Aside from their light green shade, unroasted coffee beans are generally soft and spongy to bite. They also smell grassy. However, roasting gives them different shades of brown (the popular ones being medium roast and dark roast). The process is also responsible for the mouth-watering aroma and flavor that makes you yearn for a cup.
In a nutshell, roasting causes a chemical change in green beans. This is accomplished by subjecting beans to very high temperatures before stopping the process through sudden cooling.
Understanding the Roasting Process
Roasted beans lose their fresh flavor and characteristic smell with time. Therefore, it is advisable to use them immediately after roasting or store them in their green state. Apart from retaining their flavor, green beans seldom lose their quality.
Although roasting enhances the taste of the beans, the country of origin and the environment in which coffee beans are grown affect the final product’s quality. Furthermore, the age of the coffee, the processing, and brewing method, plus the grind, also affect the flavor. However, the roast level provides the primary basis of the expected taste.
Roasting happens in three levels:
- Large-scale production for commercial reasons.
- Specialty or boutique roasting to produce small amounts of the product.
- Home-made roasts for family consumption.
For large-scale production, hot-air roasters and drum roasters are the two main types of bean roasters used during the process. Other roasters include tangential, packed-bed, and centrifugal machines. Hot-air roasters work by blowing hot hair through a screen or grate underneath the beans. This results in a swirling motion and even distribution of heat that ensures that beans roast evenly.
Drum roasters are cylinder-shaped compartments (or sometimes drums) that rest sideways into which coffee beans are packed and heated from underneath using gas, electricity, or an open flame. The machine also spins in a circle to distribute heat and ensure even roasting of coffee beans.
When roasting reaches perfection, the beans are quickly cooled, which stops the process. The operation is referred to as quenching in the professional coffee roasting space. Roasted beans are then immediately packed into bags to allow for degassing before being shipped to different outlets. In some cases, the roasting company grinds the roasts before packing and releasing the final product into the market.
The Stages of Roasting
When subjected to heat, green coffee beans turn pale, and in some instances, they may turn white. No significant physical or chemical change takes place as the beans start absorbing heat. This is the first coffee roasting stage.
Continued heating changes the shade of the beans into orange or tan. It is the second stage, and it involves limited chemical changes such as the Maillard Reaction. Apart from color changes, the aroma also changes from a grassy one to an irresistible pleasant smell that begs for brewing. But wait – roasting is still in progress.
At the third stage of roasting, beans will start puffing up and popping. This first popping (first crack) occurs when the roaster is heated to between 350 °F and 400 °F. The beans at this point will have a light brown shade. They also weigh lesser due to loss of moisture. In the third stage, the heat is not enough to break the beans’ oils. As a result, light roast coffee beans lack oil on their surface.
Removing the beans from the heat at the first crack gives you light roast coffee. Other coffee roasters call it Light City Roast, Cinnamon Roast, or New England Roast. Because this coffee roast retains most of the original green bean characteristics, it is commonly used to make cuppings. It also has the highest acidity and caffeine levels.
More heating rapidly changes the coffee beans’ flavor—fifteen minutes is enough to change the taste. If you remove the coffee beans from the roaster between the first and the second crack, you get medium roast coffee. The ideal temperature for medium roasts ranges between 410 °F and 430 °F. Besides an enhanced taste, medium roast coffees have a darker shade and thicker body than light roasts. The beans also lack an oily surface.
Medium roast is commonly known as American Roast because it is well-liked in the US. City Roast, Regular Roast, and Breakfast Roast are the other popular names for a medium. Furthermore, medium roasts can be left to heat a little longer, which results in the medium-dark coffee roast. The beans will have a slightly oily surface because more heat causes the oils to start breaking. They also have a more savory flavor and lower acidity and caffeine levels. Medium-dark roast is commonly identified as Full City Roast, After Dinner, or Vienna Roast.
The next roasting stage results in the second crack. For this second popping to happen, the bean’s interior needs to be heated to at least 465 °F. The extreme temperatures break the coffee beans’ oils, which move from the beans’ interior to the surface, giving them an oily appearance – a distinct characteristic of dark roast coffee.
Since beans are left in the roaster for the longest period, they lose a lot of moisture, making them less dense. Dark roast coffee beans also have the least caffeine and acidity levels, and can be easily identified with their bitter/smoky taste. They mix well with milk to make lattes and cappuccinos.
Coffee beans at the dark-roast level lose most of their original characteristics, making it difficult to pick the origin of the green beans. Furthermore, purchasing dark roast coffees can be challenging because of their numerous names, which are used interchangeably. Remember to check carefully before buying. Here are some common names for dark-roasts:
- French Roast
- Viennese Roast
- European Roast
- High Roast
- Continental Roast
- New Orleans Roast
- Italian Roast
- Espresso Roast
- Spanish Roast
Dark Roast or Medium Roast – Which is better?
You can buy or DIY dark roast or medium roast coffee. It depends on which flavor suits you. However, recall that dark roast coffee beans have a bolder taste than medium roast beans. Also, dark roasts have lesser acid and caffeine levels.
Secondly, dark roast beans have an oily sheen which results from extreme temperatures during roasting. Expect to see the oil in your brewed cup of coffee.
Thirdly, if you have no health-related reasons to not take a cup, why not enjoy either during specific occasions? For instance, go for dark roast during your regular busy day. When you have access to premium beans, choose medium roast and enjoy!