Search "is cold brew less acidic" and one number keeps coming up: 67. Cold brew is "67% less acidic." Sometimes "up to 67% less acid." It is on product pages, café menus and blog posts, repeated often enough that it reads like settled fact.
So I went looking for where the number comes from, and I read a peer-reviewed study that directly compares cold and hot brew acidity, end to end. This post is what I found. The short version is that cold brew and hot coffee differ in acidity in a real, measurable way, but not the way the 67% figure implies, and the math behind pH makes the figure very hard to square with the published data.
One thing up front, because it matters for everything below: Bare Brew has not measured the pH or titratable acidity of our own can. So this post contains no acidity number for our product. If you ever see one attributed to us, it did not come from a measurement.
Where "67% less acidic" shows up
The figure is most closely tied to home cold brew systems. Retail product copy for the Toddy Cold Brew System, for example, states that the cold-brew method "creates up to 67% less acid" (Mill Coffee & Tea product listing, read September 2026). From there it has been copied into articles and product descriptions, often with the "up to" dropped.
I looked for the study behind it. I could not find one published in a peer-reviewed journal that measures a 67% reduction in acidity between hot and cold brew made from the same coffee. That does not prove no internal test ever happened. It means that if one did, it has not been published in a form anyone can check, and a number nobody can check should not be printed on a can.
What the peer-reviewed data actually measured
The study is Rao and Fuller, "Acidity and Antioxidant Activity of Cold Brew Coffee," Scientific Reports 8:16030 (2018), doi:10.1038/s41598-018-34392-w. It is open access. Here is the setup, because the details decide what the results can and cannot tell you:
- Coffees: six light roasts, pre-ground, bought from commercial vendors: Brazil, Colombia, Mexico, Myanmar, and two regions of Ethiopia.
- Cold brew method: 35 g of coffee in 350 mL of filtered water, steeped 7 hours at room temperature (21 to 25 °C), then paper-filtered.
- Hot brew method: the same coffee-to-water ratio, boiling water poured over grounds in a French press, 6 minutes, then paper-filtered.
- Measured: pH, total titratable acidity (titrated to pH 6 and pH 8), three chlorogenic acid isomers, and antioxidant activity.
And here is what they found:
| Measure | Hot brew | Cold brew | What the authors concluded |
|---|---|---|---|
| pH range across the six coffees | 4.85 to 5.10 | 4.96 to 5.13 | Comparable. Brewing temperature "did not result in distinguishable pH values." |
| Total titratable acidity | Higher | Lower in all six coffees | Hot water pulls out more acids that pH does not register. |
| Antioxidant activity | Higher | Lower | Hot brew extracted more antioxidant compounds. |
Source: Rao & Fuller, Scientific Reports, 2018. Ranges are the lowest and highest sample means reported in the paper.
So there are two honest statements about cold brew acidity, and they point in different directions:
- By pH, cold brew and hot coffee were effectively the same in this study.
- By total titratable acidity, cold brew was lower for every coffee tested.
Both are true at once, and the difference between them is the whole story.
pH vs. titratable acidity, in plain English
pH measures the hydrogen ions that are free in the liquid at that moment. Titratable acidity measures all the acid that can be neutralized, including acid molecules that have not released their hydrogen yet. Coffee contains dozens of acids (citric, malic, quinic, chlorogenic and more), many of them weak acids that mostly hold onto their protons. That is why the two numbers can move independently. The paper found little correlation between pH and titratable acidity in either brew, echoing earlier work by Gloess and colleagues (2013).
Which one matters to you depends on the question. Taste researchers the paper cites found perceived sourness tracks titratable acidity better than pH. The "less acidic" health claim, meanwhile, usually implies pH. The 67% figure never says which it means, which is part of why it survives.
The math: what would 67% less acidic even require?
This is where the number falls apart if you read it as pH.
pH is logarithmic. Each whole pH unit is a tenfold change in hydrogen-ion concentration. So "67% less acidic," read as 67% fewer free hydrogen ions, means the cold brew has one-third the hydrogen ions of the hot brew. The pH shift that requires is:
log10(1 ÷ 0.33) ≈ 0.48 pH units.
In other words, if hot coffee sits at pH 4.85, a cold brew made from the same beans would need to come in around 5.33 to be 67% less acidic.
Now compare that to the data. The entire spread of every sample mean in the study, all six coffees, both methods, lowest to highest, was 4.85 to 5.13. That is 0.28 pH units. The 67% claim needs a gap of about 0.48 units between two brews of the same coffee, which is about 1.7 times the full range the study observed across different origins and methods combined. And no cold brew sample in the paper reached 5.33. The highest was 5.13.
| Claimed reduction in free hydrogen ions | pH increase required | Seen in Rao & Fuller for the same coffee? |
|---|---|---|
| 67% | ~0.48 | No. Entire study range was 0.28. |
| 50% | ~0.30 | No. Also wider than the entire study range. |
| 25% | ~0.12 | Authors reported no distinguishable pH difference by method. |
Calculation: pH increase = log10(1 ÷ (1 − reduction)). Our arithmetic, applied to the paper's published ranges.
