How Does a Roaster Decide on a Lightly Roasted Profile?

Roast level is a roaster's choice of flavor expression rather than a fixed standard, and lightly roasted coffee sits at the bright, acidic end of that range. Flavor depends roughly 60 percent on the green bean, 30 percent on the roasting process, and 10 percent on brewing, so the same bean roasted light or dark can taste like two different coffees.

Roasters read color against a standard palette (Cinnamon, City, Vienna, French), but actual readings often deviate. The gap between first crack and second crack spans only about ten degrees Celsius, and beans such as Mandheling, Yirgacheffe, and Geisha are dropped at different points depending on variety and the style a roaster wants to carry forward.

Sixty percent of coffee flavor depends on the green beans themselves, thirty percent comes from the roasting process, and only ten percent is determined by brewing. For a roaster, choosing what roast level to use is often an expression of their understanding of the coffee beans, and there is no absolute right or wrong. This article, drawing on the practical experience of Front Street Coffee, systematically sorts out the criteria for determining roast level: color value standards and actual deviations, the reference significance of drop temperature, the critical range of only about ten degrees Celsius between first crack and second crack, and the two major decision-making logics of historical inheritance and bean variety appearance. Using Mandheling, Yirgacheffe, and Geisha as examples, it explains the trade-offs and considerations behind dark roasting and light roasting, helping coffee enthusiasts understand the formation of roasting styles more comprehensively.

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In the flavor composition of coffee, green beans account for about sixty percent, roasting about thirty percent, and brewing only ten percent. It can be seen that there are quite a few variables affecting the final flavor of coffee. So from the standpoint of a roaster, how exactly should one determine what degree a bean is suitable to be roasted to? Today, Front Street will discuss the thinking behind determining roasting style.

Two points need to be explained first. First, coffee is roasted to different degrees because each roaster has a different understanding of the coffee beans. There may be no absolute right or wrong; it is simply a choice of flavor expression, not a universally existing standard. Second, roast level itself is not a strictly unified ruler.

Normally, people define roast level by the color of the coffee beans, that is, by referring to a standard color palette. The common textbook terms such as Cinnamon, City, Vienna, French, and Dark French come precisely from this. But this set of standards is only a general international naming convention, and exceptions are common in actual roasting, and these exceptions are not rare. For example, beans from certain regions do not color easily; if roasting continues, they will bring out burnt bitterness, so roasting can only stop there. Although the color is very light, the flavor has already taken shape. Beans from other regions may appear darker because they have a higher caramel content after roasting. In these situations, color value can only serve as a reference.

Some people also use drop temperature as the basis for roast level, but there are differences between roasters of different brands or technical approaches, and the comparison of drop temperatures between different machines also varies greatly. This is precisely why 230 to 240 degrees often appears in Japanese roasting curves.

The essence of roasting is to transform the chemical and physical properties of green coffee beans into roasted coffee products. The entire process lasts ten to fifteen minutes, with temperatures reaching over two hundred degrees Celsius. During this time it undergoes multiple chemical changes, producing the popcorn-like sounds of first crack and second crack, while also losing moisture, causing the green beans to expand and change in color, taste, aroma, and density. As roasting progresses, chlorogenic acid gradually disappears, releasing familiar and pleasant fruit acids, such as acetic acid, citric acid, and malic acid contained in wine. When roasting is just right, these beautiful acids are appropriately presented, thus creating the special flavor of coffee.

Theoretically, after first crack, any point in time can be chosen for dropping. But to avoid risk, beans are usually not dropped immediately after first crack; instead, they need to develop another two or three degrees to make the aroma fuller. In other words, from two degrees Celsius after first crack to a little after second crack, a total range of only 10 degrees Celsius, we roughly simplify into three styles: light roast, medium roast, and dark roast. From this it can be seen that their drop temperatures actually do not differ much; sometimes there may be only a two- or three-degree difference, yet the appearance is already clearly different. Therefore we describe the roast level of a coffee bean by combining color, shape, and taste.

From the perspective of roasting:

As Front Street mentioned in newcomer assessments, light roast refers to coffee beans from the middle of first crack to just after the end of first crack. At the early stage of enzymatic action and Maillard reaction, the organic acids in the coffee beans have not yet been completely decomposed, so the acidity is more prominent and the bitterness is so light it is hardly noticeable, making it very suitable for friends who like acidic coffee.

