Coffee Acidity: the Science & the Experience

Posted on January 25, 2013

When you hear the word “acidity,” you might think sour, tangy, bitter, sharp. But the term is used in at least three ways in the coffee world:


1.  Coffee enthusiasts & aficionados identify acidity as the dry, bright & sparkling sensation that sets a high-quality, high-grown coffee apart from a mundane, lower-grown coffee. Admittedly, this is the rather snooty way of looking at the issue, though it is true that many highly-prized coffees are grown at high elevation & are characterized by their bright, nuanced qualities.


2.  On the scientific side, acidity is something to be measured on the pH scale, which uses 7.0 as an indicator of neutrality, numbers under 7 as more acidic & numbers above 7 as lower-acid (or basic). Lemon juice registers at about 2.0; milk at 6.5. A typical higher-acid breakfast blend coffee might land somewhere around 4.7. (Note that "black coffee" is marked on the scale below as a 5; this is an average & certainly not universal.)    


3.  Many other coffee drinkers see acidity as something that makes their tummy hurt—an unpleasant, astringent quality that disrupts their enjoyment of their daily brew.


More & more lately, many coffee drinkers are starting to look for “low-acid” coffees, usually because of a doctor’s recommendation or simply a yucky feeling in their stomach after drinking their daily cup (or ten). And while we could get out the pH strips from the old science kit & start testing every cup, the truth is that it’s more complicated than that. pH level doesn’t always equate directly to a person’s experience of a particular coffee. Luckily, though, there are other ways to identify coffees that are low-acid.


“Treating the beans or dumping antacid compounds into them, or dark roasting them to the limit of possibility,” says Kenneth Davids of Coffee Review, “is not nearly as effective in producing a fine flavorful low-acid cup as finding a lower grown coffee with naturally low acidity that has been picked & processed with care & brought to a moderate roast that develops the sugars without burning them.” Here at HG, we never add anything, instead relying on a naturally-lower-acid green bean & a medium-to-dark roast level that compliments origin. Dark roasting reduces acidity, but it can also mask origin profiles—so it’s important to consider the origin qualities of the green beans before roasting the heck out of them. Some coffees with robust, burly flavor qualities like dark chocolate & earthiness can hold up to a darker roast & still let those qualities shine through. But more delicate qualities, like citrus, berry, or herbal notes, are likely to disappear behind the qualities of the roast itself.


At risk of contradicting what I said above about pH not always equating to physical experience of a coffee, I should share that in some of his research, Davids was surprised to find that tasters’ perceptions of acidity (tanginess or brightness on the palate) were actually quite good at tracking actual pH levels of the coffees. So if you’re on the quest for a low-acid option, try a few varieties & trust your senses. Your experience is the most important thing!


Cold-brewing extracts considerably less of everything from coffees, including acids, so that’s definitely an option. Many enjoy the sweet smoothness of cold brew – which joins our Coffee Bar menu during the warmer months. You can buy your own cold brew system as well; we recommend the Filtron. Choosing a milk-based espresso drink like a latte or cappuccino is another great way to enjoy a little coffee without irritating a sensitive stomach.


Higher Grounds’ lowest-acid coffees are dark roast Sumatran (which fits the lower-acid-by-origin AND the dark roast bill), dark roast Peruvian Pangoa, dark roast Mexican Yachil, & medium-dark roast Bolivian Caranavi.



[Thanks to Kenneth Davids of Coffee Review for much of this information.]


