Sauerkraut - an overview | ScienceDirect Topics (2024)

24.7 Concluding Remarks

Sauerkraut is a nutritious fermented vegetable food, highly appreciated for its particular sensory characteristics. There is strong scientific evidence that sauerkraut provides numerous health benefits, such as antioxidant and anticarcinogenic effects, but also by attenuating inflammation and DNA damage. Moreover, sauerkraut is a natural unexplored source of probiotic bacteria that can be potentially used as a starter culture in other vegetable fermentation processes. The health-promoting properties of sauerkraut are attributed to its high levels of bioactive constituents, especially glucosinolate breakdown products. The data pointing to health promotion of sauerkraut are currently coming from invitro and epidemiological studies. Unfortunately, clinical data supporting the potentially health benefits of sauerkraut remain scarce. Therefore, intervention studies are mandatory to confirm the beneficial properties of sauerkraut. Such studies would allow the demonstration of the disease-prevention properties of this fermented vegetable, of great importance since health care costs continue to rise.

Sauerkraut

Sauerkraut is a fermented product made from cabbage and has its roots in central Europe. Germans and the Alsatians prepare sauerkraut as their national dish (Sauerkraut, 2009). Sauerkraut has also been used in Germany for medicinal purposes; traditionally in many parts of southern Germany, some families would feed their children raw sauerkraut two times every week – this was believed to support and strengthen the intestines of the sick children. Sauerkraut is also traditionally produced in the Balkans using whole heads of cabbage instead of shredded cabbage. It is usually produced by spontaneous fermentation. In spontaneous sauerkraut fermentation, Leuconostoc mesenteroides initiate the fermentation process, followed by the growth of other lactic acid bacteria (LAB), mainly Lactobacillus brevis, Pediococcus pentosaceus, and Lactobacillus plantarum species, among which L. plantarum is responsible for the second phase of fermentation and high acidity of the produced sauerkraut. The dominant species, present in the fermentation, shift within 1 week from less acid-tolerant heterolactic to more acid-tolerant hom*olactic fermenting LAB species. Shredded cabbage fermentations start with 10⁶colony-forming unit (cfu)g⁻¹ aerobic microorganisms, 10⁶cfug⁻¹ enterobacteriaceae, and less than 10²cfug⁻¹ yeasts and molds (Tamang and Kailasapathy, 2010). According to Tamang and Kailasapathy (2010), during the first 2 or 3 days of sauerkraut fermentation, less acid-tolerant LAB dominate, but after that more acid-tolerant LAB predominate. Each of these populations reaches concentrations of 10⁸–10⁹cfug⁻¹. The fermentation is complete in 2 weeks and at that time the most acid-resistant L. plantarum predominates. Salt concentration and fermentation temperature can also affect the growth of the naturally present microorganisms and the sensory properties of the sauerkraut (Wiander and Ryhanen, 2005). Two percentage of salt is usually added to the traditional fermentation, and to reduce salt waste.

In a study of two commercial sauerkrauts, Plengvidhya et al. (2007) reported that glucose and fructose were the primary fermentable sugars in the cabbage, with concentrations of 1.5% and 2.2%, respectively, and sucrose concentration was less than 0.2%. Lactic acid, acetic acid, and mannitol were produced, and on the 14th day the pH value of all the tanks increased from 3.4 to 3.7.

27.3.5.1 Sauerkraut

Sauerkraut has been very popular in many European countries due to its sensorial properties and favorable nutritional value. The fermentation process can be carried out spontaneously or by adding starter cultures (controlled fermentation). Among microorganisms contributing to sauerkraut production, Leuconostoc mesenteroides, Lactobacillus plantarum, Lactobacillus brevis, Pediococcus, and Enterococccus are of special importance.

The BA content of sauerkraut is highly influenced by cabbage variety, fermentation conditions (temperature, pH value change, oxygen access, or sodium chloride content), microbial starters used for fermentation and bacterial contamination. The main amines found in sauerkraut are Put, Him, Tym, and Cad, while Spm and Spd occurred only in small amounts (Kalac etal., 2000a, 2000b; Spicka etal., 2002).

Kalac etal. (1999) tested more than 120 sauerkraut products from Czech and Austrian manufacturers and the concentrations of BA varied greatly (Put 2.8–529.0mg/kg, Cad 0–293.0mg/kg, Tym 0–37.5mg/kg, Spd 0–47.0mg/kg, Him 0–229.0mg/kg). In spontaneously fermented sauerkraut, Tym (85–578mg/kg) was present at the highest levels after 12months of storage, followed by Put (10–233mg/kg) and Cad (2–31mg/kg). Spd concentrations were below 14mg/kg (Kalac etal., 2000a). A high level of Put (265–446mg/kg), Tym (85–212mg/kg), and Cad (60–122mg/kg) in control sauerkraut variants was significantly suppressed by Lactobacillus plantarum and Microsil (Kalac etal., 2000b). The accumulation of BA in spontaneously fermented Chinese sauerkraut exhibited Put (24–45mg/kg), Cad (10–35mg/kg), and Tym (30–38mg/kg) concentrations that increased with the fermentation time. However, in sauerkraut inoculated with L. plantarum and Zygosaccharomyces rouxii, BA contents decreased significantly (Wu etal., 2014).

