Fermentation: how it works and what it is used for

The term fermentation actually means a more or less long and complex chain of chemical reactions that are activated by yeasts, bacteria, or enzymes in animal tissues in the absence of oxygen. Let's find out all about this process and understand what it is for. Fermentation can be explained as a way to release energy from sugar when there is no oxygen left in the cytoplasm. This chemical process is activated by yeasts and bacteria to 'extract' the energy contained in glucose. Even in our muscles, they can activate it, especially after prolonged physical effort. In this case, what is produced in the so-called lactic acid, which causes that sense of soreness that we feel after intense physical activity? Let's find out all about this issue and try to understand what the main types of fermentation are.

What is fermentation and how it happens

Louis Pasteur is the inventor of the term 'fermentation.' The scientist used it for the first time in the 19th century to define a chemical process triggered by many organisms to extract energy from sugar and carry out their vital functions. 'Breath without oxygen,' we could say.

In fact, it is very reminiscent of cellular respiration even if, unlike the latter, it occurs in the absence of oxygen (anaerobic environment). If we want, it is also one of the simplest methods that organisms use to derive energy from food in the absence of molecular oxygen. And it is perhaps one of the most primitive mechanisms that science has ever described.

The enzyme that causes fermentation creates a chain of chemical reactions. It is a sort of domino effect with different processes depending on the type of fermentation with which we are dealing. These processes end with the production of very specific products and by-products. The agents that trigger fermentation are generally yeasts, fungi, and bacteria, single-celled organisms dispersed in the substances that make up bread, wine, beer, and milk. It is due to these microorganisms that the main fermentative phenomena we know have come to life.

What Changes In Food

Fermentation increases its complexity. Not only is that, due to this process, nutritional contents also changed. Fermented foods are, in fact, more digestible and healthy, given that they produce numerous substances useful for health.

Why is it important to bring this technique into our daily lives?

"There are several aspects to consider, first of all, the taste. In fermented foods, we find the best and tastiest aromas and flavors ever, just go into a shop that sells delicacies to let us be enveloped by heady scents. Another aspect is conservation. It is something that escapes us because we are used to the refrigerator and the freezer, but until 200 years ago, producing fermented foods was the most common method for storing certain foods. Cheese is the strategy for storing milk for a long time, for cold cuts always to have meat. 

A portion of fermented food also brings multiple benefits from predigestion, as microorganisms simplify some substances present in food, making it more digestible. The detoxification, the action of bacteria makes it harmless very toxic substances such as hydrogen cyanide, a poison present in the cassava, root at the base of the diet of many people. Or it is difficult to digest the creation of nutrients; those contain vitamins, organic acids, and fatty acids that we find in fermented foods, for bacteria a by-product of fermentation, for us a great added value.

The stages of fermentation

Fermentation is a process in which two phases can be distinguished as:

1. Glycolysis

2. The regeneration of NADH in NAD +

During glycolysis, sugar is transformed into two pyruvic acid molecules, and two ATP and two NADH molecules are produced simultaneously. The former are high energy molecules readily available; the others require oxygen to release the energy content. With the regeneration of NADH, the cell produces NAD +, which is the chemical reduction of the NADH released of its energetic load.

Depending on the type of fermentation, NAD + is regenerated in different ways.

The fermentation is used by man to obtain food or pharmaceutical substances. If we think of Saccharomyces cerevisiae, aka brewer’s yeast, then the preparation of beer and bread immediately comes to mind. This yeast, in fact, is known as beer yeast and is introduced in the dough of bread and cakes to activate a particular type of alcoholic fermentation. The carbon dioxide released causes the pasta to swell, making it suitable for cooking.

Types of fermentation

Lactic fermentation

From a chemical point of view, this transformation affects a glucose molecule and ends with the production of pyruvic acid and lactic acid. The agents involved are the bacteria Streptococcus and Lactobacillus, which transform glucose into lactic acid.

Due to them, the chain of reactions in which lactic acid modifies some milk proteins means that the consistency of the liquid changes to become yogurt, which is possible to make at home even without a yogurt maker.

