Percieved Acidity

Have you ever heard someone say coffee is too acidic for them? Perhaps they mean they don't prefer that flavor. Maybe they mean it does something to them physically.   What is acidity? Is it even a factor we should consider? 

When we speak about acidity in coffee, we are not really speaking about the measurement of acid (pH). Instead, we are describing our perception of flavor. All coffee acidity lands somewhere between milk/saliva (6pH) and tomato juice or beer (4pH). Coffee is slightly more acidic than the saliva in your mouth. Weird, huh? I propose then, most of the variation we taste in acidity is due to the types of acids found rather than the concentration of them. We perceive a certain acid compound as lemon instead of lime or orange because lemon is higher on the pH scale than orange, so our brains immediately connect that flavor to its level of acidity. This is the difference between perceived acidity and measurable acidity.  


Previously, we talked about acid content linked to crop elevation. The range of variation between the highest-grown coffees and the lowest is narrow. Jeff Borack over at Angel's Cup measured the acidity in three coffees from different altitudes. The results are revealing:  

Sumatran coffee (low acidity) - 4.6pH

Panamanian coffee (medium acidity) - 4.5pH

Kenyan coffee (high acidity) - 4.3pH

Our experimenter said there is  "a small but direct correlation with flavor and pH." The Sumatran was "particularly flat," and the Kenyan variety used is one of the most acidic. Although there may be some correlations between taste and acidity, it is more important to recognize that the variation in numbers are small and the range of perception enormous. A small change in numbers here shows up as dramatic changes in flavor. 

Other factors that contribute to lower measured acidity are roast level and water brewing temperature. Cold brew has less acid because cold water extracts different compounds than hot water. Water is a solvent, whereas hot water is an aggressive solvent, reaching deeper and extracting more compounds. As coffee is roasted to darker levels, acids also diminish. We'll discuss that later. 

There is another factor of acidity to consider: does it cause stomach issues? The conclusion after Angel's Cup experiment is that "the difference in pH between very acidic and very flat coffees is probably not significant enough to cause or prevent stomach issues." Although there is evidence showing lower-grown coffee has less acid, it's negligible to claim it would be better or worse for anyone claiming it causes stomach irritation. More likely, the caffeine content activates the systems of the bowels and even increases the development of stomach acid. There could also be particular varieties of coffee that agree or disagree with people. More factors than acid content are responsible for acid reflux and other issues.

There are three identifiable factors that show measurably lower acid content: low altitude, darker roast, and cold water brewing. Our goals in choosing coffees and the way we tend to roast don't contribute to low acid. Pleasantly perceived acidity is important in coffee. It gives the cup life and vibrancy. Without it, a coffee would be described as dull, flat, or boring. We buy, roast, and brew to find a balance of clarity, sweetness, and pleasant acidity. 

Keep exploring, 
Daniel McCullers
Lead Roaster


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