What should be avoided when cooking a sauce to prevent curdling?

Using low-fat milk instead of cream can lead to curdling when cooking a sauce, particularly if the sauce is subjected to high heat. Cream has a higher fat content, which helps stabilize the sauce and prevents the proteins in the dairy from coagulating. In contrast, low-fat milk lacks this fat content, making it more prone to curdling, especially if the cooking process involves significant heat or acidity, which can denature the proteins and cause them to clump together.

The other practices listed, such as adding fresh herbs, heating slowly and gently, and avoiding bringing the sauce to a boil, are all beneficial techniques in sauce-making. Adding fresh herbs can enhance flavor without affecting the texture, while gentle heating allows for a more controlled cooking process that helps maintain a smooth consistency. Not allowing the sauce to boil is critical because boiling can cause the milk proteins to curdle, so maintaining a gentle simmer is often recommended in sauce preparation.