Which types of icing must be stored tightly covered to prevent drying out?

Fondant, fudge, flat icing, and royal icing all require tight storage to maintain their desired texture and prevent drying out.

Fondant, a sugar-based icing, can dry out quickly when exposed to air, leading to cracking and a loss of pliability, which is crucial for decorations on cakes. Proper storage ensures it remains usable for covering cakes or sculpting decorations.

Fudge icing, known for its smooth texture and rich flavor, also requires moisture retention. Storing it covered helps prevent it from hardening, ensuring it remains spreadable for use on cakes or as a filling.

Flat icing, which is typically a sugar and water mixture, can dry to a hard shell. Keeping it tightly covered prevents this from happening and allows it to retain the right consistency for application.

Royal icing, made from egg whites and powdered sugar, is particularly user-sensitive, as it can dry out and harden quickly if not stored correctly. This type of icing is used for intricate decorations and piping, making it crucial to maintain its workability through proper storage.

In contrast, the other options have different storage requirements due to their compositions and uses, which do not necessitate the same level of airtight containment to preserve their quality.