1, expired or spoiled ingredients: if expired or spoiled corn or cream is used, these ingredients themselves may have soured, which can cause the entire soup to taste sour.

2. Improper storage: If cream of corn soup is not properly refrigerated or stored under improper conditions, bacteria, mold and other microorganisms can multiply rapidly, causing the soup to spoil and develop a sour taste.

3. Incomplete cooking: If corn or other ingredients are not cooked completely, bacteria or yeast will continue to ferment and produce a sour flavor.

4. Contamination: If unclean cooking utensils, knives or storage containers are used during cooking or storage, or if proper hand washing and hygiene measures are not taken during the process, bacterial contamination can cause the soup to spoil and ferment to produce a sour flavor.