Medium roast usually refers to the period from the end of first crack to before second crack. At this time, the roasting process undergoes caramelization and more Maillard reactions. Although there is still acidic aroma, it is already clearly weaker than in light roast. At this point, acidity and bitterness are more balanced, so the sweet and clean flavor becomes more prominent and very easy to drink, shifting to caramel, chocolate, and similar notes as the main theme. This type of roast level often allows specialty coffee to release its best characteristics, and it is also the roast level most commonly used by Front Street Coffee (FrontStreet Coffee).

Dark roast usually refers to beans after second crack. Caramelization is nearing its end, and Maillard reaction dominates, producing aromas such as resin, spice, and carbonization.

So how do we decide these different roast levels?

The first basis is history. In the past, consumers did not have high demands for coffee flavor and paid more attention to its function. During that long period, the roast level of coffee was surprisingly consistent—dark. Therefore, during this period lasting hundreds of years, the styles formed in major coffee-producing regions were mainly full-bodied, such as Mandheling, Brazil, Colombia, and also Blue Mountain. By comparison, Blue Mountain was full-bodied yet not noticeably burnt-bitter, and perhaps this was also an important factor in coffee becoming the king of coffee in the old era. The influence of this roasting was profound, and even today, the habit of some consumers asking for sugar and milk when ordering coffee comes from this.

Therefore, in choosing roast profiles, for coffee beans from these classic regions, we will keep them as close as possible to the era back then and maintain the classic full-bodied taste.

Take Mandheling as an example. Mandheling's unique "heavy taste" gives it a feeling of unrestrained satisfaction, like galloping through the world. Not a few men like it, and now many women like it too. Indonesia is the largest archipelagic country in the world and is known as the country of a thousand islands. Indonesia's relatively high altitude, volcanic ash soil, and its climate characteristics are all excellent conditions suitable for the growth of Arabica coffee trees. Sumatra has long been known as the Island of Spices. Coffee trees in the mountains keep company with wild animals, cloves, nutmeg, and pepper; combined with the unique three-stage drying method (wet-hulling), this creates Mandheling's unique flavor: distinctive herbal notes, the deep fragrance of forest wood, moderate acidity, rich and mellow yet like life's sweetness and bitterness, and a strong sweet aftertaste.

Mandheling coffee beans are relatively large and the bean texture is relatively hard. In order to highlight its famous body, low acidity, and local herbal flavor, Front Street uses dark roast. If Mandheling coffee beans were lightly roasted or medium roasted, the taste might not achieve the full-bodied feeling everyone likes, and the acidity would become more obviously prominent, no longer the Mandheling coffee everyone likes. Of course, if someone likes acidic Mandheling, they can also try medium roast. But then again, if it has no Mandheling flavor, do we still call it Mandheling?

The second basis is the appearance and characteristics of the bean. For example, Yirgacheffe coffee beans are chosen for light roast. It is not that this region shows good acidity, but rather the opposite: it is precisely the very light roast that causes its acidity to show.

Yirgacheffe Ethiopia—in order to sell most of the coffee beans, coffee farmers do not, like the traditional countries just mentioned such as Brazil, Mandheling, and Colombia, like to grade commodities by size. Ethiopian coffee will have large and small beans; only defective beans that would bring bad flavors are excluded. For the phenomenon of uneven sizes, the variety is usually labeled as Heirloom [Heirloom native variety] for the green bean variety.

Front Street often mentions in articles that Ethiopian beans come in large and small sizes. During roasting, the large coffee beans must be roasted through, but the small coffee beans must not be roasted burnt. The safer way is to drop them as quickly as possible. Some people ask, doesn't high skill allow for very even roasting? The woody structure of coffee beans themselves determines that their heat conductivity is very slow. If the difference between large beans and small beans is too great, this conductivity cannot achieve even transfer. Although one can lower the heat after dehydration and slowly prolong the roasting time, this frog-in-warm-water method can pull the bean color to look even, yet in aroma characteristics it inevitably leads to blandness because of the overly long roast. This is also a trade-off. For the floral and fruity acidity of Ethiopian beans, Front Street, like most roasters, uses light roast.

Another example is Geisha. Its floral and fruity profile differs from most varieties of coffee, and many reviews take this characteristic as indicating a medium-light roast. The Geisha variety has one characteristic: its long, narrow shape makes its volume larger than some varieties, especially compared with Ethiopian beans that have already been unanimously recognized as light roast. It often takes two or three small beans to match one Geisha bean. Whether you like it or not, its roasting requires a longer time. On the other hand, according to roasting principles, roasting as much as possible without causing burnt bitterness will produce more aromatic characteristics and lead to more flavor changes. This is the pursuit of roasting.

Whether roaster or drinker, people have different understandings and views of coffee. Sometimes there may be no completely standard answer, only different choices.

The above content is compiled by CoffeeHunters, a coffee news website.