The Science Behind Why You Need Sugar For Homemade Frozen Yogurt

According to the characters in the TV show "The Good Place," frozen yogurt is a "food that people think they enjoy, but that's also kind of a bummer." These are fighting words that vindicate the people who would always pick ice cream over frozen yogurt.

But frozen yogurt — or froyo — has its charm and fans. Yes, it is similar in texture and taste to ice cream, but it is made using yogurt instead of cream. Frozen yogurt is often touted as a healthier option compared to ice cream because yogurt has a lower fat content than heavy cream, although the use of artificial sugar and sweeteners can offset this.

Can you make frozen yogurt by scoping up some yogurt and chucking it in the freezer? Well, yes and no. Yes, it becomes frozen, but it will be an unappetizing block with icy bits instead of the smooth, velvety texture you would expect from commercial frozen yogurt. For that, you need to incorporate sugar in the freezing process for two reasons. First, it ensures you get the right texture, and second, it provides sweetness to counter the tangy taste of yogurt.

Before we get into the science lessons, let's remind ourselves about the contents of yogurt. 3½ ounces of yogurt has about 3½ grams of protein  whey or casein) and is approximately 88% water. This water will noticeably start separating from the yogurt after a few days. When you put the yogurt in the freezer, the water will form large ice crystals that make the yogurt grainy, akin to sorbet, rather than the smooth, creamy texture you might expect.

To counter this, add sugar to yogurt before freezing it. Sugar draws out the water molecules from the yogurt, preventing the formation of large ice crystals. This helps the yogurt freeze consistently so that each mouthful feels the same. 

The sugar also contributes to the level of solids, which adds body and texture to the frozen yogurt. This helps it become malleable or something we can scoop with a spoon. Without it, it will be a block of ice that we need to eat like a popsicle. While there is nothing wrong with it, the best part of frozen yogurt is eating it with various toppings, so it needs to be soft enough to be transferred to a bowl but not too soft that it becomes runny.

Yogurt is essentially fermented milk, so it will always taste sour and tangy. While that works for many dishes, frozen desserts are best when slightly sweeter. Adding sugar to the yogurt before freezing also means there is a good balance of sweet and tangy.

While the addition of sugar is a good tip for making homemade frozen yogurt, the other consideration is the type of yogurt. It helps if you use yogurt that already has lesser water content, such as Greek yogurt, which is essentially strained regular yogurt. You can take it up a notch and experiment with labneh, which is yogurt strained to the point it has no moisture and becomes spreadable rather than liquid-like. With each type of yogurt, the texture and taste of the frozen yogurt will differ slightly, but it comes down to personal preferences.

Finally, consider how you would like to eat it. Maybe some blueberry frozen yogurt to get your five servings of fruits and vegetables for the day, topped with M&Ms, or desiccated coconut for texture.