The pH of Tomatoes – Acidic or Basic?

Tomatoes are one of the most prevalent and commonly consumed fruits around the world, mostly due to its nutritious density, which promotes healthy skin, eyes, and heart. To be exact, tomatoes are the fourth most consumed fruit/vegetable in the world. Tomatoes are available in several forms, including soup, puree, sauce, and juice, and are simple to cultivate.

So, what is the tomato’s pH value? The pH range of fresh tomatoes is between 4.3 and 4.9, indicating that they are acidic by nature. Because of the addition of additives and the cooking process, the pH of various tomato-based products will vary. Because a preservative is added to canned tomatoes to improve their shelf life, their pH ranges from 3.5 and 4.7, which is lower than the pH of fresh tomatoes. The pH range for tomato puree and tomato juice is between 4.1 and 4.6.

Tomatoes have health benefits due to the presence of nutrients such as folic acid, lutein, choline, lycopene, etc.

The proportion of these nutrients changes depending on how mature the food is and how it is prepared.

In order to evaluate the nutritional value and, thus, the benefits, it is crucial for us to calculate the pH of tomatoes.

There are deeper dimensions to pH, particularly the pH of tomatoes, that are crucial to comprehending the acidic character, as will be detailed below-

Why are tomatoes naturally acidic?

In chemistry studies, it is a general rule of thumb that acidic substances taste sour and alkaline or basic substances taste bitter.

Therefore, this test can be used as a preliminary indicator of whether a food is acidic or alkaline.

As tomatoes are sour in flavour, it is simple to assert that they are acidic by nature.

But just what makes them acidic is the question we seek to solve. In addition to folic acid, tomatoes also contain citric acid, ascorbic acid, and malic acid.

All of them are weak organic acids, making tomatoes naturally weakly acidic. Initially, when tomatoes are unripe and green, malic acid constitutes the majority of all acids present.

As the fruit approaches maturity and begins to turn cherry red in colour, citric acid becomes the predominant one.

Malic acid is a dicarboxylic acid that contributes to the sour taste of many fruits.

It is vital to the human body because it is engaged in the Krebs cycle, which is the process by which living organisms produce energy.

However, it is highly acidic and excessive consumption can cause acidity and heartburn. Therefore, one should not consume so many unripe tomatoes that they cause bodily issues.

Citric acid is a tricarboxylic acid and weak organic acid that gives most citrus fruits their sour taste.

Tomatoes contain it, albeit in smaller quantities than lemons, oranges, and other citrus-rich foods. Additionally, citric acid is a crucial intermediary responsible for nutritional absorption in the body.

What conclusion does pH have about tomatoes?

The pH indicates the acidity of the tomatoes, which can be used as an indicator of their degree of ripeness.

It has an inversely proportionate link; the ripeness of a tomato is inversely proportional to its acidity.

For instance, if a tomato is more ripe, its pH will be closer to 5, and if it is less ripe, it will be in the 4.5-4.6 pH range.

Therefore, tomatoes are purchased following a pH analysis, which is preparatory for their intended usage.

In the case of tomato-based purees or sauces, for instance, fewer ripe tomatoes can be utilised because additional chemicals and preservatives can be employed to compensate for the acidity.

If the tomatoes are to be used to make a juice or as a fresh vegetable, however, fully ripe tomatoes should be selected.

Why do various tomato products have varying pH levels?

Fresh tomatoes, canned tomatoes, tomato puree, tomato sauce, and tomato soup are the numerous varieties of tomato products available.

The change in pH is due to the process through which the tomatoes are transformed into these end products.

As a result of the use of a preservative, which is similarly acidic, the pH of canned items is often lower.

3.5 is the pH of tinned tomatoes.

These preservatives provide enough acidity to prevent bacterial development.

If there is any growth, it can be eliminated by rapidly heating and cooling the area.

In tomato puree, these preservatives are present in greater quantities, and the tomatoes themselves are more acidic for this particular application, thus the pH is even lower.

Is the acidity of tomatoes disagreeable or harmful to human health?

This issue cannot be answered precisely because it is very reliant on the individual’s digestive system.

Tomatoes’ acidity does not pose a threat to human health, despite the fact that their pH is not very high and is within the normal range for foods that humans can ingest.

However, consuming an excessive amount of tomatoes might increase gastric acid production, resulting in acidity and heartburn.

Contrary to the eastern medicinal philosophy, which considers tomatoes to be alkalizing when digested because they reduce blood acidity and create an acid-alkaline balance in the body, this notion is false.

How can the acidity/pH of tomatoes be altered?

There are two ways to adjust the acidity: by selecting tomatoes with a higher acidity or by adding preservatives during the canning process to extend the shelf life of the product.

In this section, we will therefore focus on decreasing the acidity of tomatoes, which may be necessary for specific applications.

To decrease the acidity, it is necessary to neutralise the acid with an alkali. Therefore, baking soda and a weak acid to react with a weak edible alkali is the optimal choice.

Cooking tomatoes with baking soda can lessen their acidity, so diminishing their sour flavour.

The amount of baking soda to be used depends on the number of tomatoes undergoing this treatment and their acidity.


The pH range of tomatoes varies between 4.1 and 4.6, depending on their ripeness and cooking method. The pH of tomatoes is a crucial criterion for determining their quality and is therefore employed as a quality control measure or test.

Due to the presence of citric and malic acid, tomato products are naturally acidic; however, it is possible to adjust the acidity and flavour of tomatoes. Tomatoes’ extraordinary health benefits must inspire extensive research in biology and medicine.

Read more: Is NH3 Ionic Or Covalent?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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