Roasting coffee takes technical skill and precision, but it also takes creativity and intuition. In contemporary coffee culture, the advent of specialty coffee, the explosion of small coffee shops, and the ever divisive debate over the best roast (light vs. dark–hint, it’s light) all mean that as a coffee roaster you need to know the intricacies of coffee roasting while still being able to be flexible enough to meet all of your coffee buyers’ needs. I want to focus on the science behind coffee roasting in this blog. Having a depth of knowledge about the process your coffee beans are going through can greatly enhance your end results and your ability to service a variety of customers.
When you roast coffee, you begin with green coffee beans. These beans have been extracted from the coffee fruit, either by washing the fruit fully away, washing the fruit partially away and letting the remainder of the fruit linger on the bean as it dries, or leaving the entirety of the fruit on the bean to dry.
Despite this “drying” process, green coffee beans still have an internal water content. As you roast the beans, this water content is released in the form of steam. Even for the lightest roasts, most of the water content in your beans is going to be dissipated.
The roasting process also causes the coffee bean to expand; this is due to a combination of the movement of gasses and the release of the water content. The expansion of gas and release of water creates air pockets inside of the bean. The tissue of the coffee bean, lacking water, becomes truly dry, as well as brittle. This brittleness is important in making the beans easier to grind and in making those grinds more water-soluble. Because of the water loss and the expansion in size (that does not result by adding mass to the bean) be beans also lose density, becoming lighter.
The browning that occurs as you roast is a result of the natural sugars in the bean caramelizing. The brown color also comes from melanoids that are produced in a reaction between the sugars and amino acids in the beans. This color change is called the Maillard reaction and occurs in other foods as well; it changes not only the color but also the flavor of the food product. This process also results in the chemical changes that create new aromatic compounds in the beans.
The more darkly you roast the beans, the more the oils are going to migrate to the outer surface, which is what gives dark roasts that shiny quality.
Coffee roasting is a chemical reaction, meaning the process of adding heat through convection, radiation and heat contact changes the chemical composition of the beans. These chemical changes are what create the dynamic aromas associated with different roasting stages.
In coffee roasting, when the actual structural changes begin to occur. The crack comes from the shift from endothermic reactions, where the heat is penetrating the coffee bean, to exothermic reactions, when the heated internal gasses begin to escape the bean. The heat is forced out of the bean in the form of steam and this is when the caramelization process begins. It is soon after this that you’ll want to remove your beans from the heat if you are looking for a light roast. The crack is actually more akin to the pop of popping popcorn.
If you continue to roast well past this, there will also be a second auditory crack. Pressure has been building inside of the bean as the sugars caramelize, the oils begin migrating to the outer surface and the bean’s size expands. This second crack indicates that the bean is beginning to fracture because of the built up texture that needs to escape.
The resulting flavors and aromas are dependent on a lot of elements, like the darkness of your roast and the origins of the beans. Different varieties of bean have different flavor profiles. The flavors are influenced by the processing that occurs, whether the fruit is washed entirely away or allowed to absorb into the drying bean. Blending also influences the flavor of a coffee. Single origins refer to coffees that have not been blended; they come from one farm and often from one specific plot of land on that farm. Blending is a more common practice because it makes the most sense for large batch roasting. You can blend your beans before your roast them. One way to have more control over the final flavor profile is to roast each bean type separately, cup it to discern the flavors, and then combine based on which flavors will be complement each other.
This is where intuition and creativity come into play. The technicality of the roasting process requires you to monitor temperature, volume, speed of agitation and so forth. When deciding how much to roast a batch of coffee and how to blend it with other batches, you are relying on your instincts about what taste good together and what amount of roasting will enhance or detract from the natural aromatics in the coffee. As a coffee roaster, the ability to “cup” coffee is essential so that you can taste your roasts and adjust them until they’re just right. Cupping involves steeping the ground coffee in hot water and analyzing the aromatics and flavor profiles. With a new batch of beans, you’ll want to do this at every roasting level (unless you’re morally opposed to light or dark roasts) to determine which one is best suited to that particular bean. While the aromatics of the dry coffee are a pretty reliable indicator of the flavor profile and aromatics of the brewed coffee, adding water can have occasionally unexpected results. Find the perfect roast for each bean, identify the flavor profiles and then strategize about what combination will result in optimal flavor.
Once you’ve got that absolutely unique product perfected, don’t forget to choose an absolutely unique package to put it in and label to sell it with. The thing about coffee is that there’s a lot of it on the market and one of the best ways to get people to notice your top-of-the-line blend is to catch their eye with a clear, fantastic logo, keep their attention with dynamic and informative descriptions, and give them security with a sturdy, coffee-loving package. PBFY.com has some of the best offerings for food and coffee packaging, with a variety of designs, some of the lowest prices, and deals to help you save money so you can focus on making more of it.