In this article, we will discuss the simplified way of the fermentation process, the factors impacting the fermentation process and a few fermentation techniques.
What is Fermentation?
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The fermentation is a metabolic process using some organisms for energy and nutrients from certain organic compounds. Fermentation is an anaerobic reaction, an imperative characteristic of this process which means that it arises in the absence of oxygen.
Many microorganisms use fermentation as an energy production mechanism in the form of ATP. Energy is acquired through the deprivation of organic molecules, such as starch or sugar, through fermentation.
Yeasts ferment sugars and convert them into alcohol, while bacteria convert certain carbohydrates into lactic acid. Fermentation also occurs in fruits, fungi and in mammalian muscles.
This natural fermentation process has been widely used by modern man to obtain products of interest, such as beer, wine, yogurt, and cheeses, among others. The study of fermentation is called cymology.
Fermentation Process
Like other metabolic processes of obtaining energy, fermentation begins with glycolysis. This metabolic reaction is based on the degradation of glucose molecules to obtain important energy molecules. During this process, glucose is degraded by oxidation and NADH and pyruvate molecules are generated.
In aerobic reactions (which use oxygen), NADH and pyruvate participate in a mechanism called oxidative phosphorylation, a process that is carried out in the mitochondrial membrane and is highly efficient in generating energy in the form of ATP molecules.
In contrast, fermentation does not lead to such an efficient production of energy because some molecules, such as NADH, cannot release their electrons to become NAD + again, which is the oxidized form of the molecule and is required to help generate more ATP molecules.
Consequently, other metabolic reactions occur that ensure that NADH molecules donate their electrons to another organic molecule, such as glycolysis pyruvate. This oxidation of NADH to NAD + allows glycolysis to continue working.
Different Types Of Fermentation
➢ Alcoholic Fermentation
In alcoholic fermentation, NADH molecules donate their electrons to other molecules derived from pyruvate, and thus alcohol is produced. The alcohol that is produced is specifically ethanol or ethyl alcohol and is a process that occurs in two steps.
The first step shows that a carboxyl group of pyruvate is released, which is released in the form of carbon dioxide, thus leaving acetaldehyde that is a two-carbon molecule.
The second step then shows that the NADH passes electrons to the acetaldehyde produced previously, which produces ethanol and regenerates NAD +, which is necessary to maintain glycolysis and, consequently, the supply of pyruvate.
Yeasts perform the alcoholic fermentation that is used in the production of common alcoholic beverages, such as beer and wine, as well as in the making of bread.
It is important to note that alcohol is toxic in large quantities, both for yeasts and for humans, which has established tolerance levels ranging from approximately 5 to 21%.
➢ Lactic Fermentation
In this process the NADH molecules transfer its electrons straight to pyruvate, thus producing a lactate molecule in the fermentation called the lactic acid. The microorganisms that produce yogurt do so through lactic fermentation, as well as the red blood cells present in the humanoid physique.
Lactic fermentation can also transpire in muscle cells, but only in convinced environments; for example, when the physical workout is extreme and oxygen supply is not as much of required.
The lactic acid produced in the muscles is transported by the bloodstream to the liver, where it is converted back into the pyruvate to be reused in other energy production reactions.
Microorganisms Involved in Food Fermentation
The best common collections of bacteria involved in foodstuff fermentation are the following:
➢ Bacteria
The lactic acid bacteria of the genera Lactobacillus, Pediococcus, also include Streptococcus, and Oenococcus, are considered to be the most vital bacteria in fermented foods. These are followed by the species called Acetobacter, which is used to oxidize alcohol in the acetic acid.
Moreover, the acetic acid fermentation has been widely used to not only produce fruit vinegar but also the cider vinegar. The third group of important bacteria in fermentation are the species of Bacillus subtilis, also include the B.licheniformis, and B.Pumilus, which increase the pH of the medium.
Bacillus subtilis is considered to be the dominant species in the production of molecules that increase the alkalinity of the medium, such as ammonia. This makes the environment unsuitable for the completion of decomposing organisms, which helps preserve food.
➢ Yeasts
Yeasts can have beneficial and non-beneficial effects on food fermentation just like bacteria and molds. A variety of yeasts such as Pichia spoil food, while Candida is used for the production of proteins of interest.
The most beneficial yeast in terms of beneficial food fermentations is from the family of Saccharomyces. It is about S. cerevisiae that is usually involved in the production of bread and alcohol during the process of fermentation of wine. The carlbergenisis variety of the Saccharomyces cerevisiae family is the yeast involved in beer production.
The ellipsoids variety of the Saccharomyces cerevisiae family is widely used in winemaking. On the other hand, the Schizosaccharomyces pombe and S. boulders are also named as the dominant yeasts that are used in the production of various traditional fermented beverages.
It has been found that the Schizosaccharomyces pombe species have the ability to not only degrade the malic acid in ethanol and carbon dioxide but have also been utilized successfully to reduce acidity in plum musts and grapes.
➢ Molds
Molds are also considered as vital organisms in food processing, both in degradation and conservation. Many molds have the ability to create and compose enzymes of commercial importance, which include Aspergillus niger pectinase.
Aspergillus species are required in the production of citric acid from remnants of apple pulp. Aspergillus species are often held responsible for unwanted changes in foods that cause decay and spoilage.
Furthermore, Penicillium species are linked with the development of ripening and taste in cheeses, whereas the Ceratocystis species are required in the production of fruit flavor. On the other hand, Penicillium is the causative agent for the production of toxins such as patulin.
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