Lactic fermentation

Lactic fermentation. It is an anaerobic metabolic pathway that occurs in the cell’s cytosol , in which glucose is partially oxidized for energy and where the waste product is lactic acid . This process is carried out by many bacteria (called lactic bacteria), some protozoa, and it occurs in animal tissues, in certain protozoa, fungi and bacteria.

Summary

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  • 1 History
    • 1 First applications in the industry
  • 2 Lactic acid bacteria and lactic cultures
    • 1 Industrial interest
    • 2 Biological process
    • 3 Foods undergoing the lactic fermentation process
  • 3 General considerations
    • 1 Process
    • 2 Lacto-bacteria
  • 4 Specific lactic fermentations
    • 1 Fermentation of milk
    • 2 Lactic fermentation in vegetables
    • 3 Lactic fermentation of legumes
    • 4 Lactic fermentation in meat and fish
  • 5 Culinary preparations
  • 6 See also
  • 7 References
  • 8 Bibliography

History

Lactic acid (known as 2-hydroxy-propanoic acid ) was part of the first investigations in the history of organic chemical chemistry as it was a relatively simple molecule: C 3 H 6 O 3 . It is identified by the Swedish chemist Carl Wilhelm Scheele in 1780 from sour milk. Its abundance in nature is mainly due to the frequency of the biological process that affects milk , the fermentation of fruits and vegetables , as well as sausages. It is precisely the spontaneity of this biological process that suggests that lactic fermentation has accompanied man since prehistoric times . [1] The process may exist even in the early stages of life on earth. Fermentation processes in general have accompanied the feeding processes in the history of humanity.

In the west during the period of the Roman Empire, fish sauce was fermented, there being four types: garum, liquamen, allec, and muria. Garum was a lactic fermentation to which carbohydrates were added. [2] In the Asian cuisines have frequently used the lactic fermentations in food processing since prehistoric times.

In traditional Chinese cuisine the use of fermented dairy products , called “Lao”, has played an important role in the nomadic Han peoples of northern China . Lactic fermentations have supposed to be an advance to nomadic tribes from different parts of the earth, they provide a way to preserve and maintain food for long periods of time.

In the Mongol empire , during the 12th century , koumiss emerged  as an ideal dairy fermentation for feeding warriors on horseback. Milk from any animal was introduced into a leather hide, and the fermentation provided a liquid that remained unchanged for weeks.

The fermentation of the cabbages caused that in the Middle Ages the sailing ships of Northern Europe decreased the appearance of cases of scurvy . Scurvy is an avitaminosis disease caused by a lack of vitamin C , a vitamin that could be ingested in sauerkraut that could be kept edible for long months in the holds of ships. [3] Traveler James Cook   used sauerkraut as food on all his expeditions. Previously, the Roman writer Columela mentions in his work Re Rusticathe ability to keep cabbages in a brine for long periods of time. The fermentation process was not understood, it was performed through a ritual to certain foods. It was not until the middle of the 19th century when it began to be understood that it is a biological process.

First applications in the industry

One of the first industrial applications was the use of lactic acid as a fabric bleaching agent in the early pre-industrial textile industry. The French chemist Louis Joseph Gay-Lussac in collaboration with Théophile-Jules Pelouze carry out research with fermented beets in which he obtains lactic acid.

In 1808, Jöns Jacob Berzelius discovered that lactic acid is released into the muscles by making intense physical efforts.

In 1856 Louis Pasteur discovered lactobacillus and its role in the production of lactic acid, the clue was provided to him by physicist Jean Baptiste Biot . It was from this discovery by Pasteur that the fermentation processes began to be understood.

Lactic acid begins to be produced commercially by the German company Boehringer Ingelheim in 1895. The production of lactic acid is carried out thanks to the activity of a bacterium called bacterium lactis . [4] These bacteria were differentiated from the yeasts responsible for the alcoholic fermentation of wine.

It is precisely the biologist Joseph Lister who begins to investigate the bacteria responsible for lactic fermentation in order to understand the process from a biological point of view. [5] In 1950, a Japanese company began artificially producing lactic acid without fermentation. The mechanisms of glycolysis have been known since 1940, including the final variants of alcoholic and lactic fermentation.

Lactic acid bacteria and lactic cultures

Lactic acid bacteria (BAL), or also lactic acid bacteria and lactic cultures – due to their characteristics when processed and multiplied for use as a group – comprise a clade of fermenting and lactic acid producing bacteria, a function by which They are used in the industry to give certain qualities to foods and protect them against the action of other harmful organisms. One of them may be the bactobacilli which provide the product with good care.