Categories: acidity,  brewing,  coffee bar,  Higher Grounds,  low acid coffee,  quality coffee,  roastery,  roasting,  specialty coffee,


I would like to know if these brands of coffee are available in Australia. I have painful reactons to drinking coffee and even decafe due to the acid content. Also I would like to know why so many sites make us read and copy what you have called captcha?? I find it irritating and in some cases downright annoying when it is put in such a way that makes it hard to decipher. Not in this case but others I have encountered.
Comment by Angela Campbell - posted on 04/29/2015 08:18 pm
Thank you so much for the science. My interest in the pH is as a baker in the habit of modifying recipes. Sometimes loft of a bake good is directly caused by an acid/base reaction. While there are many variations that can be made to a recipe it seems it takes a bit more care to swap coffee for lemon juice or vice versa than I expected. Now that I have a better ideal of coffee acidity range, I can play more with favorite recipes without damaging my raise once I find my tester strips. I can also experiment with different roasts to see how delicate my acid/base ratio is for relevant cases. For those with sensitivities, most acid/base raise methods should neutralize for the most part by the time baking is done, though I have never taken a ph test strip to my muffins to check that.
Comment by nox_lumen - posted on 04/24/2015 09:57 am
Hi again - Question please - Which would you recommend for less acidity stomach results? - they say the darker roasts are best for that, but I notice your Peruvian Pangoa says "very low acid" and that one is Medium Dark Roast. Would you recommend that one or the Sumatran Permata Gayo, the darker roast? Thanks!
Comment by Shelley - posted on 03/16/2015 03:15 pm
There have been many articles & studies regarding the acidity or PH value of coffee & the effects of coffee consumption on ones health.Some are in regards to digestion, others more notably are in regards to the effects of coffee on tooth decay.In regards tooth decay the damage is being done just prior to or the very beginning of the digestive process.Unfortunately in many of these studies there is little mention of whether the results of the study were from the consumption of Black coffee ( irregardless of its PH value) or coffee that has been made with a sizable percentage of hot milk added.I would be interested to know the difference in acid levels of prepared coffee both black & also coffee made with hot milk.To me, without question coffee made with 1/3 hot milk is considerably sweeter & therefore obviously more acidic than black coffee.I have read one book that suggests that coffee is an alkaline drink before digestion but has an acidic effect on ones blood after digestion which would therefore rearly make it more of an acid drink.To finnish, whether or not the beverage is beneficial to ones health i could only imagine it would depend on the individuals own metabalism & likes or dislikes.
Comment by Joe - posted on 02/22/2015 09:03 am
Is it fair, or accurate, to treat coffee as acidic? Isn't the acid in coffee organic, and as with citrus acids, a net pH increaser in the body? Again, can we call a food acidic based on its pre-ingested pH or should we use the more relevant net effects once metabolized? The following link takes you to a table describing just that. Thoughts? Refer to chart within article:
Comment by Anthony Ricci - posted on 02/13/2015 12:59 pm
Many of us avoid acidic coffees not because of stomach issues, but because we think they taste bad. I would describe just about every acidic coffee I've tasted (quite a few) as bordering on rancid, rather than "bright." Thank you for your explanation, partly for the science, and partly for explaining why some of the coffeehouses that seem to pride themselves on their coffee only serve rancid-tasting ones.
Comment by Andrea Bilger - posted on 02/09/2015 02:52 pm
Thank you for this I am glad that someone is telling the truth about "low acid" coffee. But I wanted to further your findings with some of the latest research we have been doing. As you stated coffee is less acidic than the stomach (pH5 vs pH1-3). Therefore if you drink coffee it will change the pH in your stomach to actually be less acidic. So we should be asking what else causes people to still have acid secretion and discomfort when drinking coffee if not for the pH? There is an immense amount of research looking into compounds within the beverage (like N-methylpyridinium) that causes irritation to the stomach and is responsible for the added gastric secretions. There are, however, some really cool roasting processes that help eliminate these compounds as well as protect the gastric lining against irritation. These could be a solution to the irritant issue with coffee rather than a mere band-aid in antacids or other remedies. Thanks again for the good read and glad I can share some thoughts.
Comment by Coffee Scientist - posted on 01/21/2015 07:20 pm
As a bit of a science geek, I really appreciate your complete and understandable explaination of this fairly complex subject.
Comment by Jen - posted on 01/28/2013 09:53 am

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