Andy Montoya
Swiss cheese is instantly recognizable for its holes, which are called eyes in the cheese industry. The eyes are primarily caused by a bacterial strain called Propionibacterium, which transforms lactic acid into carbon dioxide gas that gets trapped in the cheese, forming bubbles or holes. The size of these holes can vary due to factors such as temperature, storage time, and acidity levels. Interestingly, the holes in Swiss cheese have been shrinking over the years due to cleaner processing centers and modern milking methods that keep hay particles out of the milk. These hay particles were previously believed to contribute to the formation of holes by creating weaknesses in the cheese curd structure, allowing gas to form and expand.
| Characteristics | Values |
|---|---|
| Common name | Holes |
| Technical name | Eyes |
| Reason for existence | Carbon dioxide bubbles formed by bacteria |
| Bacteria type | Propionibacterium |
| Other reasons | Microscopic flecks of hay in milk |
| Hole size | Controlled by temperature, storage time, and acidity levels |
| Hole size range | Dime-sized to quarter-sized |
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What You'll Learn
The holes in Swiss cheese are called 'eyes'
The holes in Swiss cheese are called "eyes". This variety of cheese, known as Swiss cheese in the US, is called Emmental in Switzerland. It is a medium-firm cheese traditionally made with raw cow's milk. Swiss cheese is instantly recognizable for its holes, which contribute to its delightful texture and mouthwatering, slightly nutty taste.
The holes are caused by a special bacterial culture called Propionibacteria, or Props, that gets added to the cheese. These bacteria are found in hay, grasses, and soil and can find their 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 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 can vary from the size of a dime to the size of a quarter. The USDA has specifications for how big the holes in Swiss cheese can be. If the holes are too big, the cheese can't be sliced correctly. Temperature, humidity, and fermentation times all play a role in determining the final size of the holes.
In recent years, the eyes in Swiss cheese have gotten smaller because processing centers have gotten cleaner, according to the Agroscope Institute for Food Sciences, a Swiss research center. The old-fashioned barns and buckets of previous years allowed more and larger hay particulates into the process, leading to bigger eyes. In 2015, Agroscope researchers confirmed that the eyes are caused by tiny bits of hay present in the milk. When cheese is made in barns using open buckets, it's likely that hay particles will find their way into the collected milk. It's those little bits of hay that cause a weakness in the structure of the curd, allowing gas to form and create the holes.
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The size of the holes varies
The size of the holes, or "eyes" as they are known in the cheese industry, in Swiss cheese varies from the size of a dime to the size of a quarter. Several factors influence the size and distribution of the holes in the cheese-making process, including temperature, humidity, storage time, acidity levels, fermentation times, and the amount of hay particles present in the cheese.
Temperature, for instance, plays a crucial role in controlling hole size. By manipulating the temperature during cheese production, cheesemakers can influence the activity of the bacteria and the subsequent gas formation that creates the holes. Similarly, the amount of time cheese is stored and the acidity levels of the cheese can be adjusted to manage the size of the eyes.
The presence of hay particles in the cheese also contributes to the variability in hole size. The traditional method of cheese-making, which involved open buckets in barns, allowed for larger hay particulates to come into contact with the milk. As a result, the cheese developed bigger eyes. In recent years, the shift towards cleaner processing centers and the disappearance of the traditional bucket have led to smaller hay particulates or even their absence, resulting in smaller or nonexistent holes.
The type of bacteria used in the cheese-making process also impacts the size of the holes. Different bacterial cultures, such as Propionibacterium, contribute to the formation of holes by producing carbon dioxide gas. By selecting specific bacterial strains and controlling the fermentation times, cheesemakers can further influence the size and distribution of the eyes in Swiss cheese.
The variability in hole size across different varieties of Swiss cheese, such as Jarlsberg, known for its medium-sized holes, and Appenzeller, recognized for its larger holes, adds to the unique characteristics and culinary appeal of this cheese family.
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The holes are caused by bacteria
The holes in Swiss cheese, known as "eyes" in the cheese industry, are primarily caused by a bacterial strain called Propionibacterium. These bacteria are microscopic, gram-positive, and non-motile. They play a crucial role in transforming the lactic acid, which is a byproduct of other bacteria, into carbon dioxide. This carbon dioxide doesn't escape the cheese but instead gets trapped within it, forming the bubbles that we affectionately refer to as holes. The size and distribution of these holes are influenced by various factors during the cheese-making process, such as temperature, humidity, and fermentation times.
While the bacteria are the main catalysts for hole formation, other factors come into play as well. For instance, the size of the holes can vary depending on the type of Swiss cheese. Varieties like Jarlsberg are known for their medium-sized holes, while Appenzeller boasts larger holes. Additionally, modern milking methods that prevent hay from contaminating the milk have also contributed to the reduction in hole size over the years.
The process by which Swiss cheese develops its distinctive eyes is quite fascinating. After the cheese is made and brined, the blocks or wheels are placed in warm rooms. This step aids the Propionibacterium in producing carbon dioxide and helps maintain the desired consistency of the cheese. The warmth encourages the growth of these bacteria, which then release carbon dioxide gas, forming bubbles that create the eyes characteristic of Swiss cheese.