Lactic fermentation in the muscles

The same process also occurs at the muscle level in the animal tissues of vertebrates during prolonged effort. Also, in this case, fermentation is activated in the absence of oxygen and proceeds just like a regeneration process. The pyruvate is reduced to lactic acid, thus allowing glycolysis. What is formed in the muscles is called 'lactate,' which is transported into the liver through the blood and converted into glucose during the effort recovery phase?

Alcoholic fermentation

It consists of a transformation process that produces ethyl alcohol and carbon dioxide. Like the other types of fermentation, the alcoholic has also activated microorganisms (saccharomycetes) that break down glucose in the absence of oxygen, transforming it into ethanol and carbon dioxide. Unlike the lactic one, also called homolactic, this fermentation, in addition to lactic acid, also produces ethyl alcohol and carbon dioxide.

It is for this reason that in the chemical field, it is also called heterotactic fermentation.

Of all the fermentations, the alcoholic one is the most important and exploited for the production of food and alcoholic drinks. But while simple sugars are sufficient for wine, in the case of barley and wheat, the starch must first be hydrolyzed to glucose. For the preparation of beer, in particular, Saccharomyces cerevisiae is the yeast that transforms malt into beer. Furthermore, it is also crucial for the production of bread, where it activates fermentation in the form of beer yeast.

The benefits of consuming fermented vegetables

The fermentation of food is a very ancient technique; it seems that it was already known in China about 9,000 years ago through which people kept certain types of fresh food such as meat, vegetables, fish, fruit, and drinks longer.

The recipes were handed down from generation to generation, but over time they have often gone out of common use. Unfortunately, today, our daily diet is almost free of fermented foods, except for yogurt, the yeast for the preparation of bread, the craft beers, and vinegar. It would instead be very important to know or rediscover the tradition of the consumption of fermented foods, beyond the best-known ones, to enrich our dietary variability and exploit the numerous benefits of their consumption on our health.

When we talk about fermentation, we refer to a natural and spontaneous biological process through which living microorganisms such as bacteria and yeasts, metabolizing the carbohydrates contained in foods. These foods produce gas, acids, and/or alcohol, while the metabolization of any proteins makes the foods themselves more digestible, as well as enriched with vitamins and other precious substances produced by the very action of microorganisms. The bacteria and / or yeasts contained in fermented foods enrich the intestinal bacterial flora when the foods in which they are contained are consumed, preventing and correcting any conditions of intestinal dysbiosis.

Fermentation, therefore, brings numerous benefits to processed foods:

- better conservation over time

- greater digestibility

- a probiotic feature that improves intestinal health

- The new organoleptic properties such as taste and flavor

- Safety in their consumption, as fermented foods are composed of numerous and always different live microorganisms, capable of producing an acid pH, due to the release of lactic acid. As the fermentation process progresses, the acidic environment will make the development of harmful bacteria such as the feared Clostridium difficult.

Among the foods that lend themselves well to being fermented, we have meats, fish, legumes, milk, olives, fruit, but above all, vegetables. It is possible to ferment any type of vegetable even if the most used in the fermentation process are sauerkraut, onions, cucumbers, and mixed vegetables as a gardener. The consumption of fermented vegetables allows us to add the beneficial effect of the fibers contained in them to the benefits of fermentation listed above.

The fermentation of vegetables can also be done at home by following some basic steps. First of all, it is important to start from seasonal vegetables, harvested in the day or as fresh as possible, not washed with disinfectant and sterilizing substances in order not to kill the microorganisms naturally present and which will have to start fermentation.

Once the vegetables to our liking have been chosen, as in the case of the gardener, they must be sliced ​​thinly and placed in a clean glass jar, in overlapping and well-pressed planes. So that no oxygen remains, then they must be covered with a brine prepared to leave from a solution of water (chlorine-free) in which 15g to 35g of salt (not iodized) per liter of water has been dissolved. It will be a practice that will allow us to use the right recipe.

The jar is then closed hermetically, leaving about 2 cm of space from the liquid level to the lid, and it is left to ferment for about two weeks in an environment at room temperature but constant. At the end of the fermentation process, guaranteed by the formation of bubbles and the typical acid smell, the jar can be stored in the fridge (to slow down fermentation) or in the cellar, consuming the vegetables in 2-3 months. For those interested in the world of food fermentation, there are numerous courses that can be attended to learn and refine their practice.

Author: Vicki Lezama