“The Case of the Ailing Wine”
or how Louis Pasteur found an invisible culprit
You can find the previous episode here…
«Il y a plus de philosophie dans une bouteille de vin que dans tous les livres.»
“There is more philosophy in a bottle of wine than in all books.”
— Louis Pasteur
“The Crime Scene”
The Jura wine region in eastern France—small towns built of pale stone, narrow streets, vineyards spread across the hills, and people for whom winemaking is not just a craft, but a way of life passed down through generations. Every year, they make wine, and every harvest they hope once again that it will turn out well.
…Autumn, 1856.
Stone cellars keep the air cool. Rows of barrels fade into the dim light. The air carries the sweet aroma of wine—but in places, there are unpleasant notes that are hard to identify at first.
The Crime Scene: Everything seems normal—and that’s exactly what makes it suspicious
In several estates, the same pattern appears: in one barrel, the wine is clear, transparent, with a deep color. In another, it is cloudy, with a thin film on the surface. And in a third, it even has a sharp, vinegary smell.
It seems to be the same grapes, the same barrels, and the same winemakers’ hands. Yet the result is different.
Here, people have long grown accustomed to a strange pattern: part of the wine always “goes wrong”—without ”reason, without warning, as if by its own will. And the problem keeps returning.
Sometimes a problem can exist for centuries—simply because no one has looked closely enough
Identical Barrels—Different Results
In one of the estates not far from Arbois, the owner stands in his cellar, looking at the barrels as if they were a riddle.
He has checked everything he knows: the grapes were harvested on time, the barrels were thoroughly cleaned, and the capricious weather that year did not fail them.
There are no signs of tampering in this cellar. No one added anything to the barrels. The owner does not believe in ghosts. There is no visible cause.
— This cannot be happening without a reason, — the winemaker says to himself.
A pause.
— And yet, it does!
The “crime” is evident: good wine turns into bad wine, behaving unpredictably without any reasonable explanation.
He runs his hand along the rim of a barrel and frowns.
— If we cannot understand this ourselves… then we need to call someone who can.
After some time, several winemakers from the surrounding area decide to consult a specialist. Preferably someone who understands not only science, but also the life of this region itself.
Their choice falls on Louis Pasteur, a native of these parts, already known as a promising and serious scientist—a 34-year-old chemist working on tartaric acid.
But that is not the only reason. What people say about him matters even more: he does not accept explanations like “it has always been this way; nothing can be done.”
Upon arriving, Pasteur does not rush to conclusions. He carefully examines everything, asks questions, tastes samples. He takes a glass from one barrel and lifts it to the light. Then from another. And a third.
— When did this begin? — he asks.
— A few days after fermentation started.
— And before that, everything was normal?
— As always.
Pasteur thinks. Strange—everything seems the same: the same harvest, similar barrels, the same cellar—and yet the wine is different.
— Then not everything is the same, — he says to himself.
He understands that this is not abstract science—this is an economic problem for France.
Traces in the Past: 2,500 Years Without an Answer
This case did not begin in this cellar. The trail led into the past—far beyond this winery and even beyond the French region of Jura.
…🍇 Slopes around Athens, 5th century BC.
The sun is already setting. The grapes have been harvested, the juice poured into amphorae. From some of them comes a quiet hissing sound. Two winemakers sit in the shade beside rows of vessels.
Greece: They can see the process—but not its cause
Philon:
— Do you hear that? It’s “working” again. As if it’s boiling—but there’s no fire.
Demetrios:
— It’s always like this after the harvest. The juice must “mature.”
Philon:
— But why does it start on its own? We only crushed the grapes.
Demetrios:
— That’s how nature works. It is a gift from the god Dionysus.
Philon:
— And what if it’s not a god? I’ve noticed—in hot years, it bubbles more.
Demetrios:
— Then the sun helps the god.
Philon (laughing):
— And when everything turns into vinegar—is that him too?
Demetrios:
— No. That means you didn’t seal the amphorae properly. Air got inside.
Philon:
— So it has to do with air?
Demetrios:
— Perhaps. Or with heat. Or simply… it just happened.
