Why does Swiss cheese have holes?

Inquiring minds


Each week the staff at the Roseville Library answers more than 2,500 questions on every subject under the sun. Here are a couple of the most interesting ones they’ve gotten lately.


Editor’s note: With our regular library liaison away on a summer vacation, we’re reprinting some classic “Inquiring Minds” columns. The questions and answers below originally ran in June 2004.


Q. Why does Swiss cheese have holes?


A. All cheese is made by fermenting milk with bacteria culture. The different cultures give cheese their distinctive appearances and flavors. Both French brie and Wisconsin cheddar began life as plain milk. It’s the choice of bacteria cultures that make them what they are.

In the case of Swiss cheese, the same type of bacteria that gives the cheese its sweet nut-like flavor also makes the holes. Propionibacter shermani creates carbon dioxide bubbles, which get trapped in the cheese and eventually turn into those unique holes. Actually, the Swiss refer to them not as holes but as “eyes.” Apparently their size can be varied by altering the temperature, the acidity or the length of the curing time for the cheese. 

(“The World Atlas of Cheese” and internet resources.)

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