Why does Swiss cheese have holes? Some scientists set out to find the answer, and they found out that it depends on how dirty the buckets used for milk collection are.
Despite what cartoons comically suggest, the holes in Swiss cheese aren’t from mice gnawing through once whole blocks of cheese. Neither are they made by bacteria releasing carbon dioxide.
Instead, the answer is more mundane than you think: they’re made by hay flecks. According to a government agricultural institute called Agroscope, “microscopic hay particles” in the buckets used to collect milk make these holes. And as the cheese ages, these holes become bigger.
This doesn’t affect all Swiss cheese though. Some affected ones are Emmental and Appenzell.
These finding revealed something that had been bothering scientists: less holes had been appearing in Swiss cheese in the last 15 years. They now attribute this to how modern milking, where it’s less likely for hay to fall into containers.
The scientists reached their conclusion after a 130 day experiment where they sprinkled small amounts of hay dust into milk then turning it into cheese.
The study has yet to be peer reviewed.
Source:The cheese industry calls holes in cheese “eyes”. Any cheese without eyes is known as blind.