Frederic Melton
Swiss cheese, or Emmental, is known for its distinctive holes, which are called eyes in the cheese industry. For a long time, it was believed that the holes were caused by carbon dioxide released by bacteria present in the milk. However, this theory was debunked in 2015 by a Swiss agricultural institute called Agroscope, which attributed the holes to flecks of hay falling into buckets of milk during the collection process. The disappearance of traditional buckets in modern milking methods has led to a decrease in the number of holes in Swiss cheese in recent years.
| Characteristics | Values |
|---|---|
| Common name | Swiss cheese |
| Scientific name | Emmental |
| Hole size | Varies from the size of a dime to the size of a quarter |
| Hole formation | Carbon dioxide bubbles created by bacteria |
| Bacteria type | Propionibacterium freudenrichii subspecies shermanii |
| Bacteria source | Hay, grasses, and soil |
| Milk type | Raw milk |
| Pasteurization effect | Kills bacteria, including Props |
| Hole development | Microscopically small hay particles fall into milk buckets and develop into bigger holes as cheese matures |
| Hole control | Temperature, storage time, and acidity levels |
| Hole absence | Modern milking methods prevent hay from falling into milk |
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What You'll Learn
The role of bacteria in creating carbon dioxide
The holes in Swiss cheese, also known as "eyes," are created by carbon dioxide bubbles that form in the cheese during the cheese-making process. While the specific mechanism has been debated, bacteria play a crucial role in producing the carbon dioxide that forms these bubbles.
Historically, the presence of bacteria in Swiss cheese was attributed to the natural contamination of milk with bacteria from hay, grasses, and soil during the milking process. The specific bacterium responsible for eye formation in Swiss cheese is Propionibacterium freudenreichii subspecies shermanii, commonly known as "Props." This bacterium can convert milk into carbon dioxide at temperatures of around 70°F (21°C). As the cheese cools, the carbon dioxide forms bubbles, creating the distinctive eyes in Swiss cheese.
Cheesemakers have also intentionally added bacterial cultures, including Props, to milk during cheese production to ensure the formation of eyes. After the cheese is made and brined, it is placed in warm rooms, which encourages the Props to produce more carbon dioxide and helps maintain the desired consistency of the cheese.
The size of the eyes in Swiss cheese can vary and is influenced by factors such as temperature, storage time, and acidity levels. Interestingly, the size of the eyes does not affect the taste of the cheese. Traditional Swiss cheese is aged for a minimum of 60 days, and the size of the eyes can range from dime-sized to quarter-sized.
While the role of bacteria in carbon dioxide production is well-established, another factor contributing to eye formation in Swiss cheese is the presence of hay particles in the milk. Microscopically small hay particles can fall into milk collection buckets, creating weaknesses in the structure of the curd. This allows gas to form and expand, creating larger holes as the cheese matures.
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The effect of temperature on air bubbles
The holes in Swiss cheese, known as "eyes" in the cheese industry, are caused by a specific type of bacteria called Propionibacterium freudenreichii, which converts milk into carbon dioxide at a warm temperature of 70°F (21.1°C). These bacteria thrive in the warm, humid caves where cheese wheels are aged, feeding on the lactic acid produced by other bacteria. As the cheese cools, the carbon dioxide gas forms bubbles that get trapped in the cheese, creating the eyes.
Temperature plays a crucial role in the formation and size of these air bubbles. After 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 consistency. Cheesemakers can control the size of the eyes by adjusting the temperature of the milk, the humidity, and the aging time. Warmer temperatures promote the growth of bacteria and increase the production of carbon dioxide, leading to larger eyes.
On the other hand, cooler temperatures can slow down bacterial activity and reduce gas production, resulting in smaller eyes or even the absence of holes, as seen in some varieties of Swiss cheese like Gruyère. The size of the eyes does not affect the taste of the cheese, but it does contribute to its texture and mouthfeel. Larger holes create a lighter, airier feel, while smaller or absent holes result in a denser, creamier texture.
Additionally, the distribution and uniformity of the holes can be influenced by temperature variations during the cheese-making process. Different temperature zones within the cheese can affect the movement and accumulation of gas bubbles, leading to variations in hole size and distribution. Thus, temperature acts as a critical factor in shaping the unique characteristics of Swiss cheese, from the formation of holes to their size and distribution, ultimately contributing to its distinctive texture and appearance.
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Hay particles and their impact on curd structure
The holes in Swiss cheese, also known as "eyes", are the result of gas formation during the cheese-making process. This gas formation occurs due to the presence of microscopic hay particles in the milk used for cheese-making. These hay particles, which are minuscule bits of hay that fall into the milk during collection, create weaknesses in the curd structure.
The impact of hay particles on the curd structure is significant. As the cheese matures, the hay particles cause weaknesses in the structure of the curds, allowing gas to form and expand, which eventually leads to the formation of holes. This phenomenon is not limited solely to hay particles; any particulate matter can have a similar effect. The size and number of holes in Swiss cheese varieties are influenced by the quantity of hay particles present.
The traditional method of cheese-making in barns using open buckets contributed to the presence of hay particles in the milk. Modern milking methods, however, have greatly reduced the likelihood of hay particles contaminating the milk. This change in milking practices has also influenced the type of bacteria present in the milk, which has contributed to the reduction in holes.
