Why Swiss cheese has holes


In North America, Swiss cheese is any of those types of cheeses that attempt to reproduce Emmental cheese, which originates in Switzerland. The term can also refer to genuine Emmental cheese from the Emme valley region of Switzerland. It is a pale yellow cheese of medium firmness, and it is known for its characteristic holes that are produced during the maturation process.


Swiss cheese is made from cow’s milk. Three types of bacteria are used to produce Swiss cheese, the first two of which release lactic acid. The final type of bacteria consumes this lactic acid and releases propionic acid, acetate, and carbon dioxide. The propionic acid and acetate are responsible for the distinct flavor of Swiss cheese that has been produced by this authentic method. The carbon dioxide is responsible for forming the holes.


Cheese makers call the holes in Swiss cheese “eyes.” As the cheese is allowed to age, the bacterium Propionibacterium freudenreichii slowly releases carbon dioxide gas as one of its byproducts. This type of bacteria is used to make other kinds of cheeses as well, but Swiss cheese contains the highest concentration of it. As the carbon dioxide is released, pockets of the gas create the eyes for which Swiss cheeses are known. The longer it is allowed to age, the larger the holes will become. Acidity and temperature also affect the size of eyes, so these can be adjusted to control how large the eyes will become.


The size and number of eyes in true Emmental is regulated. Holes must be between about the size of a cherry and a walnut. Larger and more numerous eyes make slicing more difficult during the manufacturing process, so Swiss cheese that is produced in the United States can be considered Grade A without the longer fermentation period that produces larger holes. As a result, Swiss cheese made in America often has smaller eyes. Since a longer aging process also produces a stronger flavor, a correlation is created between large holes and strong flavor. American types tend to have less flavor.


Careful pressing of the cheese can prevent eyes from forming, and it used to be that they were actually considered as imperfections. Cheese makers would attempt to keep them from developing. Swiss cheese without eyes is referred to as “blind.”


Most of us instantly recognize that pale cheese, riddled with holes, as none other than Swiss cheese. We do not tend to stop and think much about it as we layer it on our sandwiches and crackers. It turns out, however, that what we know today as Swiss cheese is actually part of a long and rich tradition.



Keep being ewenique!


Diane Rae

Master Cheesemaker

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