Industrial interest

Among those of industrial interest are, among others, the species of the genera: Streptococcus, Lactobacillus Thermophile, Bulgarian Lactobacillus and Leuconostoc, which produce yogurt and cheese. Heterofermentative 🙁 other products are obtained apart from lactic acid such as ethanol and water). An example of this type of fermentation is the acidification of milk.

Certain bacteria (lactobacilli), when developing, use lactose (milk sugar) as an energy source. Lactose, when fermented, produces energy that is used by bacteria and lactic acid is eliminated. Milk coagulation (curd) results from the precipitation of milk proteins, and occurs due to the drop in pH due to the presence of lactic acid.

Biological process

The lactic fermentation is an anaerobic metabolic pathway Digestion occurs in the cytoplasmic matrix of the cell , in which ferments the glucose (are redox partially) for metabolic energy and a waste product which mainly is lactic acid (fermentation homolactic), in addition to other acids (heterolactic fermentation).

It is a biological process in which the sugars present in the medium (generally six-carbon sugars such as glucose , galactose and fructose ) are transformed into lactic acid. [6] The presence of lactic acid as a metabolite in food causes the deactivation of decomposition processes , and therefore lactic fermentation is traditionally used as a method of preserving food.

The bacteria capable of promoting this biological process called lactic acid bacteria . [7]

Lactic fermentation is also verified in muscle tissue when, due to intense anaerobic motor activity , there is not an adequate supply of oxygen that allows the development of aerobic respiration . When lactic acid accumulates in muscle cells it produces symptoms associated with muscle fatigue . Some cells , such as erythrocytes , lack mitochondria so that they are forced to obtain energy through lactic fermentation; on the contrary, the parenchymait dies quickly as it does not ferment, and its only source of energy is aerobic respiration .

Foods undergoing the lactic fermentation process

Foods that are subjected to this process of lactic acid fermentation are fresh vegetables such as cabbage ( sauerkraut German , or kimchi Korean ), the pickles of vegetables ( pickles ), the yogurt fermented cereal (the ogi

Nigerian , or uji in Kenya ), the loaves of sourdough or substitute products that are made without wheat or barley (the idli Indian or fucking Philippines), fermented milk (yogurt and cheese), mixtures of cereal and milk ( Egyptian kishk or Greek trahanas ), protein-rich vegetables that are meat substitutes ( Indonesian tempeh ), sauces and pasta produced by lactic fermentation of cereals and legumes ( Japanese miso , Chinese soy sauce ), the mixture of prawns and cereal (the Balao-balao and buron Dalag of Philippine ) and some luncheon meats such as salami . [8]

General considerations

The fermentation is usually produced by bacteria in the absence of air (anaerobic environment), acting on the sugar contained in plants and fruit, or seeds.

Lactic fermentation has the characteristic of also occurring in animal tissues under anaerobic conditions. Fermentation is a metabolic process in bacteria that aims to obtain energy from certain molecules: generally sugars. The energy obtained in cells from fermentation is stored in molecules such as ATP ( adenosine triphosphate ), which is formed by breaking a high-energy bond in glucose and which stores the energy released in the ATP bonds. [6]

Anaerobic fermentation, in all possible cases, begins with a first phase with glycolysis that has a metabolic route such as the Entner-Doudoroff route . Glycolysis generates pyruvate (pyruvic acid salts) as a result. The pyruvate obtained can be broken down by different anaerobic routes that lead to the formation of characteristic compounds that define the different types of fermentation.

There are two types of lactic fermentation, depending on the final product:

  • Homolactic fermentation.- The fermentative process in which its final product is only lactic acid. Technically it consists of the transformation of pyruvate into lactate in a single stage. It occurs mainly in animal tissues, in some varieties of fungi,and in lactic acid bacteria of the genera Streptococcus , Pediococcus and some species of Lactobacillus . These bacteria are characterized as homofermenters.
  • Heterolactic fermentation – Lactic acid and other compounds such as aceticand formic acids ( Bifidobacterium ), carbon dioxide and ethanol ( Leuconostoc ) are produced in this type of fermentation . Bacteria are heterofermentative.

There are fermentations such as malolactic fermentation that, following a natural process, malic acid is converted by degradation into lactic acid. Malic acid is found in some fruits, such as apples , grapes , etc. This process occurs in the maturation of red wines , as well as in the production of beers .

Process

For every glucose molecule that is oxidized by glycolysis, two NAD molecules are reduced to NADH, and two pyruvates and two ATP molecules are obtained. In fermenting organisms, given the impossibility of using the reducing power generated in the form of NADH in the electron transport chain , the reduction of an endogenous substrate (that is, a product of metabolism itself) is used as a way to recycle the NADH in NAD to allow glycolysis to continue and ATP to continue to be generated.

