Sauerkraut is finely shredded cabbage that has been fermented by various lactic acid bacteria, including Leuconostoc, Lactobacillus, and Pediococcus.
It has a long shelf-life and a distinctive sour flavor, both of which result from the lactic acid that forms when the bacteria ferment the sugars in the cabbage. It is therefore not to be confused with coleslaw, which receives its acidic taste from vinegar.
The word comes directly from the German language, which literally translates to sour cabbage.
Sauerkraut is a traditional German and Czech food, but it is also a prominent feature of traditional cuisines of The Netherlands (zuurkool), Estonia (hapukapsas), Latvia (sk?bi k?posti) and other Northern, Central and East European cuisines, such as the Northern parts of Italy (Friuli-Venezia-Giulia, Trentino), Romanian, Serbian, Croatian, Polish, Russian, Ukrainian, Hungarian and Belarusian. It is also part of the native cuisine of Alsace Lorraine in North Eastern France. Finally, it is no less popular in many parts of Northeast China, Northern China, the USA, Chile, and Canada.

Fermentation of cabbages in salt and acidic liquids dates back to prehistoric times and probably was described first by Pliny the Elder during the first century AD. Modern preparation techniques are thought to have been developed sometime between AD1550 and 1750.

In his 1772 Treatise on Scurvy, James Lind discussed the ability of German seamen to withstand long sea voyages without succumbing to scurvy compared to seamen from other countries, and pointed to their consumption of fermented cabbage as a defining difference.

In 1776, Captain James Cook was awarded the Copley Medal for demonstrating that sauerkraut could be used to allay scurvy in British crews on long sea voyages.

Preparation

Storage
Traditionally, sauerkraut is prepared in a stoneware crock and the seal is created with a piece of wet linen cloth, a board, and a heavy stone. This arrangement is not fully airtight and will lead to spoiled sauerkraut unless the surface of the brine is skimmed daily to remove molds and other aerobic contaminants that grow on the surface where there is contact with air.

An alternative that avoids this problem is a type of ceramic jar that has a trough around its lid. When this trough is filled with water, the result is an airtight seal.

Glass canning jars with clamped threadless lids may also be used effectively.

Commercial-scale sauerkraut production typically employs large airtight plastic barrels fitted with one-way valves for the gas to escape.

Whatever kind of vessel is used, it must allow the escape of fermentation gases.

Fermentation
Sauerkraut is made by a process of pickling called lacto-fermentation that is analogous to how traditional (not heat-treated) pickled cucumbers are made. Fully-cured sauerkraut keeps for several months in an airtight container stored at or below 15°C (59°F). Neither refrigeration nor pasteurization is required, although these treatments may prolong storage life. However, pasteurization will destroy all of the beneficial digestive enzymes and lactic acid bacteria, as well as the valuable vitamin C content, so it greatly diminishes the nutritional value without any significant benefit.

No special culture of lactic acid bacteria is needed because these bacteria already are present on raw cabbage. Yeasts also are present, and may yield soft sauerkraut of poor flavor when the fermentation temperature is too high. The fermentation process has three phases. In the first phase, anaerobic bacteria such as Klebsiella and Enterobacter lead the fermentation, and begin producing an acid environment that favours later bacteria. The second phase starts as the acid levels become too high for many bacteria, and Leuconostoc mesenteroides and other Leuconostoc spp. take dominance. In the third phase, various Lactobacillus species including L. brevis and L. plantarum ferment any remaining sugars, further lowering the pH.

Salt (sodium chloride) is a major component in both the fermentation process and the flavour profile of sauerkraut, and typically is added in proportions between 0.6% and 2% relative to the amount of cabbage. For preparation at home, the USDA recommends a greater amount of salt than is traditional, making the sauerkraut unpalatably salty unless rinsed before eating. Such rinsing removes much of the nutrient content and flavor. When traditional amounts of salt are used, temperature control is critical, because spoilage leading to food poisoning can occur if the fermentation temperature is too high. However, once made, sauerkraut is a very safe food because its high acidity prevents spoilage. USDA also recommends pasteurizing sauerkraut for storage. This is not necessary if the raw sauerkraut has been properly made and stored, and will needlessly diminish the nutritional value. A slimy or excessively soft texture, discoloration, or off-flavor may indicate spoilage.

Health benefits
Raw sauerkraut is an extremely healthy food. It is an excellent source of vitamin C, lactobacilli, and other nutrients. However, the low pH and abundance of healthful lactobacilli may upset the intestines of people who are not used to eating acidic foods. (In such cases, it is advisable to eat small amounts daily until the person's digestive system adjusts).

Before frozen foods and the importation of foods from the Southern hemisphere became readily available in northern and central Europe, sauerkraut provided a vital source of the aforementioned nutrients during the winter. Captain James Cook always took a store of sauerkraut on his sea voyages, since experience had taught him that it was an effective preventative of scurvy.

It is now known that the preservation of sauerkraut in an anaerobic environment (in the brine) keeps the vitamin C in it from being oxidized. There is some evidence that indicates that kimchi, and by extension, sauerkraut may be used to treat avian influenza in birds. Currently, there is no evidence of its effect on human cases.

Sauerkraut is also a source of biogenic amines such as tyramine, which may cause adverse reactions to sensitive people. It also provides various cancer fighting compounds including ITC and sulphoraphane.

Sauerkraut is made by a process of pickling called lacto-fermentation that is duplicated to how traditional (not heat-treated) pickled cucumbers and kimchi are made. Fully-cured sauerkraut keeps for various months in an airtight container stored at or below 15°C (59°F). Neither refrigeration nor pasteurization is needed, although these treatments may prolong storage life.

Sauerkraut is great with sausage and bread but i love it in a soup called bigos