How does the roasting process change coffee flavor?
Roast level drives what ends up in the cup. Green coffee beans have no real aroma or flavor on their own; heat from the roasting process creates them. Light roasts keep a cinnamon-colored surface, pronounced acidity and a light aroma, while medium roasts turn chestnut brown with mild acidity and bitterness, and dark roasts push smoke and bitterness forward as origin character fades.
American terminology splits roast levels into eight stages, from Light Roast and Cinnamon Roast through City, Full City, French and Italian Roast. Medium roasts are common in American coffee and blends because they retain the bean's original flavor. For specialty coffee, roasters pick a profile based on bean density, origin and processing, since small shifts in time and temperature change the final taste.
Green coffee beans themselves have no obvious aroma or flavor; only through roasting can they release their alluring flavors. Roasting time, temperature, method, and even the roaster's experience all have a subtle impact on the final taste in the cup. From light roast to dark roast, the color of the coffee beans, the balance of acidity and bitterness, and the layers of aroma all differ, and the suitable brewing methods and drinking preferences vary greatly as well. In this article, Front Street Coffee will systematically sort out the flavor differences among light, medium, and dark roasted coffee beans, and, combined with specific origin cases, explain how roasters choose profiles based on bean characteristics, as well as the impact of different roast levels on coffee's chemical compounds and final taste, helping coffee lovers understand the relationship between roasting and flavor more clearly.
Before green coffee beans enter the sales process, they must all undergo roasting. Raw beans smell and taste like nothing; only after roasting do they develop a brand-new and alluring aroma and flavor. During the roasting process, there are many variables that affect coffee's flavor and mouthfeel, including the length of roasting time, the roasting method, the level of roast degree, and even the amount of beans charged and the roaster's personal experience and feel—a matter of seconds can make a considerable difference. This makes roasting a craft full of variables and adds a good deal of mystery to it. In this article, Front Street Coffee (FrontStreet Coffee) will talk with everyone about the roast levels of coffee beans.
Coffee roast levels can be divided into many types. In American terminology, roast levels are subdivided into eight stages: extremely light roast / Light Roast, light roast / Cinnamon Roast, medium roast / Medium Roast, medium-light roast / High Roast, medium-dark roast / City Roast, slightly dark roast / Full City Roast, extremely dark roast / French Roast, and extremely deep roast / Italian Roast.
Generally speaking, light roast coffee beans have a cinnamon-colored surface, strong acidity, and a slight aroma; medium roast beans have a chestnut-colored surface, a light mouthfeel, are somewhat acidic with bitterness, and have a moderate aroma, retaining the coffee beans' original flavor, and are often used for American coffee or blended coffee; medium-dark roast beans have a light brown surface, a bright and lively mouthfeel, a balance of acidity and bitterness with the acidity leaning lighter, and can release the high-quality flavors in coffee—this is a standard roast level and also the roast degree most loved by the public; extremely dark roast beans have a black surface with an oily sheen, and before the coffee bean fibers carbonize, the mouthfeel is intense and complex, with strong bitterness and a rich roasted and charred aroma. It is mainly popular in Italy, and is mostly used for espresso.
You may already be very familiar with the concepts of light, medium, and dark roast coffee. But how do roasters choose a roast level? What do light roast and dark roast mean in terms of flavor? For example, when Front Street Coffee (FrontStreet Coffee) roasts a Mandheling coffee bean, it will first consider what the regional flavor of this Mandheling coffee is, and then Front Street Coffee (FrontStreet Coffee) will customize the roasting profile that best matches the optimal flavor of its origin for roasting. After roasting is completed, Front Street Coffee (FrontStreet Coffee) will conduct a cupping within 8 to 24 hours after roasting the beans. The purpose of cupping is to verify the regional flavor of this Mandheling coffee bean and whether the roasting profile needs adjustment—this is a repeated process. When this Mandheling coffee bean's roasting, cupping, and brewing stages are all at their best, and it has a certain representativeness of its origin, Front Street Coffee (FrontStreet Coffee) will put this Mandheling coffee bean on the shelf.
The roasting stage is a path every coffee bean must go through. Generally speaking, baristas treat each batch of beans differently. They will test a series of roasting profiles until the desired effect is achieved. Roasters will taste each batch of coffee beans like a coffee quality grader (Q grader), and then decide which roasting method to adopt (a combination of time and temperature). For example, when Front Street Coffee (FrontStreet Coffee) roasts Indonesian Mandheling coffee beans, based on the growing location and processing method of Indonesian Mandheling, it chooses a medium-dark roast to highlight the Indonesian Mandheling coffee beans' herbal flavor and the origin flavor characteristics of low acidity and high body.
And when Front Street Coffee (FrontStreet Coffee) roasts African beans, such as coffee beans from Ethiopia's Yirgacheffe region, it adopts a light roast method to highlight Yirgacheffe's floral aroma and lemony citrus acidity brought by the washed processing. Also because of different roast levels, the flavor of each bean is different, and the question that troubles everyone may be: which tastes better, dark roast or medium-light roast?
Front Street Coffee (FrontStreet Coffee) believes that no roast level is better than another; it completely depends on personal preference. Starbucks and other coffee shops representing the second wave of coffee tend to choose the flavors brought by dark roasting. Generally speaking, light roast beans have livelier, brighter acidity, while dark roast beans have a fuller mouthfeel and a stronger nutty flavor.
Different roast levels also affect changes in the chemical elements in coffee. The well-known coffee master Taguchi Mamoru talks in his book about how, during roasting, chlorogenic acid (Chlorogenic Acid) in coffee produces bitter substances, and these substances change differently with different roast levels. This is also why most light roast coffee beans present a bright and refreshing flavor, while dark roast presents a richer bitterness.
In fact, using light roast coffee beans is very likely to make the defects of underdeveloped beans or defective beans more obvious, so it greatly tests the roaster's skill, and each roaster's approach has its own strengths. Light roast accounts for about 40% of the global drinker market. The reason it is widely welcomed by coffee lovers is nothing other than that, compared with medium-dark roast, light roast better preserves the beauty of the coffee beans' original flavor, especially for specialty coffees with obvious aroma and characteristics. Of course, because different origins and different varieties have different bean characteristics, the suitable roasting methods also differ.
People often compare coffee roasting to a technique that combines art and science, because in addition to continuously finding through experiments the roast level and time that best present coffee's flavor, the variables also include weather, the moisture content and quality of green coffee beans, the weather during roasting, the characteristics of the roasting machine, and so on. These factors all affect coffee flavor, so in addition to bringing out coffee's best flavor, consistency must also be maintained!
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The above content is compiled by CoffeeHunters, a coffee news website.
