Nature allows man to enjoy the benefits that it contains.At the same time, these people are trying to increase wealth and create something new and to learn even the unknown.Bacteria - a tiny creation of nature, which are also learned to exploit the people.
But not only harm coupled with pathogens and disease processes, carry these prokaryotic organisms.They still are a source of important industrial process that is used by people since ancient times - fermentation.In this article we will look at what the process and how to implement specific lactic fermentation agents.
History and use of fermentation
first mention of the fact that the fermentation process used by people to obtain certain products, there were still 5000 BC.That's when the Babylonians used a method for producing products such as:
- cheese;
- wine;
- yogurt and other dairy products.
later began to receive such food in China, Egypt, the Sudan, Mexico, and other ancient states.They began to bake yeast bread, fermented vegetables, the first attempts at preservation.
lactic fermentation process used by people for thousands of years.Cheese, yogurt, yogurt were an important part of the meal at all times.The benefits of these products are known to all doctors and healers.However, the reasons for this kind of transformation is possible, for a long time remained unknown.
What fermentation conditions require the presence of microorganisms, people could not even imagine.In the middle of the XVII century Van Helmont will propose to introduce the term "ferment" for those cooking processes that are accompanied by the release of gas.After all, the word translated means "boiling."However, only in the XIX century, almost two hundred years later, the French microbiologist, chemist and physicist Louis Pasteur discovered the existence of the world of microbes, bacteria.
Since it became known that the different fermentation requires the presence of all sorts of micro-organisms invisible to the eye.Their study has made it possible over time to control fermentation and direct it to the right person direction.
essence of fermentation processes
If we talk about what the fermentation process, it is necessary to point out the biochemical nature.After all, at its core, it's just the activity of bacteria that obtain their energy for life, while developing a variety of by-products.
In general, fermentation can be described in one word - oxidation.Anaerobic disintegration of a substance under the influence of certain bacteria, which leads to the formation of a number of products.What matter is the basis, and what happens as a result is determined by the type of process.There are several options for fermentation, so has its own classification for these transformations.
Classification
total there are three main types of fermentation.
- Alcohol .Source is the oxidation of carbohydrate molecules to ethyl alcohol, carbon dioxide, water and ATP (energy source).Data conversion is effected by not only bacteria, but also fungi different genera and species.It is in this way since ancient times get products such as beer, wine, yeast for baking, alcohol.The energy that is released during the decomposition of carbohydrate takes to ensure the vital processes of the organism.That is the essence of the biological process.
- lactic fermentation is the oxidation of carbohydrates to lactic acid with the release of a number of by-products.As it is carried out and what kinds there, take a closer look on.
- butyric .This type of fermentation is important in the natural scale.It is carried out at the expense of vital activity of butyric acid bacteria that live in anaerobic conditions at the bottom of swamps, river mud, and so on.Due to the nature of their work to process huge amounts of organic components.Products include many substances, the main among which butyric acid.Also highlighted: acetone, isopropyl alcohol, carbon dioxide, acetic acid, lactic acid, ethyl alcohol and other compounds.
Each of the designated type is important both natural and industrial scale.Types of organisms performing such transformations are well studied to date, and many of them artificially cultivated to obtain high yield.
lactic fermentation: the general concept
This type of fermentation is known since the very ancient times.Another BC inhabitants of ancient Egypt and other countries were able to produce cheese, brew beer and wine, making bread, acidify vegetables and fruits.
today using special starters for fermented milk products, artificially bred strains of relevant microorganisms.Process modernized and brought to automaticity, carried out with the help of komplektatsionnogo equipment.There are many manufacturers that directly produce lactic fermentation.
essence of the whole process can be summarized in a few paragraphs.
- For the main product is taken carbohydrate source - a simple (fructose, glucose, pentose) or ester (sucrose, starch, glycogen, etc.).
- created anaerobic conditions.
- The product podselyayutsya strains of lactic acid bacteria of some kind.
- provides all the necessary external factors that are optimal for the desired product: light, temperature, presence of certain additional components, pressure.
- After completion of the fermentation product is processed and the allocation of all by-products.
course, this is only a general description of what is happening.In fact, at every stage there are many complex biochemical reactions, because the process of lactic fermentation - is the result of vital activity of living beings.
Basics of lactic fermentation
From a chemical point of view, these transformations are a series of sequential steps.
- First, there is a change of the initial substrate, that is changing the carbon chain substance (carbohydrate).This leads to the intermediates entirely different nature, belonging to different classes.For example, if the source substrate - glucose, it is rearranged to gluconic acid.
- Redox reactions are accompanied by the release of gases, the formation of by-products.The basic unit in the entire process is lactic acid.That it is produced and accumulated in the course of fermentation.However, it is not a single compound.Thus, there is a formation of molecules of acetic acid, ethyl alcohol, carbon dioxide, water, and sometimes other attendants.
