Why Does Cheese Have Holes?｜The Science Behind Aged Cheese Eyes
When you eat cheese, you might notice small or large round holes scattered across its surface and slices. This is especially true for Swiss cheese or Emmental, where neat, round holes are evenly spread throughout, almost as if someone crafted them on purpose.
So, how do these holes actually form?
Simply put, the holes in cheese are created during the aging process when gas produced by beneficial microbes becomes trapped inside the cheese body. As milk transforms into cheese, microorganisms like lactic acid bacteria become active. In specific cheeses, bacteria such as Propionibacterium produce carbon dioxide during fermentation. As this gas stays inside, it forms tiny bubbles that expand over time into the visible holes—often referred to by cheesemakers as "eyes."
This means simply keeping cheese in the fridge for a long time won't create holes. Whether holes form and how large they grow depends on the type of microbes used, moisture content, paste texture, aging temperature, and aging duration.
How Does Aging Lead to Holes?
To make cheese, milk is first curdled into a solid form called curd.
The curd is then cut into smaller pieces, and whey is drained off to control moisture and texture. Depending on the cheese type, it is salted, pressed, and aged under precise temperature and humidity conditions.
During this aging phase, microbes consume components in the milk and produce various byproducts. In certain cheeses, fermentation releases carbon dioxide gas. If the cheese structure is sufficiently firm, the gas cannot escape and remains trapped inside.
What starts as a microscopic bubble gradually pushes against the surrounding curd as gas builds up, causing the bubble to grow. When sliced, these expanded bubbles appear as round holes.
The step-by-step process is simple:
Microbial Fermentation → Gas Production → Gas Trapped in Curd → Bubble Expansion → Hole Formation
Emmental: The Classic Hole-y Cheese
When people think of cheese with holes, Emmental is usually the first that comes to mind.
As an iconic Swiss cheese, Emmental is famous for its large, distinctive round eyes. These holes are not artificially poked by cheesemakers. Instead, they form naturally as specific microbes ferment and release gas that moves through and settles within the cheese matrix.
Specifically, bacteria belonging to the Propionibacterium genus are well known for producing carbon dioxide alongside propionic acid during aging. By carefully controlling aging conditions, cheesemakers encourage these bacteria to create the signature holes found in Emmental.
Why Are Hole Sizes Different?
Even in the same style of cheese, not all holes are identical in size or frequency. Several factors influence how these eyes develop:
1. Types of Microorganisms
The specific microbes involved in ripening determine what compounds are created during fermentation. Cheeses with gas-producing strains easily form eyes, whereas those made without gas-producing bacteria remain smooth and dense.
2. Aging Temperature
Temperature directly influences microbial activity. When maintained in an optimal range, microbes thrive, producing more gas during fermentation. Conversely, incorrect temperatures disrupt microbial activity and alter hole development. In cheesemaking, how and at what temperature a cheese ages is far more crucial than simply how long it sits.
3. Moisture and Texture of the Cheese Paste
If the interior is too dense or porous enough for gas to leak out easily, bubbles cannot expand. However, when the moisture and texture are properly balanced, trapped gas forms stable, growing pockets.
4. Aging Duration
Aging time plays an essential role. As time passes, continuous microbial action and structural changes allow small initial bubbles to enlarge. Still, this shouldn't be oversimplified as "longer aging equals bigger holes." The correct cheese variety and production conditions must be established first.
Not All Cheeses Develop Holes
An important distinction must be made: simply storing any cheese in your refrigerator for a long time will not produce holes.
Different cheeses rely on distinct cultures, recipes, moisture levels, and aging environments. Varieties like Cheddar, Camembert, and Gorgonzola follow completely different biochemical pathways during ripening.
Therefore, judging a cheese's age solely by the presence of holes is inaccurate; understanding the cheese type and its specific production method is key.
Holes Are a Sign of Craft, Not a Defect
People trying specialty cheese for the first time might wonder if the holes indicate a defect or a mistake.
In cheeses like Emmental, however, these eyes are a sign of proper, successful aging. Cheesemakers don't stop at curdling milk—they actively manage microbial culture, humidity, temperature, and time to achieve the desired quality.
Rather than empty spaces or flaws, the holes in cheese are a natural masterpiece created by active microorganisms and a controlled environment as milk evolves into cheese.
What the Holes Tell Us About the Process
The eyes visible when you slice into a wheel of cheese offer a glimpse into its history.
Inside those empty pockets lies the story of hardworking microbes consuming milk nutrients, the fermentation process, structural changes in the curd, and the ambient ripening environment.
The holes in cheese are not random hollows formed by time alone. They are a natural, fascinating outcome born from the interplay between microbial gas production and changing cheese texture.
Conclusion
The holes in cheese are far more than a simple cosmetic change from long storage.
In specific varieties, ripening microorganisms ferment and generate carbon dioxide, which stays trapped inside to form growing bubbles. Over time, these bubbles expand into the round eyes we recognize.
The next time you enjoy a slice of hole-y cheese, take a moment to appreciate the invisible fermenting and aging science hidden inside every hole!
댓글
댓글 쓰기