Tomatoes tend to be sweet. When making a fresh tomato soup, that sweetness factor can become overwhelming. Instead of throwing the soup away, there are a few tricks that you can try to fix the tomato soup. If using canned tomatoes for the base of your tomato soup, make sure to read the labels before purchasing. Many canned tomatoes contain extra sugar to help preserve the tomatoes. This extra sugar can cause the tomato soup to be too sweet.
Pour the tomato soup into a saucepan. Place on a stove top burner and set to medium-high heat, bringing to a boil.
Add 1 tsp. of tomato paste to the soup. Stir continuously until the paste has dissolved and mixed in with the tomato soup. Tomato paste will cut down on the sweetness and will also thicken the soup.
Add a pinch of baking soda to the soup. Stir well and taste. The baking soda will neutralize the acid in the tomato soup and make it taste more salty. However, too much baking soda will make the tomato soup taste bitter.
Pour 1/8 tsp. of white cider vinegar into the soup. Allow the soup to cook for a few minutes, stirring occasionally. Taste the soup. If it is still too sweet, add another 1/8 tsp. of vinegar until the sweetness has lessened. Do not add vinegar if you have previously added baking soda.
Other ingredients can also combat the overpowering sweetness of the soup. Lemon or lime juice, peppers and hot spices can all help to change the taste and adjust the sweetness of tomato soup.