We All Scream for Ice Cream!
Audience: Elementary, Middle, and High School students
“Ice cream is the perfect buffer, because you can do things in a somewhat lighthearted way. Plus, people have an emotional response to ice cream; it's more than just food. So I think when you combine caring, and eating wonderful food, it's a very powerful combination.” Jerry Greenfield
An assortment of delicious ice cream flavors. Image by Brooke Lark from Unsplash.
Ice cream is one of the most popular desserts in the world, with countless flavors and variations of it across cultures. Kids and adults alike revel in its icy softness, but have you ever wondered about the science behind ice cream?
There are four basic components of ice cream: ice crystals, fat, sweeteners, and air.
The ice crystals form as the water in the ice cream begins to freeze—they are what keep it somewhat solid. It’s the size of these ice crystals that determines how smooth or grainy the ice cream is, so minimizing their size is crucial to ice cream-making.
Fat comes from both milk and heavy cream, both of which supply the “cream”-iness in ice cream. Heavy cream is the high-fat part of milk that, because of its high-fat content, rises to the top. It's skimmed off to make low-fat and fat-free milk, but is left in whole milk, which is typically homogenized so the cream is blended in. Additionally, as the fat particles coalesce—or combine—while being churned, they start to form a solid structure that traps air bubbles.
Next comes the best part: the sweeteners. As expected, these sugars or syrups add sweetness, but they also contribute to the ice cream’s texture and stability by lowering the freezing point. The freezing point of any liquid is the exact temperature when it begins to solidify due to lowered temperatures. The freezing point of water, for example, is 0 degrees celsius, or 32 degrees fahrenheit. Having a lower freezing point ensures that the ice cream doesn’t freeze rock-solid in your freezer, and instead maintains its creamy texture!
And lastly, we have the cheapest and most abundant ingredient used in ice cream: air. While the ice cream is being churned, air gets folded and whipped into it, adding to its volume and overall fluffiness. But high-quality ice cream actually contains much less air than commercial ice cream does, making it far more dense and rich. Commercial ice cream often has an overrun—the technical term describing how much air ice cream holds—of over 100%. That means ice cream with low overrun contains far more actual ice cream than a scoop with high overrun, which is mostly made of air!
Now that we know about the various components, let’s take a look at how they all come together in a fascinating chemical process called emulsion. Like oil and vinegar, these ingredients that go into ice cream don’t naturally come together, or homogenize.
So how do we mix them into such a creamy mixture?
We use emulsifiers, the ingredients that help combine these “unwilling” ingredients. They’re actually simple ingredients, with egg yolk being the most common emulsifier. Commercial ice cream production, for instance, uses emulsifiers extracted from oils. Have you seen “monoglyceride” on the ingredients list of your ice cream? Well, that's an emulsifier! Similarly, ingredients called stabilizers—like gelatin, starches, or vegetable gums—are used to improve the structure and texture of ice cream, while also reducing its melting speed. All this together makes the perfectly soft, sweet, and refreshing ice cream.
The next time you open your freezer to find your favorite flavor of ice cream—mine is cookies and cream—think back to the components behind the delectable dessert. As you feel it melt on your tongue, appreciate the chemistry and calculations involved with getting it to the perfect melting point. And as you enjoy with your family and friends, try to explain the fascinating process of ice cream creation to them!
Laiskonis, Michael. “Four Factors for Perfecting Ice Cream.” Institute of Culinary Education, 19 July. 2019, www.ice.edu/blog/science-of-ice-cream.
“The Science of Ice Cream.” ICE CREAM NATION, www.icecreamnation.org/science-of-ice-cream/.
“The Science of Ice Cream - Article.” FineCooking, 16 Apr. 2013, www.finecooking.com/article/the-science-of-ice-cream.