Bushra Griffith
Swiss cheese, with its distinctive holes, is instantly recognisable. But what causes those holes? The answer lies in the cheese-making process and the role of microbes. Bacteria cultures play a significant role in cheese-making. They consume lactic acid in the cheese, and as they do so, they produce carbon dioxide gas, which forms air pockets within the cheese. The holes in Swiss cheese are primarily due to a particular bacterial strain known as Propionibacterium freudenrichii subspecies shermanii, or P. shermanii for short. Under the specific conditions that Swiss cheese is made, the P. shermanii produce carbon dioxide gas, and as the bacteria grow, the gases they emit create round openings. However, in 2015, scientists from Agroscope, a Swiss agricultural institute, found that flecks of hay falling into the milk buckets were responsible for the holes, with bacteria creating the gas that forms the holes.
| Characteristics | Values |
|---|---|
| Reason for holes | Carbon dioxide bubbles formed by bacteria |
| Bacteria type | Propionibacteria (or Props) |
| Other bacteria | Lactic acid-producing bacteria |
| Hole size | Influenced by temperature, humidity, and fermentation times |
| Hole formation | Bubbles formed by gas-emitting bacteria, which remain after cheese is cooled |
| Hole variation | Different types of Swiss cheese have varying hole sizes and distributions |
| Hole taste impact | Holes contribute to a slightly nutty taste |
| Hole aesthetic | Holes give Swiss cheese a unique and recognizable appearance |
| Hole origin | Discovered when cheese aged near a hearth in the Swiss Alps |
| Modern hole reduction | Modern milking methods have kept hay out of milk |
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What You'll Learn
- The bacterial strain Propionibacterium freudenrichii subspecies shermanii is added to Swiss cheese
- The bacteria produce carbon dioxide gas, forming bubbles and holes in the cheese
- The size and distribution of the holes are influenced by temperature, humidity, and fermentation times
- Modern milking methods have kept hay out, resulting in smaller holes in Swiss cheese over the years
- Cheesemakers sometimes try to prevent the formation of gas and holes in their cheeses
The bacterial strain Propionibacterium freudenrichii subspecies shermanii is added to Swiss cheese
The bacterial strain Propionibacterium freudenreichii subspecies shermanii is added to Swiss cheese during the cheese-making process. This subspecies is able to withstand higher temperatures than other dairy species, which may explain its prevalence in Swiss-type cheeses such as Emmental, which involves hot and cold stages.
Propionibacterium freudenreichii is a Gram-positive, anaerobic, rod-shaped bacterium that produces propionic acid by utilizing transcarboxylase enzymes. It is one of the principal propionibacteria associated with cheese, along with P. thoenii, P. jensenii, and P. acidipropionici. These bacteria are often referred to as dairy propionic acid bacteria (PAB).
P. freudenreichii subsp. shermanii is added to Swiss cheese to contribute to the formation of holes, or "eyes," in the final product. During the cheese-making process, this subspecies ferments lactate to form acetate, propionate, and carbon dioxide. The carbon dioxide byproduct forms air pockets within the cheese, resulting in the distinctive holes. Cheesemakers can control the size of the holes by adjusting the acidity, temperature, and curing time of the mixture.
The addition of P. freudenreichii subsp. shermanii also contributes to the flavour and texture of Swiss cheese. The fermentation process led by this subspecies produces the nutty and sweet flavours characteristic of Swiss cheese. Furthermore, the holes created by the carbon dioxide gas give the cheese its light, airy texture and mouthwatering taste experience.
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The bacteria produce carbon dioxide gas, forming bubbles and holes in the cheese
Swiss cheese is known for its distinctive holes, which are called "eyes" in the cheese industry. These holes are the result of bacteria producing carbon dioxide gas, which forms bubbles and eventually leaves holes in the cheese.
The process begins with the addition of bacteria cultures, specifically Propionibacteria or "Props", to the cheese. These bacteria are naturally found in hay, grasses, and soil, and can make their way into raw milk during the milking process. The pasteurization process kills these bacteria, so cheesemakers adding pasteurized milk to Swiss cheese may add Props back in to ensure the desired eyes will form.
Once the Swiss cheese is made and brined, the blocks or wheels are placed in warm rooms. This warmth helps the Props produce carbon dioxide and keeps the cheese at the right consistency. The carbon dioxide forms bubbles within the cheese, and as the cheese cools, these bubbles leave behind the eyes that give Swiss cheese its unique appearance and texture.
The size and distribution of the holes in Swiss cheese can vary depending on factors such as temperature, humidity, and fermentation times. Different varieties of Swiss cheese, such as Jarlsberg and Appenzeller, are known for their distinct hole sizes and flavours.
While bacteria play a key role in the formation of Swiss cheese holes, recent studies have suggested that flecks of hay may also contribute. Microscopically small hay particles can fall into milk buckets, and as the cheese matures, these particles can develop into larger holes. Thus, it is the combination of bacteria producing carbon dioxide and the presence of hay particles that creates the beloved Swiss cheese eyes.
