Why are Roasted Tomatoes Not So Sour?

🍅Do you know the tips on how to make a tasty tomato sauce🍝?

Citric acid🍋 is the main component in the sourness of tomatoes. If you want to cook with less sourness, you have to remove the citric acid. Citric acid decomposes by heat🔥. One of the mechanisms is shown in this post, but mesaconic acid and acetone can also be produced. According to experiments in the reference, when citric acid was heated in oil at 180 degrees🔥 for 30 minutes or 240 degrees🔥🔥 for 10 minutes, no citric acid was detected. It may not be necessary to heat it for such a long time in actual cooking, though.

🍕This would also explain why pizza is not sour. You can easily heat tomatoes at high temperature by heating them with oil. If you are making tomato sauce or meat sauce🍝, it may be a good idea to heat the tomatoes in oil. If you are making soup🍲 or curry🍛, you will cook it with much amount of water💧, so the temperature will rise to only ~100 degrees and the sourness will remain.

🧑‍🍳If you know any other techniques to make tomato sauce taste better, let me know.


1. “The Thermal Decomposition Products of Citric Acid Added into the Vegetable Oils and their Effect on the Stability” Journal of Japan Oil Chemists’ Society, 1964, 13, 533.

2. “クエン酸の熱分解ガスクロマトグラフィーおよびその分析的応用” 分析化学, 1971, 20, 1245.

3. “Quantification of sugars and organic acids in tomato fruits” MethodsX, 2018, 5, 537.

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