Reducing Curdling in Cream Soup

Lumpy cream soup may taste fine, but it doesn’t look very appetizing. Dairy ingredients are challenging in these soups. Here’s some tips to prevent curdling:

• Prepare a warm milk/flour mixture to add to hot soup.
• Stir some hot soup liquid into cold dairy product to temper it, then add to the soup.
• Do not boil the soup after adding any dairy product, especially cheese.
• Add acid to the milk instead of milk into the acid. This is especially important for tomato soup.

Source: Understanding Food: Principles and Preparation