Frederic Melton
Swiss cheese 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 gas, creating air pockets within 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, it is now suggested that they may be caused by hay dust particles or dirt from dairy barns that contaminate the milk during collection.
| Characteristics | Values |
|---|---|
| Scientific Reason | Carbon dioxide bubbles are formed due to the bacterial culture, Propionibacterium freudenrichii subspecies shermanii, which converts milk into carbon dioxide at 70°F. When the cheese cools, air bubbles are left behind. |
| Traditional Reason | Bits of hay fell into the bucket during milking and caused the holes. |
| Other Factors | Temperature, humidity, and fermentation times influence the size and distribution of the holes. |
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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 formed by bacteria that are added to the milk at the start of the cheese-making process. Specifically, the bacteria Propionibacterium freudenreichii, or Propionibacter shermani, consumes lactic acid and releases carbon dioxide gas as a byproduct. As the cheese ages, these gas bubbles become trapped, creating the characteristic holes in Swiss cheese.
The size of the eyes in Swiss cheese can vary and is regulated by the USDA. Cheesemakers can control the size of the holes by adjusting factors such as temperature, acidity, and aging time. The presence of eyes is a crucial characteristic of Swiss cheese, setting it apart from other types of cheese.
While the popular belief is that carbon dioxide bubbles cause the holes in Swiss cheese, there is another theory proposed by a Swiss laboratory. They suggest that the holes are created by flecks of hay that fall into the milk buckets during collection. As the cheese matures, these hay particles develop into larger holes. This theory explains the decrease in hole size observed in Swiss cheeses over the last 15 years due to improved milking methods.
The process of making Swiss cheese involves adding specific bacteria to milk, which then produce carbon dioxide bubbles. These bubbles become trapped in the cheese as it ages, resulting in the formation of eyes. The size of the eyes can be controlled through temperature, storage time, and acidity levels. The unique flavor of Swiss cheese is also influenced by the activity of these bacteria.
Overall, the holes in Swiss cheese are primarily caused by carbon dioxide bubbles produced by bacteria during the cheese-making process. The size of the holes can be controlled, and the presence of eyes contributes to the distinct characteristics of Swiss cheese.
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Bacteria
The holes in Swiss cheese, also known as "eyes", are caused by bacteria. Specifically, a special bacterial culture called Propionibacteria, or "Props", is added to the cheese. These bacteria are found in hay, grasses, and soil, and can naturally find their way into raw milk when cows are milked. The pasteurization process kills these bacteria, so if pasteurized milk is used as the base for Swiss cheese, cheesemakers add Propionibacteria 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 Propionibacteria produce carbon dioxide and keep the cheese at the right consistency. The production of carbon dioxide by the bacteria results in the formation of air pockets within the cheese. The warm temperature of around 70 degrees Fahrenheit also contributes to the softness and malleability of the cheese, allowing the formation of round openings as the bacteria grow and emit gases.
The size of the eyes in Swiss cheese can vary from dime-sized to quarter-sized, and larger holes generally indicate a more intense and developed flavor. The activity level of the Propionibacter shermani bacteria influences the flavor and size of the eyes. Cheese that has been aged longer features increased flavor-enhancing bacteria, resulting in larger holes and a more pronounced flavor.
The absence of eyes in a batch of Swiss cheese is considered a defect, and such cheese is referred to as "blind". The size of the eyes can be controlled by cheesemakers through temperature, storage time, and acidity levels, allowing them to create Swiss cheese with varying hole sizes and flavors.
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Hay dust particles
The holes in Swiss cheese, also known as "eyes", are caused by hay dust particles from dairy barns that find their way into the milk during the cheese-making process. This discovery was made by Agroscope, a Swiss agricultural institute, in 2015, overturning the long-held belief that the holes were caused by bacteria producing carbon dioxide.
The traditional method of milking cows involved using buckets, and bits of hay that fell into the buckets ended up in the milk. Today, milk for cheese-making is usually extracted using modern methods that prevent hay dust from contaminating the milk, which explains why Swiss cheese today has fewer holes than it used to.
