Pickling, also known as brining or corning, is the process of preserving food by anaerobic fermentation in brine (a solution of salt in water), to produce lactic acid, or marinating and storing it in an acid solution, usually vinegar (acetic acid). The resulting food is called a pickle. This procedure gives the food a sour taste.
The distinguishing feature is a pH less than 4.6, which is sufficient to kill most necrobacteria. Pickling can preserve perishable foods for months. Antimicrobial herbs and spices, such as mustard, garlic, cinnamon or cloves, are often added.
If the food contains sufficient moisture, a pickling brine may be produced simply by adding dry salt. For example, sauerkraut and Korean kimchi, are produced by salting the vegetables to draw out excess water. Natural fermentation at room temperature, by lactic acid bacteria, produces the required acidity. Other pickles are made by placing vegetable in vinegar. Unlike the canning process, pickling, which includes fermentation, requires that the food not be completely sterile before it is sealed. The acidity or salinity of the solution, the temperature of fermentation, and the exclusion of oxygen determine which microorganisms dominate, and determine the flavor of the end product. (McGee 2004, p. 291-296)
When both salt concentration and temperature are low, Leuconostoc mesenteroides dominates, producing a mix of acids, alcohol, and aroma compounds. At higher temperatures Lactobacillus plantarum dominates, which produces primarily lactic acid. Many pickles start with Leuconostoc, and change to Lactobacillus with higher acidity. (McGee 2004, p. 291-296)
Pickling began as a way to preserve food for out-of-season use and for long journeys, especially by sea. Salt pork and salt beef were common staples for sailors before the days of steam engines. Although the process was originally used to preserve foods, pickles are frequently eaten because people enjoy the resulting flavor. Pickling may also improve the nutritious value of food by introducing B vitamins produced by bacteria.