Can egg whites be whipped twice?

Here's why:

* Structure Breakdown: Once egg whites are whipped, they form a stable structure due to the denaturation of protein molecules and trapping of air bubbles. Whipping them again disrupts this structure, leading to a less stable foam.

* Loss of Air: The second whipping tends to break down existing air bubbles rather than incorporating new ones, resulting in a less voluminous foam.

* Increased Density: The broken-down protein structure makes the foam denser and less airy, which is undesirable for most recipes.

Exceptions:

* Adding New Ingredients: If you add additional ingredients like sugar, lemon juice, or cream of tartar during the second whipping, it can help stabilize the foam and give it a slightly better consistency.

* Specific Recipes: Some recipes, like meringue cookies, involve a second whipping after incorporating sugar. However, this is typically done with a specific purpose and technique, not for achieving a stiff peak again.

Recommendation:

If you need to whip egg whites for a recipe that requires stiff peaks, it's best to start fresh with new egg whites. This ensures the best possible texture and volume.