In lactic fermentation, the endogenous substrate used is pyruvate itself, the product of glycolysis, which is reduced to lactic acid. The lactic acid , since it gives acidity to the medium, has excellent food preservatives .

Glycolysis:

Glucose (C 6 H 12 O 6 ) + 2 ADP + 2 Pi + 2 NAD —> 2 Pyruvate (C 3 H 4 O 3 ) + 2 ATP + 2 NADH + 2 H +

Reduction of pyruvate to lactate:

2 Pyruvate (C 3 H 4 O 3 ) + 2 NADH + 2 H + —> 2 Lactate (C 3 H 6 O 3 ) + 2 NAD

Fermentation of one mole of glucose generates two moles of lactic acid.

Lacto-bacteria

Lacto-bacteria belong to the gram positive group of bacteria , they are unable to breathe oxygen, unable to form spores , cocci or tubes. They lack cytochromes and are unable to synthesize porphyrins . Their main characteristic is that they produce lactic acid when they are in the presence of carbohydrates. Historically, bacteria from the genus Lactobacillus , Leuconostoc , Pediococcus and Streptococcusare the species considered as lactic. Most of them are homo-fermentative. Some others have been identified, but have a minor role in lactic fermentation.

Specific lactic fermentations

Most types of lactic fermentation that occur in the food industry are due to the great storage capacity of lactic acid, resulting from fermentation. Three well-differentiated groups can be found in this process, on the one hand the fermentation of milk, the fermentation of vegetables, and finally that of legumes and seeds. This type of fermentation is favored by the addition of salt , or even a brine (in concentrations between 10% and 20%). The introduction of lactic fermentation in the food industry allows the process to be carried out in such a way that the food is first fermented, and then pasteurized.

This final pasteurization process can only be done in some foods due to their rheological properties , being easier to perform in those that can flow. With the exception of milk and cheeses that usually start from already pasteurized milk, which is then inoculated with the cultures responsible for initiating fermentation. The bacteria responsible for lactic fermentation can be different in each case, and often the fermentation is plural. That is, various bacterial cultures can compete / collaborate in the final generation of lactic acid as a metabolite. Often the primary fermentation develops and ends up leading to the secondary fermentations favored by the pH.

Milk fermentation

Much of the fermented milk products are achieved through this type of fermentation. The sugar that intervenes in the fermentation is lactose and approximately 30% is consumed during the process. [9] The milk fermentation process is complex and various theories such as microbiology, biochemistry, enzymology, chemistry, and physics are involved. The possible variation of fermentations allows almost 400 possible denominations of fermented milk products to exist throughout the world. They range from the most traditional products to the most refined procedures in the food industry.

An example of this type of fermentation is the acidification of milk . Certain bacteria ( Lactobacillus , Streptococcus ), when growing in milk, use lactose (milk sugar) as an energy source. Lactose, when fermented, produces energy that is used by bacteria and lactic acid is eliminated. Coagulation of milk ( curd ) results from the precipitation of milk proteins ], and occurs due to the decrease in pH ( acidification ) due to the presence of lactic acid. This process is the basis for obtaining the yogurt . Examples of the latter are thesauerkraut and grain silage for forage.

Lactic fermentation in vegetables

Vegetables can be subjected to lactic fermentation and it is usually carried out at temperatures between 16 and 35ºC. [3]Temperature is one of the significant parameters of lactic fermentation of vegetables. Salt is used in small proportions in order to slow down the evolution of bacteria that degrade and do not participate in the fermentation process. Salt is important in the lactic fermentation of vegetables, as well as adding a seasoning that adds flavor to the final product. If too much salt is added, the lactic bacteria are hindered in their fermentation process, changing the profile of the lactic bacteria that work in the process. The amount of salt added depends on the type of vegetable, for example olives and cucumbers are between 5-8%, cabbages 2%, but vegetables such as carrots and garlic can reach concentrations of 15-20 %.

In Mexico one of the fermented products of this type is jalapeño , although most of this commercialized product has not undergone fermentation but rather a process of marinated in vinegar. [10]

In some cases it is called the pickling process . Some of the most popular ones depend on the local abundance due to their cultivation, in the case of the popular olive in the Mediterranean area that is subjected to a lactic fermentation that ends up being the table olive : varieties. [11] The bacterium responsible for lactic fermentation of table olives is lactobacillus . Other varieties found are lactobacillus plantarum and lactobacillus pentosus found in most of the fermentations investigated. The olives ferment in brines that are in concentrations of approximately 8% concentration.

