凝乳（curd）是指一种将牛乳和羊乳等乳类发酵之后制作和乳制品，也是起司的一种，是茅屋起司的原料之一，可直接生食。凝乳经常在中欧和东欧食用。凝乳含有较多的脂肪。凝乳的制作方法和食用方法因地区而异。在美国的一些地区，如威斯康星州，凝乳经常和扎面包一起食用或直接生吃。

Curds are a dairy product obtained by coagulating milk in a process called curdling. The coagulation can be caused by adding rennet or any edible acidic substance such as lemon juice or vinegar, and then allowing it to sit. The increased acidity causes the milk proteins (casein) to tangle into solid masses, or curds. Milk that has been left to sour (raw milk alone or pasteurized milk with added lactic acid bacteria) will also naturally produce curds, and sour milk cheeses are produced this way. Producing cheese curds is one of the first steps in cheesemaking; the curds are pressed and drained to varying amounts for different styles of cheese and different secondary agents (molds for blue cheeses, etc.) are introduced before the desired aging finishes the cheese. The remaining liquid, which contains only whey proteins, is the whey. In cow's milk, 80% of the proteins are caseins.