Acidic fruits are fruits with a pH below 4.6, which includes most of the fruits you eat every day. The pH scale runs from 0 (most acidic) to 14 (most alkaline), with 7 being neutral. Lemons and limes sit at the extreme end with pH values as low as 2.0, while tomatoes hover near the cutoff around 4.0 to 4.6. Understanding which fruits are acidic matters for digestive comfort, dental health, and even home food preservation.
How the pH Scale Applies to Fruit
The pH scale is logarithmic, meaning each whole number represents a tenfold difference in acidity. A lemon at pH 2.0 is ten times more acidic than a grapefruit at pH 3.0, and a hundred times more acidic than a tomato at pH 4.0. Nearly all fresh fruits fall somewhere between 2.0 and 5.0, placing them firmly on the acidic side. The natural acids responsible for this, primarily citric acid, malic acid, and tartaric acid, are what give fruit its tart or sour flavor.
The Most Acidic Fruits
Citrus fruits dominate the high-acidity category. Limes have the lowest pH of any common fruit, ranging from 2.0 to 2.8. Lemons are nearly identical at 2.0 to 2.6. Grapefruits come in at 3.0 to 3.75, and oranges are milder at 3.3 to 4.3, depending on the variety and where they were grown (Florida oranges tend to be slightly less acidic than California oranges).
Plenty of non-citrus fruits are highly acidic too. Cranberries, pineapples, and pomegranates all fall below pH 4.0. Strawberries, cherries, and grapes typically land in the 3.0 to 4.0 range. Even fruits that don’t taste particularly sour, like blueberries, can be surprisingly acidic.
Tomatoes: Fruit or Vegetable, Definitely Acidic
Tomatoes are botanically a fruit, and they sit right at the boundary of what food scientists consider “high acid.” Fresh tomatoes and tomato pulp typically have a pH between 4.0 and 4.6. This matters most for home canning, where the 4.6 cutoff determines whether a food is safe to process in a water bath or requires pressure canning. Some modern tomato varieties bred for sweetness can creep above 4.6, which is why canning recipes often call for added lemon juice.
Ripeness also shifts the equation. Research on vine-held tomatoes found that pH increases by about 0.01 to 0.02 units per day after the fruit reaches peak ripeness. That might sound tiny, but over a few weeks it adds up. Overripe tomatoes lose citric acid as they age, becoming measurably less acidic. The same general principle applies to other fruits: the riper the fruit, the less acidic it tends to be, though the change is usually modest.
Acidic in Your Mouth, Alkaline in Your Body
Here’s where things get counterintuitive. A fruit can be highly acidic going in and have the opposite effect once your body processes it. Researchers measure this using a metric called the Potential Renal Acid Load (PRAL), which estimates whether a food produces acid or alkaline byproducts after digestion. A negative PRAL score means the food has an alkaline effect on your body.
Almost every fruit, no matter how sour, has a negative PRAL score. Lemon juice scores -2.5. Oranges score -2.7. Strawberries come in at -2.2, pineapple at -2.7, and raisins at a remarkably alkaline -21.0. This happens because the organic acids in fruit get broken down during metabolism, leaving behind alkaline mineral compounds like potassium and magnesium. So while a lemon will absolutely burn a canker sore, it doesn’t make your blood more acidic. Your body’s pH stays tightly regulated regardless of what you eat.
Effects on Acid Reflux
For people with gastroesophageal reflux (GERD), acidic fruits are a well-known trigger. Citrus fruits are the biggest offenders. The high acidity of grapefruit and oranges relaxes the sphincter muscle at the base of the esophagus, allowing stomach acid to flow upward. Tomatoes and tomato-based products like marinara sauce and ketchup have the same effect.
If you experience reflux, you don’t necessarily need to avoid all fruit. Lower-acid options like bananas, melons, and pears are generally well tolerated. Eating acidic fruits with a meal rather than on an empty stomach can also reduce symptoms, since other foods help buffer the acid.
Effects on Tooth Enamel
Tooth enamel starts to dissolve when exposed to a pH below roughly 5.5. Since nearly every fruit falls below this threshold, frequent or prolonged contact between fruit acids and teeth can erode enamel over time. Research published in Frontiers in Dental Medicine confirmed that even a pH of 3.8, which is less acidic than most citrus fruits, is “far lower than the critical dissolution pH” and actively dissolves enamel surfaces.
This doesn’t mean you should stop eating fruit. The risk comes from habits like sipping lemon water throughout the day, sucking on citrus slices, or holding juice in your mouth. Drinking acidic beverages through a straw, rinsing with plain water afterward, and waiting at least 30 minutes before brushing (brushing softened enamel can cause more damage) all help protect your teeth.
Common Fruits Ranked by Acidity
- Very high acidity (pH 2.0 to 3.0): limes, lemons, cranberries
- High acidity (pH 3.0 to 3.5): grapefruits, pomegranates, grapes
- Moderate acidity (pH 3.5 to 4.5): oranges, strawberries, pineapples, cherries, tomatoes, apples, peaches
- Low acidity (pH 4.5 to 5.5): bananas, mangoes, papayas, figs
- Near neutral (pH 5.5+): watermelon, cantaloupe, honeydew
Keep in mind that these are ranges. A perfectly ripe mango from one region might differ noticeably from an underripe one grown elsewhere. Growing conditions, variety, and ripeness all shift the final pH.
Why Acidity Matters for Food Preservation
The 4.6 pH cutoff isn’t arbitrary. It’s the point below which the bacterium that causes botulism cannot grow. This is why high-acid fruits like berries, citrus, and most stone fruits can be safely preserved in a simple water bath canner, while low-acid foods need the higher temperatures of pressure canning. If you’re canning tomatoes or figs, which naturally hover near that 4.6 line, adding a tablespoon of bottled lemon juice per pint is standard practice to guarantee safe acidity levels.