Sauerkraut

Sauerkrauts, widely consumed in many European countries and in the United States, are manufactured by spontaneous lactic fermentation of white cabbage (Brassica oleracea L. var. capitata). After removal of the core and outer leaves, fresh cabbage is shredded and mixed with 2–3% (w/w) salt before allowing for natural fermentation. Cabbages are quickly surrounded by brine and covered with plastic sheeting draped over the tank, to ensure air exclusion. Sauerkraut production typically relies on a sequential microbial process that involves hetero- and hom*ofermentative lactic acid bacteria, such as Leuconostoc spp. and Weissella spp. in the early phase and Lactobacillus spp., Lactococcus lactis, and Pediococcus spp. in the subsequent phases. Lactobacillus plantarum prevails during late fermentation, leading to further acidification and a final pH of ~3.5–3.8. Sauerkraut brine is an important by-product of the cabbage fermentation industry and may be used as a substrate for the production of carotenoids by Rhodotorula rubra. Sauerkraut fermentation lasts several weeks, depending on the fermentation conditions, sensory attributes, the autochthonous microbiota of cabbages, and the related sugar contents. Secondary fermentations, such as those carried out by yeasts, are undesirable.

Sauerkraut

Sauerkraut is the product resulting from the natural lactic acid fermentation of salted, shredded cabbage. The German word literally translated means acid (sauer) cabbage (kraut). The heads of cabbage are trimmed to remove the outer green, broken, or dirty leaves, and the core is bored or partly removed. Subsequently, the cabbage is shredded into 0.7–2mm wide strips that, in most cases, are salted with 0.7–2.5% salt. The shredded cabbage is placed into fermentation containers. Filling and pressing the cabbage into the fermenters together with added salt lead to an osmotic withdrawal of water out of tissue cells and, as a consequence, brine is formed. Finally, the surface of the filled containers must be covered carefully in order to exclude oxygen and microbial contamination. Usually, a sheet of plastic large enough to cover more than the area of the top of the fermenter is used. Depending on the temperature, a ‘spontaneous’ fermentation will start within a few hours to 1–2 days and will continue between 7 days and several weeks. The microbial growth sequence of spontaneously fermenting cabbage is invariably initiated by Leuconostoc mesenteroides, followed by heterofermentative LAB, and finally hom*ofermentative LAB. A completely fermented sauerkraut contains 1.8–2.3% acid (calculated as lactic acid) giving a pH of 3.5 or less. Lactic and acetic acids are the predominating acids, but other organic acids such as succinic, malic, and propionic acids may also be formed in smaller quantities. Ethanol, mannitol, CO₂, and other compounds are produced in variable amounts as a result of the metabolism of heterofermentative LAB. Sauerkraut may be packaged in cans, glass jars, or plastic bags. Refrigerated sauerkraut, packaged in glass or plastic, is an unpasteurized product to which preservatives (e.g., sodium benzoate or potassium metabisulfite) are added. Pasteurized sauerkraut, packaged in cans or glass jars, can be made by pasteurization at 74–82°C for 3min.

Sauerkraut

Sauerkraut is a vegetable food widely consumed in many European countries. It has usually been prepared by spontaneous lactic fermentation of shredded cabbage (Brassica oleracea L. variety capitata), both by manufacturers and in households. Fresh cabbage is trimmed of outer leaves and shredded and successively mixed with salt to obtain a final concentration of approximately 2% NaCl (wt/wt). The cabbage is quickly surrounded by brine and then covered with plastic sheeting draped over the tank. Water is added to improve anaerobic conditions and prevent contact with air, which may cause a loss of microbiological quality. After 24–48h, anaerobic conditions are established thanks to the exhaustion of oxygen and CO₂ production from heterofermentative lactic acid bacteria. The combination of salt concentration and temperature (18°C) allows a spontaneous lactic acid fermentation, although variations of these conditions are not uncommon and affect the competitiveness of the naturally present microorganisms. The microbial species typically isolated during sauerkraut fermentation are Leuc. mesenteroides, P. pentosaceus, L. brevis, and L. plantarum. Leuc. mesenteroides and Weissella spp. typically dominate the early stages of fermentation because they are present in larger cell numbers and have faster growth compared with the other lactic acid bacteria in cabbage juice. The increase of lactic acid concentration inhibits the multiplication of Leuc. mesenteroides while it promotes the growth of acid-tolerant species, such as L. brevis and in some cases L. curvatus, Lactobacillus sakei, E. faecalis, Lactococcus lactis subsp. lactis, and P. pentosaceus. L. plantarum becomes predominant in the latter stage, about 5–7 days after the beginning of fermentation, contributing to a further decrease of the pH value (∼3.5). The end products resulting from both the stages of fermentation may include mannitol and acetic acid (∼1% each) and lactic acid, which may exceed 2%, depending on how long the hom*olactic fermentation is allowed to continue.

