Heat Forgiving Frostings

• There are three frostings which handle the heat the best: fondant, meringue icing and cooked buttercream. Fondant made with gelatin or marshmallows, powdered sugar and shortening cannot be refrigerated and can sit out at room temperature for three to four days. Because fondant is made with shortening, it doesn’t melt; fondants made with chocolate are more susceptible to melting in the heat. Meringues and buttercreams made by whipping egg whites and combing with a cooked sugar syrup usually call for pounds of butter. Substituting part or all of the butter for shortening makes the frosting more heat resistant. Decorations which are heat tolerant include hard candy and marzipan, made from a paste of ground almonds.

The Coolest Ingredients

• If your frosting is made with butter, it will start to melt once the temperature reaches 88 degrees Fahrenheit. Shortening, on the other hand, stays firm much longer, able to handle temps as high as 106 F. Buttercream made with all shortening and whipped with cornstarch can handle high humidity and is safe to leave out of the refrigerator for up to two weeks. Quality is important when choosing the ingredients for heat-resistant frosting. Sugar made from cane as opposed to beets won’t get that grainy taste as temperatures rise and frosting softens. Try using flavored extracts to replace more heat sensitive ingredients such as cream cheese and butter.

Specialized Stuff

• Professional bakers and cake makers have tweaked classic recipes for cooked buttercream frostings to come up with recipes that are especially sturdy in high heat and humidity. These recipes use specialized ingredients such as high ration shortening and powdered Dream Whip. High ratio shortening makes frosting with an especially smooth texture. Made from pure lard without salt or water, the added emulsifiers help keep frosting stable even in high humidity. Powdered Dream Whip is a non-dairy powder found in the baking aisle of grocery stores. Use it to mix up shortening-based buttercream frosting that sets with a crust and is especially tolerant in warm temperatures.

Food Safety Concerns

• The question of leaving a cake out at room temperature can become a food-safety issue depending on the ingredients used in the frosting. Most icings are safe at room temperature -- even those made with whipped egg whites -- due to the large amounts of sugar used. Cream cheese is the exception to this rule. Frosting made with cream cheese cannot be left out in the heat for more than one hour on a hot day over 90 F. Other frostings that require refrigeration in order to preserve their texture include those made with whipped cream and egg yolks, which can separate if left out longer than six hours at room temperature.