Randy Chandler
Swiss cheese, or Emmental, is known for its distinctive holes, which are called eyes in the cheese-making world. The holes are caused by carbon dioxide bubbles that form in the cheese as a result of bacterial activity. Specifically, a bacterial strain called Propionibacterium consumes lactic acid and releases carbon dioxide, creating air pockets in the cheese. The size and distribution of the holes can vary depending on factors such as temperature, humidity, and fermentation times. While it was previously believed that the holes were caused by bacteria in the milk, modern research suggests that they may actually be caused by hay dust particles from dairy barns that contaminate the milk during collection.
| Characteristics | Values |
|---|---|
| Scientific Reason | Carbon dioxide bubbles form in the cheese due to bacteria cultures |
| The bacteria cultures are added to the cheese and produce carbon dioxide gas by consuming lactic acid | |
| The gas forms air pockets within the cheese | |
| The bacteria cultures are called Propionibacteria or Props | |
| Props are found in hay, grasses and soil and 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, cheesemakers add some Props back in so eyes will form | |
| The cheese is then placed in warm rooms, which helps the Props produce carbon dioxide and also keeps the cheese at the right consistency | |
| The holes are also called "eyes" | |
| Swiss cheese without eyes is known as "blind" | |
| Traditional Reason | Bits of hay fell into the milk buckets and caused the holes |
| Milk for cheese-making is now usually extracted using modern methods, which explains why there are fewer holes in Swiss cheese now | |
| The disappearance of the traditional bucket during milking caused the difference | |
| The holes are caused by hay dust particles from the dairy barns that find their way into the milk |
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What You'll Learn
Carbon dioxide bubbles
The holes in Swiss cheese, also known as "eyes", are caused by carbon dioxide bubbles. These bubbles are produced by bacteria, specifically Propionibacterium freudenreichii, which is added to the cheese. This bacterium feeds on the lactic acid left behind by other bacteria and releases carbon dioxide as a byproduct. The carbon dioxide forms bubbles as it tries to escape the dense cheese, leaving behind air pockets.
The size and distribution of these eyes can vary, and this is regulated by the USDA. The number and size of the holes in Swiss cheese are related to its flavour. Larger holes indicate a more intense and developed flavour, as the bacteria have had more time to work and create a greater number of bubbles.
The formation of eyes in Swiss cheese is dependent on the presence of nucleation sites for the carbon dioxide bubbles to form around. In the past, these nucleation sites were provided by bits of hay or dust in the milk, which entered the milk during the collection process when traditional buckets were used. However, with modern, ultra-clean production methods, there are fewer nucleation sites, resulting in smaller or fewer eyes in the cheese.
Cheesemakers have to take specific steps to ensure the formation of eyes in Swiss cheese. After the cheese is made and brined, the blocks are placed in warm rooms, which helps the bacteria produce carbon dioxide and maintain the right consistency. The pasteurization process kills the bacteria in the milk, so if pasteurized milk is used as the base, cheesemakers add the bacteria back in so that eyes will form.
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Bacteria cultures
The holes in Swiss cheese, known as "eyes" in the cheese industry, are caused by a specific bacterial culture called Propionibacteria, or "Props" for short. These bacteria are naturally present in hay, grasses, and soil, and can make their way into raw milk during the milking process. When cows' milk is pasteurized, the Props are killed, so cheesemakers add them back in when making Swiss cheese to ensure the eyes will form.
After the cheese is made and brined, the blocks or wheels are placed in warm rooms, which encourages the Props to produce carbon dioxide and helps maintain the right consistency. The carbon dioxide forms air pockets within the cheese, resulting in the distinctive holes.
The size of the eyes can vary from dime-sized to quarter-sized, and larger holes generally indicate a more intense and developed flavor. This is because larger holes allow for increased activity of the Propionibacter shermani bacteria, which enhances the flavor.
In addition to Propionibacteria, Swiss cheese also includes bacteria from the Streptococcus and Lactobacillus genera. Lactobacillus is crucial as it gives Swiss cheese its texture, sharpness, and nutty flavor. Lactobacillus and Streptococcus thermophilus excrete lactic acid, which is then consumed by the Propionibacteria and converted into carbon dioxide.
Overall, the unique blend of bacterial cultures in Swiss cheese contributes to both its distinctive flavor and its characteristic eyes.
