Strawberry cake with whipped cream
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Some foods, like that loaf in your bread box, can sit out for days without problems. Cake can be one of those foods, but generally it's best and safest to keep it in the refrigerator once your event is over. Cake and frosting are fairly durable, but there are a few things you'll need to watch out for.

Causes of Cake Spoilage

Cake itself is fairly resistant to most forms of spoilage. If a plain cake is left to sit out, it will usually become dry and stale, but it won't make you sick to eat it. In fact, the world's bakers have any number of ways to use up stale cake and transform it into new, equally tasty desserts.

That doesn't mean you should just fearlessly tuck into those leftovers, though. Any areas where there's moisture trapped in the cake – between the cake and its plate, for example, or even between the cake and its icing – there's potential for mold to develop. Some cakes also have fillings or toppings with perishable ingredients, from fresh fruit to whipped cream and egg-based custards and meringues. Eggs are the chanciest of these, because they can create actual food safety concerns.

Quality vs. Food Safety

Mostly, when you talk about the expiration of cake, you're talking about its eating qualities. A whipped cream cake left out overnight will be shrunken and cracked in the morning, and it may taste a bit of sour milk, but it's not likely to make you ill. Similarly, a days-old cake kept in the refrigerator will be stale and dry, but fine to eat as long as it's a plain cake with no fillings.

Custard-based fillings are different. Their high fat and protein content make them an ideal breeding ground for microorganisms, so any cake with this kind of filling absolutely has to be refrigerated. Bakers and cake decorators keep a cake fridge for just that reason, or they use refrigerated showcases for retail display purposes. When it's time to bring out the cake, follow the same rule as for any other perishable food: It should be kept at room temperature for a maximum of two hours.

This is important, because potentially dangerous bacteria like listeria and salmonella don't advertise. If you take a bite of cake that's moldy or covered in cream that's spoiled, you'll know right away and spit it out. Harmful bacteria, or pathogens, are different. You can't see, smell or taste them, so following the standard food safety guidelines is your only real defense.

Don't Throw It Out

If you're not going to be able to use up your cake in a reasonable time – and really, there's only so much cake you can eat in a span of a few days – that doesn't mean you should throw it out. Simple cakes can be frozen, icing and all, or you can preserve any cake, stale or not, for repurposing into new treats.

Start by separating the cake's layers and scraping away any icing or fillings. Slice the cake evenly, and arrange the slices on a parchment-lined sheet pan. Bake them at your oven's lowest setting, or dehydrate them in a food dehydrator until they're perfectly dry. Then you can seal them airtight, either in pieces or as crumbs, and keep them in your pantry or – better yet – your freezer, until they're needed.

Uses for Stale Cake

The uses for leftover cake are almost limitless, and you don't need to be a master baker to turn them into a sweet treat for your next party or bout of binge-watching. A few choices include:

  • Combining cake crumbs with leftover icing, chocolate or other flavorings to make cake pops.
  • Combining the crumbs with rum or bourbon instead to make rum balls or bourbon balls.
  • Using fingers of stale cake in place of ladyfingers in desserts like tiramisu.
  • Soaking pieces of stale cake in sherry and then layering them with custard and other ingredients to make a trifle.
  • Sprinkling cake crumbs between layers of phyllo pastry to help keep them separate and crisp as they bake.
  • Making "bread pudding" or "French toast," but with cake instead of bread.
  • Making crumb crusts for pies, tarts and ice cream cakes.