Ask any hipster and they will tell you Dark Roasts are out, Light Roasts are in. Light Roasts are complex, refined, have good acidity. Dark Roasts, well, Dark Roasts just aren’t cool anymore. I mean, Starbucks over roasts their coffee and we all know that Starbucks is not cool. Light Roasts are Third Wave and Third Wave is sophisticated and distinctive.
Along with the trend towards Light Roast is a new found appreciation for Acidity. Professional coffee cuppers use acidity as a way to evaluate crop quality. Acidity is what gives a coffee its brightness, its liveliness. In years past, acidity would be expressed in simple terms: good acidity, fair acidity or poor acidity. Good Acidity can be likened to carbonation in a soda, without it the beverage is flat. But acidity can also reveal defects in a coffee, too. Not all acidity is good, and a trained cupper would be able to determine problems in a coffee based on the type of acidity present.
Of the plus 1000 different chemical compounds identified in coffee about 50 or so are acids. Many of these are volatile compounds and diminish in roasting. Light Roasts tend to emphasize these acidic compounds and bring them to the fore. This is why coffee tasters in the import/export trade roast their samples very light to expose these particular defects. This evaluative roast style is known as a trade roast. Trade Cupping or Defect Cupping is a necessary skill for any coffee professional but one would be remiss into assuming that this is some higher form of taste. Trade Roast is an evaluative model for traders, these roasts are meant to be tasted, not necessarily consumed. At least not in any quantity. Coffee cuppers slurp and spit out the coffee, thus avoiding both the caffeine and the effects this acid has on one’s stomach.
Coffee’s acidity comes from a combination of its inherent acidity along with the coffee bean’s production cycle: growing, processing, and roasting. Coffee’s inherent acidity is chlorogenic acid, which, along with caffeine, is part of the plant’s defense against insects. Chlorogenic acid breaks down in roasting into quinic and caffetic acids depending on the amount of time the coffee is exposed to heat. Roasting machines with poor heat transference produce more of these acids resulting in a tinny, bitter taste. Too much time at temperature results in excessive amounts of quinic acitity. This can happen also if brewed coffee is allowed to sit on a burner, the combination of heat, water and the organic compounds result in a distinct quinine flavor that is most unpleasant.
One of the more desired acids is Citric Acid. Citric acid is a pleasant tart flavor that brings to mind lemons of fresh oranges. This indicates that the coffee has been properly prepared and is fresh. However, too much of this acid is usually associated with early crop coffee and indicates new harvest making the experience more “grassy” than citric. Experienced cuppers will tend to opt away from these lots and wait for later deliveries, giving the coffee a chance to mature. If the flavor persists it is an indication that too many immature green coffee cherries are making their way through. I have notice in my own travels that first time cuppers often take a liking to this taste largely due to the fact that it is the first taste that they learn to identify. This acid is less volatile than other acids and so cannot be “roasted” out. Its easy to identify, since most of us are familiar with citric acid from citrus fruits.
Another common acid is malic. I have noticed an increase in this acid over the years as sun grown coffee has become more commonplace. It is due to excessive day/night time temperature deviations and reflects poor respiration of the coffee tree. Shaded coffee farms have more stable temperatures which benefits the plants night time expiration. This acid has a distinct tart apple peel taste that lingers on the palette.
Acetic acids come about from the just pulped coffee beans sitting in the fermentation tank. The time in the fermentation tank is critical since the enzymes break down the silver skin on the coffee beans. Too much time, or if the temperature is too high, however, results in a vinegar like taste. Sometimes this is confused with wineyness.
Most of these acids will decrease in roasting, aside from the Quinic, but as more roasters opt for a Light Roast these acids come to define the coffee’s flavor. I hear a lot of pontificating about this coffee’s blueberry taste, or apricot, plum, or jammy, as if they are talking about their favorite wine. As a result, many growers are purposely trying to increase the coffee’s acidity by various preparation techniques that increase acidity. This is why there is a return to dry, or natural process drying of the coffee cherries; or leaving the pulped beans linger in the mucilage and calling it “honey processed.”
While these coffees will stand out on a cupping table, they are not appropriate for the kitchen table. The one thing that these acids have in common is that they invariably lead to a soury cup. You can mask some of these flavors by increasing the brew temperature, but as the cup cools so returns the sour. What’s more, these acids tend affect a person’s body, resulting in an edgy, uncomfortable feeling. Some assume it is caffeine, but it is these acids.
Recently I have had customers come in and complain about drinking coffee that upsets their stomach. Some have gone off coffee because of this experience. Often they have gone into some new, hip, coffee roaster and are “educated” about “real” coffee flavor. Too many of these roasters know only acidity when it comes to coffee flavor. Much like the person just discovering craft beer only recognizing hops. To these folks acidity IS flavor, therefore, more acidity equals more flavor. There is more to coffee’s flavor just acidity. A true roastmaster will fully develop the roast so that there is a balance of all the desirable attributes in a given coffee.
The Coffee Heretic 