Recipes engineered for perfection—what exactly does that mean? We take you inside Cook’s Illustrated’s science experiments.
Dishes like beef stroganoff, chicken paprikash, and many of the Moroccan stews known as tagines wouldn’t be complete without a little sour cream or yogurt stirred in at the end. However, these cultured dairy products are sensitive to heat and can easily curdle if the stew is too hot or reheated. We wondered if another dairy product would provide a more stable tang.
We stirred dollops of whole-milk yogurt, full-fat sour cream, and crème fraîche (which boasts much more fat) into water that we brought to just a simmer (185 degrees). After letting the samples sit for 10 seconds, we examined the liquid for signs of curdling.
Both the yogurt and the sour cream mixtures quickly curdled, while the crème fraîche mixture remained perfectly creamy.
Curdling occurs when excessive heat causes the whey proteins in dairy to denature (unfold) and bind with casein proteins, forming clumps of larger proteins. The greater amount of butterfat in crème fraîche (30 to 40 percent, versus 18 to 20 percent and roughly 4 percent in sour cream and yogurt, respectively) protects against this process by more thoroughly coating the proteins and preventing them from binding together. Plus, with more fat, crème fraîche has far fewer proteins to bind together in the first place. It’s now our go-to dairy product for hot dishes; in fact, we found that crème fraîche is so resistant to curdling that it can withstand reheating.
MAKE IT NOW: You can make crème fraîche with our DIY recipe.