Coffee Roast Process

So the coffee is grown, harvested and prepared for the next step – roasting. Some people who make coffee drink from the raw coffee beans would say that this phase is useless. They are right in some way – the beverage prepared from the green berries is very fragrant with specific taste and a lot of acidity that lessens with the subsequent roasting. It may seem that this process is very easy and directed towards the coffee roast only. But the whole operation isn’t as simple as it looks like. While roasting coffee berries, such components as aroma, savor, taste, aftertaste, bitterness and body are created, equilibrated, eliminated or improved. The same is with the coffee bean itself- it is not simply roasted till a certain degree, it is subjected to various chemical processing and has many roasting levels. Below are the stages which coffee beans undergo while roasting.

Before starting to describe these stages, let’s make it clear to which main criteria the going-to-be-mentioned phases are identified.

There are 2 principal ways of recognizing the type of coffee roasting - audible and visual. By audible we mean that the roast quality is identified through the number of crackles on different temperature levels. The visual means that variations in the bean color with a certain temperature grade shows the roast condition as well. Thus, both criteria define the type of future coffee roasting.

But let’s get back to the subject, i.e. the coffee roast phases.

Green coffee beans or green color phase - the initial color of the coffee berries after they have been subjected to milling, a preparatory phase.

Yellow color phase – this color appears at a temperature 200°-250°F (~86? -109?C) that is the inner bean temperature. This is the initial after milling phase where the bean emits wet grassy smell while the humidity is released from it. A vapor can often be seen rising above the roaster during this stage of process.

Light color phase – at the 250° -300°F (~109? -134?C )internal coffee berry temperature the bean changes its yellow tinge to a light brown to cinnamon shade. The phase is characteristic for its light body and bitterness. The beans are dry, without any trace of oil. This is a slight roast insufficient for the coffee to fully reveal its true capabilities.

First crackle phase – at the 355°F (~161?C) the bean begins to crack but it is still covered with spots and has an irregular coloring. While crunching, the coffee berries grow in size and the humidity continues to being released from the bean. This phase is distinctive for giving the heat off the beans, thus the berries are first exothermic but they tend to quickly turn into endothermic. So be sure that the roaster is providing enough heat for the coffee roast process not to be stopped.

Medium color phase - occurs at the 400° -415°F (~183? -191?C) and is also called City or American roast. It has medium brown color, starts acquiring some dark color and taste that is the original coffee aroma but may not be to somebody’s liking. The beans are still dry but at this stage they lose the unhealthy carbon dioxide and totally get rid of water.
Medium – Dark color phase – takes place at 415°-425°F (~191? -197?C) and is of saturated brown color. The oil begins to appear on the bean surface still in very small quantity. The bitterness is gently reduced to a lowest notch and the coffee gains its full weight that is perfect for brewing a thoroughly blended espresso. The phase not only changes its color, it also shows its first signs of the second crack start which however doesn’t influence it a lot. The stage is commonly known under the name Full City Roast.

Dark color phase – occurs at 450°-465°F (~209? -217?C) and marks the stage when the original coffee nature is replaced with the roasted coffee essence. The roast possesses dark brown almost black color. The coffee berries are almost or fully covered with oil, any original odors are minimized. The aroma slightly evaporates whereas the coffee body gathers its complete strength. The roast is famous under the name of Viennese or Continental Roast.

Very dark, virtually black color phase – is the last coffee roast stage occurring at the 475°-530°F (~222? -249?C). At this level the bean is completely covered with oil, possesses a black color and is used for American espresso brewing. The stage is characteristic for losing all the original coffee nuances, reducing the coffee flavor to an insignificant quantity and decreasing the body strength. The roast is well-known under such names as French Roast, Italian Roast, New Orleans Roast, and Spanish Roast.

So the roast has already taken its place and the beans are prepared for brewing all kinds of coffee. The type of roast determines the taste of you preferred beverage, its aroma and strength and is of course directed towards vast area of thirsty coffee lovers who chose their kind of coffee by personal judgment.

See also: Blending Brewing Coffee Recipes Cupping Flavored Coffee Gourmet Coffee Grinding Latte Art