Evaporated milk is not to be confused with condensed milk even though in some countries it is referred to as unsweetened condensed milk. Basically, evaporated milk is unsweetened and condensed milk (when called just condensed milk) is sweetened with added sugar.
Evaporated milk is fresh milk with 60 per cent of the water extracted. Once canned, it has a much longer shelf life than ordinary fresh milk and takes up much less space. In the days before fridges were readily available, evaporated milk was a popular way of storing and transporting milk. Once the right amount of water is added back in, it is virtually the same as fresh milk.
Although the process had been used for centuries, especially in ancient nomadic communities that wanted to carry milk with them with as much load-saving as possible, it wasn’t until the 1920s that it became commercially available at low prices.
The process also gives it its distinct caramelised flavour. Homogenised milk has 60 per cent of the water extracted before it is chilled, stabilized, sterilized for 15 minutes at 240-245°F / 115-118°C, and packaged. The evaporation concentrates the nutrients, which is why it contains more calories than fresh milk.
Apart from it’s original use as reconstituted ordinary milk, evaporated milk has a wide variety of culinary uses in its condensed form. It is often used as a cream-like topping for desserts and fruit, especially if fresh cream isn’t available. It is often added as a whitener or creamer to coffee and tea. Generally speaking, the average shelf life of commercially produced evaporated milk is around 15 months, so it is a useful store-cupboard stable.
Some recipes specifically call for evaporated milk. Basically, these are recipes looking to add a creamy texture but not sweetness. It can be used in both sweet and savoury dishes. It is not usually advisable to use unsweetened evaporated milk and sweetened condensed milk interchangeably, so it’s best to stick t whichever version the recipe calls for.