Fermented foods have a long history in many cultures. Today, two of the most well-known instances of traditional fermented cabbage side dishes are sauerkraut and Korean kimchi. The Roman writers Cato (in his De Agri Cultura) and Columella (in his De re Rustica) mentioned preserving cabbages and turnips with salt. It is believed to have been introduced to Europe in its present form 1,000 years later by Genghis Khan after invading China. The Tartars took it in their saddlebags to Europe. There it took root mostly in Eastern European and Germanic cuisines, but also in other countries including France, where the name became choucroute.
Before frozen foods, refrigeration, and cheap transport from warmer areas became readily available in northern and central Europe, sauerkraut, like other preserved foods, provided a source of nutrients during the winter. James Cook always took a store of sauerkraut on his sea voyages, since experience had taught him it prevented scurvy.
In Germany, sauerkraut is often flavored with juniper berries. Traditionally it is served with pork, Strasbourg sausage or frankfurters, bacon, smoked pork or smoked Morteau or Montbéliard sausages, accompanied typically by roasted or steamed potatoes or dumplings.
Sauerkraut is the most important ingredient in the shchi, a traditional soup of Russia where it has been known as far back as the 9th century, the time of the import of cabbage from Byzantium.
Sauerkraut, along with pork, is eaten traditionally in Pennsylvania on New Years Day. The tradition, started by the Pennsylvania Dutch, is thought to bring good luck for the upcoming year.
Sauerkraut is made by a process of pickling called lacto-fermentation that is analogous to how traditional (not heat-treated) pickled cucumbers and kimchi are made. The cabbage is finely shredded, layered with salt and left to ferment. Fully cured sauerkraut keeps for several months in an airtight container stored at 15 °C (60 °F) or below. Neither refrigeration nor pasteurization is required, although these treatments prolong storage life.
Fermentation by lactobacilli is introduced naturally, as these air-borne bacteria culture on raw cabbage leaves where they grow. 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, collectively sometimes referred to as population dynamics. In the first phase, anaerobic bacteria such as Klebsiella and Enterobacter lead the fermentation, and begin producing an acidic 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. Properly cured sauerkraut is sufficiently acidic to prevent a favorable environment for the growth of Clostridium botulinum, the toxins of which cause botulism.
A 2004 genomic study found an unexpectedly large diversity of lactic acid bacteria in sauerkraut, and that previous studies had oversimplified this diversity. Weissella was found to be a major organism in the initial, heterofermentative stage, up to day 7. It was also found that Lactobacillus brevis and Pediococcus pentosaceus had smaller population numbers in the first 14 days than previous studies had reported.
The Dutch sauerkraut industry found that inoculating a new batch of sauerkraut with an old batch resulted in an excessively sour product. This sourdough process is known as "backslopping" or "inoculum enrichment"; when used in making sauerkraut, first- and second-stage population dynamics, important to developing flavor, are bypassed. This is due primarily to the greater initial activity of species L. plantarum.
If unpasteurized and uncooked, sauerkraut also contains live lactobacilli and beneficial microbes and is rich in enzymes. The fiber and supply of probiotics improve digestion and promote the growth of healthy bowel flora, protecting against many diseases of the digestive tract.
Sauerkraut has been used in Europe for centuries to treat stomach ulcers, and its effectiveness for soothing the digestive tract has been well established by numerous studies.
During the American Civil War, the physician John Jay Terrell (1829–1922) was able to successfully reduce the death rate from disease among prisoners of war; he attributed this to the practice of feeding his patients raw sauerkraut.
Sauerkraut is a time-honored folk remedy for canker sores. It is used by rinsing the mouth with sauerkraut juice for about 30 seconds several times a day, or by placing a wad of sauerkraut against the affected area for a minute or so before chewing and swallowing the kraut.
The October 23, 2002 issue of the Journal of Agriculture and Food Chemistry reported that Finnish researchers found the isothiocyanates produced in sauerkraut fermentation inhibit the growth of cancer cells in test tube and animal studies. A Polish study in 2010 concluded that "... induction of the key detoxifying enzymes by cabbage juices, particularly sauerkraut, may be responsible for their chemopreventive activity demonstrated by epidemiological studies and in animal models".
Sauerkraut is high in the antioxidants lutein and zeaxanthin, both associated with preserving ocular health.
Due to its necessity in the pickling process, sauerkraut may be very high in sodium, which can increase short-term water retention and blood pressure issues. This may exacerbate pre-existing kidney disease or hypertension. Furthermore, while not necessarily life-threatening, excessive consumption of sauerkraut may lead to bloating and flatulence due to the trisaccharide raffinose, which the human small intestine cannot break down.
During World War I, due to concerns the American public would reject a product with a German name, American sauerkraut makers relabeled their product as "Liberty cabbage" for the duration of the war. (See also: Freedom fries.)
During World War I, British and Commonwealth forces used the word Kraut derived from the dish as a derogatory term for the German people.
During World War II, the term coined by the British was picked up by American Forces.
Many other vegetables are preserved by a similar process.
^Moret, Sabrina et al.; Smela, Dana; Populin, Tiziana; Conte, Lanfranco S. (2005). "A survey on free biogenic amine content of fresh and preserved vegetables". Food Chemistry (Elsevier) 89 (3): 355–361. doi:10.1016/j.foodchem.2004.02.050.
^Pu, C. et al.; Xia, C; Xie, C; Li, K (November 2001). "Research on the dynamic variation and elimination of nitrite content in sauerkraut during pickling". Wei Sheng Yan Jiu30 (6): 352–4. PMID12561618.