The most popular case in the countries of Europe and part of the United States is the fermentation of cabbage or cabbage ( brassica olereacea L. var. Capitata ) which is called sauerkraut (sauerkraut). This vegetable is usually prepared by removing the hard core from its interior, after having been finely cut, and mixed with salt (in a concentration of approximately 2% by weight), ferments lactically in a closed container without contact with air and light. The purpose of the salt is that, through the osmotic effect, the water is extracted from the tissues. Fermentation is carried out using fermentative hetero-lactic bacteria:

In Asian cuisine it is Chinese cabbage that participates in Korean kimchi . In the field of chili peppers. In North African North African cuisine, pickled lemons are often used as a condiment for various dishes . This type of ingredient is usually found in Moroccan cuisine .

Lactic fermentation of legumes

Legumes have been part of human food since its inception. Furthermore, in modern times it is a primary ingredient in vegetarian diets due to its protein content. However, the use of pulses reflects diets deficient in lysine . As soybeans ( Glycine max of the legume family ) are traditionally fermented in some Asian countries, fermented pastes are obtained in this way, as is the case with miso, which are made by fermenting soy beans in a brine with concentrations below 10% until the mixture is acidic. Miso is used in soups, in the preparation of cakes such as okonomiyaki . The fermented black bean (known as Douchi ) is one of the precursors of soy sauce . Tempeh . Some algae are subjected to lactic fermentation, such is the case of kombu .

The Sumbala is a typical seed cuisine West Africa . [12] Same as the kenkey . Some alcoholic fermentations, such as the cocoa beans (Theobroma cacao L.), also have lactic fermentation that provide a special flavor. [13]

The lactic fermentation of cereals improves the quality of food by improving its flavor , as well as its nutritional properties, eliminating some of the toxic properties of its products. [14]

Lactic fermentation in meat and fish

The microorganisms used in meat fermentation consist of a group of lactic acid bacteria ( Lactobacillus , Pediococcus ) with the collaboration of Micrococcaceae ( Staphylococcus , Micrococcus ), Streptomyces , Debaryomyces and Penicillium . [8] These microorganisms, through anaerobic activity, convert glycogen from dead tissues into lactic acid ( post-mortem glycolysis ).

The amount of glycogen depends on the quality, and type of tissue, before the death of the animal. This phenomenon is interrupted by enzymes, in such a way that post-mortem glycolysis is not completed. The meat industry employs commercial crop mixtures, one of the best known is duplopherically 66 . These mixtures are inoculated in the drying phase by means of salt in the industrial elaboration of some sausages : generally sausages .

Some preservation methods applied to meat promote the appearance of lactic bacteria, which is why the minimum possible inclusion of salt in this type of food is monitored. In this way, some high-consumption sausages in countries such as chorizo and fuet in Spain undergo a lactic fermentation during the ripening phase. Similar occurs with salami and sopressatta in Italy . These fermentations produce a complex flavor and aroma, also providing resistance to putrefaction (food preservation).

From the garum and the Roman sauce the fermentation of fish and shellfish is usually accompanied by carbohydrate foods such as rice (case of Asia). The sushi started well in its history . [15] In which the fish was fermented with rice making it moldy using aspergillus oryzae . In the tahilandesa kitchen is the RAA pla which is usually prepared with rice. [16] Some of the fish species that are likely to be fermented are the Puntius sarana .

In the case of fish, it is usually found under a mixture, for example fish / salt in order to dry the tissues, favoring lactic fermentation. Other possible fish sauce / pasta mixes, or even fish / salt / carbohydrates.

Culinary preparations

In Mexican cuisine , some fermented sauces are prepared , some are marketed, as is the case of tabasco sauce made with the lactic fermentation of tabasco chile . Jalapeño has a similar process that is pickled whole or sliced, and can also be served in puree as a form of sauce. On the other hand, among the spicy sauces already fermented in Southeast Asia, there is the popular sriracha , and among the non-spicy soy sauce (fermentation of a mixture of soy beans and wheat).

Soy is usually fermented, giving rise to a wide variety of by-products that enter into culinary processes. The pickled tofu is produced in many forms in the cooking of China, as in the case of the Lufu . The Chinese pickles participate in salads, and the like pickles mixed (assorted pickles) kitchen Western and Indian pickles   (South Asian Pickles). Also the relish  that serve as accompaniment, and that are pre-fermented preparations. Within this same category are homemade barbecue sauces that are used in roasts for their acid content.

In bread making are often used sourdoughs (called sourdough ) that perform lactic fermentation previously [14] which gives a special bread sour taste. Mainly due to the activity of the Lactobacillus sanfranciscensis crop .

In Indian cuisine he uses Idli which is a breakfast prepared with fermented black lentils served with rice . Within the world of condiments in western India, chutney are popular as lactic fermentations of fruits and vegetables.

 

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