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Hay dust particles
The holes in Swiss cheese, also known as "eyes", are caused by a variety of factors, including the presence of hay dust particles, bacteria, temperature, humidity, and fermentation times. The size and distribution of the holes can vary among different varieties of Swiss cheese, such as Jarlsberg and Appenzeller, which are known for their medium-sized and larger holes, respectively.
Historically, the milk used for cheese-making was collected in buckets, and bits of hay or hay dust particles would fall into the buckets and eventually cause the holes in the cheese. Modern processing techniques have improved sanitation and reduced the presence of hay and hay dust in milk, resulting in smaller holes or the absence of holes in Swiss cheese.
The cheese-making process involves the addition of bacterial cultures, specifically Propionibacterium freudenrichii subspecies shermanii, which converts milk into carbon dioxide at warm temperatures of around 70°F. As the cheese cools, the carbon dioxide forms air bubbles, creating the holes in the Swiss cheese.
The holes in Swiss cheese are not only aesthetically appealing but also contribute to the cheese's texture and flavour. The holes provide a light and airy feel, and the slight nuttiness in taste enhances the overall culinary experience. Thus, the presence of hay dust particles, along with other factors, plays a crucial role in shaping the distinctive characteristics of Swiss cheese.
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Milk collection methods
The holes in Swiss cheese, also known as "
Traditionally, milk for cheese-making was collected using buckets, and bits of hay that fell into the buckets caused the holes. Today, milk for cheese-making is usually extracted using modern methods, which is why Swiss cheese today has fewer holes.
To make Swiss cheese, the first step is to heat the milk to 84°F (or 86°F if using raw milk with higher fat). This can be done by placing the milk in a pot or sink of very warm water. It is important to heat the milk slowly and stir well. Once the milk reaches the desired temperature, a culture is added, along with calcium chloride and propionic shermanii. The powder is sprinkled on the surface of the milk and allowed to rehydrate before stirring. The milk then sits quietly for 40-45 minutes while the culture works and the rennet coagulates the curd. As the milk thickens, it continues to firm until a curd forms. The curd mass is then cut into 3/8 inch pieces, and the curds are allowed to rest and then stirred gently. After this, the curds are left to settle at the bottom of the vat.
The next step is to remove 1/3 of the whey, which reduces lactose and slows down bacteria and acid production. This step is key to creating the elastic texture of Swiss cheese. The curds are then dried out by slowly increasing the heat to 102°F by adding hot water at 130°F.
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Temperature and humidity
After the Swiss cheese is made and brined, it is placed in warm rooms. This warmth encourages the bacterial activity, promoting the release of carbon dioxide and contributing to the formation and expansion of the bubbles. The temperature in these aging rooms is carefully controlled to maintain the ideal conditions for the desired size and distribution of the holes.
The length of time the cheese spends in these warm rooms, known as fermentation time, is also crucial. Longer aging at higher temperatures contributes to the development of larger holes. This is because the enzymes and bacteria have more time to act and create bigger "eyes." However, this also presents challenges for mass producers, as the larger holes make mechanical slicing more difficult, increasing production costs.
In addition to temperature, humidity also influences the hole formation process. The presence of hay particles, which are affected by humidity levels, can impact the size of the holes. Higher humidity can lead to more moisture in the air, potentially affecting the size and distribution of hay particles that enter the cheese. These hay particles can then influence the size of the holes by weakening the curd structure.
Overall, temperature and humidity are critical factors in the development of Swiss cheese's distinctive holes. The warmth encourages bacterial activity and carbon dioxide production, while the humidity can influence the size and distribution of hay particles, which in turn affect the size and consistency of the holes. Cheesemakers carefully manipulate these factors to create the desired hole size and distribution, contributing to the unique appearance, texture, and flavour of Swiss cheese.
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Frequently asked questions
The holes in Swiss cheese, also known as "eyes", are caused by a specific bacterial strain known as Propionibacterium. These bacteria consume lactic acid and transform it into carbon dioxide, forming air pockets within the cheese.
Modern processing techniques have reduced the presence of hay dust particles in the milk, which are responsible for the holes. Additionally, the pasteurization process kills the Propionibacteria bacteria, so cheesemakers must add them back in to form the eyes.
Temperature, humidity, and fermentation times all play a role in determining the size and distribution of the holes. Cheesemakers can manipulate these factors to create the desired hole size and pattern.
No, not all Swiss cheeses have holes. Some varieties, such as Emmental and Gruyère, do not have the signature holes. Additionally, there are Swiss cheese varieties without eyes, known as "blind".
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