensure a stable oven temperature. If the drum is too hot when the next batch is added, the coffee may burn. If the drum is left to cool too much, it will take longer for the beans to reach the first crack and alter the roasting characteristics of the next batch. Therefore, consistency is an important part of a consistent roast profile and minimizing roast defects.
In addition, roasters can reduce heat and increase airflow after a strong first crack that will lengthen the time between the first and second crack. This will give the beans more time to grow without having to roast them thoroughly. However, the exact time will vary depending on the machine and batch size. This will take a master’s understanding of roasters, batches and tastings to find a standard process for you.
Coffee beans will exude unique flavors if the roasting process is carefully and professionally controlled. If you want to experience extremely bright roasted specialty coffee beans, come to XLIII Coffee – The brand developed from the forerunner 43 Factory Coffee Roaster!