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- pH, titratable acidity, and sourness are different
- Direct pH measurements in moka coffee
- What does titratable acidity add beyond pH?
- Which acids were measured in moka coffee?
- Does lower pH mean the moka will taste more sour?
- How water affects the acidity question
- How acidity relates to extraction and concentration
- Does roast determine moka pH?
Quick answer
Moka coffee does not have one fixed pH or one universal “acidity” value. In a 2024 experiment using a 6-cup Bialetti Moka Express with 25 g coffee and 250 g water, one light-specialty condition measured pH 4.87 ± 0.04 and 15.73 ± 1.8 mL NaOH diluted titratable acidity, while a reported dark condition measured pH 5.15 ± 0.01 and 10.57 ± 0.75 mL NaOH. pH, titratable acidity, quantified acids, and perceived sourness are related but not interchangeable.
pH, titratable acidity, and sourness are different
The word “acidity” can refer to several different things in coffee.
pH describes hydrogen-ion activity on a logarithmic scale. It does not measure the total amount of acid present.
Titratable acidity (TA) measures how much base is required to reach a defined titration endpoint under the study protocol. It captures acid and buffering behavior differently from pH.
A laboratory can also quantify individual organic acids or chlorogenic acids. Those concentrations are again different quantities.
Finally, perceived acidity or sourness is sensory. It can be statistically related to chemical measurements in a particular experiment without becoming another name for pH.
| Measure | Typical expression | What it measures | What it cannot establish alone |
|---|---|---|---|
| pH | pH units | Hydrogen-ion activity on a logarithmic scale. | Total acid quantity or how sour a person will perceive the cup. |
| Titratable acidity | Study-defined volume/concentration of titrant | Acid-buffering material under a defined titration protocol. | A pH value or a universal sensory score. |
| Quantified acids | For example mg/L | Concentration of specific chemical compounds or source-defined totals. | Overall sensory acidity without threshold/matrix context. |
| Perceived acidity / sourness | Sensory score or descriptor | Human perception under the study design. | A direct laboratory measurement of pH or total acids. |
Direct pH measurements in moka coffee
Santanatoglia and colleagues used a 6-cup Bialetti Moka Express, 25 g of ground coffee, and 250 g water, with three replicates per brewing method.
For the light specialty Ethiopia condition, the moka beverage measured pH 4.87 ± 0.04. A reported dark condition measured pH 5.15 ± 0.01.
Those two values come from the same study architecture yet differ across coffee/roast conditions. That alone is enough to reject the idea that “moka coffee has pH X” as a permanent specification.
The coffees themselves differ, not just the roast label. Treating 4.87 vs 5.15 as a controlled light-versus-dark roast experiment would therefore overstate what the comparison establishes.
| Coffee / roast condition | Moka recipe | Output | TDS | pH | Diluted titratable acidity | Context |
|---|---|---|---|---|---|---|
| Light specialty Ethiopia | 6-cup Bialetti; 25 g coffee; 250 g water | 202.4 ± 0.6 g | 2.61 ± 0.01% | 4.87 ± 0.04 | 15.73 ± 1.8 mL NaOH | Direct experimental condition; not a universal light-roast value. |
| Reported dark condition | 6-cup Bialetti; 25 g coffee; 250 g water | 206.8 ± 3.1 g | 2.72 ± 0.02% | 5.15 ± 0.01 | 10.57 ± 0.75 mL NaOH | Direct experimental condition; not a universal dark-roast value. |
The light condition had the lower pH and higher diluted TA of these two recovered moka rows. That relationship belongs to this experiment. It should not be rewritten as a rule that every light roast has lower pH or higher TA than every dark roast.
What does titratable acidity add beyond pH?
pH and TA respond to different aspects of the beverage chemistry.
Two liquids can have similar pH while differing in the amount of base required to titrate them, because buffering and the mixture of acids matter. Conversely, a change in pH does not tell you by itself how the full titratable-acid system changed.
That is why the 2024 paper reports both. In the two moka conditions shown above, pH moves from 4.87 to 5.15, while diluted TA moves from 15.73 to 10.57 mL NaOH.
Those values can be discussed together because they belong to the same experimental framework. They cannot be converted into each other.
Which acids were measured in moka coffee?
The 2024 experiment quantified organic acids and caffeoylquinic/chlorogenic-acid-related compounds alongside caffeine and the physicochemical measurements.
Those compound-level results matter because “acidity” is not one substance. Different acids and chlorogenic-acid-related compounds contribute different chemical information, and their sensory relevance depends on concentration, thresholds, and the beverage matrix.
Individual acid values can only be compared when the compound identity, units, and analytical basis match.
Does lower pH mean the moka will taste more sour?
Not by itself.
The Santanatoglia study found relationships among chemical measurements and sensory responses, but those relationships differed by coffee group. The authors report that pH and TA were influenced by caffeoylquinic acids in specialty coffees, while caffeoylquinic acids were more strongly associated with perceived sourness in the mainstream coffee condition. Organic-acid concentration also had predictive value for perceived acidity in the specialty coffees under the study’s statistical model.
That is useful evidence that chemistry and sensory perception are connected. It is not evidence that a household pH reading can diagnose why one moka tastes unpleasantly sour.
If your practical question is how to diagnose or reduce unwanted sourness, use the sour moka troubleshooting guide. That page covers grind, heat, coffee choice, flow behavior, and safe adjustment sequence.
How water affects the acidity question
Water chemistry can change extraction and sensory expression.
The 2024 experiment kept its water source controlled across brewing methods and reports a commercial water with 161 mg/L dry residue. That helps define the experimental context; it does not establish 161 mg/L as an ideal moka-water target.
For hardness, alkalinity, tap/filtered/bottled water, and scale implications, use the dedicated water for moka pot coffee guide.
How acidity relates to extraction and concentration
The same 2024 dataset also reports TDS and source-defined extraction yield for the moka conditions shown here. Those measurements help describe the experimental system but are not alternate acidity measurements.
For example, the light condition combined pH 4.87 ± 0.04, 2.61 ± 0.01% TDS, and 21.13 ± 0.90% extraction yield. Each number has a different denominator and interpretation.
The moka TDS and extraction-yield guide covers those measurements in detail. Greater extraction, higher concentration, and greater acidity describe different properties.
Does roast determine moka pH?
The two reported conditions show that pH can differ when coffee/roast condition changes, but they do not isolate roast as the only cause.
If the question is which coffee or roast to choose for flavor, use the best coffee for moka pot guide.