We Be Chillin’

Happily for me, ice cream is one of those food topics where I don’t have to choose between history and science, because the two go hand-in-hand. The history of ice cream is the history of refrigeration. Oh happy me.

The history of refrigeration starts of course with ice, the preservative powers of which have been apparent to humans since, well…just about forever. We know that prehistoric man preserved game in snow after successful winter hunts, and that over time the practice evolved into seasonal ice harvesting, whereby blocks of ice cut from frozen lakes or ponds were stored either in caves or pits lined with wood or straw. The first records of ice harvesting date to about 1000 BC in China, though the practice is certainly much older than that. Later records show that the Egyptians, the Hebrews, Babylonians, Greeks and Romans all made good use of either seasonal or mountain snow and ice. Great for preserving food, it doubled as a sweet treat combined with honey.

Since a good idea is a good idea, ice harvesting endured all the way down to the advent of modern refrigeration. I remember seeing my first ice cave on a visit to Monticello as boy (Jefferson was notorious for his love of sweet ices and ice creams). Ice houses were common all over the developed world well into the 20th century.

Yet there was one advance in cooling technology that can be traced back as far as the Middle Ages: cooling salt/water reactions. The Arabs, the premier technological innovators of the day, discovered that adding certain salts, notably saltpeter (sodium and/or potassium nitrate), to water lowered its temperature. The technique was employed on a small scale to create cooling baths for containers of food and drink right up through the middle of the 17th century, at which point it was discovered that saltpeter added to ice slush yielded temperatures that were actually below the freezing point of water.

What could such cold temperatures possibly be good for? Hmm…let me think now…let me think…