The presence of hay particles in the milk also plays a role in eye formation. In traditional cheese-making, milk was collected in open buckets, allowing tiny bits of hay to fall into the milk. These hay particles create weaknesses in the structure of the curd, providing an opportunity for gas to form and create the eyes. Modern milking methods, which have largely eliminated the presence of hay, have resulted in smaller or even nonexistent eyes in Swiss cheese.
The holes in Swiss cheese are not just a curiosity but also contribute to its unique flavour and texture. They create an intricate flavour profile and a light, airy feel that makes each bite of Swiss cheese a tiny flavour explosion. The size of the holes is carefully controlled by cheesemakers to ensure the cheese can be correctly sliced and retains its iconic appearance, whimsy, and sophistication.
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Hay particles contribute to hole formation
Swiss cheese is known for its holes, which cheesemakers refer to as "eyes". For over a century, it was believed that these holes were caused by carbon dioxide released by bacteria in the cheese. However, in 2015, scientists from Agroscope, a Swiss agricultural institute, discovered that the holes are actually caused by hay particles in the milk used to make the cheese.
The traditional method of milking cows involved using open buckets, which allowed hay particles to fall into the milk. These hay particles create weaknesses in the structure of the curd, allowing gas to form and create the holes. Over the past 10 to 15 years, the switch to modern milking machines that prevent hay particles from entering the milk has resulted in smaller and less frequent holes in Swiss cheese.
To test this theory, Agroscope scientists observed the cheese-ripening process over 130 days using computed tomography, or CT scans. They found that by controlling the number of hay particles in the milk, they could also control the number of holes that appeared in the cheese. This discovery provides an explanation for the gradual decrease in the size and number of holes in Swiss cheeses such as Emmentaler, Tilsiter, and Appenzell.
Hay particles are not the only factor contributing to hole formation. John Jaeggi, a researcher at the University of Wisconsin's Center for Dairy Research, explains that the process is similar to the formation of raindrops around dust particles. Other types of particulate matter can also cause holes in cheese, and the specific bacterial culture added to Swiss cheese, Propionibacteria or "Props", also plays a role in the formation of carbon dioxide gas and the creation of holes.
For cheesemakers who want to produce Swiss cheese with holes, the recommendation is to add hay particles during the cheese-making process. This addition of hay particles helps create the distinctive "eyes" that are characteristic of Swiss cheese varieties such as Emmentaler and Appenzell.
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Modern methods have reduced hole size
Swiss cheese is famous for its holes, known as "eyes" in the cheese industry. These holes are caused by carbon dioxide bubbles that form in the cheese as a result of bacteria consuming lactic acid. However, in recent years, the holes in Swiss cheese have gotten smaller, and sometimes they are even nonexistent. So, what's behind this reduction in hole size? The answer lies in the modernization of dairy farms and milking methods.
Traditionally, cheese was made in barns using open buckets, which allowed hay particles to contaminate the milk. These hay particles created weaknesses in the structure of the curd, providing an opportunity for gas to form and create holes. However, with the introduction of modern milk extraction techniques, the incidence of hay contamination has decreased significantly. Today, milk is extracted using advanced equipment and systems that prioritize hygiene, effectively eliminating the presence of foreign particles.
The change in milking methods has also impacted the type and amount of bacteria present in the milk. Previously, the bacteria in Swiss cheese wheels would produce carbon dioxide, forming bubbles that eventually popped and created holes. With fewer hay particles to feed on, the bacteria responsible for producing carbon dioxide have decreased, resulting in fewer and smaller holes. Modern milking practices often involve temperature control during cheesemaking, allowing cheesemakers to influence hole size by adjusting temperatures.
The reduction in hole size has not gone unnoticed by cheese enthusiasts, particularly those who appreciate the unique flavour that larger holes contribute to. Larger holes indicate a more intense and developed flavour due to the increased presence of flavour-enhancing bacteria during aging. This distinction is evident when comparing American-produced Swiss cheese, known for its smaller holes and milder flavour, to its European counterpart with larger holes and a richer, nuttier taste. Nonetheless, modern methods have successfully minimized the occurrence of hay particles, resulting in the smaller holes characteristic of contemporary Swiss cheese.
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Frequently asked questions
The holes in Swiss cheese, known as "eyes", are caused by carbon dioxide bubbles that form in the cheese. This occurs due to a bacterial strain called Propionibacterium, which feeds on lactic acid and produces carbon dioxide. The gas gets trapped, forming the holes.
No, not all Swiss cheeses have identical holes. Different varieties of Swiss cheese, such as Jarlsberg and Appenzeller, will have varying numbers and sizes of holes. Factors such as temperature, humidity, and fermentation times influence the hole size and distribution.
The holes in Swiss cheese have been shrinking due to modern milking methods that prevent hay particles from contaminating the milk. Traditional methods of cheese-making in barns with open buckets allowed hay particles to enter the milk, creating larger holes.
The holes in Swiss cheese do contribute to its unique flavour and texture. They create a light, airy feel and a slightly nutty taste. However, the size of the holes does not seem to impact the overall flavour of the cheese.
