Why does Swiss cheese have holes in it?
December 06, 2019 4:58PM
Cheese (all cheese that is) is made by adding bacteria to milk, which produces lactic acid and helps give the cheese its taste. One specific bacteria added to Swiss cheese called Propionibacterium shermani produces carbon dioxide. Due to the density of the cheese, the carbon dioxide forms bubbles, which get larger and eventually burst, leaving the trademark holes.
More recent research suggests that these bubbles form around microscopic debris in the milk, which compromises the structure of the cheese in those spots. Swiss cheese has gotten less holey over the years, and some scientists credit that to cleaner modern milking methods—fewer particles means fewer holes.
Cheesemakers call these holes "eyes" and can control their size by adjusting the temperature, acidity, and curing time of the cheese.