Scientists Discover the Origin of Swiss Cheese’s Holes

By Carl Engelking | May 29, 2015 2:18 pm


Sandwich lovers around the world will forever remember 2015 as the year scientists solved the great Swiss cheese mystery.

After nearly a century of research, scientists in Switzerland — of course — have finally discovered why Swiss cheese has holes, and it has nothing to do with hungry mice. Rather, it’s tiny flecks of hay that fall into the milk during production that give Swiss cheese its distinctive appearance, according to experts from Agroscope, a governmental agriculture research group.

The Hole Deal

In 1917, American William Clark became the first scientist to systematically study the origin of Swiss cheese’s holes, and he published a detailed paper in the Journal of Dairy Science. He concluded that carbon dioxide burps from microscopic bacteria floating in the milk. Still, Clark couldn’t provide an exact description of the bubble-forming mechanism, and ever since he published his landmark study, myriad researchers around the world have attempted to pin down the origin of Swiss cheese’s holes.

But in a report released Thursday, experts at Agroscope believe they’ve solved this vexing scientific riddle. Scientists took multiple CT scans of Swiss cheese as it developed over 130 days to track where and how holes formed. They found that altering the number of hay particles in milk used to make cheese allowed them to control the number of holes that appeared.

Disappearing Holes

Their findings also explain why, over the past 10 to 15 years, Swiss cheese in the stores has fewer and fewer holes. Today, milk is filtered through modern-day milking machines, and it isn’t exposed to the barn’s open environment, so hay particles don’t get a chance to settle in the milk and form holes.

“It’s the disappearance of the traditional bucket” used during milking, Agroscope spokesman Regis Nyffeler told The Guardian.

We’ll see how long Agroscope’s hay particle explanation holds up, because other researchers, it’s safe to assume, are already searching for holes in the theory.


Photo credit: Tim UR/Shutterstock

CATEGORIZED UNDER: Living World, top posts
MORE ABOUT: agriculture
  • Uncle Al

    Dope the culture medium with insoluble nucleation centers. We know what horses do in hay. Substitute microcrystalline cellulose, lycopodium powder, pine pollen, or pulverized rice hulls.

    • Ali Alsaleh

      what does this have to do with the cheese holes?

  • angela

    This is so neat, I really enjoyed this article especially because I have always wondered why swiss had holes! Who would of ever thought that the holes were caused by hay fleeks?
    I hope that all the holes don’t disappear.

  • leanoracordova

    Have you been using Pay*Pal address ?in the event if you have you can make an additional 440 bucks a week in your pay-check by just Freelancing from your living room for four HOURS per day.. —>

  • Ali Alsaleh

    Do rats realy like cheese or is it just a myth

    • Ali Alsaleh

      No its just a myth Ali.A

  • daqu

    Just because the holes are correlated to the amount of hay does not means that the hay particles make the holes directly!

    Plant material often contains microorganisms, Perhaps a number of a certain kind of bacteria are carried along with hay particles, and then it’s the bacteria burping CO2 that cause the bubbles

    • MildredCLewis



    • sevines

      Don’t confuse people with actual science.

  • AlDavisJr

    Has Swiss Cheese ever been made in the US?? I grew up on a dairy farm, and we had no hay in the barn, ever. And milk filtration at the production level was thru fairly fine filters.

  • Overburdened_Planet

    Years ago, I saw a documentary that showed a large vat of cheese in a small room with open windows somewhere in Europe and learned bacteria in the air contributed to its culturing and flavor.

  • David Ehrlich

    If this is the reason Emmenthaler has holes, the scientists must explain why other Swiss cheeses, which have traditionally been prepared in a similar manner lack holes.

  • Enrique Goban

    “We’ll see how long Agroscope’s hay particle explanation holds up,
    because other researchers, it’s safe to assume, are already searching
    for holes in the theory.”

    Lame science joke.

  • Michelle Marie

    That’s…quite a discovery.

  • Purry

    Lol this is science?? I cant believe people are buying this….. IF there is NO hay in commercial processing, how are there holes then? And why dont other cheeses that contain hay have wholes?? This is mainstream psuedo science at its finest, make an observation and make something up around the observation.

  • Mark C. Danzig

    I think the holes add to the taste!


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