Roma tomatoes are not significantly less acidic than other common tomato varieties. Their pH typically falls in the same range as most tomatoes, between 4.2 and 4.6, and they contain similar concentrations of citric acid, the dominant acid in all tomato fruit. That said, the way Romas taste and how you use them can make acidity more or less noticeable, which is likely why this question comes up so often.
How Roma Acidity Compares to Other Varieties
Citric acid is the primary acid in virtually all tomatoes, with malic acid playing a secondary role. In lab measurements of mature fruit, a Roma-type tomato (the “Pizza” cultivar) showed a citrate concentration of about 30 millimoles per liter, while a standard slicing variety like Rutgers measured around 35 millimoles. That’s a modest difference, not enough to put Romas in a separate category. Another variety in the same study came in at 23 millimoles, lower than the Roma. The spread among individual tomato cultivars is wide, but it doesn’t break neatly along the line of “Roma vs. everything else.”
Where Romas do differ is in their flesh-to-juice ratio. They have thicker walls, fewer seeds, and less of the gel and liquid that carries dissolved acids. So when you bite into a Roma, you encounter less free juice, which can make it feel milder on your tongue even though the acid concentration in that juice is comparable to a beefsteak or globe tomato.
Why Romas Can Taste Less Sour
Perceived sourness in a tomato depends less on raw acid content and more on the balance between sugars and acids. Researchers call this the sugar-to-acid ratio, and it’s the single biggest driver of how sweet or tart a tomato tastes. Roma VF, one of the most widely grown Roma cultivars, actually showed relatively high titratable acidity in storage trials, but it also had higher sugar content. At harvest, its sugar-to-acid ratio was around 5.5, which climbed to about 11.4 after a month of ripening off the vine.
Fresh-market tomatoes (the ones bred for slicing and eating raw) generally have a higher sugar-to-acid ratio than processing types like Romas. That means a ripe beefsteak from a farmers’ market may actually taste sweeter and less acidic than a Roma, even if their pH values are nearly identical. The takeaway: variety matters, but ripeness and sugar content matter more for how sour a tomato tastes.
How Ripeness Changes Acidity
If you’re trying to minimize acidity, ripeness is the lever you have the most control over. Green tomatoes are more acidic than ripe ones. As a tomato ripens on the vine, citric acid breaks down and pH rises. Research on processing tomatoes (the category Romas belong to) found that leaving ripe fruit on the vine increased pH by 0.01 to 0.02 units per day, driven by a steady loss of citric acid. Over a few weeks, that adds up.
In practical terms, a deeply red, fully vine-ripened Roma will be less acidic than one picked at the “breaker” stage (just turning from green to pink) and ripened on your counter. If acid content matters to you, let them ripen as long as possible before picking, or buy them at peak ripeness and use them quickly.
What This Means for Home Canning
Many people search for low-acid tomatoes because they’re canning at home, and acidity is a safety issue. Tomatoes sit right at the border between high-acid and low-acid foods, and some varieties, including certain Romas, can drift above pH 4.6 when very ripe. Above that threshold, the risk of botulism in a sealed jar becomes real.
The National Center for Home Food Preservation recommends acidifying all canned tomatoes regardless of variety. The standard addition is two tablespoons of bottled lemon juice or half a teaspoon of citric acid per quart jar. For pints, cut those amounts in half. You can also use four tablespoons of 5% vinegar per quart, though it may affect flavor. A pinch of sugar can offset the added tartness. These steps are required even if you pressure-can rather than water-bath can, because the pressure processing guidelines for tomatoes were developed with acidification included.
One important detail: never can tomatoes harvested from dead or frost-killed vines. Frost damage disrupts normal acid levels and makes the fruit unpredictable for safe preservation.
Acid Reflux and Tomato Choices
If your real concern is heartburn rather than canning, the variety of tomato you choose matters less than how you prepare it. Tomato sauces, pastes, and cooked-down products concentrate the acid, which is one reason tomato sauce is a classic heartburn trigger. Harvard Health notes that a fresh tomato may not bother you even if tomato sauce does.
Romas are most commonly used for sauces and pastes, so ironically, the way people typically prepare them may cause more reflux than eating a raw slicing tomato in a salad. If you’re sensitive, try eating Romas fresh and raw rather than cooked into a concentrated sauce. Pairing tomatoes with less acidic ingredients, or reducing cooking time so the sauce doesn’t reduce as much, can also help.
Truly Lower-Acid Varieties
If you specifically need a tomato with lower acidity, certain heirloom and specialty varieties are bred for that trait. Yellow and orange tomatoes tend to have less citric acid than red ones, giving them a milder, sweeter flavor profile. Varieties like Yellow Pear, Lemon Boy, and some large yellow heirlooms consistently measure at the higher end of the pH scale (closer to 4.6 or above). These are genuinely less acidic, not just perceived as such because of sugar balance.
Roma tomatoes, by contrast, are standard red processing tomatoes. They’re excellent for thick sauces because of their meaty texture and low moisture, but “low acid” isn’t an accurate label for them. If you enjoy Romas and find them mild enough for your needs, there’s no reason to switch. Just don’t assume they’re safe to can without acidification, and don’t count on them being gentler on reflux than any other red tomato variety.