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Why Does Swiss Cheese Have Holes in it?

In the world of cheese aficionados, Swiss cheese holds a special place. Its nutty flavor and iconic appearance, adorned with those characteristic holes, or "eyes," evoke images of Alpine pastures and time-honored cheese-making traditions. Yet, for the longest time, the origin of these enigmatic holes remained shrouded in mystery, leaving cheese lovers pondering the age-old question: Why does Swiss cheese have holes?

Swiss Cheese

The journey to uncovering this cheese conundrum is as intriguing as the cheese itself. Legend has it that a chemist named William Mansfield Clark, back in 1912, first proposed the theory that a particular strain of bacteria, emerging during the cheese's aging process, was responsible for the hole formation. This bacteria, it was said, released carbon dioxide, which manifested as bubbles in the cheese, leaving behind those familiar cavities.

However, as time went on, doubts surfaced. Commercially produced Swiss cheese seemed to be losing its holey charm. It wasn't until 2015 that the veil of uncertainty was finally lifted, revealing an unexpected culprit: hay dust.

Yes, you read that right—hay dust. It turns out that microscopic particles of hay, or other particulate matter, play a pivotal role in the hole formation process of traditional Swiss cheeses like Appenzeller and Emmentaler. During the cheese's aging journey, these tiny hay flecks create weak spots within the curd. As carbon dioxide accumulates within these weakened areas, it forms bubbles, ultimately resulting in the formation of those beloved holes.

Swiss Cheese

But what about the disappearing holes, you may wonder? Well, it seems that modern milking practices inadvertently played a role in this phenomenon. With increased emphasis on cleanliness, the presence of hay particles in milk became increasingly rare. Consequently, fewer holes were formed in the cheese, much to the dismay of hole-loving cheese enthusiasts.

Delving deeper into the cheese-making magic, we uncover another player in this holey saga: Propionibacterium freudenreichii subspecies shermanii, affectionately known as P. shermanii. This additional bacteria, thriving under the specific conditions of Swiss cheese production, contributes to the hole-forming process by releasing carbon dioxide. Picture blowing bubbles with chewing gum—the pressure exerted by the growing bacteria mimics this process, shaping the cheese into those distinctive round cavities.

The temperature at which Swiss cheese is crafted also plays a crucial role. Made at around 70 degrees Fahrenheit, the cheese remains soft and pliable, allowing the gases produced by the bacteria to shape it. Once the cheese is cooled to approximately 40°F, these holes become fixed, giving Swiss cheese its characteristic appearance.

In essence, the allure of Swiss cheese lies not only in its delectable flavor but also in the intricate dance of bacteria, hay dust, and tradition that gives rise to its iconic appearance. So, the next time you savor a slice of holey Swiss cheese, you can appreciate the fascinating journey that brought those delightful "eyes" to your plate.


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