It can feel quite discouraging to spend time baking and decorating a cake only to have it taste dry when you serve it. The cakes you buy from bakeries taste moist, and the leftover cake tends to last longer. Bakeries have secrets for baking, storing and decorating that help make bakery cakes more moist. You can help your cakes maintain moisture by adding fat, drenching them with a simple syrup before assembly and storing them correctly.
The moistness of the cake after it has been baked depends on the fat content. The higher the fat content, the more moist the cake will taste. Commercial cakes taste very moist because of the tropical oil used. You do not need to use a tropical oil, though. Look for a recipe that has a high fat content from eggs, dairy, butter or vegetable oil. People often recommend adding 2 or 3 tbsp of mayonnaise, which is just eggs and oil. Light cake recipes, with low fat content, will always taste drier.
After your cake has baked and cooled, freeze it until you plan to decorate it. Wrap the cake in cling film well, and put it in the freezer. You should slice it into two or three horizontal layers for filling before you freeze it so that you can assemble it quickly when you take it out. It does not take long for a cake to defrost enough to decorate it. Do not leave it on the counter, in a cupboard or in the fridge, where it will dry out more quickly.
Bakeries use many types of syrups, made with a small portion of water to a larger portion of sugar. These syrups can be flavoured or plain. Black forest cakes often have a kirsch cherry flavoured syrup. A simple syrup usually has 1 part water to 3 parts sugar brought to a boil just until the sugar dissolves completely. This syrup is brushed on each layer before filling and decorating, to add moisture to the cake. Store simple syrup in the fridge well wrapped for up to a month, or until it starts to re-crystalize.
After decorating your cake, make sure you store it properly before serving. Investing in a good cake caddie with a cover will help. You want to prevent heat and the air from drying the cake out. Store the cake in the fridge, covered. You should store any leftovers in the same way although, to save space, you can cut the leftovers into serving sizes and store the pieces in smaller containers. You can freeze some pieces in airtight containers to eat later.