It’s known for its sweet and nutty flavor, its buttery yellow color and its distinctive holes, but over the years, Swiss cheese’s distinctive “eyes” have been disappearing. Now, the AFP reports that scientists have debunked a popular theory and discovered the real secret behind Swiss cheese’s holes — hay particles in milk.
Though urban legend has it that mice eat holes into Swiss cheese varieties like Emmentaler and Appenzeller, it’s been theorized since 1917 that bacterial growth creates gases that make holes in the cheese as it ferments and ages. In fact, cheesemakers have identified three types of holes in Swiss cheese: Nissler holes (the smallest), “eyes,” (the medium-sized and most abundant holes) and “large blow holes” (which can make blocks of cheese undesirable because they make slicing difficult).
Now, the AFP reports that a new study by Swiss researchers at Agroscope has poked holes in that original theory, revealing that the eyes are caused by something different: tiny bits of hay that cling to the side of buckets used during milking. They claim that the hay particles stay in the milk and eventually cause the holes. As the traditional milk bucket method disappears, an Agroscope spokesman told the AFP, Swiss cheese varieties are slowly losing their holes.
Is this too much fuss over a few cheesy indentations? Consider this: the USDA actually has a grading system for Swiss cheeses based on (you guessed it) the size and characteristics of its holes. It’s all part of a voluntary program designed to facilitate the marketing of Swiss cheese in the United State. Eyes can be characterized as everything from “overset” to “collapsed,” “dead,” “nesty,” or “frog mouthed,” but only cheese with uniform, perfectly-sized eyes can be classified as Grade A.