In addition to simply describing milk that has gone bad, the culinary term souring may be used to describe a method of food preparation. Souring is completed by adding an acid to food, rapidly modifying the food's chemical as well as physical composition. Once complete, the technique creates a similar result to pickling food.
Rather than souring foods, many products that require this flavoring process are instead pickled or fermented. Since both of these methods require a lengthier amount of time, chemical sourness is often implemented with the addition of lemon or lime juice, vinegar, and other acidic compounds. Using these agents not only drastically cuts time needed for product preparation down from days to minutes, it also makes the method of cooking more accessible to the home cook, who may not have the skills or materials necessary for lengthier applications.
Cooks should take note that the amount of time required to sour food can greatly vary, depending upon the food and the flavor desired. While some simple sour dishes only need minutes to complete, others may require hours for the full process. Either way, the method is still much faster to execute than traditional pickling or fermentation.
Fermented milk products are ironically a prime example of the souring process. Common household foods, from cheese to yogurt, are soured. Sour cream is an obvious chemically soured food item. Other much loved dairy products that require some type of sour agent in their preparation include crème fraîche, curds, and and cultured buttermilk.
Many grain products also feature sourness rendered from this method of food preparation. Sourdough and sour mash are some popular foods that feature the process. Other foods, from appetizers to desserts, may also require a sour element.
Souring food does not always include adding an acidic element. Some foods may sour on account of their own natural microbes. An example of this would be a very popular dairy food, yogurt. This type of souring should be heavily monitored, however, to avoid spoiling and possible health concerns.
When souring at home, a fresh lemon or lime is often recommended as the souring medium. Another easy alternative would be to substitute distilled white vinegar. Most foods do not require a heavy dose of the sour element. A small amount is usually sufficient to render the substance acidulated. Cooks may add additional drops of the sour substance to flavor according to their preferences as well.