Why are the expensive, high-quality coffees on the market acidic? How have Blue Mountain and Geisha coffees evolved? What determines the acidity and bitterness of coffee?

Why Is Most Coffee Sour Today? A Journey from Bitter to Bright

I remember last year when a well-known blogger visited a coffee shop to experience expensive pour-over coffee, only to make a pained expression after tasting sour coffee for the first time. Suddenly, discussions about sour coffee erupted everywhere. Among these, one statement sparked heated debate: "Most coffee today is sour!"

It's undeniable that in today's specialty coffee market, sour coffee occupies a large proportion. Walk into any coffee shop and order a pour-over coffee, and chances are you'll be served sour coffee. This leaves many friends who still perceive coffee as primarily bitter quite confused. While there are indeed coffees dominated by bitterness, these only represent a very small portion. Even espresso, traditionally known for its bitterness, has begun moving toward sour flavors, developing SOE (Single Origin Espresso) that emphasizes regional characteristics. As friends who have read FrontStreet Coffee's articles know, coffee's sourness and bitterness are mainly determined by roast level. The lighter the roast, the sourer the coffee; the darker the roast, the bitterer the coffee. This means coffee roasting has shifted from dark to light over time. So the question arises: why is most coffee today lightly roasted and sour?

The Evolution of Coffee Flavor Profiles

Why is most coffee sour today? Many friends might think FrontStreet Coffee is about to say again: "Since the concept of specialty coffee was released..." Very well, you guessed correctly! Although FrontStreet Coffee wants to say this, the shift in coffee flavor from bitter to sour wasn't solely driven by Ms. Erna Knutsen's specialty coffee concept! This phenomenon was also driven by: changes in coffee cultivation at origins, evolving roasting knowledge among coffee roasters, changes in mainstream coffee extraction methods, shifting consumer taste preferences, and a series of other factors! Through the combined effect of these factors, coffee gradually transformed from bitter to sour. So today, FrontStreet Coffee will discuss these factors to share how coffee flavors evolved step by step from uniform bitterness to a vibrant spectrum of sourness!

The Historical Dominance of Dark Roast

In the article "How Ethiopians Drink Coffee," we learn that before modern roasting machines appeared, people could only cook coffee beans using kitchen utensils to stir-fry them. However, no matter how they stir-fried, iron pans made it difficult to heat coffee beans evenly. Therefore, to avoid undercooking, people at that time would roast coffee beans until they reached a nearly carbonized black color. As long as they reached this degree, there would be no undercooked beans. At this level of roasting, the oils in the coffee beans would emerge early to the surface due to excessive structural expansion. Thus, black beans coated with a layer of oil gained a special alias—"black gold."

According to modern roasting theory, this type of coffee is in a state after the second crack has ended. So we can imagine how intense its bitterness must be! Although bitter, the coffee's aroma was incredibly rich. Gradually, this type of coffee gained its audience, and people's initial impression of coffee flavor took shape. As times progressed, coffee beans gained their own dedicated roasting machines. First came the birth of drum roasters, then semi-hot air drum roasters. Although roasting conditions improved, the concept of dark roast had been deeply ingrained over several hundred years, so roasting coffee until the second crack remained the mainstream understanding at that time.

The Second Wave and Deep Roast Dominance

Additionally, the mainstream extraction methods of that time and the quality of coffee beans were important factors that allowed dark roast coffee to become mainstream. In the early twentieth century, it was precisely when the second wave of coffee was sweeping the globe. Through Italian immigration, espresso spread widely throughout the world. What spread abroad was not only the preparation method of espresso but also the concept of using dark roast coffee beans. Furthermore, at that time, coffee beans were mainly exported as bulk commodities, with generally poor quality, many defects, and complex flavors that needed the burnt aroma and bitterness brought out by deep roasting to mask these negative flavors. Therefore, under the combined effect of these two factors, dark roast coffee remained the mainstream of the era. It was precisely because of this that Blue Mountain coffee was able to become king in that era with its excellent quality!