- energy output in the form of molecules of adenosine triphosphate (ATP).In one molecule of glucose necessary to 2 molecules of ATP, if the starting substrate more complex structure, such as cellulose, then three molecules of ATP.This energy is used lactic acid bacteria for further activity.
Naturally, if the understanding of the biochemical transformations in detail, it is necessary to specify all the intermediate molecules and complexes.Such as for example:
- pyruvic acid;
- adenosine diphosphate;
- nikotinamindifosfata molecule as a carrier of hydrogen and others.
However, this question deserves special attention and must be considered from the perspective of biochemistry, so its touch in this article will not.A more detailed look at what the technology of milk products and what types of fermentation under review there.
homofermentative fermentation
homofermentative fermentation of lactic acid involves the use of special forms of pathogens and different from heterofermentative get the product and quantity.It occurs on the glycolytic pathway in cells of the microorganism.The point is, as a whole from any fermentation in the conversion of carbohydrates into lactic acid.The main advantage of such a process is that the yield of the desired product was 90%.And only the remaining part goes to the side connections.
fermentation bacteria of the type of the following types:
- Streptococcus lactis.
- Lactobacillus casei.
- Lactobacillus acidophilus and others.
What other substances are formed as a result of homofermentative fermentation?These are compounds such as:
- ethyl alcohol;
- volatile acid;
- carbon dioxide;
- fumaric and succinic acid.
However, this method of producing the industry of dairy products is almost never used.He remained in nature as the initial stage of glycolysis, it happens in the muscle cells of mammals during extensive physical activities.
Technology of desired products for human consumption involves the use of carbohydrate source as:
- glucose;
- sucrose;
- fructose;
- mannose;
- starch and others.
A homofermentative bacteria are not able to oxidize many of these compounds, so their use as starter cultures in the production is not possible.
heterofermentative lactic fermentation
This method is exactly the industrial application, thanks to which is carried out throughout the production of dairy products, canned vegetables is carried out, there is harvesting silage for livestock feed.
The main difference from the previously described - is that lactic fermentation is carried out by agents of the formation of a larger number of by-products.Only 50% of the sugar is processed in the lactic acid bacteria, while the rest goes to the formation of molecules such as:
- acetic acid;
- glycerol;
- carbon dioxide;
- ethyl alcohol and other.
What is better and cheaper than the formation of 90% pure lactic acid by homofermentative method?The thing is, that when the main product produced by too much, the livelihoods of many bacteria is inhibited at all.In addition, many products lose palatability, to acquire through side connections.For example, a pleasant aroma of canned vegetables provide acetic acid and isoamyl alcohol.If these compounds are not the result of conservation will be quite different.
lactic acid yield of 50% is sufficient to inhibit the development and activity of foreign fungi and microorganisms in the system.Because even 1-2% cause too strong acidification of the environment, which can not exist any other organisms besides lactic acid bacteria.The whole process is carried out by the pentose phosphate pathway.
Terms heterofermentative fermentation during the process should be as follows:
- good and fresh yeast is added to the initial stage;
- optimum environmental conditions, which are selected individually for each product;
- -quality and well-regulated equipment;
- all the necessary technical devices for the process.
Among the external conditions of particular importance is the process temperature.It should not be too high, but the cold and brake sharply entire course of fermentation.
Today there are specialized container for fermentation, which automatically creates all the necessary conditions for proper and comfortable work of microorganisms.
Equipment required
As we have noted above, among the most important attributes to be noted fermentation vessel.If we talk about the procedure's home, then you should pay attention to the cleanliness of utensils used in the conservation, production of yogurt and other products.One way to achieve a reduction in the number of foreign populations of microorganisms is sterilizing containers before using them.
What cookware is suitable for heterofermentative fermentation?This can be glass or plastic quality (polypropylene, polyethylene) container that is capable of tight-fitting lid.
In industry use special devices for disinfection and purification of containers before the fermentation process.
The bacteria used in the process
If we talk about the cultures of bacteria that are used to create canned and dairy products, it is possible to designate some of the most common types of organisms.
- Bulgarian bacillus acidophilus.
- Lactobacillus species Sporolactobacillus inulinus.
- Bifidobacteria.
- Leykonostoki.
- Lactic acid cocci.
- Lactobacillus species L. Casei.
- bacteria of the genus Streptococcus and others.
On the basis of the combination and pure cultures of organisms identified, made to ferment dairy products.They are publicly available, they can buy anyone.The most important thing is to observe the conditions of the fermentation process to benefit from the resulting product.
What products obtained by the fermentation of this?
If we talk about what kind of fermentation products can be obtained with the help of lactic acid bacteria, it is possible to name a few major categories.
- Fermented foods (fermented baked milk, yogurt, Varentsov, yogurt, cottage cheese, sour cream, butter, acidophilic products and others).
- Feed silos for farm animals.
- lactic acid, which is used in the manufacture of soft drinks, tanning furs and so on.
- Bakery, cheese production.
- Canning fruits and vegetables.
All this proves the importance of certain types of bacteria in people's lives, their industrial activities.
