Why are Coffee Beans Light Roasted? Why Did Light Roast Coffee Emerge?

Why Yirgacheffe Coffee is Light Roasted

While many people still think of coffee as something that needs sugar and milk, Yirgacheffe has quietly penetrated specialty coffee shops even in small towns, demonstrating how rapidly specialty coffee has developed. So why has Yirgacheffe, with its delicate fruit acidity, become a representative of this movement? And why must it be light roasted?

We most often describe Yirgacheffe's flavor as lemon, citrus, and also the previously popular grapefruit - this is also how most medium-light roasted beans are characterized. Light roasted coffee contains higher amounts of decanol, n-hexanol, vinyl formate, isoprenol, and other compounds that give us those citrus flavors.

The Rise of Fruit Acidity in Coffee

The emergence of fruit acidity in coffee comes partly from our need for change after drinking bitter coffee for many years, especially when we began to specifically categorize flavors by origin. This has given acidic coffees a legitimate place. For those who have been drinking Mandheling for decades, Yirgacheffe might seem unpleasantly acidic, but for young people, it's a beverage that completely subverts their impression of coffee.

Coffee beans are not light roasted to express citrus flavors - rather, when coffee beans are light roasted, they naturally express citrus flavors. Beyond terroir, roasting more often determines the basic framework of coffee flavor.

The Science of Coffee Roasting

Those who have slightly studied coffee roasting will know the concepts of first crack and second crack. Different machines may have some temperature variations, but taking the machine used by FrontStreet Coffee as an example, coffee beans reach first crack at around 183°C. For most beans, we define a discharge temperature of 191°C as medium-light roast. When it reaches 193-195°C, it becomes medium roast. After developing for another 20-30 seconds, it enters second crack at 197-202°C.

Different machines, different beans, and their heat absorption will have some variations in discharge temperature. This difference comes from the heat conduction of the coffee beans. But basically, first crack and second crack are used as indicators of coffee bean maturity. The difference between light and medium roast is just 10-20 seconds, or a difference of 2-3 degrees in discharge temperature. Although this difference is small, the heat conduction mechanism of the coffee beans themselves will cause huge differences in coffee flavor. During this roasting process, as the roast level goes from light to dark, the sequence of coffee flavor presentation is acidity - aroma - body - bitterness. In other words, if you want the flavor to tend toward distinct acidity characteristics, the coffee beans cannot be deeply roasted, nor can they be.

Challenges of Roasting Ethiopian Coffee

The size, shape, density, and moisture content of raw coffee beans, combined with flavor considerations, must be comprehensively evaluated. The larger the coffee beans, the higher the altitude and density, the more moisture content they have, and the more roasting energy they need. Then there's the shape of the raw beans - the more similar in size the beans are, the more similar the results will be.

Due to the origin characteristics of Ethiopian beans, most belong to "Heirloom native varieties." The bean varieties and local grading system have resulted in this origin having both large and small beans of uneven shapes. During roasting, smaller beans obviously cannot withstand the impact of heat as well. If the heat is not controlled properly, the large beans will be roasted while the small beans are burnt. Without delving into the impact of roasting development on coffee beans, judging simply by unripe, ripe, and burnt - for roasting coffee beans of mixed sizes, the safest and most conservative method is to roast them quickly and discharge them as soon as they are ripe.

Some might question: isn't good roasting supposed to make beans look very uniform? For Mandheling, Colombia, Brazil, Blue Mountain - where individual bean differences are not large and medium-dark roasting dominates - this is indeed the case. Because individual differences are not large, each bean needs the same amount of heat to reach the same degree of roasting.

Yirgacheffe can also use the "slow roasting" method to make the beans more uniform. Those who like to make soup will have this experience: after the water boils, turn the heat to very low - what Cantonese people often call "old fire beautiful soup." What's the trade-off? Overcooking for too long will make the soup ingredients tasteless.

The Roasting Trade-off

Is it better to gain some body with a uniform appearance, or to use the Nordic-style rapid temperature rise and quick discharge method to obtain some distinctly acidic flavors? For roasting, this is a trade-off. Many people also like to use Ethiopian coffee as the base bean for blends. In this case, they usually need some fuller, more body-emphasizing beans to pair with it.

Because fruit acidity and floral notes have created a strong impression as signature characteristics of medium-light roasts, some larger American beans have also come to be called light roast. However, in reality, what one bean merchant calls medium-light roasted American beans very likely needs to be roasted darker than Ethiopian beans. This is just a need for text or flavor description - larger beans naturally need more heat and temperature to roast to maturity.

The Necessity of Light Roasting

Higher altitude, slower growth, more internal characteristics, and harder beans all require deeper roasting. In the early stages of the Maillard reaction, more raw materials inside the beans will produce more aromatic substances under the caramelization reaction, making the aroma more abundant. This is what roasting pursues - why not do it? Light roasting is actually a choice made out of necessity.

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