What is sweetened condensed milk and where does it come from?

That from reader Robert L., and what a good question it is. I myself once wondered who ever thought to “condense” milk, sugar it heavily, and deliver it in syrup form in cans. The whole idea just seemed screwy to me.

In fact several inventors in the early 19th Century spent years trying to develop that very thing. Then as now, cow’s milk was a staple food in Europe and America. The problem was, in an increasingly urban, industrial society, how to get milk to non-farm dwellers in a timely fashion before it spoiled. Nicholas Appert, the French inventor of canning and savior of the Napoleonic armies, wrestled with the problem of preserving milk but never quite perfected it. Why?

Appert had mostly figured out that if you heat food (boil it) in an airless container long enough, it can be kept almost indefinitely. The problem was his process was time and labor-intensive, requiring an extended boiling of the cans, sometimes for periods of hours. Quite a lot of trouble to go to for a small quantity of a liquid that was made mostly of water. Add to that the fact that all the boiling was hard on the milk, so additives like oil and chalk has to be added to help maintain color and texture. Appert produced a product was thus both nasty and expensive. There had to be a better way.

Inventors around Europe and in America had already come to the conclusion that concentrating or “reducing” milk (i.e. removing most of its water) was they key to its viability as a preserved, shippable and profitable product. But how to do it? Long exposure to high heat severely compromises milk’s taste, color and texture. But what if there was a way to bring milk to the boil — thus ridding it of much of its moisture — at a temperature low enough that it’s quality wouldn’t be compromised? Under what conditions could something like that possibly occur? The answer of course: in a vacuum.

And so a multitude of “vacuum pan” experiments got underway, some on the Continent and some in England. However none produced a concentrated milk product on a scale and of a quality that compared to that made here in America by a fellow named Gail Borden. Borden, already famous in food preservation circles for his invention of a “meat biscuit” for the military, opened his factory in 1856. His first customers for his drastically reduced and highly sweetened milk “syrup” were doctors (especially pediatricians) and passenger ships, who until then relied on live cows to supply travelers with milk. The market was steady but rather small.

That all changed when the US Military realized the potential of condensed milk as a food ration. A 14-ounce can delivers 1300 calories, an ounce each of protein and fat, and 7 ounces of carbs — a huge nutritional payoff relative to its volume. Fortunately for Borden, the government’s realization happened just in time for the Civil War, and the Union bought it by the ton. Union troops came to enjoy condensed milk and spread word of it when the war was over. A new American staple was born. Of course it wasn’t long before other militaries — and other societies — came to see the virtues of condensed milk as well. Today you can find the stuff all over the world.