Could the 67% mean titratable acidity instead? Possibly. Cold brew did come in lower on that measure for every coffee in the study. But the size of the gap varied by coffee and by titration endpoint, and I am not going to boil it down into a new headline percentage, because turning a variable result into one tidy number is exactly how 67% got here in the first place.
What this study cannot tell you
Being straight about the limits matters as much as the findings:
- Light roasts only. Roast level changes acid chemistry. The study did not test medium or dark roasts.
- One cold brew recipe. Seven hours at room temperature. Commercial cold brew is made in many different ways, with different ratios, times, temperatures and filtration.
- No Honduran coffee. Origin affected results within the study, so results for other origins are inference, not data.
- No symptoms were measured. The paper measured chemistry in a lab, not how anyone's body responded. The authors note that claims about cold brew and digestive comfort are common and that more research is needed.
That last point deserves its own line. If coffee bothers your stomach or you deal with reflux, a brewing method is not a treatment and a marketing percentage is not medical advice. That conversation belongs with your doctor.
The trade-off nobody puts on the can
The same study that found lower titratable acidity in cold brew also found lower antioxidant activity. Hot water extracted more of the compounds behind both. The authors suggest the two findings may be linked: some of the extra acids hot water pulls out may be the same compounds responsible for the higher antioxidant readings.
I am not telling you that to argue for hot coffee or against cold brew. I am telling you because a brand that only quotes the half of a study that flatters it is doing the same thing as the 67% number, just more quietly.
What is actually on our can
Since this post is about printing only what can be checked, here is everything we state about Bare Brew cold brew, all of it from the can label and our product listing:
- 2 ingredients: Honduran Arabica coffee and water
- 320mg caffeine per 12 fl oz can
- 0g sugar, 20 calories, 5g total carbohydrate
- 15mg sodium, 350mg potassium
- Medium to medium-dark roast, slow-steeped
What is not on that list: an acidity percentage, a pH value, or a claim about your stomach. We have not measured our can's pH or titratable acidity, and the peer-reviewed study above used different beans, a different roast and a different recipe, so borrowing its numbers would be guessing. When we have our own measurement, done properly and documented, we will publish the method alongside the number.
If you want to go deeper on reading labels, I wrote about how the FDA's 0.49g rounding rule shapes "zero sugar" claims and about what the research says about caffeine and blood sugar at 320mg. For side-by-side label numbers across the category, see our label-transcribed cold brew caffeine data for 18 products and the zero sugar cold brew buyer's guide. And if you brew at home, this guide covers the variables (grind, time, temperature) that drive the acid differences described above.
Founder's Take
A number like 67% travels because it is easy to repeat. It gets copied from a product page into an article, from an article into a caption, and somewhere along the way the "up to" falls off and the source stops travelling with it at all. That is how a percentage nobody can trace ends up sitting across a whole category looking like a fact.
The easy move for a cold brew brand is to swap in a softer version, "significantly less acidic" or "up to" something. That is not better, it is the same claim with the number hidden. We do not print an acidity claim in any form, because we have not measured it. What I can do is show you the research that exists, what it measured, and where the popular claim runs out of road. If that makes our marketing a little less exciting than a big round percentage, I am fine with that. The whole point of a 2-ingredient can is that there is nothing on it you have to take on faith.
If you want to see what that looks like in practice, the label is the pitch: Honduran Arabica, water, 320mg caffeine, 0g sugar. Cans run $6.00 each in a 4-pack, $5.50 in a 6-pack and $4.50 in a 12-pack, with $8.99 flat shipping on every US order.
— Miles, founder, Bare Brew
FAQ
Is cold brew less acidic than hot coffee?
It depends on the measure. In Rao and Fuller's 2018 study in Scientific Reports, cold brew and hot coffee had comparable pH (4.85 to 5.13 across all samples), but cold brew had lower total titratable acidity for all six coffees tested.
Where does the "67% less acidic" claim come from?
It is widely repeated in marketing for home cold brew systems and cold brew products. We could not find a peer-reviewed study that measured a 67% acidity reduction between hot and cold brew made from the same coffee.
What is the pH of cold brew coffee?
In Rao and Fuller (2018), cold brew samples ranged from pH 4.96 to 5.13 and hot brew samples from 4.85 to 5.10. Those were light roasts brewed with one recipe; other beans, roasts and methods will differ.
Does Bare Brew publish an acidity number?
No. We have not measured the pH or titratable acidity of our can, so we do not state one. Our label lists 2 ingredients, 320mg caffeine, 0g sugar, 20 calories and 5g carbohydrate per 12 fl oz can.
Is cold brew better for acid reflux?
The study measured chemistry, not symptoms, and the authors say more research is needed. If coffee causes you reflux or stomach discomfort, talk to your doctor.
Sources: Rao, N.Z. & Fuller, M. "Acidity and Antioxidant Activity of Cold Brew Coffee." Scientific Reports 8, 16030 (2018). Gloess, A.N. et al. "Comparison of nine common coffee extraction methods." Eur. Food Res. Technol. 236, 607–627 (2013), as cited in Rao & Fuller. Toddy product copy as published by Mill Coffee & Tea, read September 25, 2026. Bare Brew product facts from the can label and Shopify product listing.
