Ice Cream Chemistry

I like many things, food is one of them, and another is science. But I usually think of them as completely separate things. So I was really surprised when I walked into my chemistry class one day and saw food ingredients. For as long as I’ve been in school, food has always been kept separate from science, we’d do labs in the classroom and then go to the cafeteria for food. The first rule of lab safety is “no food allowed” because of the possibility of accidentally ingesting harmful chemicals. So I was really confused when I looked up at the whiteboard and saw a recipe. The ingredients were pretty typical: milk, heavy cream, sugar, and vanilla, but the process was ridiculous. We combined all of the ingredients in small ziplock plastic bags, then we took larger bags and filled them with ice and rock salt. This is where the chemistry comes in. The water from the ice and the salt combine to form a solution, and we took advantage of the colligative properties of solutions. The colligative property that we took advantage of is that as a solution increases in concentration, its freezing point decreases. So by adding a lot of salt to ice, we created a super cold solution that, according to Mr. Carley, would be cold enough to freeze the milk cream and sugar mixture into ice cream. I wasn’t convinced, so I skeptically followed the recipie. I combined the ingredients in a smaller bag, sealed it, put it into the larger bag with ice and rock salt, and then I shook it for a while. After about 10 minutes I saw the result, inside the smaller bag was a velvety, silky frozen treat. I took a spoonful and it was smooth and delicious. Chemistry had never tasted so good.

Vikram M