What’s the difference between cheese and yogurt?
We often fall into the trap of placing dairy products into defined categories. I think a better approach is to imagine them existing on a spectrum. In some contexts, they’re close together; in other contexts, much further apart. Both yogurt and cheese utilize starter cultures to produce acidity. However, in both, the exact type(s) of cultures can vary. Some cheeses use cultures such as Streptococcus thermophilus and Lactobacillus bulgaricus. Yogurt can also use cultures like Lactobacillus acidophilus and Bifidobacterium. These culture blends contribute to the unique flavor and aroma profiles of yogurt since they produce lactic acid by breaking down lactose.
Let’s consider acidity. The acidity of dairy products can also be thought of as a spectrum. A pH of 7.0 is considered neutral. So at the low end (barely acidic), we have milk with a pH around 6.7. At the high end, yogurt’s pH is around 4.5. Most cheeses fall somewhere in between plain milk and yogurt. These differences in pH can be attributed to the aforementioned cultures, which produce lactic acid by breaking down lactose.
Continuing the switch from categories to spectrums, let’s think about heat treatment of milk. At one end of the spectrum, we have raw milk cheeses, where the milk isn’t heated much above body temperature. At the other end, we have many yogurts, where the milk is heated to very high temperatures. (In the middle, we have cheeses made with thermized and pasteurized milk.)
In yogurt, this high heat treatment is performed in order to denature, or unfold, whey proteins, which allows them to hold onto more water, increasing the yogurt’s final moisture content. Yogurt’s moisture content is usually around 75%-87%, depending on whether it’s a concentrated variety like Greek yogurt or a looser style.
Most cheeses have a much lower moisture content(e.g. cheddar at ~38%). This is because large amounts of whey are drained during the manufacture of many cheeses. That’s not the case for most yogurts—Greek yogurt, which is strained, is an exception—leading to their spoonable texture.
Special thanks to Pat Polowski, the cheese scientist behind cheesecience.org.