Swiss scientists from Agroscope, a state-funded agricultural research center, just announced that they’ve figured out what causes holes in Swiss cheese. Believe it or not, they’ve been investigating the cause for over a century now, so this news is a serious game-changer.

The answer isn’t “mice.” Agroscope says it also isn’t “bacteria.” Are you ready for it?

Hay Is The Reason For Swiss Cheese Holes

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According to Agroscope, old-school cheesemaking methods resulted in “microscopically small hay particles” falling into milk collection buckets. Then cheesemakers would go to work, and those tiny particles of hay would develop into larger holes as the cheese matured.

The Testing Process

SwissInfo reports that researchers observed cheese ripening over the course of 130 days, and used computed tomography (CT) scanning to study where and how holes in the cheese formed in an in-depth manner.

The discovery was announced yesterday, and Agroscope scientists attribute modern milking techniques that have become widespread in the past 10 to 15 years as leading to a lower incidence of holes in traditional Swiss cheeses like Emmental.

Agroscope also advises that cheesemakers who wish to control the amount of holes in their cheese can experiment with adding small amounts of hay dust to their products.

Not So Fast

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The BBC notes that Agroscope’s announcement—while promising—has not yet been subject to peer review.

Additionally, it’s not clear by what process the hay particles create the holes. Since cheesemaking relies on harnessing specific, desirable bacteria and fungi to create the products that cheesemakers want, it’s reasonable to question whether some specific bacterial strain(s) are attracted by the hay.

It’s also worth remembering that until yesterday, bacterial assumptions about Swiss cheese holes had been guided by scientist William Mansfield Clark’s July 1917 paper on the subject in the Journal of Dairy Science. As our available depth of knowledge evolves, so will our understanding of what makes our favorite cheeses so delicious.


As scientists Benjamin Wolfe and Rachel Dutton noted in a paper published in July 2014 in the journal Cell, a single gram of a good cheese can contain as many as 10 billion microbial cells from a combination of bacteria and fungi that even master cheesemakers don’t fully understand yet. That’s why they undertook genetic analysis of 137 cheeses from 10 different countries for that paper, reports Wired.

Jonathan Eisen, a microbial diversity researcher at UC Davis, summed it up nicely:

“People have figured out how to do all these cool things to make different kinds of cheeses, but we don’t really understand what’s going on in terms of the microbes.”

[via the AFP]