Leuconostoc fallax

Leuconostoc fallax is isolated from sauerkraut, from which a great diversity of strains is described. Regarding the main phenotypic traits, this species is not really different from L. mesenteroides, but it is quite distinct when DNA analysis is performed. It is now considered to be a new species in the genus, even though it is peripheral on the phylogenetic tree. Contrary to Leuconostoc in general, however, strains of this species cannot decarboxylate malic acid to lactic acid. A strain of L. fallax isolated from Gerbera sap is acid and ethanol tolerant (up to 9%v/v).

6.2.2.6 Pickled vegetable products

Leuconostoc mesenteroides initiates the lactic acid fermentation of sauerkraut and vegetable pickles. It can tolerate fairly high concentrations of salt and sugar compared to other lactic acid bacteria. It produces CO₂ and acids, which rapidly lower the pH and inhibit the development of spoilage microorganisms. The CO₂ replaces oxygen, to produce an anaerobic environment that is suitable for growth of subsequent Lactobacillus spp. Removal of oxygen also preserves the colour of vegetables and stabilises ascorbic acid. Olives and cucumbers are submerged in 2–6% brine, which inhibits the growth of putrefactive spoilage bacteria. The brine is inoculated with either Lactobacillus plantarum alone or a mixed culture with Pediococcus pentocacus or P. cerevisiae. Alternatively, a naturally occurring sequence of lactic acid bacteria grows in the anaerobic conditions to produce approximately 1% lactic acid. Nitrogen gas may be continuously purged through the vessel to remove carbon dioxide and to prevent cucumbers splitting. Other methods of pickling involve different salt concentrations: for example in ‘dry salting’ to make sauerkraut or kim-chi, alternate layers of vegetable and granular salt are packed into tanks. Juice is extracted by the salt to form a brine and the fermentation takes place as described above. In each case preservation is achieved by the combination of acid and salt, and where products are packed into jars, by pasteurisation. Videos of pickle production are available at www.youtube.com/watch?v=W-bJwWqbSbA and www.youtube.com/watch?v=SE8gKjvzbz0.

Should Fermented Foods be Consumed to Improve Gut Health?

The consumption of traditionally fermented foods, such as sauerkraut, kefir, yogurt, miso, and others has been associated with several health benefits, but direct evidence for the benefits of various foods remains limited. Intake of fermented foods has been associated with weight maintenance (Mozaffarian et al., 2011) and a reduced risk of type 2 diabetes (Chen et al., 2014) and cardiovascular disease (Tapsell, 2015), with several randomized, controlled trials supporting a causal link between fermented foods and improvement in metabolic parameters (e.g., Kim et al., 2011).

Fermented foods provide the benefits associated with nutrients contained in the foods, of course, but additional benefits may accrue from the transformation of the substrates by live microbes and/or from the presence of live microbes at the time of consumption. Various researchers have proposed that—depending on the raw materials and the microbe(s) involved in the fermentation process—a fermented food could in theory inhibit the growth of pathogens in the gut, improve food digestibility, or enhance vitamin synthesis or absorption (Marco et al., 2017). In addition, while the species of lactobacilli and bifidobacteria found in many fermented foods do not qualify as probiotics because they are uncharacterized, these species may be either identical to or share traits with known probiotic species (Marco et al., 2017); thus, a reasonable argument can be made that they provide health benefits and therefore should be consumed as part of a health-promoting diet.

9.6 Kasseler (Austria and Germany)

Kasseler is a traditional ham product and primarily eaten together with sauerkraut and dumplings. The pork loin, boneless or bone in, skin and fat removed, is used in a very similar way to that of a master ham (see above) with the additives used being more or less the same. The prepared loin is injected at 15–25% and occasionally slightly tumbled afterwards for around 500 rev. Tumbling is more common for boneless loins, as the bones in bone-in products damage the other pieces of meat during tumbling. Non-tumbled meat is frequently placed in cover brine for 12–24 h before being hung. The next stage is drying at 60–70 °C, followed by smoking at 65–70 °C and finally cooking with steam or a hot-water bath at 74–78 °C until a core temperature of 68–70 °C is obtained. The chilled product is sliced and usually vacuum packed. Restaurants serve the slices hot with dumplings and sauerkraut.