Souring

Souring is a food preparation technique that causes a physical and chemical change in food by exposing it to an acid. This acid can be added explicitly, or can be produced within the food itself by a microbe, such as Lactobacillus.
Souring is similar to pickling or fermentation, but souring typically occurs in minutes or hours, while pickling and fermentation can take a much longer amount of time.

Examples

products produced by souring include:
Clabber,
Cheese,
Crème fraîche,
Cultured buttermilk,
Curd,
Filmjölk,
Kefir,
Paneer,
Smetana,
Soured milk,
Sour cream, and
Yogurt.
Grain products include:
Idli,
Sourdough, and
Sour mash.
Others foods produced by souring include:
Ceviche, Kinilaw, and
Key lime pie.