Yogurt, Japanese miso, pickles, Korean kimchi, sauerkraut, chocolate, kefir, vinegar, tempeh, cider, beer, soy sauce, kombucha. But also bread, wine and cheese, the undisputed protagonists of our culinary tradition.
What do foods so different in taste, smell, and origin have in common?
Only one thing: fermentation. It means that during their preparation, certain microorganisms intervene that alter their properties, texture, and … longevity. It is one of the many things that happen in front of everyone’s eyes, every day and which, because it is invisible, we ignore. Yet it permeates our world.
Fermented foods are part of the gastronomic culture of all populations and have, with little humility, marked their history. And yes, they do taste like home.
But what is fermentation from a scientific point of view? How did it arrive on our tables?
BRIEF HISTORY OF FERMENTATION
Fermentation is a very ancient technique used to preserve food that, at the same time, allows new food to be created. It is one of many discoveries that happened by accident and whose benefits we have been exploiting for millennia without really understanding why. In the face of its mechanisms that have long remained obscure, the variety of foods we have produced through fermentation is immense and applies to even very different raw materials.
Throughout history, since the time of the Sumerians and ancient Egyptians, man has observed that in some cases letting foods rest, “aging,” allowed them to last much longer while maintaining a pleasant taste. Fermenting milk to turn it into yogurt and cheese, hanging meat in caves to make sausages whose putrefaction is inhibited. Initially empirical observations that over the millennia, thanks to technology and scientific discoveries, we have directed and controlled so that these transformations also return us to increasingly desired, sought-after flavors.
Of course not all fermentations are good: uncontrolled ones rot food, make it toxic.
And it is curious, think about it: it is precisely through judicious use of certain microorganisms that we can prevent others from damaging foods.
Unraveling the mysteries behind fermentation processes is French chemist and microbiologist Louis Pasteur, who around 1860 understood the role of microorganisms in this process. The existence of bacteria was already known in his time, but it was thought that the degradation processes of matter occurred spontaneously, due to chemical reactions that had nothing to do with biology. Pasteur then reversed the paradigm, identifying these organisms as the cause of the process. The rest, as they say, is history.
With the scientific discoveries of recent centuries, we now know and reproduce fermentation processes in industry. That is, we control it very precisely.
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The term fermentation is derived from the Latin verb |
But what happens during fermentation processes? Who is responsible for it?
THE SCIENCE OF FERMENTATION
As mentioned, it is microorganisms that give rise to fermentation processes. We are talking specifically about yeasts-unicellular fungi-and bacteria.
Microorganisms are the most widespread and diverse form of life on our planet. They are able to adapt and evolve quickly and colonize all the ecosystems around us. Even the stranger ones that we do not imagine as hospitable, such as deserts and acid lakes. They grow on us and within us, constituting the human microbiota. Can you imagine that there are ten times more microorganisms in our bodies than human cells? The ratio seems to be 10 to 1.
And they are valuable allies: they make up the intestinal flora, which helps us digest, they live on our skin protecting us from pathogens, they are in our genital organs to ensure the right pH. They affect many of the aspects of our lives, even sleep. In short, they are everywhere.
In general, microorganisms reproduce by fermentation. Bacteria and yeasts are able, with their enzymes, to break down organic substances such as sugars into simpler molecules. What they do in essence is feed on them, and to do so they release the energy that was stored in these molecules so that it is available for their survival and growth. Once nutrients are processed, they release waste molecules that have various consequences on the food and, subsequently, in our bodies. It is precisely these molecules that make fermentation possible!
THE EFFECTS OF FERMENTATION ON FOOD
Different fermentation processes can occur depending on the starting conditions, involving:
– type of bacteria or yeast
– nature of the substrate it feeds on
– presence or absence of oxygen
– temperature
– pH
As conditions change, the result changes. Let’s keep in mind that the topic is complex and very varied: for bread alone, we know how much flavors and textures, alveolations and aromas change, just by varying the type of flour and the presence of gluten in it, for example. Imagine this complexity considering all the variables: how many possible outcomes would we get? Now let us multiply the discussion for all foods and raw materials that it is possible to ferment. Each is a small universe capable of generating a polyhedron of flavors.