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The size and distribution of the holes are influenced by temperature, humidity, and fermentation times
The holey Swiss cheese is a result of the cheese-making process, specifically the role of microbes. The bacteria cultures consume lactic acid in the cheese and produce carbon dioxide gas, which forms air pockets within the cheese. The size and distribution of these holes are influenced by temperature, humidity, and fermentation times.
Temperature plays a crucial role in the formation of Swiss cheese holes. The cheese is made at a warm temperature of around 70°F (21°C). At this temperature, the cheese is soft and malleable, allowing the bacteria to grow and create gas pockets. As the cheese cools down to around 40°F (4°C), the holes become more defined and remain in place.
Humidity also affects the size and distribution of the holes. In the traditional Swiss cheese-making process, the cheese was aged during the winter months in cellars or beside a hearth with a fire. The varying levels of humidity and temperature during these months influenced the maturation process, impacting the size and distribution of the holes.
Additionally, fermentation times play a role in hole formation. The longer the fermentation process, the larger the holes tend to be. This is because a longer fermentation period allows more time for bacteria to produce carbon dioxide and create larger gas pockets.
The combination of temperature, humidity, and fermentation time creates the unique hole pattern in Swiss cheese, contributing to its distinctive appearance and slightly nutty taste. These factors, manipulated by the artistry of cheesemakers, sculpt the holes in this gastronomic masterpiece, making each variety of Swiss cheese unique.
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Modern milking methods have kept hay out, resulting in smaller holes in Swiss cheese over the years
Swiss cheese is instantly recognisable for its holes, which contribute to its nutty taste, light texture, and unique appearance. These holes, also known as "eyes", are caused by a combination of bacterial cultures and hay particles.
The bacterial cultures, specifically Propionibacteria or "Props", are added to the cheese during production. These bacteria consume lactic acid and release carbon dioxide gas, forming bubbles within the cheese that eventually become holes. The size and distribution of these holes can be influenced by temperature, humidity, and fermentation times.
Hay particles, on the other hand, can enter the milk during the milking process, when grass and flowers consumed by cows fall into the milk vat, or when milk is stored in buckets alongside hay. These particles affect the size of the holes by weakening the curd structure.
Over the years, the holes in Swiss cheese have reportedly become smaller. This change has been attributed to modern milking methods that have effectively kept hay out of the milk. By reducing the presence of hay particles, these methods have indirectly influenced the hole formation process, resulting in smaller holes in Swiss cheese.
Thus, the reduction of hay particles through modern milking methods has played a significant role in the evolution of Swiss cheese, contributing to the smaller holes observed in recent years.
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Cheesemakers sometimes try to prevent the formation of gas and holes in their cheeses
Swiss cheese, or Emmental cheese as it is known in Switzerland, is famous for its holes, which are called "eyes" in the cheese industry. The eyes are caused by bacteria, specifically Propionibacterium freudenrichii subspecies shermanii, or P. shermanii for short, which produce carbon dioxide gas as they consume lactic acid. The gas forms bubbles in the cheese, which eventually become holes.
However, cheesemakers sometimes try to prevent the formation of gas and holes in their cheeses, especially in harder varieties. This is because, in harder cheeses, gas does not form nice, round eyes but instead creates unsightly crevices, cracks, and splits.
Cheesemakers can prevent the formation of gas and holes by using pasteurized milk, which does not contain the bacteria responsible for hole formation. They can also employ modern milking methods, which help to keep hay out of the milk. Hay particles, or flecks of hay, have been found to contribute to the formation of holes in Swiss cheese. In 2015, scientists from Agroscope, a Swiss agricultural institute, discovered that microscopically small hay particles would fall into buckets of milk, leading to the development of bigger holes as the cheese matured.
Additionally, temperature, humidity, and fermentation times play a role in the size and distribution of holes in Swiss cheese. By controlling these factors, cheesemakers can influence the final outcome and reduce the formation of holes.
The prevention of gas and hole formation in cheese is particularly relevant in the United States, where a modified version of Swiss cheese called Baby Swiss is produced. This variety tends to have smaller eyes than traditional Swiss cheese.
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Frequently asked questions
Swiss cheese has holes, also known as "eyes", because of carbon dioxide bubbles that form in the cheese. These bubbles are produced by bacteria that convert lactic acid into carbon dioxide.
The bacteria responsible for creating the holes in Swiss cheese is called Propionibacterium freudenrichii subspecies shermanii, or P. shermanii for short.
The presence of holes in Swiss cheese depends on various factors such as temperature, humidity, and fermentation times. Additionally, modern milking methods that keep hay out have resulted in fewer holes in Swiss cheese.
Yes, other cheeses that have holes include Gouda, Fontina, and Baby Swiss, a modified version of Swiss cheese made in the US. These cheeses may have smaller holes or "eyes".
Yes, the holes in Swiss cheese contribute to its nutty taste and light, airy texture. The larger the holes, the stronger the flavour of the cheese.
