We recently received a few inquiries asking if we had any low acid coffees, so we decided to test the pH of our five coffee profiles using a digital pH meter! Like many things with coffee, the more we found out, the more excited we became, and the more questions we had!
It turns out that we do not have any coffees that can be considered “low acid”, and that the pH of the 5 roast profiles tended to be affected by roast level and country of origin. Here are the 5 coffees (lower pH = higher acidity):
|Profile||Roast Level||End Temp.||Country||pH|
The Extra Bold (our darkest roast) and the Classic (medium roast from Brazil) had the same pH - they both had the lowest acidity in the group. Even though the Classic is roasted lighter than the Bold, it was from Brazil, and we believe this is the factor that tipped the scale towards lower acidity.
We are inspired to test more of our coffee profiles from different countries in months to come. Keep on reading below to learn more about measurable and perceived acidity!
Much of the research we read about coffee & acidity/stomach health pointed to conflicting results: one study would conclude that coffee definitely caused an increase in stomach acid, and another study would conclude the opposite. What is clear is that there doesn’t seem to be an overarching general recommendation for all people. So, if you’re looking for a lower acid coffee, it’s best to work with a medical professional and try out different things: darker roasts, different coffee origins, or decaffeinated coffees.
For some context on this acid party, let’s draw the distinction between measurable acidity (pH) & perceived acidity. The former is objectively measurable and quantifiable, while the latter is not.
The pH scale measures how acidic or basic a substance is. On this scale, 7 is neutral: substances that rate lower than 7 are considered acidic, and those that rate higher than 7 are considered basic. Coffee generally falls between 4.5 and 5, though “low acid” coffees can reach up to 6. For context, orange juice is around 4, and both tea and carbonated water tend to be between 5 and 5.5.
And for those rabbit-hole lovers out there, for even more context, the pH scale happens to be a logarithmic scale, as opposed to a linear scale. In a linear scale, each number change represents a static unit - for example, in a linear scale, if I have 4 apples and you have 5 apples, you have one more apple than me. Each change on the scale is represented by 1.
For a logarithmic scale, in contrast, the change between numbers represents a ten-fold increase or decrease. So, on a logarithmic scale representing our apples, if I had 4 apples, and you have 5 apples, you actually have 4 x 10 more apples than me!
Just putting this here to illustrate that even a small difference in pH between coffees represents a much larger number: a coffee with a pH of 5 is 80% higher in acid than a coffee with a pH of 5.8.
Using our definition of measurable acidity above, we can quantitatively say that if a substance has a pH of lower than 7, it is acidic. Having a quantitative measurement is helpful for obtaining an objective comparison.
Our taste buds definitely have opinions on which beverages seem more acidic to us, but unfortunately, we can’t definitively measure the acidity of orange juice or coffee just by tasting it - our tongues can only give us a subjective, qualitative analysis.
Also, Perceived acidity is especially prized in Specialty Coffee, and you’ll often hear it tossed around as just “acidity”. The perceived acidity of a coffee is its fruit-like character: juicy coffees with a clean finish. Just remember, a coffee’s perceived acidity is not the same thing as its pH.
Water & pH
Before we even started making the coffee, we looked at the water we were going to use. Did you know that the water you use will affect the pH of your coffee? We did a quick test of 4 different kinds of water:
Unfiltered NYC tap water - 6.72
Filtered NYC tap water - 6.66
Poland Spring bottled spring water - 6.48
*Distilled water - 5.58
We found it interesting that our filtered water is less acidic than unfiltered. We always use our filtered water to brew coffee, so this is the water we used for the coffees we tested below. It’s just a simple carbon in-line filter to clean up odor and taste.
*We put distilled water there for a comparative basis, but you should never brew coffee with distilled water - it will remove too many coffee solubles from the grounds and result in an incredibly bitter taste.
Here are the pH results of the 5 Driftaway coffee profiles. We added roast level, end temp (the highest temperature reached in the roaster), and country for context.
|Roast Level &
|Bold||Medium-Dark: 437°F||Costa Rica||5.00|
|Extra Bold||Dark: 450°F||Peru||5.05|
As we said above, there are a lot of other variables to explore, and we’re inspired to track those other variables in the months to come. For example, in addition to the 5 coffees above, we also tested different varieties of coffee at the same light roast:
|Colombia & Castillo||4.73|