Philon looks at the row of amphorae. From the outside—identical. Inside—not at all.
— Strange. Some turn out well, others don’t.
Demetrios:
— It has always been this way.
👉 The Greeks actively observe the process, connect it with nature and the gods, and already notice the influence of temperature and air—but explain it through mythology. They do not yet realize that they are asking the same question as the winemaker in Jura more than two thousand years later.
They saw the process. But they did not see its cause
…🕯️ Burgundy, around 1140—a Cistercian monastery
Centuries pass. A monastery cellar of the Cistercian order near Dijon. Stone vaults, oak barrels. It is quieter here. Colder. Order is felt in everything—from the masonry of the walls to the rows of barrels. The cellar smells of wine and dampness. In the candlelight, the surface of the wine in one of the barrels barely ripples.
Monks: Cleanliness becomes a rule—but the cause remains a mystery
Brother Étienne:
— Look, Brother Guillaume… it’s bubbling again. And warming up.
Brother Guillaume:
— That is as it should be. The juice is decomposing.
Étienne:
— But it’s a strange kind of decomposition. Usually, it only makes things worse. Yet here, it becomes wine.
Guillaume:
— Not all decay is evil. There is decay that leads to purification.
Étienne:
— I’ve noticed: if the barrels are not well cleaned, the taste spoils.
Guillaume:
— Cleanliness is the path to order. Even in wine.
Étienne:
— But what exactly is changing in it?
Guillaume (after a pause):
— That which the Lord has placed within it.
👉 The philosophy of the time: fermentation is seen as a form of “proper decomposition.” There are already hypotheses—cleanliness and environmental conditions matter—but the explanation remains theological.
Cleanliness was already important. But no one yet knew why
…🏰 Bordeaux, around 1680—the cellars of Château Haut-Brion
Several more centuries pass. The trail leads to southwestern France, to the region of Bordeaux—where winemaking becomes not just a craft, but an art and a trade.
The cellars here are more orderly. The work—more precise. Knowledge is passed on not only from father to son, but also through records, observations, and comparisons. Yet the problem remains the same.
Two winemakers stand by the barrels.
Jean:
— I’ll tell you this: it’s the transformation of sugar into alcohol. Real chemistry.
Pierre:
— But what starts it?
Jean:
— Heat. And perhaps air.
Pierre opens the lid of a barrel, leans in, inhales.
— I’ve noticed: if the must is left open too long, the taste gets worse.
Jean:
— Then air spoils it.
Pierre:
— Or maybe it helps at first… and then spoils it?
Jean (irritated):
— We add nothing to the juice—yet the process still begins. On its own.
Pierre:
— Maybe there is already something in the juice… something invisible?
Jean (with a smirk):
— If you can’t see it, then it isn’t there.
Pierre (quietly):
— But it makes the wine. Some barrels turn out well, others don’t.
Jean:
— It has always been this way.
👉 Here we can already feel the influence of early science: winemakers speak of chemistry, argue about the role of air, and try to explain the process without referring to the gods. The first hints of intuition about an “invisible factor”—just ”one step away from Pasteur.
They were very close to the answer. But they lacked one proof
The problem remained unsolved. To answer this question, a person was needed who would not accept “it has always been this way.”
The Investigator Who Didn’t Believe in “It Just Happened”
In the 19th century, this mystery finally found not just an answer, but its culprit. But before naming it, we should say a few words about the “investigator” who uncovered it. His name was Louis Pasteur.
Pasteur loved wine and understood it—but unlike others, he wanted to know why it turned out the way it did
Burgundy, the Jura wine region. Nearby is Switzerland—a meeting point of French and German influences. Here, one senses discipline, thrift, and respect for craftsmanship.
Jura is not Bordeaux or Burgundy, yet grapes are grown everywhere here, and wine is made in small estates and family wineries. It is part of everyday life. Every autumn—the grape harvest, the pressing, the full barrels in the cellars. And every year—the same risk: will it succeed or spoil? Why does good wine emerge in one barrel, while another turns into vinegar?
