Calories in Yogurt, plain, nonfat

What makes yogurt so powerful?

The transformation of milk into plain nonfat yogurt relies on a precise bacterial partnership. By FDA standards, commercial yogurt must be fermented using Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. These two species work symbiotically: S. thermophilus rapidly lowers the milk's pH, creating an ideal environment for L. bulgaricus, which in turn breaks down milk proteins into amino acids that feed its partner. As they consume lactose, they excrete lactic acid. When the pH drops to around 4.6—the isoelectric point of casein proteins—those proteins lose their negative charge and unfold into a tangled three-dimensional mesh, trapping water and forming the characteristic gel. Because nonfat yogurt lacks milk fat globules to disrupt the protein network, it can actually form a slightly firmer curd, though it lacks the rich mouthfeel that fat provides. The resulting lactic acid also acts as a natural preservative, inhibiting spoilage organisms and giving the yogurt its signature tart flavor.