Yogurt, also spelled yoghurt or yoghourt, is a thick, custard- or pudding-like food, made by the natural bacterial fermentation of milk. Many people enjoy it plain or flavored with breakfast, lunch, or as a snack, and it's also an ingredient in a number of other dishes.
The process of making yogurt involves fermenting cream or milk with live and active bacterial cultures; this is accomplished by adding bacteria directly to the dairy product. Commercial varieties are usually made with a culture of Lactobacillus acidophilus and Streptococcus thermophilis, although some manufacturers use Lactobacillus bulgaricus rather than L. acidophilus. Yogurt made at home is usually started by adding a small amount of a commercial product to boiled milk.
In Western cultures, yogurt is enjoyed in a variety of ways, most popularly as a cool dish mixed with fruit. It can be used to make healthy shakes or frozen to eat like ice cream as well. Yogurt can also be used when cooking, in place of milk, sour cream, and even some cheeses. In Middle Eastern cultures, it's frequently served with meat, meat sauces, and vegetables. It can also be mixed with various other sauces or used as a tangy dollop on top of a meal.
When purchasing store-bought yogurt, consumers should always check the label for live cultures. If it has been pasteurized or heated after the cultures have been added, it's likely that the cultures will die. When properly made, it will keep well in a refrigerator at 40°F (4°C) for up to ten days. After this amount of time, the cultures often become weak.
Historically, some of the first yogurt most likely consisted of goat’s milk that fermented in the goatskin bags carried by early nomadic people of Turkish origin. Today, it's primarily made with cow’s milk in the United States, but it is also made with the milk of goats, sheep, buffalo, and even camels in other parts of the world.
It is easy and inexpensive to make yogurt at home. A cook can simply boil milk, lower its temperature to 112°F (45°C) and then add a spoonful of the store-bought variety to a small amount of the milk. She should stir it well, and then add the rest of the warm milk. The whole batch must be kept at this temperature for four to six hours so it can set. When the yogurt is ready, it should be refrigerated immediately. It can be enjoyed plain or with fresh fruit, jam, granola, honey, or any other flavor desired.