Frederic Melton
Cheese is made up of curds, which are the protein and fatty solids in milk. The holes in cheese, also known as eyes, are caused by the formation of gas due to microbial metabolism. Specifically, bacteria are added to produce gas, which accumulates in air pockets in the cheese, forming bubbles. The gas produced is carbon dioxide (CO2). The size of the holes varies depending on the type of cheese. For example, Swiss cheese and Dutch-type cheeses such as Emmentaler and Gouda are known for their characteristic holes.
| Characteristics | Values |
|---|---|
| Formation of holes | The formation of holes in cheese is due to the release of carbon dioxide (CO2) gas by bacteria during microbial metabolism |
| Bacteria involved | Propionibacterium freundenreichii |
| Type of cheese | Swiss-type and Dutch-type cheeses, e.g. Emmentaler and Gouda |
| Other factors | The cheese must be flexible while aging to allow for the formation of gas bubbles |
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What You'll Learn
Propionibacterium freundenreichii bacteria
The holes in cheese, known as "eyes", are caused by the formation of gas due to microbial metabolism. This gas is carbon dioxide (CO2). Cheesemakers add certain bacteria to get eye formation, as those bacteria produce gas, the CO2 will accumulate in any air pockets present in the cheese, at loose curd junctions, or other nucleation sites present. With more and more gas, a bubble is formed, and we have eyes!
Propionibacterium freudenreichii bacteria are often added as a starter culture to consume lactic acid, a byproduct of lactose in milk, and exude carbon dioxide gas. These bacteria are responsible for the eyes in Swiss cheese and are added to the vat to initiate the process of eye formation. As the bacteria produce carbon dioxide gas, it accumulates and forms bubbles, which slowly turn into the eyes we see in Swiss cheese.
The process of creating eyes in Swiss cheese involves the Propionibacterium freundenreichii bacteria producing carbon dioxide gas, which accumulates in air pockets, at curd junctions, or other nucleation sites. These gas bubbles slowly turn into the varying-sized air pockets that become trapped within the rind of the cheese. When the cheese is cut into, these holes appear as eyes.
To ensure the formation of eyes, cheesemakers must ensure that the cheese body is flexible while it is aging. This pliability allows gas bubbles to form nice, round eyes. The story doesn't end with the eyes, though. The by-products of the bacterial reaction also contribute to the overall flavour of Swiss cheese. For example, the breakdown of citric acid by bacteria produces diacetyl, which gives Swiss cheese its characteristic butter flavour.
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Carbon dioxide gas bubbles
The holes in cheddar cheese, also known as "eyes", are formed by bubbles of carbon dioxide gas. The process of cheesemaking involves the addition of starter cultures, which contain bacteria. These bacteria consume lactic acid, a byproduct of lactose in milk, and produce carbon dioxide gas bubbles as a result. Over time, these bubbles accumulate and form air pockets of varying sizes that become trapped within the cheese's rind. When the cheese is cut, these air pockets are revealed as holes or "eyes".
The formation of eyes in cheese is not limited to cheddar but is also characteristic of other cheese varieties, such as Swiss-type and Dutch-type cheeses like Emmentaler and Gouda. The presence of eyes in these cheeses is attributed to the same bacterial activity and the production of carbon dioxide gas.
Cheesemakers carefully control the process to ensure the development of desirable eye formation. The flexibility of the cheese body during aging is crucial for the formation of round eyes. By manipulating the pliability of the cheese, cheesemakers can encourage the formation of gas bubbles and create the desired eye structure.
The size and distribution of the eyes can vary, resulting in different hole sizes and patterns in the cheese. The bacteria responsible for gas production, such as Propionibacterium freundenreichii, play a significant role in determining the characteristics of the eyes. Additionally, the breakdown of citric acid, naturally present in milk, by specific bacteria like Leuconostoc and Lactococcus species, contributes to the formation of carbon dioxide gas and the development of eyes in certain cheeses.