1822, the town of Dole—this is where the future scientist Pasteur was born.
His father, a former soldier and tanner, taught Louis a simple rule:
— It is not enough to see. What matters is to understand why things are the way they are.
…👨👦 Arbois, 1832—a conversation with his father
A workshop. His father works with leather. Pasteur is ten years old, fond of drawing. Louis sketches a portrait with charcoal, occasionally wiping his stained fingers on his apron.
With his father: Louis learns to observe—soon, he will want to understand
Father:
— Drawing again?
Louis:
— I’m trying to make it look like reality.
— That’s good. But life demands more than resemblance.
— What does it demand?
Father (after a pause):
— Understanding. Why everything is the way it is, and not otherwise.
— Can that be learned?
— If you are persistent — yes.
👉 This trait would define Louis throughout his life—not a sudden flash of genius, but persistence and attention to detail.
…👨👦 Arbois, around 1837—the classroom
A small school in Arbois. A chalkboard, wooden desks, the smell of ink and damp plaster. On the board it is written:
“Fermentation is the decomposition of organic substances.”
The teacher turns to the class.
— Write this down. This is an established fact.
The students scratch their pens across paper. Louis does not write.
Teacher:
— Pasteur, why are you not writing?
Louis:
— I… don’t quite understand. Why does decomposition create wine, and not just rot?
— Because it is a special kind of decomposition.
Louis:
— And how is it different?
Teacher:
— That is a question of natural philosophy.
Louis (after a pause):
— But can’t it be tested?
Silence. The teacher looks at him more closely:
— Not everything in the world can be tested, Pasteur.
Louis:
— Then how do we know it is true?
Teacher (more slowly):
— We know it is true because it is accepted in science.
Louis:
— But what if it isn’t?
A long pause. The teacher (now without irritation):
— Are you suggesting we test it?
— Yes.
— Then you will have to learn how to conduct experiments. And be prepared for the possibility that the results may not please you.
At school, he was told:
— Not everything in the world can be tested.
He remembered this. But he did not accept it.
— But it can be tested, can’t it?
🎓 Paris, early 1840s—first steps in big science
The capital hums differently than Arbois. Everything here is faster. Louder. More confident.
In the lecture halls of the École Normale Supérieure, people say not “perhaps” but “proven.”
On the board—formulas. On the tables—flasks, crystals, acids.
And most importantly—here, answers already exist.
First lecture
Professor:
— Gentlemen, science moves from observation to law. And once a law is established, it is not to be questioned without serious grounds.
The students take notes. Louis does too—but more slowly.
The professor continues:
— Crystals of tartaric acid, as you know, have a strictly defined shape.
Pasteur looks up and pauses in thought.
👨🎓 After the lecture
A corridor. The sound of voices, footsteps, the smell of chalk.
One of the students:
— Why so thoughtful, Louis?
Pasteur:
— He said “strictly defined.”
Student:
— Well, yes. That’s how it is.
Pasteur:
— But what if it isn’t? I want to see it with my own eyes.
🔬 In the laboratory
Evening. Almost no one is left. On the table—crystals. Small, nearly identical. But if you look long enough, something doesn’t match.
First look through the microscope: One look—and the world is never the same again
Louis picks one up. Then another. Turns them. Compares.
Assistant:
— What are you looking for, Pasteur?
— A difference.
Assistant:
— In what?
Pasteur:
— I don’t know yet. But it’s there.
In Paris, he learned the most important thing—not to accept the order of things as given.
If a difference exists, it can be seen. You just have to look long enough.
If something looks the same, it does not necessarily mean that it is
By the mid-1850s, Louis was in his early thirties. No longer a young student, but not yet a recognized authority. What he was, however, was someone who did not believe that things simply happened “on their own.”
When, in the autumn of 1856, he looked at the barrels in a wine cellar in the Jura region, he already knew what to look for—and where to look.
The real investigation begins not in the cellar — but under the microscope
🔬 Working with the “evidence”
…Paris, laboratory—winter of 1856
The laboratory is quieter than the cellar. There is no smell of wine here—only alcohol, glass, and cold air.
