Frederic Melton
Cheese is a dairy product made from milk, usually from cows, buffalo, goats, or sheep. It is produced in a range of flavours, textures, and forms through the coagulation of milk protein. The process of cheesemaking involves separating milk into solid curds and liquid whey by coagulating the casein protein in milk. This is done by adding bacterial enzymes or acids such as vinegar or lemon juice to cause the casein to coagulate. The solid curds are then separated from the liquid whey and pressed into finished cheese. Bacteria play a crucial role in converting milk sugars into lactic acid, which lowers the pH and inhibits spoilage. Different types of bacteria, such as Lactococcus, Lactobacillus, and Streptococcus, are used to impart distinct characteristics to the cheese. The variety of microorganisms used in cheesemaking, including bacteria, yeast, and mould, contribute to the unique flavours, textures, and aromas of the final product.
| Characteristics | Values |
|---|---|
| Number of microbial species in a single cheese type | More than 100 |
| Number of microbial species in long-ripened cheeses like Roquefort | Hundreds |
| Number of microbial species in a single gram of fully ripened cheese rind | 10 billion |
| Main role of lactic acid bacteria | Converting milk sugar, lactose, into lactic acid |
| Bacteria that converts acetic acid into propionic acid and carbon dioxide | Propionobacter shermanii |
| Bacteria that gives a sweet flavor to cheeses like aged Gouda | Lactobacillus helveticus |
| Bacteria that gives orange color pigments | Brevibacterium linens and yeast |
| Bacteria that gives brainy" appearance to some cheeses | Geotrichum candidum |
| Bacteria that gives distinctive aroma to surface-ripened cheeses | Corynebacteria |
| Bacteria that gives buttery flavor to cheese | Leuconostoc mesenteroides and Lactococcus lactis ssp lactis biovar. diacetylactis |
| Bacteria that gives mushroom and ammonia flavor to white mold cheeses | Penicillium camemberti |
| Bacteria that gives sharp flavor to cheese | Thermophilic bacteria |
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What You'll Learn
- Bacteria and fungi are added at different stages of the cheese-making process
- Bacteria break down milk proteins and sugars, changing their chemical composition
- Bacteria are responsible for the distinctive smell of cheeses
- Bacteria are essential for the ageing and ripening of cheeses
- Different types of bacteria are used for different types of cheese
Bacteria and fungi are added at different stages of the cheese-making process
The first step in the cheese-making process is to add bacteria to the milk to start the acidification process. These bacteria convert the lactose (milk sugar) to lactic acid and lower the milk's pH. There are two types of bacteria used for this process: mesophilic bacteria, which thrive at room temperature but die at higher temperatures, and thermophilic bacteria, which thrive at higher temperatures (around 55°C) and are used to make sharper cheeses such as Gruyère, Parmesan, and Romano.
After the milk has been acidified, rennet is added to complete the curdling. The solid curds are then separated from the liquid whey and pressed into finished cheese. Some cheeses have aromatic molds on the rind, or outer layer, or throughout. The majority of cheeses are made with starter bacteria from the Lactococcus, Lactobacillus, or Streptococcus genera. Lactobacillus helveticus is an example of a culture commonly used in Swiss and alpine cheeses.
During the aging process, the cheese is left in a temperature- and humidity-controlled environment, where bacteria continue to break down proteins, further altering the flavour and texture of the final cheese. In some cases, molds are added to the milk during the preliminary cheese-making steps or to the curds before they are hooped. The piercing of blue cheeses during the aging process is done to encourage mold growth by introducing oxygen.
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Bacteria break down milk proteins and sugars, changing their chemical composition
Bacteria play a crucial role in the cheese-making process by breaking down milk proteins and sugars, thereby altering their chemical composition. This transformation is achieved through microbial fermentation, where bacteria act as protein catalysts. The process involves breaking down complex substances, such as milk proteins and sugars, into simpler products that are more stable and can be stored for extended periods.
Lactic acid bacteria (LAB), including Lactobacilli and Streptococci, are commonly used as "starter cultures" in cheese production. These bacteria convert lactose, the milk sugar, into lactic acid, lowering the pH of the mixture and inhibiting the growth of spoilage organisms. This conversion is a crucial step in preserving milk as cheese, allowing it to be consumed months or even years later.
