🔄 Condensing

Condensing means removing part of the water from milk. The milk is evaporated in a vacuum. At low pressure it boils at only 65–70 °C, so it does not burn and its taste changes less. About 60% of the water is removed from condensed milk.

There are two main products. Sweetened condensed milk contains about 45% sugar. Sugar binds water, and microbes find it hard to multiply in such conditions. So the cans are not even heated after filling. The tricky part is lactose: sweetened condensed milk has more of it than can dissolve. To stop it forming large crystals that crunch on the teeth, a “seed” of tiny crystals is added and the product is cooled quickly. Unsweetened condensed milk (evaporated milk) keeps because it is sterilised in the can at 110–120 °C.

The first to condense milk was the Frenchman Nicolas Appert, around 1820. In 1835 the Englishman William Newton suggested adding sugar. The first successful factory was opened by the American Gail Borden in 1864. Dulce de leche, cajeta and khoa are also made by slowly boiling milk down with sugar. For kulfi, milk is also boiled down first.