The role of bacteria in hole formation has been widely recognised. A specific type of bacteria, Propionibacter shermani, is added to the milk at the start of the cheesemaking process. This bacterium consumes lactic acid and releases carbon dioxide gas bubbles, which become trapped within the curd. As the cheese ages, these bubbles expand and gradually form the holes.
In summary, the impact of hay particles on the curd structure in Swiss cheese is significant, as they create weaknesses that allow gas to form and expand, resulting in the characteristic holes. Modern milking methods have reduced the presence of hay particles, contributing to smaller holes or their absence in Swiss cheese.
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Modern milking methods and their influence on hole formation
Modern milking methods have significantly impacted the hole formation in Swiss cheese, leading to a decrease in the size and number of holes. The traditional method of collecting milk in open buckets allowed tiny bits of hay or dirt to mix with the milk, creating weaknesses in the curd structure and facilitating hole formation. However, with the modernization of dairy farming practices, the use of sealed containers and direct milk extraction from udders has reduced the incidence of hay particles in the milk.
The modernization of dairy farms, including the adoption of automated and antiseptic milking methods, has inadvertently influenced the prevalence and size of holes in Swiss cheese. The shift from traditional buckets to modern processing centers has resulted in a significant reduction in the presence of hay particles, which were once a primary contributor to hole formation. This change in milking containers has been identified as a critical factor in the decrease in hole size and frequency.
Temperature control during the cheesemaking process is another modern milking technique that influences hole formation. By adjusting the temperature, cheesemakers can impact the size of the holes. Higher temperatures promote the production of carbon dioxide gas by bacteria, resulting in larger bubbles that form the characteristic holes. On the other hand, cooling the cheese to lower temperatures helps stabilize the bubbles and ensures they remain in place during aging.
The specific type of bacteria added during cheesemaking, Propionibacter shermani, also plays a crucial role in gas formation and hole creation. This bacterium consumes lactic acid and releases carbon dioxide gas bubbles, which become trapped within the cheese's rind, gradually forming holes. Modern milking practices may inadvertently influence the activity of this bacterium, impacting the hole formation process.
In summary, modern milking methods, including the use of sealed containers, direct milk extraction, and temperature control, have significantly reduced the presence of hay particles and influenced bacterial activity. These changes have resulted in a decrease in the size and number of holes in Swiss cheese, contributing to the observed changes in the appearance of Swiss cheese over the years.
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The process of pasteurization and its effect on bacteria levels
Swiss cheese is traditionally made with raw milk, but some varieties are now made with pasteurized milk. Pasteurization is a process of sterilizing milk by heating it to a high temperature for a set period, killing off bacteria and other microbes. The milk is heated to a temperature of around 72°C for 15 seconds and then cooled before being used to make cheese. This process deactivates enzymes in the milk and naturally occurring bacteria.
The decision to use pasteurized or raw milk in cheese production involves various factors, including history, tradition, food safety, laws, technique, logistics, and flavour. Proponents of pasteurized milk cheese emphasize the potential risks associated with consuming raw milk cheese, especially when sold on a mass market scale. They argue that pasteurization eliminates harmful bacteria and ensures the cheese's safety for consumption. On the other hand, supporters of raw milk cheese highlight its long history of safe consumption and the rarity of negative health effects.
The use of raw milk in cheese production is a controversial topic. While raw milk can harbour harmful bacteria such as Salmonella, E. coli, and Listeria, which can cause severe foodborne illnesses, the risk of getting sick from consuming raw milk cheese is generally low. The quality of the milk, the sanitation protocols, and the manufacturing processes all play a role in the safety of the final product. In 2016, the FDA tested 1,600 samples of raw-milk cheeses and found less than 1% of the samples to be contaminated.
Pasteurization plays a crucial role in ensuring the safety of Swiss cheese by eliminating harmful bacteria. It can also offer certain health benefits, such as reducing the risk of lactose intolerance by breaking down lactose sugar in milk. Pasteurized Swiss cheese has a milder flavour than raw milk cheese due to the deactivation of enzymes and bacteria that contribute to the development of aroma and flavour during maturation. The maturation of raw milk cheese results in a more intense flavour profile.
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Frequently asked questions
The holes in Swiss cheese, also known as "eyes", are created by carbon dioxide bubbles that form in the cheese during the cheese-making process. These bubbles are a result of the bacteria Propionibacterium freudenrichii subspecies shermanii, which is found in hay, grasses, and soil, and can make its way into raw milk when cows are milked.
Traditionally, cheese was made in barns using open buckets, where it was likely for hay particles to contaminate the milk. These particles cause weaknesses in the cheese curd structure, allowing gas to form and create holes. Today, milk for cheese-making is extracted using modern methods, reducing the likelihood of hay contamination and resulting in smaller holes or no holes at all.
No, the size of the holes does not impact the taste of Swiss cheese. However, the length of time the cheese is aged for does affect its flavour. For example, Baby Swiss, which has smaller holes due to a shorter aging period, has a milder flavour than Traditional Swiss, which is aged for a minimum of 60 days.
