Cheese stinks because bacteria and molds growing in it break down fats and proteins into small, potent molecules that happen to smell terrible to our noses. The same types of microbes that cause body odor are deliberately cultivated on certain cheeses, which is why a ripe wedge of washed-rind cheese can smell remarkably like sweaty feet. The intensity depends on the type of cheese, how it was made, and how long it has aged.
Three Pathways That Create Cheese Odor
Cheese aroma develops through three main metabolic processes carried out by bacteria and fungi. The first, proteolysis, is the breakdown of milk proteins into amino acids. Those amino acids are then further broken apart into smaller compounds, many of which are volatile, meaning they easily become airborne and reach your nose. This pathway is considered the origin of some of the most impactful aroma compounds in cheese.
The second process, lipolysis, is the breakdown of milk fat into free fatty acids. Short-chain fatty acids like butyric acid have a sharp, rancid smell that contributes to the pungency of aged cheeses. The third, glycolysis, involves bacteria fermenting the milk sugar lactose into lactic acid and other byproducts. Together, these three pathways generate dozens of volatile compounds, and their balance determines whether a cheese smells mildly nutty or aggressively funky.
The Feet Connection Is Real
If you’ve ever thought a strong cheese smelled like feet, you weren’t imagining it. A bacterium called Brevibacterium linens is one of the key organisms used to ripen surface-ripened cheeses, and it also lives naturally on human skin, particularly between the toes. On both cheese rinds and feet, it does essentially the same thing: it breaks down amino acids and produces sulfur-containing compounds.
Specifically, B. linens converts the amino acid methionine into methanethiol, a gas with a sulfurous, cabbage-like smell. It also converts leucine into isovaleric acid, which has a sour, sweaty odor. These are two of the main chemicals responsible for foot odor. When cheesemakers intentionally introduce B. linens to a cheese, they’re harnessing the exact same chemistry that makes gym socks smell the way they do.
Why Washed-Rind Cheeses Smell the Worst
Cheeses like Époisses, Taleggio, and Limburger are repeatedly washed with brine (saltwater) or alcohol during aging. This washing serves a specific purpose: it creates surface conditions that favor B. linens and related bacteria while suppressing mold growth. The salt from the brine solution also introduces secondary microflora that contribute additional odor compounds.
Before B. linens can thrive, the cheese surface needs to become less acidic. Cheesemakers often apply yeasts to the rind first, which consume lactic acid and raise the pH, creating a more hospitable environment for the odor-producing bacteria. This careful sequencing of microbial growth, yeasts first, then bacteria, is what allows washed-rind cheeses to develop their notoriously powerful smell over weeks or months of aging.
In 2004, a French cheese called Vieux-Boulogne was ranked the smelliest cheese in the world by Guinness World Records. It beat out 14 other contenders when tested by a panel of 19 human judges and an electronic nose that measured the gaseous molecules each sealed cheese released.
What Makes Blue Cheese Smell Different
Blue cheeses like Roquefort, Stilton, and Gorgonzola get their distinctive pungent aroma from an entirely different organism: a mold called Penicillium roqueforti. Rather than breaking down proteins like B. linens does, this mold primarily attacks fatty acids and converts them into a family of compounds called methyl ketones.
The conversion follows a simple pattern. The mold takes a fatty acid and strips off one carbon atom, producing a ketone that is one carbon shorter than the original fat. For example, it converts an eight-carbon fatty acid (caprylic acid) into a seven-carbon ketone called 2-heptanone, and a six-carbon fatty acid into 2-pentanone. Each of these ketones has its own sharp, peppery, slightly medicinal smell. Together, they produce the unmistakable blue cheese aroma that people tend to either love or find revolting.
Temperature Changes the Smell
You may have noticed that cheese smells much stronger at room temperature than straight out of the refrigerator. This is because volatile aroma compounds become more active as temperature rises. At cold temperatures, many of these molecules stay trapped in the cheese’s fat and protein matrix. As the cheese warms, fats soften and release those compounds into the air more readily.
Research on hard goat cheeses found that even a 2-degree difference in processing temperature (38°C versus 40°C) produced measurably higher concentrations of volatile compounds. The warmer cheese was described as more mature and complex in flavor. This is also why cheese experts recommend serving most cheeses at room temperature: more volatiles means more aroma, which translates to more flavor. The tradeoff is that what you gain in taste, you also gain in smell.
Why It Smells Bad but Tastes Good
Many people find that cheeses they can barely stand to sniff are delicious once they actually eat them. This isn’t just psychological. Your brain processes smell differently depending on whether the odor enters through your nostrils (sniffing) or rises up through the back of your throat while chewing. When you sniff a cheese, you get the full blast of its most volatile and often most offensive compounds. When you eat it, the aroma mixes with taste signals from your tongue (salt, fat, umami), and your brain interprets the combination as something much more pleasant.
The texture and fat content of cheese also play a role. Fat coats your mouth and slows the release of volatile compounds, softening the sensory experience. This is partly why a triple-cream brie tastes rich and mild despite having a rind that smells like a damp basement. The same molecules are present, but your body experiences them differently when they arrive through food rather than through the air.