Why “72-Hour Fermentation” Is Just A Marketing Myth
Open a bakery’s Instagram today and you’ll see it everywhere:
slow fermentation.
56-hour fermentation.
72-hour fermentation.
The number sits on the label like a badge — proof of patience, proof of craft, proof that this loaf is better than the one beside it.
It’s a compelling story. More time should mean more flavour, more complexity, more care.
But somewhere between the original idea of slowing dough down and the number printed on today’s packaging, something changed.
Time slowly became a substitute for understanding fermentation.
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Where cold retard actually came from
Cold retard isn’t a new invention.
Long before it became a marketing phrase, bakers used cool conditions for one practical reason: scheduling.
Shape the dough at night. Slow it down overnight. Bake it fresh the next morning.
The cold didn’t exist to make bread automatically better.
It existed to give the baker more control.
In its original form, cold retard was simply one technique among many for managing fermentation. It was never intended as proof that more hours automatically produced a better loaf.
The cold was a tool.
Not a competition.
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When home baking inherited an industrial comparison
To understand why duration became the dominant measure of sourdough quality, it helps to understand where the comparison began.
Industrial bread—the standard white loaf most consumers grew up with—often moves from mixing to baking in roughly 60 to 120 minutes. Speed is built into the system because commercial yeast is selected to work quickly, and fast production is economically essential.
When sourdough entered mainstream conversation, the contrast was genuine.
A naturally leavened dough commonly ferments for six to twelve hours, not including the time required to maintain an active starter.
Compared with industrial bread, sourdough genuinely was slower.
The problem wasn’t the comparison.
The problem was what happened next.
“Long fermentation” gradually became shorthand for everything that made sourdough different—more flavour, greater complexity, easier digestibility and a less industrial process.
But fermentation was never valuable because it occupied more hours.
It was valuable because those extra hours allowed microorganisms to transform the dough.
As sourdough spread through social media, that distinction slowly disappeared.
People remembered the time.
They forgot the biology.
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The only tool most home bakers had
Professional bakers often slow fermentation in environments around 15–20°C.
At these temperatures, both wild yeast and lactic acid bacteria remain metabolically active. Fermentation continues, but at a slower, more manageable pace.
Most home bakers didn’t own proofing cabinets, wine chillers or temperature-controlled rooms.
They owned refrigerators.
Around 4°C became the default—not because it represented the ideal fermentation temperature, but because it was the only practical option available.
As home baking exploded, refrigeration became synonymous with long fermentation.
The hours grew longer.
The temperature grew colder.
And eventually the number itself became the selling point.
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The temperature that changed everything
Here’s the detail that often gets overlooked.
Sourdough isn’t fermented by time.
It’s fermented by microorganisms.
Wild yeast and lactic acid bacteria each have temperature ranges where they are most metabolically active.
Wild yeast is responsible for producing carbon dioxide, which inflates the dough and creates an open, light crumb.
LAB produces organic acids and many of the compounds responsible for flavour development while also influencing enzyme activity within the dough.
As temperature falls, both organisms slow down.
But they don’t slow down equally.
At around 15–20°C, fermentation simply becomes more gradual.
At around 4°C, the picture changes dramatically.
Wild yeast enters a near-dormant state. Cellular reproduction effectively ceases, and carbon dioxide production falls to negligible levels.
LAB tolerates refrigeration considerably better.
Although bacterial growth is greatly reduced at 4°C, some of the LAB strains remain metabolically active, continuing to produce and accumulate organic acids. Wild yeast, however, enters a prolonged lag phase in which CO₂ production is minimal.
This creates an imbalance between acid production and gas generation, resulting in dough that develops relatively greater acidity while gaining less volume.
Consequently, cold-retarded loaves are often denser and more sour than those fermented predominantly at ambient temperature.
In other words, the clock keeps running.
The microbes do not.
Not at the same biological intensity.
This is why two doughs that each spend 24 hours under different temperature conditions are not biologically equivalent.
Twenty-four hours is simply elapsed time.
Fermentation depends on microbial activity, not the number printed on a label.
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A modest technique became a marketing number
None of this means cold retard is a bad technique.
It remains an extremely useful tool for production scheduling, workflow and, when used intentionally, flavour development.
The problem isn’t refrigeration.
The problem is treating refrigeration time as though it measures fermentation itself.
Somewhere along the way, a practical production technique became a marketing metric.
“72-hour fermentation” began to imply greater craftsmanship simply because the number was larger.
But a loaf isn’t more fermented simply because it spent more time inside a refrigerator.
The biology determines fermentation.
The clock merely records time.
Being fermented and being stored for three days are two very different things.
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So what should you actually be asking?
Not,
“How many hours?”
Ask instead:
Was the dough given the conditions its microorganisms needed to carry out fermentation?
Because time only matters when biology is happening inside it.
And that’s something no number on a label can tell you.
It’s something you can taste.