Is Tomato Soup Acidic? Unpacking the Science Behind Your Favorite Comfort Food

December 27, 2025 •

4 min read

Tomatoes naturally have a low pH, typically ranging from 4.0 to 4.5, making them inherently acidic. As a result, yes, tomato soup is acidic, and its sour tang can affect those with sensitive stomachs or conditions like acid reflux.

Quick Summary

Tomatoes contain naturally occurring acids like citric and malic acid, which make the soup acidic. The final pH is influenced by ripeness, processing, and added ingredients like dairy or baking soda. Techniques exist to balance the flavor and soothe digestion.

Key Points

Yes, tomato soup is acidic: The primary ingredient, tomatoes, naturally contain citric and malic acids, giving the soup a low pH and a tangy flavor.
Acidity varies: The ripeness of tomatoes, use of canned products, and cooking methods all influence the final acidity of the soup.
Neutralize with baking soda: Adding a small pinch of baking soda is a scientifically sound way to neutralize excess acidity and prevent dairy from curdling.
Use dairy to balance: Cream, milk, or yogurt can help balance the tartness and create a smoother flavor profile.
Consider alternative additions: Sweet vegetables like carrots or onions can naturally counteract the sourness without a strong neutralizing effect.
Mindful of acid reflux: Individuals with sensitive stomachs or acid reflux may experience discomfort from tomato soup due to its acidity and its effect on the lower esophageal sphincter.
Sugar is a flavor mask: Adding sugar does not neutralize acidity but can mask the sour taste by increasing sweetness.

Understanding Acidity and pH

To grasp why tomato soup is acidic, one must first understand the pH scale. This scale measures how acidic or basic (alkaline) a substance is, with a range from 0 to 14. A pH of 7 is neutral, anything below 7 is acidic, and anything above 7 is basic. Tomatoes, the primary ingredient, typically have a pH between 4.0 and 4.5, firmly in the acidic range. This inherent acidity is due to organic acids like citric and malic acid present in the fruit. When these tomatoes are processed and cooked into a soup, this acidity persists.

Factors Influencing Tomato Soup's Acidity

The acidity of your tomato soup isn't a fixed value; it can vary based on several factors, from the tomatoes used to the preparation method.

Tomato Type and Ripeness: Certain varieties of tomatoes, such as green or underripe ones, tend to be more acidic than fully ripe ones. Smaller, cherry tomatoes often have a higher sugar-to-acid ratio, resulting in a sweeter taste despite their natural acidity.
Added Ingredients: Creamy tomato soups often include dairy products like milk or heavy cream. The fat in cream helps prevent curdling when added to acidic ingredients and can help balance the flavor. Ingredients with alkaline properties, such as baking soda, are often added specifically to neutralize the acid.
Cooking Process: The way you prepare the soup also plays a role. Longer, slower cooking can sometimes mellow the tomatoes' natural acidity. Roasting the tomatoes before making the soup can also caramelize their sugars, enhancing sweetness and balancing the sourness.
Canned vs. Fresh: Canned tomato products, such as purée or crushed tomatoes, can be highly acidic, sometimes with a pH as low as 4.0. The canning process itself, for safety reasons, requires a pH below 4.6, so manufacturers sometimes add citric acid.

Making Tomato Soup Less Acidic

For those who experience discomfort from acidic foods, or simply prefer a milder flavor, there are several culinary tricks to reduce the acidity of tomato soup.

Add a Pinch of Baking Soda: A small amount of baking soda, which is alkaline, can neutralize the acid in the soup. Start with a quarter teaspoon for a few cups of soup, and stir until it stops fizzing. Taste and add more if needed. This is also a common method for preventing milk or cream from curdling.
Incorporate Dairy: Adding ingredients like heavy cream, sour cream, or even yogurt can mellow the acidity. The fat and proteins in dairy help to buffer the sourness, resulting in a smoother, richer flavor profile.
Use Sweet Vegetables: Carrots, onions, or sweet potatoes can be added to the soup to naturally counteract the tartness with their sweetness. A popular method involves simmering a whole peeled carrot in the soup and removing it before serving.
Balance with Sugar: While sugar does not neutralize acidity, a small amount can make the soup taste less sour by enhancing the perception of sweetness. It's a flavor balancer rather than a chemical neutralizer.

Acid Reflux and Tomato Soup: A Comparison


Feature	Tomato Soup	Mild, Cream-Based Soup (e.g., Potato)
pH Level	Acidic (approx. 4.0-4.5)	Near neutral (approx. 6.0-7.0)
Effect on LES	May cause relaxation, allowing stomach acid to back up	Less likely to trigger relaxation of the LES
Trigger Potential	High potential for triggering heartburn, especially on an empty stomach	Low potential for triggering heartburn
Main Acids	Citric acid, malic acid	N/A
Flavor Profile	Tangy, bright, and savory	Mild, creamy, and savory
Remedies for Acidity	Baking soda, cream, sweet vegetables	Not typically required

Expert Perspectives on Tomato Acidity

Digestive health experts at organizations like GASTRO NYC and Healthline consistently highlight that tomatoes and tomato-based products are triggers for acid reflux due to their inherent acidity. They advise individuals prone to symptoms like heartburn or GERD to limit or avoid these foods. However, as shown by various cooking resources, it is possible to prepare tomato soup in a way that minimizes its acidic impact through the addition of neutralizing or balancing ingredients. For those with severe or chronic conditions, consulting a healthcare provider or a reflux specialist for personalized dietary advice is recommended. For a deeper dive into managing acid reflux through diet, you can explore resources like the Tampa Bay Reflux Center's blog.

Conclusion

Ultimately, the answer to the question "Is tomato soup acidic?" is a definitive yes, thanks to the natural composition of its primary ingredient. The exact level of acidity, however, is not static and depends on factors like tomato variety, ripeness, and the cooking method. While its tart nature can be a concern for individuals with acid reflux or sensitive digestive systems, a variety of culinary techniques, from adding alkaline baking soda to incorporating creamy ingredients, can effectively balance the flavor and mitigate potential discomfort. By understanding the science behind the taste, you can enjoy a delicious and comforting bowl of tomato soup tailored to your preferences and dietary needs.

Frequently Asked Questions

Tomato products generally have a pH level between 4.0 and 4.7, depending on ripeness, processing, and added ingredients. This places it firmly in the acidic category on the pH scale.

Yes, for many people, the high acidity in tomato soup can trigger or worsen acid reflux symptoms by causing the lower esophageal sphincter to relax, allowing stomach acid to back up into the esophagus.

You can reduce the acidity by adding a small amount of baking soda, incorporating dairy products like cream, or simmering with sweet vegetables like carrots to naturally balance the flavor.

No, adding sugar does not chemically neutralize the acid. It simply masks the sourness by adding sweetness, affecting the flavor profile without changing the pH level.

Baking soda is a base (alkaline) that, when added in small amounts, will react with and neutralize the acidic compounds in tomato soup, balancing its pH.

Cream of tomato soup can be perceived as less acidic because the fats and proteins in the cream help to buffer the acidity. For some recipes, the addition of baking soda is also used to prevent curdling and further reduce tartness.

Not necessarily, but they are consistently acidic. Canned tomato products often have citric acid added to ensure they meet the minimum acidity required for safe canning, which results in a consistent, low pH.