The size and distribution of the holes in Swiss cheese are influenced by various factors during the cheese-making process, such as temperature, humidity, and fermentation times. The holes contribute to the cheese's nutty taste, light and airy texture, and unique appearance, making it a popular choice for sandwiches, fondue, and cheese platters.
The presence of these bacteria is essential for the formation of holes in Swiss cheese. However, the pasteurization process kills the bacteria in the milk, so if pasteurized milk is used as the base for Swiss cheese, cheesemakers add the bacteria back in to ensure the formation of eyes.
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Temperature, humidity, and fermentation times
The hole size and distribution in Swiss cheese are influenced by various factors, including temperature, humidity, and fermentation times. These factors play a crucial role in determining the final outcome and the distinct characteristics of each Swiss cheese variety.
Temperature control is essential during the cheese-making process. After the Swiss cheese is made and brined, the blocks or wheels are placed in warm rooms to help the bacteria produce carbon dioxide and maintain the desired cheese consistency. The ideal temperature for the bacteria to convert milk into carbon dioxide is around 70°F.
Humidity also plays a role in the hole-forming process. Maintaining the right humidity level in the warm rooms helps create the optimal environment for bacterial activity and influences the size and distribution of the holes.
Additionally, fermentation times can impact the size and distribution of the holes in Swiss cheese. Longer fermentation times can affect the activity of the bacteria and the formation of carbon dioxide bubbles, resulting in variations in hole size and distribution.
The interaction of these factors, temperature, humidity, and fermentation times, allows cheesemakers to sculpt the holes in Swiss cheese, creating a gastronomic masterpiece that delights consumers with its unique appearance, texture, and flavour.
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Modern processing techniques
Milking Containers: Traditionally, cheese was made in barns using open buckets, which allowed hay particles to contaminate the milk easily. Today, the use of modern containers, such as sealed buckets, pipes, and filters, during the milking process has reduced the likelihood of hay particles entering the milk. This change in containers is a significant factor in the reduction of holes in Swiss cheese.
Automated and Antiseptic Milking: The adoption of more automated and antiseptic milking methods has led to cleaner environments and reduced the incidence of hay particles in the milk. This shift towards more controlled and hygienic practices has resulted in fewer imperfections and weaker curds, reducing the number and size of holes.
Milk Extraction Methods: Modern milk extraction techniques often involve closed and controlled systems that prevent the entry of unwanted particles like hay. By minimizing the risk of hay contamination, these methods have contributed to the decrease in hole formation.
Pasteurization: The pasteurization process kills bacteria in the milk, including Propionibacteria (Props), which are responsible for producing carbon dioxide and creating the holes. When pasteurized milk is used for Swiss cheese, cheesemakers add Props back in to ensure the formation of eyes. This controlled addition of bacteria allows for more consistent hole formation.
These modern processing techniques have led to a notable change in the appearance of Swiss cheese, with smaller and less frequent holes observed in recent years. While some may view this as a positive development, others may consider it a departure from the traditional characteristics of Swiss cheese, which has long been associated with its distinctive holes or "eyes."
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Frequently asked questions
The holes in Swiss cheese, also known as "eyes", are caused by carbon dioxide bubbles that form in the cheese during the cheese-making process. Specifically, a bacterial strain known as Propionibacterium consumes lactic acid and releases carbon dioxide, forming air pockets within the cheese.
Yes, various factors influence the size and distribution of the holes in Swiss cheese during the cheese-making process. These include temperature, humidity, and fermentation times. Additionally, the disappearance of traditional buckets used during milking, which could introduce hay dust particles into the milk, has also been speculated to contribute to the reduction in hole size in modern Swiss cheese.
While Swiss cheese is typically associated with holes, not all varieties have them. The presence or absence of holes depends on the specific bacterial cultures and conditions used during cheese-making. For example, Swiss cheeses like Emmental and Gruyère, which are traditional varieties, do not have the signature holes.
