Vegetable Fermentation. It involves a complexity of physical, chemical and microbiological factors that have been well characterized in recent decades. Microbial activities during natural fermentation and storage of vegetables has been divided into four stages: initiation of fermentation, primary fermentation, secondary fermentation, and post-fermentation.
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- 1 Fermentation
- 2 Sauerkraut or Sauerkraut
- 3 General method of production
- 4 Defects that may arise
- 5 Source
Fermentation is produced by the action of different types of microorganisms ( bacteria , yeasts and fungi ) on food, producing chemical changes that transform the original product and transmit pleasant characteristics to taste.
The fermentation process enables preservation when acids or alcohol are produced. However, in most cases, the transformation of the original food is so profound that a totally different product is generated from the initial one. This is the case of alcoholic beverages, vinegar and others.
The best-known fermentation of foods are those carried out with the intervention of yeasts and bacteria for the production of alcohol , acetic acid ( vinegar ) and lactic acid.
Sauerkraut or Sauerkraut
The lactic acid produced from the sugars available from vegetables by the action of bacteria, enables their natural preservation and gives a special flavor to these products. Conservation is facilitated with the addition of salt and when anaerobic conditions (without oxygen ) are maintained at adequate temperatures for the growth of the microorganisms involved in the process.
The best known product that can be produced and preserved by lactic acid fermentation of cabbage, is the so-called “Sauerkraut”, which in German means sour cabbage and that the French names “Choucroute” (aged cabbage). In Spanish it is identified by names in other languages or by sour cabbage or “Chocruta”. The production of this canning, so popular in some European countries , was developed when the knowledge of food Microbiology was still incipient. It is a food highly prized for its healthy, nutritional and digestive properties.
The original procedure used in the preparation of sauerkraut, has also been applied by the authors of this work to other vegetables such as carrots, squash, green tomatoes and others.
The main advantage of this form of preservation is that only small amounts of salt are required in its elaboration, since the fermentation takes place from the sugars contained in the natural juices of the vegetables and the bacteria that accompany them.
General production method
The general method of production is very simple. It starts from the vegetables finely cut into strips or small pieces. Subsequently, about 2.5% salt by weight is added. The latter is done by initially mixing the salt with the crushed vegetables or sprinkling the salt between successive layers of the food.
The bales are placed in the container where the fermentation takes place. Vegetables in both cases are compressed well as they are introduced into the container, forming successive layers as if it were being made in biological silage.
At the end, a layer of salt is sprinkled on the surface and a weight is placed to keep the mass of the vegetables pressed or compressed to favor anaerobic conditions.
This can be accomplished with a polythene bag filled with water that fits the entire mouth of the container and in turn avoids contact with the weather. The containers should be covered with a cloth that is placed on the surface to avoid contamination by insects or dust from the atmosphere .
Fermentation is completed between 4-6 weeks, where a lactic acid concentration of 1.5-1.7% and a pH of 3.4-3.7 are reached. however, it can definitely be cold-packed in smaller, previously sterilized jars after the first or third week and fermentation is finished in these hermetically sealed containers. The jars can also be pasteurized with the product and thus stop fermentation.
During the fermentation or silage process, the container containing the vegetables must remain in a quiet bind and avoid movements or excessive manipulation.
Defects that may arise
The most important defects of fermented vegetables are due to undesirable growths of fungi, yeasts and bacteria. The product, then, results in undesirable, soft, viscous, or spoiled or rotten looking flavors. The main causes may be: excessive or poorly distributed amount of salt, exposure of the product to air , too much pressure and inadequate temperature . In the case of cabbage, a pinkish coloration may occur due to the presence of yeast .
After fermentation is complete, fungus can also grow on the surface if the preserve is not hermetically sealed. This causes an increase in pH and subsequently facilitates the growth of bacteria.