‘Cheese stink’ is actually microbes ‘talking’ to each other, a critical function for flavor

MEDFORD, Mass. — Cheese is delicious, but let’s face it, sometimes its smell can deter even the most dedicated of cheese lovers. Unpleasant though it might be, cheese smells are actually a sign of cheese quality and flavor. Have you ever heard someone say “the stinkier the cheese, the better it tastes”?

Recently, researchers from Tufts University made an interesting discovery when it comes to cheese smells. Cheese stink, produced by fungi, can affect the balance of bacteria in the cheese. Since this balance is critical for cheese flavor and quality, manipulating the smells could be one more way cheesemakers refine their art.

Explaining the science of cheese stink

The smells produced by cheese fungi are actually chemical compounds called “volatile organic compounds” (VOCs). VOCs help microbes interact with their environment. Until the Tufts researchers performed their experiments, no one really looked into VOCs of cheese and how they contribute to the making of one of humanity’s most beloved foods.

The researchers performed a microbial dating experiment of sorts, pairing 16 different cheese bacteria with five different cheese fungi. They observed a wide range of growth responses in the bacteria. For example, one bacterial species called Vibrio casei seemed to love fungal VOCs, growing rapidly in the presence of all five fungi. Other bacteria were a bit pickier, growing only in response to a single type of fungus. Two very common cheese bacteria actually stopped growing in the presence of a type of fungus called Galactomyces.

The researchers determined that bacterial growth changed as a direct result of changes in gene expression. In other words, fungal VOCs could actually flip genetic switches in bacteria that enable them to eat the VOCs and grow better.

“The bacteria are able to actually eat what we perceive as smells,” says Casey Cosetta, first author of the study, in a university release. “That’s important because the cheese itself provides little in the way of easily metabolized sugars such as glucose. With VOCs, the fungi are really providing a useful assist to the bacteria to help them thrive.”

Using smells to make better food

The study authors say that their findings are important for cheesemakers that mature different cheese types in the same space. VOCs from one type of cheese could travel over to the bacteria on a different type of cheese. Depending on whether those VOCs are helpful or harmful to those bacteria, the cheese could either ripen correctly or spoil.

However, knowing how bacteria respond to VOCs isn’t important just for cheese making.

“Now that we know that airborne chemicals can control the composition of microbiomes, we can start to think about how to control the composition of other microbiomes, for example in agriculture to improve soil quality and crop production and in medicine to help manage diseases affected by the hundreds of species of bacteria in the body,” adds study co-author Benjamin Wolfe.

Now that’s something to chew on the next time you bite into a deliciously stinky piece of cheese.

The study appears in the journal Environmental Microbiology.

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