Simplifying greatly, the final effects on the food concern:
Taste/smell
Just think of how much the milk changes once it is made into a cheese such as gorgonzola, taleggio or parmesan. More or less of us have all tasted both the raw material, which has not undergone processing, and the fermented material. The change is so radical that, if they didn’t tell us, we wouldn’t be able to trace the milk back to one of these strong-tasting cheeses–and maybe not even stracchino. Now try to think the same with sour-tasting foods such as sauerkraut or kimchi. Sight helps us distinguish the nature of their vegetables, but taste betrays them. Microorganisms and molecules transform the taste and smell of fermented foods, giving rise to whole new worlds.
Storage time
Before the advent of the refrigerator, food technologies, intensive and extensive farming, and food abundance, survival also came through supplies. Those who were able to set aside abundant food in anticipation of periods of drought or severe cold were more likely to make it through climatically difficult times. Fermentation, along with other preservation methods such as drying and salting, has decreed the success and decline of individuals and entire families. Depending on the food and the fermentation that has occurred within it, the life time changes by a great deal. Parmesan cheese can last for years while gorgonzola, even in the refrigerator, will have a shorter life once the wheel is opened. In spite of this it will have been worth it eh, no doubt about it, because compared to fresh milk its life has already been greatly extended.
Number of ferments
The replication of the microorganisms responsible for fermentation results in a ferment-rich food, a friendly way of calling bacteria. An important distinction must be made at this point, because there are foods that are obtained by fermentation but then do not contain live microorganisms within them. Such is the case with bread, which makes use of the leavening capacity of Saccharomyces cerevisiae but does not contain any in a viable form when we eat it. It is in fact killed during baking due to the high temperatures of the ovens. This is also the case with beer, soy sauce and many other foods. In fact, for food safety issues, many fermentation-derived products undergo pasteurization processes before being released to the market.
Other foods, such as yogurt, cheeses, and some fermented vegetables, can be found in viable form, but it is not certain: even these products may undergo pasteurization or general sterilization processes for food safety issues. We therefore take general definitions with a grain of salt.
PREBIOTICS, PROBIOTICS and POSTBIOTICS.
When talking about microorganisms in food and their effects, terms that are perfect for marketing but difficult to interpret correctly are often used. Let’s have clarity:
Prebiotics: consist of non-digestible food-derived fibers that promote the growth and activity of one or more beneficial bacterial species in the gut because they act as nutrients. Prebiotics are found in certain foods such as whole grains, legumes, vegetables such as asparagus, artichokes, chicory, and onions, as well as milk and yogurt.
Probiotics
: are “live” microorganisms that are also present in the intestinal tract, such as bacteria and yeasts, of which there are dozens of different species. They are normally present in our intestines and when ingested, have the ability to survive the gastrointestinal tract. They have a beneficial effect on health because they fight pathogenic microorganisms and aid digestion. Examples of probiotic bacteria are Bifidobacteria and Lactobacilli, also called lactic acid bacteria. Today we find them present in various functional foods, such as fermented milks. Lactic acid bacteria can also be found in plant-based foods, from sauerkraut to miso to tempeh to kombucha tea.
Postbiotics: These are the inanimate microorganisms themselves or their components (cells, enzymes, fatty acids, etc…) released during their fermentation process. Although they are inactive, they play a role in the well-being of the host. These molecules are many and have different chemical properties. They are released outside the cell by forming a heterogeneous group of substances: enzymes, cell wall fragments and fatty acids . In our body they can act on the immune system by going on to modify the flora of intestinal bacteria. They help modulate the immune response.
FAMOUS FERMENTATIONS
Without claiming to develop the topic in depth, let’s look at some of the fermentations that occur in the foods we routinely consume.
ALCOHOLIC FERMENTATION
It occurs in the absence of oxygen by Saccharomyces cerevisiae, the very famous brewer’s yeast we all know. A small army of yeasts feeds on the sugars in grains, in the case of beer, or grapes in the case of wine, to produce as waste material ethyl alcohol, or ethanol, and carbon dioxide. It is not possible to talk about beer and wine and reduce their production, smell and taste to this one reaction, of course. In addition to yeast, other microorganisms of different natures are present on the skin of the berries, and as with all foods with complex flavors, it is the variety of factors that define the finished product.
I gave you the example of beer and wine, but in truth much of the ethanol we find in spirits is produced in industry. It can be done synthetically, starting with a molecule called ethylene, or by … fermentation. In this case we are talking about huge bioreactors containing microorganisms that digest sugars and produce ethanol!
