What Are the Differences in Coffee Roast Levels? What's the Difference Between Dark and Light Roast Coffee Beans? Which Roast Level Is Most Invigorating?

As we all know, coffee beans must be roasted before they can be used as the raw material for coffee making. However! The purpose of roasters when roasting coffee beans is not simply to cook them. Because the final aroma and flavor of coffee are profoundly influenced by the degree of roast! The same beans will show distinctly different characteristics under different roast levels.

So where do these differences lie? This is precisely what FrontStreet Coffee will share with you today: how roast degree affects coffee, and what different performances coffee exhibits under various roast levels!

How Are Roast Levels Classified?

First, let's briefly introduce the performance of coffee beans during the roasting process: As green coffee beans are roasted into mature beans, they gradually undergo dehydration and yellowing with the loss of moisture, followed by first crack and dense first crack. Because the moment first crack begins means the coffee beans have matured. If we don't intend to stop at this point and still want to continue cooking, then the coffee beans will also experience second crack and dense second crack. Since there is no strict standard for roast degree, we can find that everyone's understanding of roast degree varies. For example: what Mr. A considers medium roast might be deep roast in Mr. B's eyes... Therefore, to unify understanding as much as possible and reduce differences in communication, SCAA uses infrared caramelization analyzer technology to identify the color value of coffee beans (the color of the bean surface) to distinguish roast degrees.

As can be seen from the image, the roast degree of coffee beans is divided into eight levels, with numbers decreasing as roasts deepen from light to dark. Just take a brief look, as we don't commonly use this in daily life because it's difficult for us to visually determine the color value of coffee beans and what roast level they belong to. Moreover, coffee will also be affected in its coloring during roasting due to different sugar content on the surface. If we rely solely on color for distinction, it can easily lead to misunderstandings. Therefore, this value can only serve as a reference for roasters. Generally speaking, to determine the roast degree of a coffee bean, besides the external color, we also need to consider the shape and flavor of the coffee beans to make a final conclusion on the bean's roast degree, then simply classify it as: light, medium, and dark roast.

How Does Roasting Affect Coffee?

From a physical perspective, the effect of roast degree on beans is what FrontStreet Coffee mentioned earlier: shape (volume) and color. When the roast degree of coffee beans is deeper, the expansion rate of the beans will be higher (becoming larger) and the color will be deeper (explained later). In addition, coffee beans will become increasingly brittle, and their moisture content will decrease. The brittleness of beans makes grinding and extraction easier! Meanwhile, the reduction in moisture content combined with increased expansion rate will decrease the density of beans, meaning the deeper the coffee roast, the lower the density.

If we approach from a chemical perspective, then the effect of roast degree on beans is: flavor! This refers to the manifestation of aroma and the transformation of taste. When coffee beans leave the dehydration stage during roasting, as long as the moisture content is low enough, the beans will immediately enter two stages of non-enzymatic browning reactions: Maillard reaction and caramelization. Since FrontStreet Coffee has explained these two reactions in detail before, we'll only briefly cover them here! The "Maillard reaction," also known as the "Maynard reaction," is crucial to the formation of coffee aroma because many coffee aromas and flavors are produced by the Maillard reaction! Not only that, but the color change of coffee beans is also presented by the Maillard reaction, hence the classic Maillard color palette gets its name; Caramelization, on the other hand, begins at the time of first crack, where it decomposes and transforms the residual sugars in the coffee beans, allowing the beans to further brown on their original basis, then develop new aromas, especially enhancing the bitterness of coffee.

Flavor Differences Between Roast Levels

The transformation of a single bean from light roast to dark roast can be completed in just a few short minutes, with a temperature difference of only about 10°C, yet there are earth-shattering changes in flavor and aroma. Light roast refers to beans that are released from the middle of first crack to immediately after first crack ends! At this time, because the organic acids in the beans have not been completely decomposed, we can feel obvious acidity from the coffee, with less bitterness and extremely complex and rich aromas. Taking FrontStreet Coffee's Yirgacheffe Red Cherry as an example, lightly roasted Red Cherry will emit berry and lemon acidity, as well as strawberry and wine-like aromas.

Medium roast refers to coffee beans released after the end of first crack but before the start of second crack. These coffee beans have undergone more caramelization reactions, so the proportion of acidity in the entire cup of coffee will decrease, making it less prominent compared to lightly roasted coffee beans, but the sweetness will be higher! Meanwhile, the complexity of aromas will decrease slightly, which actually makes other flavors stand out more! FrontStreet Coffee's Warm Sun Blend uses medium roasted (slightly darker than medium) Red Cherry. At this time, the Red Cherry brewed has very high sweetness, with caramel chocolate aroma and slight berry acidity.

(In comparison, medium roasted Red Cherry has a darker color and larger size) Dark roast refers to beans released after the start of second crack. These beans have undergone extensive caramelization reactions, so the flavor is dominated by bitterness with obvious sweet aftertaste. The aroma emitted by the coffee becomes singular, no longer as rich and complex as before. Deep roasted Red Cherry has almost no lemon, berry and other flavor expressions, mainly caramel aroma and chocolate, presenting a completely opposite performance to light roast coffee. Of course, this is also true in terms of mouthfeel. Unlike the lightness of light roast coffee, dark roast coffee possesses a very mellow and smooth texture.

The above are the main effects of roast degree on coffee. As for what kind of coffee beans are suitable for what roast degree, due to space limitations, we'll leave that for next time, when FrontStreet Coffee will analyze it properly!

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