Randy Chandler
Swiss cheese, also known as Emmental, gets its holes, or eyes, from carbon dioxide bubbles released by bacteria during the cheese-making process. The bacteria responsible for this is Propionibacteria, or Props, which is found in hay, grasses, and soil, and can make its way into raw milk when cows are milked. Modern milking methods have resulted in fewer holes in Swiss cheese over the years, as it is now less likely for hay to fall into the milk containers.
| Characteristics | Values |
|---|---|
| What are the holes called? | Eyes |
| What causes the holes? | Carbon dioxide bubbles, produced by bacteria |
| What type of bacteria? | Propionibacteria, or Props (Propionibacterium freudenrichii subspecies shermanii, or P. shermanii) |
| Where do these bacteria come from? | They are naturally found in hay, grasses, and soil, and can get into raw milk during milking |
| What happens during pasteurization? | The pasteurization process kills bacteria in milk, so cheesemakers add Props back in to form eyes |
| How do the holes form? | The cheese is kept at a warm temperature, making it soft and malleable. As the bacteria grow, they emit gas, creating round openings. When the cheese is cooled, the holes stay in place. |
| What happens when holes don't form? | Cheesemakers say the batch is blind |
| What other factors influence the formation of holes? | The amount and type of bacteria, the salting method, temperature, and aging time |
| Why are there fewer holes nowadays? | Modern milking methods have reduced the likelihood of hay falling into milk containers |
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What You'll Learn
The holes are called 'eyes' by cheesemakers
Cheesemakers refer to the holes in Swiss cheese as "eyes". The eyes are considered a desirable feature of Swiss cheese and when they are missing, the batch is deemed ["blind"]. The eyes are caused by a special bacterial culture called Propionibacteria, or "Props", which is found in hay, grasses, and soil, and can find its way into raw milk naturally when cows are milked. The pasteurization process kills the bacteria in milk, so if pasteurized milk is used as the base for Swiss cheese, cheesemakers add some Props back in so that eyes will form. After the cheese is made and brined, the blocks or wheels are placed in warm rooms, which helps the Props produce carbon dioxide and keeps the cheese at the right consistency. The size of the eyes can vary from the size of a dime to the size of a quarter.
Other cheeses also have eyes, but they are caused by different bacteria or conditions. For example, Gouda can have small, pea-sized holes, and it is not uncommon for various raw milk cheeses to have eyes, thanks to the natural bacteria, although the conditions might not always be right for eyes to form. Cheesemakers usually try to prevent the formation of gas in their cheeses, especially in harder cheeses, where gas tends to create unsightly crevices, cracks, and splits.
The eyes in Swiss cheese were long believed to be caused by carbon dioxide released by bacteria present in the milk. This theory was first proposed in 1917 by William Clark and was accepted as fact for almost 100 years. However, in 2015, a study by Agroscope, a Swiss agricultural institute, challenged this theory, suggesting instead that the holes are created by flecks of hay that fall into buckets during the milk collection process. This theory explains why fewer holes have appeared in Swiss cheeses over the last 15 years, as modern milking methods have made it less likely for hay to contaminate the milk.
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They are caused by bacteria
The holes in Swiss cheese, known as "eyes," are indeed largely caused by bacteria, specifically a strain of bacteria called Propionibacterium freudenreichii. This bacteria is crucial to the unique characteristics of Swiss cheese and is added to the milk during the cheesemaking process. The bacteria produce tiny CO2 gas bubbles as they consume the lactic acid that is present in the cheese curds. These microscopic bubbles then cluster together to form larger pockets of gas, which eventually create the distinctive holes in the cheese. The size and distribution of these holes are influenced by a variety of factors, including the acidity of the curd, the temperature, and the duration of ripening. Cheesemakers can manipulate these factors to create Swiss cheese with the desired size and number of eyes.
The bacteria Propionibacterium freudenreichii plays a critical role in the development of flavor and aroma in Swiss cheese, in addition to its role in eye formation. During the aging process, these bacteria break down milk proteins, releasing a range of compounds that contribute to the complex flavor profile of Swiss cheese. This includes buttery, nutty, and sweet notes, as well as a subtle tanginess. The bacteria also contribute to the texture of the cheese, helping to create a smooth, creamy mouthfeel.
While the presence of bacteria is essential to the formation of eyes in Swiss cheese, it's important to note that the process is carefully controlled. The bacteria are added in specific amounts and under specific conditions to ensure the desired outcome. Additionally, the cheesemaking environment is carefully monitored to prevent the growth of unwanted bacteria that could spoil the cheese or pose a health risk. In this way, cheesemakers can harness the power of bacteria to create a consistent and safe product with the characteristic eyes that consumers expect from Swiss cheese.
The use of bacteria in cheesemaking is not unique to Swiss cheese, although the specific bacteria and the resulting effects on the cheese vary. For example, in cheeses like Blue Cheese and Gorgonzola, different strains of bacteria are introduced to create the distinctive veining and pungent flavors associated with these varieties. In contrast, cheeses like Cheddar may use bacteria to develop flavor but do not aim to create the same type of holes as Swiss cheese. Each type of cheese has its own unique bacterial profile and cheesemaking process, contributing to the vast diversity of cheeses available worldwide.
