Coffee roasting is probably the one thing that every barista should know about and learn. Roasting coffee, after all, is the best not so kept secret if you want to develop flavor. But what really happens during roasting? How can you achieve the tastiest coffee?
Importance of Coffee Roasting
Coffee beans are basically seeds that matured in a coffee cherry. The beans are processed and dried into coffee beans. The beans take on a green color before roasting with a grassy and beany aroma. Green coffee beans don’t have the slightest coffee smell to them at all.
Every time you roast coffee, you actually develop around 800 up to 1,000 different aroma compounds, and these compounds are responsible for the coffee flavor. Roast profiling lets you affect the aroma compounds’ existence in coffee while determining its flavor at the same time.
Stages of Roasting Coffee
Roasting means turning green coffee beans to brown. You can do it in several different ways, and this affects the flavor.
Roasting has three primary stages. First is the drying stage, followed by the browning stage, and finally, the roasting stage or development stage. Here is a quick overview of these three different stages:
1. Drying Stage
Coffee beans have a humidity of 8% to 12%. It should be dried first before the start of the actual roasting process. The drying stage often lasts for 4 to 8 minutes using a traditional drum roaster. The temperature is often 160⁰C at the end of the drying stage.
You have to be extra careful when using drum roasters to avoid burning the beans because of the excessive heat at the beginning. The drying stage is important as well to collect energy for the beans since the final stage of roasting produces heat or exothermic.
2. Browning Stage
The coffee will begin to smell like toasted hay and bread from 160⁰C. It is the time when the aroma precursors are beginning to convert into aroma compounds. Although the browning stage technically follows after the drying stage, drying still continues throughout the browning stage.
The Maillard reaction begins during the browning stage, and this is the reason for the browning. During the Maillard reaction, amino acids and reducing sugars react to produce hundreds of different color and aroma compounds called melanoids.
It is also the stage when there is a natural slowing down with the roast. Some roastmasters also prefer slowing it down to ensure the development of flavors. The coffee begins to pop when the browning stage ends. It is known as the first crack and marks the beginning of the development stage.
3. Roasting or Development Stage
At the start of the development stage, an exothermic reaction begins, with the coffee cracking, The bean has already acquired energy during the drying and browning stages, and this makes the coffee explode. The development time refers to the development of the desired aroma compounds. If the roast is not slowed down during the development stage, it will give you a smoky-tasting coffee with an extremely sharp flavor.
The length of the development stage is often 15% to 25% of the overall roast time which depends on the roast degree and desired flavor profile.
The Roast Degree
The roast degree is among the most critical indicators of the roast. You can measure it by tasting or a color meter. Roasters often like to enhance the own flavors of coffee and choose the roast degree. Light roasted coffees are typically more acidic, while dark roasted ones are more bitter.
Fruity flavors are also more common on light roasted coffee and burnt and roasty flavors are typical on dark roasts. The fruitier flavor of light roasted coffee is because of the high amounts of 5-hydroxymethylfurfural, an organic compound. The increase in the amount of sulfuric compound produces burnt and roasty flavors.
The general rule of thumb here is that it is safe to assume that light roasts bring out the raw coffee’s character better. Distinguishing light roasts from each other is easier to do than their dark roasted counterparts.
The Roast Time
Even though roast degree plays the biggest part in the flavor profile of coffee, the total roast time and the time of every stage are equally important factors. Roasting fast will let you get the more coveted aroma compounds. Just make sure that you don’t burn the beans.
The total flavor of coffee, which is a combination of nutty, berry-like, fruity, and chocolatey, is stronger. The amount of the aroma compounds that were formed during the start of the development stage is also higher when the roasting time is fast.
However, there are instances when fast roasting is not really a wise idea, either because of the characteristics of coffee or the roaster design. Fast roasting improves all of the coffee’s flavors. If you don’t want your coffee to have some flavors, you should try adjusting the roast profile.
Acidity, for instance, is a commonly desired flavor. On espresso blends, however, people often prefer low acidity. The coffee turns less acidic when the roasting slower organic acids have additional time for breaking down. It is when it might be a good idea to slow roast.
Different Roaster Designs
Roaster designs are different, and every design affects the thermodynamics of coffee roasting. It is also possible to produce different tasting cups of coffee using different machines. The smaller roasters often use drum roasters and here, the beans rotate inside a drum heated under it with either indirect or direct flame. It increases the volume of the roasters’ energy.
While it is very stable to roast with these types of machines, the roastmaster must think up to minutes ahead of time. Drum roasters are ideal for slow roasting since the excessively high temperature at the start of the roast may end up burning the beans from the outside.
Fluidized bed roasters have also existed in the market for a long time. The roaster here doesn’t get directly heated by hot air, allowing faster control of the roaster. Getting more aroma to the coffee and roasting faster is also possible with fluidized bed roasters without burning the beans from the outside.
Knowing the basics of coffee roasting can help you enjoy the best-tasting coffee ever!
