Sauerkraut

Sauerkraut

This article is majorly focused on what sauerkraut is, spontaneous fermentation, The shift in microbial community and defects of sauerkraut fermentation.

Sauerkraut

Sauerkraut is "acidic cabbage." It results from a spontaneous fermentation by bacteria indigenous to cabbage in the presence of 2 to 3% salt. 

The fermentation yields lactic acid as the predominant product. This lactic acid, along with other minor end products of fermentation, gives sauerkraut its typical flavour and texture.

Spontaneous fermentation 

As no starter cultures are added to the system, this is a spontaneous fermentation. The wild flora of the cabbage leaves is relied upon to include the organisms responsible for a desirable fermentation that will enhance preservation and organoleptic acceptability. The floral succession is governed mainly by the pH of the growth medium.

Natural lactic acid bacteria carry out fermentation. No heat process to inactivate other microflora.

The shift in microbial community

The fermentation depends on a consortium of bacteria representing different genera and species. 

A given organism or group of organisms initiates growth and gets established for a certain period. 

Due to the accumulation of inhibitory compounds, growth slows down and gives way to other species that are less sensitive to those factors.

A definite sequence of lactic acid bacterial species is required, initiated by the heterofermentative Leuconostoc mesenteroides.

Followed by heterofermentative rods such as Lactobacillus brevis, homofermentative Lactobacillus plantarum, and Pediococcus

• Leuconostoc mesenteroides have relatively a short lag phase and 

• The acidic environment around (0.6%-0.8%, as lactic acid) inhibits non-lactic competitors and favours other lactic acid bacteria.

• Once the acid approaches 1.0%, inhibition of Leuconostoc mesenteroides takes place.

Then successively, Lactobacillus brevis, Lactobacillus plantarum, Pediococcus cerevisiae increase rapidly.

Contribute to the major end-products, including lactic acid, acetic acid, carbon dioxide, ethanol

Minor end products

Volatile compounds such as diacetyl, acetaldehyde, sulphur compounds, ethyl butyrate, etc.

• Final acidity 1.7%, 

• pH 3.4-3.6

The sauerkraut fermentation process utilizes the wild microflora in the raw cabbage to produce lactic acid. This creates a highly acidic environment. The lactic acid is what gives the sauerkraut its characteristic sour flavour. Salt is added to the raw cabbage to draw out much of the moisture and to inhibit salt intolerant bacteria.

This allows the acid-producing bacteria to get a strong foothold and dominate the population.

Throughout the fermentation, oxygen has to be excluded. The presence of oxygen would permit the growth of some spoilage organisms, particularly the acid-loving moulds and yeasts.

To prepare sauerkraut, the cabbage must be shredded to produce a large surface area for the growth of the microbes and to extract the plant juice nutrients, which will be metabolized by the microbes. 

Sodium chloride (table salt) is added to a concentration of 3% to provide OPTIMUM CONDITIONS FOR GROWTH of the desired fermenting bacteria to help EXTRACT the tissue juices and to INHIBIT the growth of undesirable microbes that would ruin the cabbage.

The cabbage-salt mixture is compressed down to squeeze out the juices and incubated at room temperature in covered containers. The cover inhibits the entry of OXYGEN into the mixture and allows ANAEROBIC FERMENTATION to occur. At the end of the fermentation period, the pH should be ~ 2.0, and the sauerkraut should contain about 1% lactic acid.

Defects of sauerkraut fermentation

• Discoloration (oxidation)

• Loss of acidity

• Off flavour and odours (mouldy, yeasty, rancid)

• Slimy

• Softened kraut and pink-coloured kraut due to aerobic growth of moulds and/yeasts

Conclusion

This article was majorly focused on what sauerkraut is, spontaneous fermentation, The shift in microbial community and defects of sauerkraut fermentation.

References

Laboratory Exercise in Sauerkraut Fermentation. https://www.jlindquist.com/generalmicro/324sauerkraut.html

Kraut and Kimche Recipes - Learn How to Raise Chickens. https://www.backyardchickens.com/threads/kraut-and-kimche-recipes.435052/