After you learn how to be a barista you might want to know more about the art and science of coffee roasting. Roasting is one of the variables that affect the final taste of the coffee you just had this morning. Roasting reveals the full flavor and potential of a green coffee bean and makes it ready to brew a delicious espresso.
Most coffee roasting machines use both conduction and convection. Conduction is the physical transfer of heat from the drum to the beans. Convection is heat travelling by air currents. The balance of both forces makes a great coffee roast.
In this online barista training course you will learn the basics of the coffee roasting.
- Dehydrating the bean and removing excess moisture content. The coffee will smell green and grassy. The beans will start changing its color to yellowish.
- Yellowing stage (between 212 and 240 F) The beans go through a temperatures range where the basic chemical reactions start happening. The beans themselves get darker. You’ll sense bread baking aroma.
- First crack (between 250 and 300 F). When you hear a cracking sound it means that the beans are dried out. Thermic reactions, which put heat into the coffee, end and become extra thermic reactions where the bean starts releasing its own energy. The bean is light brown color.
- Roast development stage (between 350 and 400 F). Here’s where a coffee bean starts building simple sugars. After melting them a bean develops caramel, sugary tasting characteristics. You can stop roasting here or move to the next stage.
- Second crack (between 425 and 435 F). Under even higher temperatures a coffee bean start producing a popping sound. The beans release more oil and loose acidity.
- As the beans drop out of the drum you want to stop the roasting process as soon as possible by quickly cooling the beans.
Use fresh beans to extract your espresso because old coffee tends to lack body, be thin, boring with less character or acidity. Remember how old is your coffee when you extract an espresso shot. Freshly roasted coffee tend to be more gassy and bubbly. If espresso blend is aged you’ll need to dose more coffee to compensate for the gas loss.
Roasting type is often a matter of taste. Don’t be afraid to experiment when you roast your coffee. Let your eyes and your nose be the guide when to stop roasting.
You can roast your coffee at home and save a fortune and create your unique blends or try roasting at your coffee shop if it’s equipped with a coffee roaster. That’s a great skill, which will give you a deeper understanding of your coffee and where your espresso comes from.
There‘s no one unified standardization of roasting types. One of the ways to categorize roasting types is by color. Thus, light, medium, medium-dark and dark roasts are distinguished.
Lighter roasts have more acidity and slightly more caffeine, while darker roasts show more bitter and even carbony tasting profile. Lighter roasts also best reveal the origin of the bean, they might have fruity, chocolate and nutty notes. In darker beans the origin flavor and acidity are almost gone, smoky flavors are more evident.