In England, they often call it Mr. Whippy. In parts of Europe, it's known as American ice cream. Parts of Vermont refer to it as Creemee. But anywhere it's eaten, people can tell you it tastes good.
Soft serve is a classic sweet treat that has been enjoyed since the 1940s. As anyone who has ever stopped by a Mister Softee can attest to, although it is definitely ice cream, it's a bit different from what you might buy in a grocery store. There are several competing claims about who first invented soft serve–Tom Carvel, the Dairy Queen family and even Margaret Thatcher are all names that come up. But wherever it came from, here's how it works:
It shares a lot with regular ice cream
In its purest form soft serve is basically just regular ice cream at a different point in its process, according to the University of Guelph. After the ice cream ingredients are mixed together, the university writes, a machine “both freezes a portion of the water and whips air into the frozen mixture.” Ice cream is between 30 and 60 per cent air–without it, you’d crack your teeth on an ice cube made of dairy. At this point in the process, if the mixture is drawn into a cone, it's soft serve. If it's put into a tub and frozen until it's even colder, it becomes ice cream.
In a sense, soft serve is really just melted ice cream. In fact, one of soft serve’s originators, Tom Carvel, hit on the idea when he had to sell melting ice cream out of his broken-down shipping truck.
The difference is (partially) in the air
All ice cream is technically foam–at least that's what chemists would tell you. “In ice cream–liquid particles of fat–called fat globules–are spread throughout a mixture of water, sugar and ice, along with air bubbles,” writes Brian Rohrig for ChemMatters. The air bubbles are essential to giving ice cream its texture. In soft serve, writes Vanessa Farquharson for the National Post, “all that air leaves less room for dairy fat.”
Carvel’s original soft serve was just a warmer, softer version of the ice cream he normally sold, but modern soft serve contains significantly more air than frozen ice creams. Think of it as foamier. An at-least-partially apocryphal story about 1980s British Prime Minister Margaret Thatcher suggests that when she was working as a food chemist, she helped invent the technique that added even more air to soft serve–cold air, not hot air, but the political metaphor still works. Soft serve can consist mostly of air, writes Daniela Galarza for Eater, while "regular" ice cream has to be less than 30 percent air.
A side effect of all this air is that soft serve is much warmer than regular ice cream, Rohrig writes. Regular ice cream is about 10 degrees Fahrenheit, while soft serve is about 21 degrees Fahrenheit. But they're both delicious.