The holes in Swiss cheese, caused by bacteria, are a fascinating example of how humans have harnessed the power of microorganisms to create a beloved and iconic food product. Through careful control of the cheesemaking process, cheesemakers can ensure consistent results, producing Swiss cheese with its signature eyes batch after batch. This combination of art and science has led to a delicious and distinctive cheese that has become a staple in kitchens and restaurants worldwide. So, the next time you enjoy a slice of Swiss cheese, remember the crucial role played by Propionibacterium freudenreichii in creating those perfect holes.
Additionally, the bacterial culture used in Swiss cheese production also contributes to the overall texture and consistency of the cheese. As the bacteria grow and multiply, they help bind the cheese curds together, affecting the overall texture and mouthfeel of the final product. Cheesemakers can adjust the amount and type of bacterial culture used to achieve the desired texture, ranging from creamy and smooth to slightly grainy or firm. This versatility in texture, along with the distinctive flavor and eye formation, makes Swiss cheese a popular choice for a wide range of culinary applications.
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Modern milking methods have reduced the number of eyes
The "eyes" in Swiss cheese are caused by a special bacterial culture called Propionibacteria, or "Props", which is found in hay, grasses, and soil. These bacteria find their way into raw milk naturally when cows are milked. The pasteurization process kills the bacteria in milk, including Props, so if pasteurized milk is used as the base for Swiss cheese, cheesemakers add some Props back in so that eyes will form. After the cheese is made and brined, the blocks or wheels are placed in warm rooms, which helps the Props produce carbon dioxide and also keeps the cheese at the right consistency.
The size of the eyes in Swiss cheese can vary from the size of a dime to the size of a quarter. When the eyes are missing, cheesemakers say the batch is "blind". Other varieties of Swiss cheese, such as Baby Swiss and Jarlsburg, are types of Emmental that have different amounts of moisture, fat, and bacterial cultures. Baby Swiss tends to have smaller eyes, while Jarlsburg has eyes caused by different bacteria or conditions.
Cheese is made from milk, and the type of cheese produced varies based on the source of milk. Bacteria are added to the milk, creating chemical reactions that cause it to change into solid "curds" and liquid "whey". The amount and type of bacteria influence the taste and texture of the cheese. Other factors that impact the type of cheese produced include the salting method, temperature, and aging time.
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The size of the eyes varies
The eyes in Swiss cheese are caused by a special bacterial culture called Propionibacteria, or Props, that gets added to the cheese. This bacteria is found in hay, grasses, and soil, and can find its way into raw milk naturally when cows are milked. The pasteurization process kills the bacteria in milk, so if pasteurized milk is used as the base for Swiss cheese, cheesemakers add some Props back in so that eyes will form. After the Swiss cheese is made and brined, the blocks or wheels are placed in warm rooms, which helps the Props produce carbon dioxide and keep the cheese at the right consistency. The size of the eyes that form varies depending on the type of cheese and the conditions under which it is made.
For example, while Swiss cheese made in Switzerland is called Emmental, in the US, cheesemakers create a modified version called Baby Swiss, which tends to have smaller eyes. Gouda cheese, which originated in the Netherlands, is sometimes made with cultures that produce a small amount of gas and tiny eyes. In most cases, cheesemakers try to prevent the formation of gas in their cheeses, especially in harder varieties, as gas tends to create unsightly crevices, cracks, and splits rather than the desired round eyes.
The size of the eyes in Swiss cheese can vary from the size of a dime to the size of a quarter. The variation in eye size is likely due to differences in the amount and type of bacteria, as well as other factors such as the salting method, temperature, and aging time. These factors influence the taste and texture of the final product, resulting in different sizes of eyes in Swiss cheese.
It is worth noting that the absence of eyes in Swiss cheese is considered a defect, and such cheese is referred to as "blind" Swiss. Even without the eyes, the cheese will still have the characteristic flavour of Swiss cheese.
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Other cheeses with eyes include Gouda and Fontina
The holes in Swiss cheese are called "eyes" by cheesemakers. They are caused by a special bacterial culture called Propionibacteria, or Props, that gets added to the cheese. These bacteria produce carbon dioxide gas, which accumulates in any air pockets, loose curd junctions, or other nucleation sites present in the cheese. As more gas is produced, it forms bubbles, which eventually pop, leaving behind the distinctive holes or eyes in the cheese.
In addition to Gouda and Fontina, other cheeses with eyes include Jarlsberg from Norway, Havarti from Denmark, and Edam from the Netherlands. These cheeses all have distinctive holes or eyes that are formed by the production of gas during the cheese-making process, contributing to their unique appearance and texture.
It is worth noting that the absence of eyes in Swiss cheese is considered a defect, and such cheese is called "blind" Swiss. The eyes not only contribute to the visual appeal of the cheese but also play a role in its flavor development. The bacteria that form the eyes also produce compounds that enhance the characteristic nutty flavor of Swiss cheese.
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Frequently asked questions
The holes in Swiss cheese, also known as "eyes", are created by carbon dioxide bubbles during the cheese-making process. Specifically, they are caused by a special bacterial culture called Propionibacteria, or "Props", which is found in hay, grasses, and soil, and can make its way into raw milk naturally during milking.
Modern milking methods have made it less likely for hay and grass particles to contaminate the milk, resulting in fewer holes in Swiss cheese over time.
Yes, other types of cheese that have holes include Gouda, Baby Swiss, Jarlsberg, and Fontina.
No, the holes are not caused by mice or other rodents. This idea was popularized by old wives' tales and cartoons but has been debunked by modern science.
