Why did your crab soup turn sour when canned tomatoes were added and was reheated in a lidded pot?

There are a few possible reasons why your crab soup turned sour after adding canned tomatoes and reheating it in a lidded pot:

1. The Tomatoes:

* Acidic Tomatoes: Canned tomatoes can be quite acidic, especially if they are whole, crushed, or diced tomatoes rather than stewed tomatoes. This acidity can interact with other ingredients in the soup, potentially leading to a sour taste.

* Damaged Tomatoes: If the canned tomatoes were damaged or spoiled, they could introduce bacteria that would cause the soup to sour.

2. The Reheating Process:

* Anaerobic Environment: A lidded pot creates an anaerobic environment, meaning there's limited oxygen. This environment can encourage the growth of bacteria that can cause spoilage and a sour taste.

* Overheating: Reheating the soup for too long or at too high a temperature can break down some of the ingredients, releasing acids and creating an unpleasant sour taste.

3. Other Factors:

* Other Ingredients: Some ingredients in the soup, like seafood or dairy products, can be more prone to spoilage and can contribute to a sour taste.

* Storage: If the soup was stored improperly before reheating, such as at room temperature for too long, bacteria may have already begun to grow.

Tips to Prevent Souring:

* Use Stewed Tomatoes: Stewed tomatoes tend to be less acidic than other types of canned tomatoes.

* Add Tomatoes Last: Add the canned tomatoes at the very end of the cooking process, just before serving. This reduces their exposure to heat and limits the chance of spoilage.

* Reheat Uncovered: Reheat the soup uncovered to allow oxygen to circulate and inhibit bacterial growth.

* Cool Quickly: After reheating, cool the soup quickly to prevent bacterial growth.

* Use Fresh Ingredients: Fresh tomatoes can be a good alternative to canned tomatoes.

If your crab soup is already sour, unfortunately, there's not much you can do to fix it. You might try adding a tablespoon of sugar to help balance the acidity, but the sour taste is likely to persist. It's best to discard the soup and try again using the tips above to prevent souring in the future.