The Turning Point: Quality Recognition

Jamaica's coffee industry began as early as around 1750 but remained in a lukewarm state. Until 1950, Jamaica established the Coffee Industry Board, which was mainly responsible for coordinating the management of Blue Mountain coffee's cultivation, processing, and grading procedures. Soon, the quality of Blue Mountain coffee improved dramatically. At that time, the flavor profile of deep roast coffee outside of Blue Mountain mostly showed intense and stimulating burnt bitterness. Only Blue Mountain coffee, although also deeply roasted, was bitter without being burnt, rich without being harsh, with an extremely clean mouthfeel. In this way, Blue Mountain coffee ascended to the throne of coffee emperor through its quality, combined with brilliant marketing by the Japanese. It was precisely this event that made people begin to realize the importance of quality, and thus coffee reached a turning point.

The Third Wave: The Rise of Light Roast

In 1974, Ms. Erna Knutsen introduced the concept of specialty coffee, emphasizing the unique flavors of regional origins to make people realize that quality management in the upstream coffee supply chain was also very important. In the following years, the quality of coffee beans improved significantly, allowing coffee roasters to re-examine their roasting approaches! Previously, it was the inconsistent quality of coffee beans that greatly limited roasting. Even before the concept of specialty coffee was proposed, innovative roasters had already attempted to reduce the roast level of coffee beans to make them less deep, less bitter. But they quickly discovered that due to inconsistent bean quality, if roasting was stopped before the second crack, many undercooked beans would be mixed in, causing the coffee to taste astringent. Nowadays, this limitation has been broken, and coffee beans will soon usher in a completely new roasting direction.

The first to break this situation was the European region of Norway. Because they had been exposed to coffee for a relatively short time, they hadn't been brainwashed by too many concepts of bitter coffee. Thus, the so-called "rebellious" and non-mainstream Nordic roast was born at that time. The "light" roast of that time would actually be considered a medium roast today, but at that time, it was already very, very light. In the understanding of roasters from other countries at that time, coffee roasted to this degree was simply undercooked, tasting sour, astringent, and very sharp! However, after tasting this alternative light roast coffee, guess what happened!

Everyone was speechless after tasting! Rich berry flavors burst in the mouth, with lively sourness and a sweet-tart taste like juice. This was completely different from the sharp, astringent, dull, and hard-to-drink light roast coffee in people's impressions. By early 2003, roasters deeply inspired by Nordic light roast published the "Three Waves Evolution Theory of Specialty Coffee" at the Specialty Coffee Association of America (SCAA), which marked the beginning of the third wave of coffee's specialization into specialty coffee! This paper mainly explained one thing: how important appropriate roasting is to better showcase coffee's own characteristics.

The American Light Roast Revolution

The publication of this paper sparked a completely new coffee roasting trend in America! Many well-known American coffee shops率先 adopted and launched medium-light roast coffees. Although their roasts weren't as extreme as Nordic light roasts, coffee was no longer uniformly bitter; coffee roasting began to diversify. The reason Geisha coffee was able to become famous in 2004, besides the support of its origin and bean characteristics, was also greatly helped by the appropriate roast level! After all, before Geisha became famous, there were already many coffees that could emit floral and fruit aromas, but under deep roasting, these flavors were almost completely masked, with very little aroma that could be captured by taste buds. Therefore, in 2004, Geisha was able to astonish everyone and reach an unprecedented height.

The Era of Sour Coffee

At this point, the era of sour coffee officially began. To better showcase the beans' own characteristics, people mostly adopted light roasting to "cook" them. The best way to reflect these "special existences" was the single-origin coffee preparation method, among which pour-over coffee stood out with its advantages of being lightweight, fast, and clean. Soon, the convenient pour-over coffee began to gain popularity. Light roast coffee brewed through pour-over not only had full flavors but also very rich layers. This lowered the barrier to drinking coffee, allowing people who couldn't handle bitterness to more easily accept coffee.

As the culture and atmosphere of specialty coffee became richer and richer, more and more people were influenced. Thus, after 2015, specialty coffee shops focused on single-origin coffee began to grow at an explosive rate. In these coffee shops, sour coffee occupied the vast majority, which would create the illusion for many outsiders who didn't understand coffee that sour coffee was everywhere! Of course, although most coffee today is sour, we also can't forget that there are still coffees like Blue Mountain, Mandheling, and Brazilian coffee on the market that maintain tradition, using medium-dark roasts to allow everyone to taste the classic flavors that have been passed down for hundreds of years.

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