ACETIC FERMENTATION
It consists of the oxidation of ethanol to acetic acid. It is operated by bacteria, particularly belonging to the genus Acetobacter, in the presence of oxygen. This is what happens when wine spoils and becomes-vinegar! Acetobacteria consume oxygen in the surrounding environment and produce carbon dioxide.
YOGURT
It is milk fermented by the lactic acid bacteria Lactobacillus bulgaricus and Streptococcus thermophilus, our friends and tenants. They use lactose, the milk sugar, as nutrition. As a product of digestion they generate lactic acid, which affects the taste and causes the milk to coagulate-this explains the characteristic texture of yogurt! At the same time, other biochemical reactions take place, also involving proteins, with formation of nutritionally important compounds: free amino acids, vitamins, etc.
CACAO AND COFFEE.
Not everyone knows that cocoa beans the coffee beans, then their seeds, after harvest undergo a period of fermentation carried out by naturally occurring and/or added bacteria and yeasts. These microorganisms ferment sugars and other substances, producing the aroma precursors that will later develop in the roasting stage and give cocoa and coffee the aromas and flavors we love so much.
There would be many more fermentations to tell, but we do not have time or way to do it here. Instead, let us move on to the last important topic to be covered, which concerns our well-being
FERMENTS AND HEALTH
In recent years we are witnessing the fashion for fermented foods, which are catching on in different forms and have scaled our borders arriving from all over the world. This is the case with kimchi, Korean spicy fermented cabbage, but also with Japanese miso, made from soybeans and koji, an edible mold that is grown on rice. And then tempeh, which is made from yellow soybeans and another variety of mold and is used in cooking as a meat substitute. There are plenty of products, and interest in the market is reaching very high heights. If we like the taste of these products, we are in their golden age!
There is a small and important but in this scenario: it happens frequently to see the term fermented associated with exaggerated health benefits. Let’s try to shed some light on this alleged connection, which is widely used by advertisers and drives more consumers to purchase.
What’s true: bacteria that operate fermentation are able to produce vitamins and other substances needed by our bodies. They also help our microbiota to stay rich and healthy, while at the same time disfavoring the survival of pathogenic bacterial strains. A healthy microbiota is able to modulate our immune system.
What is unclear: A balanced microbiota would seem to counteract the occurrence of many diseases in humans: diabetes, high blood pressure, and bladder cancer.
Guide to reading this information
The data that research is gathering on fermented foods should be taken with extreme caution. Indeed, the same authors of the articles that speak of promising results admit that further evidence from methodologically robust research is needed before arriving at clear and definitive directions for the public. In fact, the studies conducted on the subject are observational: they cannot give any indication of a cause-and-effect relationship.
Let’s keep in mind that to have a measurable effect on our bodies, these foods should contain microorganisms at a high concentration, but this fact is hardly stated on food packages. Finally, the strains of bacteria should be alive but as we have said before they are not always so-andfor good reason.
The last and fundamental consideration on the topic then concerns nutrition as a whole. The greatest risk in taking these studies as true is twofold:
- we might unbalance our diet thinking that these foods somehow counterbalance bad habits, which we might increase in the meantime
- we take the focus away from what is most important: lifestyle as a whole.
Our diet in general should be based on fruits, vegetables, grains, dairy products and legumes. Fermented foods are good and can help us feel good, but like any food they are only a small part of the total. They cannot and should not promise miracles and should always be considered within a broad overall context of health concept, which also encompasses physical activity.
So fermented foods absolutely yes, but let’s consider them in the proper, scaled-down way that they deserve.
SOURCES
– Jakubczyk KP et al, Characteristics and biochemical composition of kombucha – fermented tea, Med Og Nauk Zdr., April 2020
– Lehninger A. L., Principles of biochemistry (Zanichelli).
– Montanari G., Omnia Fermenta (Chiriotti Publishers).
– Reade et al, Fermentation art and science at Nordic Food Lab, chapter in The Routledge handbook of sustainable food and gastronomy (Routledge)
– Galasso L., Yeast (
Saccharomyces cerevisiae
) and human society, www.antropologialimentare.it
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https://dottoremaeveroche.it/cibi-fermentati-fanno-bene-a-salute-e-batteri-intestinali