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Microbial metabolism
The holes in cheese, known as "eyes", are caused by the formation of carbon dioxide gas due to microbial metabolism. This process occurs when bacteria, added by cheesemakers, produce carbon dioxide gas, which accumulates in air pockets, loose curd junctions, or other nucleation sites within the cheese. As more gas is produced, bubbles begin to form, resulting in the eyes characteristic of certain cheeses.
The type of bacteria added to the cheese vat influences the formation of eyes. For example, Propionibacterium freundenreichii bacteria are responsible for the holes in Swiss cheese. Additionally, the flexibility of the cheese body during aging is crucial for eye development. Cheesemakers ensure that the cheese has enough pliability to allow for the formation of round, well-defined eyes.
The presence of eyes not only contributes to the unique appearance of certain cheeses but also influences their flavour. The breakdown of citric acid by bacteria, such as Leuconostoc mesenteroides and Lactococcus lactis ssp. lactis biovar. diacetylactis, results in the production of carbon dioxide, diacetyl (which imparts a buttery flavour), and other compounds that enhance the overall flavour profile of the cheese.
It is important to distinguish between the gas-formed eyes and mechanical openings in some cheeses. For instance, Colby and Colby Jack cheeses exhibit small jagged openings that are a result of how the curds knit together during the pressing process, rather than microbial metabolism. Furthermore, gas formation caused by spoilage microorganisms, such as Clostridium tyrobutyricum, is also distinct from the eyes formed by controlled bacterial cultures.
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Citric acid breakdown
The holes in cheese, also known as "eyes", are caused by the formation of gas due to microbial metabolism. This gas is carbon dioxide (CO2). The CO2 accumulates in any air pockets present in the cheese, as well as at loose curd junctions or other nucleation sites, forming bubbles.
Cheesemakers add certain bacteria to get eye formation. These bacteria produce gas, which accumulates and forms bubbles. These bubbles then turn slowly into varying-sized air pockets that become trapped within the rind of a cheese. When cut into, these holes appear in the form of eyes.
Eyes develop at nucleation sites in cheese. When cheesemakers produce eyed cheeses, they ensure that there is enough pliability to allow gas bubbles to form nice round eyes. The cheese body must be flexible while it is aging for eyes to form.
In Gouda cheese, the eyes are due to the breakdown of citric acid by bacteria such as Leuconostoc mesenteroides and Lactococcus lactis ssp. lactis biovar. diacetylactis. These bacteria metabolize the small amounts of citric acid naturally present in milk into CO2, diacetyl (which has a butter flavor), and other compounds. These compounds also contribute to the characteristic flavor of Gouda-style cheeses.
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Nucleation sites
The holes in cheese, also known as "eyes", are caused by the formation of gas due to microbial metabolism. This gas is carbon dioxide (CO2). It is produced by certain bacteria, which, once added to the vat, consume lactic acid (a byproduct of lactose in milk) and exude bubbles of carbon dioxide gas. As more gas is accumulated in air pockets, loose curd junctions, or other nucleation sites present in the cheese, larger bubbles are formed. Thus, we have eyes!
Cheese is made up of curds, which are the protein and fatty solids in milk. When making cheese, the milk is first acidified, breaking it into its solid and liquid parts. The liquid part, called whey, is drained off, leaving the curds to join together and turn into cheese.
To produce "eyes", cheesemakers add specific bacteria to the starter culture. These bacteria produce carbon dioxide gas, which accumulates in any air pockets, at loose curd junctions, or other nucleation sites present in the cheese. With more and more gas, a bubble is formed.
For eyes to form, the cheese body must remain flexible while it is aging. Cheesemakers ensure that there is enough pliability to allow gas bubbles to form nice round eyes.
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Frequently asked questions
The holes in cheddar cheese are caused by bacteria that are added by cheesemakers, which produce carbon dioxide gas. These gas bubbles accumulate and form bubbles that get trapped within the rind of the cheese.
The holes in cheese are called "eyes".
The eyes can vary in size, ranging from small jagged openings to large round holes.
Cheesemakers add bacteria to get eye formation and contribute to the overall flavor of the cheese.
No, not all cheeses have eyes. Swiss and Gouda cheeses are known for their characteristic eyes, while other cheeses like Colby have small jagged openings that are not considered eyes.
