The Sweet Science of Ice Cream: How A Favorite Treat Comes Together

Some unwitting parents might’ve come up against a real stumper this summer as part of a classic childhood science experiment: making ice cream. It’s an easy enough process; sugar, heavy cream, a splash of vanilla or cocoa powder in one plastic bag, ice and salt in a second layer of plastic, then shake until you have ice cream. 

But why salt, when in a couple months we’ll be using the same material to melt ice from our sidewalks? Well, interestingly, the same process is at play. 

When salt is added to ice and water, it does two things. According to Ariel Fenster, PhD, who develops educational content for McGill, salt lowers the freezing point of water, meaning when making icecream, the ice is able to be colder than 32 degrees and stay there. The insulated environment of an icecream maker or even a ceramic bowl also keeps things colder for longer.

Salt also creates a solvent with water, and the same process can happen even when water is frozen into ice. This creates the melt you commonly see on roadways, but you’ll also notice a bit of water in the ice and salt side when making ice cream. This melt happens because the chemical reaction of salt and water bonding together releases heat, which melts the ice. The more salt you add, the more melting will occur– that’s why we use super salty chunks of crystalized salt on the road, but a bit of table salt works just fine for at-home ice cream making.  

For home ice cream sommeliers, heavy cream is the other key element to that silky, sweet ice cream texture. We actually whip the cream as we mix, meaning the thicker the cream, the easier it is for the ice cream to hold its shape. 

Classic whipped cream, too, is a chemical change. At its core, heavy cream that you find on the shelf is essentially an emulsion of fat and water. When you whisk it, the mix of oil and water begins to trap air, forming that fluffy, light texture we love in our desserts. Most recipes will combine whole milk with heavy cream, so that the mixture will thicken but won’t form the same stiff peaks. Essentially, by thinning out the cream with milk, we slow down the mixing process so that the ice cream can churn without becoming too hard. 

So there you have it! The delicious science behind your favorite frozen treat is a lot more simple than it looks.