Although these milk products have similar names, condensed and evaporated milk are not the same thing, and they can't be used interchangeably when cooking. They are both concentrated forms of milk that have had much of their water removed by high-heat cooking. Both milks are shelf-stable and do not need to be refrigerated—but that's where the similarities end. Condensed milk is sweet and gooey, due to the fact that it is made of 40 percent to 45 percent sugar, which is cooked down and then mixed with whole milk.
Evaporated milk, on the other hand, doesn't contain any sugar. It's simply milk heated until the water is cooked off, resulting in a consistency similar to cream. Evaporated milk is available in whole, low-fat, and fat-free.
Cooking With Condensed Milk
Since condensed milk contains sugar, it's important that you read your recipe carefully to know whether you need evaporated or condensed milk. In baked goods, condensed milk lends tenderness, moisture, and flavor to the recipe, as well as color to the crust. Condensed milk is very popular for use in desserts and sweets—it's a prime ingredient in an old-fashioned key lime pie.
Caramelized condensed milk is an heirloom favorite and a popular topping for desserts. It's traditionally made by boiling a sealed can of condensed milk for two to three hours. The can must be permitted to cool down completely before opening to avoid any danger of explosion and/or burn injuries. As enjoyable as this topping is, it's not advisable to use this approach in your home kitchen. Luckily, a much safer method exists—you can make caramelized condensed milk by slowly heating sweetened condensed milk (poured from the can) in a double boiler.
Cooking With Evaporated Milk
Evaporated milk can stand high temperatures without curdling, making it a good choice in recipes for adding creaminess to thick sauces, puddings, and crockpot recipes. It's also good as a coating liquid for breading meats, fish, and poultry. If need be, cold whole evaporated milk can be whipped, but it will collapse quickly—whip just prior to serving and don't expect to store any leftovers.
The natural lactose sugar is concentrated in evaporated milk, so you may need to reduce the sugar when using it as a fresh milk substitute in recipes. To substitute evaporated milk for fresh milk, one cup of whole milk is equivalent to 1/2 cup evaporated milk plus 1/2 cup water. However, you should only substitute for cooking, not for drinking. The intense, high-heat process required to make evaporated milk, as well as processing it into tins, does not make for a palatable substitute for fresh milk to drink as a beverage on its own. However, in a pinch, It can be diluted to use on cereal. Older generations often used evaporated or condensed milk as a creamer for coffee or tea.
When using reconstituted evaporated milk in recipes, you shouldn't notice any taste difference at all, except in yeast bread where the result will be slightly sweeter. Evaporated milk can be substituted in equal amounts for cream or half-and-half in most recipes.