A tomato is acidic. The pH of a tomato typically ranges from 4.0 to 4.5, which is below the neutral pH of 7. This means that tomatoes have a higher concentration of hydrogen ions (H+) compared to hydroxide ions (OH-), making them acidic. The acidity of tomatoes is primarily due to the presence of organic acids such as citric acid, malic acid, and oxalic acid, among others. These acids contribute to the sour taste of tomatoes.