On the table—several flasks. Each contains wine. At first glance, they look almost identical.
But Pasteur knows: these are different “witnesses.”
Clue #1
Pasteur works calmly, without haste. First—a sample from a “good” barrel.
He takes a pipette. A drop of liquid—onto a glass slide. Slowly, he brings it under the microscope. He adjusts the focus. A little closer. Then more.
And suddenly—movement. In his field of view appear tiny, rounded bodies. Almost identical. As if they are moving.
Pasteur makes a note.
Clue #2
The second sample. The picture changes. The shapes are elongated, irregular. The movement is different.
Clue #3
The third. A new picture. New differences.
He does not jump to conclusions. He takes new drops and repeats everything again.
The result is the same.
— If this were just chemistry, the picture would be the same. But it isn’t.
Different shapes… different processes.
🦠 The emergence of a “suspect”
He looks again into the microscope. Now—not just observing. Searching.
And he sees: in one sample — some organisms. In another—different ones.
Pasteur does not say it aloud yet. But the thought is already there:
— If the processes are different, then they are carried out by different agents. This is not happening on its own.
This was no longer chemistry. This was life
⚖️ The Revelation
What had for centuries been considered an act of nature, decay, or mere chemistry
turned out to be the work of living organisms.
Invisible—yet entirely real.
For the first time, the “crime” had identifiable culprits, each with their own “fingerprints.” Some of them turn grape juice into good wine. Others spoil it.
And suddenly, the key question becomes clear: why identical barrels from the same harvest produce different results.
Because they do not contain the same thing
The “culprit” had been found. All that remained was to “catch” it.
The discovery of yeast: No longer a hypothesis—but an observable fact
🍇 Return to the winemakers
When Pasteur returns to the wine cellar, he speaks differently now.
The winemakers listen with caution.
— You’re saying these are… living organisms? — one of them asks.
— Yes.
— But we cannot see them.
— That does not mean they are not there.
Pasteur shows samples, explains, compares. Not everything is immediately clear.
But one thing is certain: this is not chance.
📊 Consequences
Once the cause is known — it can be controlled.
Cleanliness in production ceases to be just a “good habit”—it ”becomes a necessity.
The conditions for making wine cease to be guesswork—they become a tool.
Winemaking begins to transform from a craft into a science.
If there is a culprit – it can be stopped
🔥 Epilogue—The Next Step
Pasteur does not stop there.
If wine is spoiled by living organisms, a new question arises:
— Can they be fought?
The answer turns out to be both simple and revolutionary. If wine is gently heated—without bringing it to a boil—these invisible “culprits” die.
This is how the method later called pasteurization appears.
Pasteurization: Gentle heating is enough to stop the process
Wine ceases to be a whim of nature or a matter of chance.
Identical barrels—similar results.
In that era, this had another important meaning. Clean drinking water was rare, and fermented beverages were often safer.
It is no coincidence that Louis Pasteur said:
“Le vin est la plus saine et la plus hygiénique des boissons.”
“Wine is the healthiest and most hygienic of all beverages.”
He said this not so much as a wine lover, but as someone who understood what was happening inside it.
🧠 Final
Pasteur proved that fermentation is not “decomposition” and not a “trick of nature.” It is the work of living organisms—simply too small to be seen without a microscope.
In good wine, some organisms are at work. In spoiled wine — others.
For the first time, it became clear:
Wine is not just a liquid. It is a controllable living ecosystem
After his research, it became clear: the quality of wine depends on the control of microorganisms, cleanliness of equipment is critical, fermentation can be managed—not just awaited.
👉 This marks the beginning of scientific winemaking and fermentation control.
Sometimes the greatest discoveries are simply the ability to see what has always been there
Pasteur made his discovery too early—several decades before the Nobel Prize even existed. Today, it would undoubtedly be considered work worthy of a Nobel Prize in chemistry or medicine.
This investigation began with spoiled wine.
But in reality, it was about something deeper—that the world does not become understandable on its own.
It must be observed. Compared. Questioned.
And sometimes—simply looked at a little longer than everyone else
To be continued…
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