During the cheese-making process, bacteria continue to play a role in developing the cheese's distinctive characteristics. For example, specific bacteria can produce enzymes that break down milk proteins, resulting in a ripened layer surrounding a firm interior, as seen in cheeses like Camembert and Brie. This enzymatic breakdown also creates flavour compounds that contribute to the overall taste profile of the cheese.
Additionally, bacteria are responsible for the formation of holes in certain cheeses. Propionibacter shermanii, for instance, can convert acetic acid into propionic acid and carbon dioxide. The carbon dioxide forms the holes characteristic of Emmental and other Swiss cheeses, while the propionic acid contributes to their sharp bouquet.
The presence of bacteria in cheese is not limited to the initial stages of production. As cheese ages, it undergoes a process called ecological succession, where lactic acid bacteria and early microbial colonists are replaced by other bacterial species and, eventually, fungi. This succession contributes to the development of the cheese's unique characteristics, including its flavour, smell, and texture.
In conclusion, bacteria are essential in the cheese-making process, not just for their initial role in breaking down milk proteins and sugars but also for their ongoing contribution to the chemical composition and sensory attributes of the final cheese product.
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Bacteria are responsible for the distinctive smell of cheeses
Cheese is a dairy product that is produced in a variety of flavours, textures, and forms. It is made by coagulating the milk protein casein and then separating the milk into solid curds and liquid whey. The liquid whey is drained away, and the curds are salted, shaped, and left to ripen in a controlled environment. The smell of a cheese is a key factor in enjoying its flavour.
Microorganisms, including bacteria, are used in each step of the cheesemaking process and determine the flavour and texture of the final cheese. The broad groups of cheese-making microbes include many varieties of bacteria, yeast, and filamentous fungi (moulds).
Lactic acid bacteria are often called "starter cultures" as they play a major role in converting the basic milk sugar, lactose, into lactic acid. This lowers the cheese's pH and makes the cheese inhospitable to spoilage organisms. The two main families of lactic acid bacteria are lactococci (sphere-shaped, lactic-acid-producing bacteria) and lactobacilli (rod-shaped, lactic-acid-producing bacteria). Streptococci can also play an important role in initial cheese ripening and are very important in yoghurt-making. While many of these bacteria die off after the initial step of cheesemaking, some survive and continue to contribute to the cheese's flavour.
The bacteria Brevibacterium linens, for example, is one of the most common bacteria that make up "smear" bacteria. These bacteria are responsible for the strong smell of cheeses such as Epoisses, Münster, and Limburger. Propionibacter shermanii is another example of bacteria that can contribute to the smell of cheese. These bacteria can digest acetic acid and convert it to sharp, sweaty-smelling propionic acid and carbon dioxide. The carbon dioxide is what gives Emmental and other Swiss cheeses their characteristic "holes", and the propionic acid contributes to their complex, sharp bouquet.
In summary, bacteria are responsible for the distinctive smell of cheeses. They do this by breaking down milk proteins, altering the flavour and texture of the cheese, and producing compounds that give rise to the distinctive aroma of cheese.
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Bacteria are essential for the ageing and ripening of cheeses
Bacteria are often added to cheese as "starter cultures" to kickstart the cheese-making process. These bacteria convert the lactose (milk sugar) into lactic acid, lowering the milk's pH and inhibiting the growth of spoilage organisms. The two main families of lactic acid bacteria are lactococci (sphere-shaped) and lactobacilli (rod-shaped). These bacteria also play a significant role in the flavour development of aged cheeses.
During the ripening process, bacteria continue to break down proteins and sugars in the cheese, further altering its flavour and texture. This is a crucial step in developing the distinctive flavour, smell, and texture of aged cheeses. The specific bacteria involved in this process can vary, and their activity depends on factors such as temperature and humidity. For example, thermophilic bacteria, which thrive at higher temperatures, are used to make sharper cheeses like Gruyère, Parmesan, and Romano.
In addition to lactic acid bacteria, other bacteria such as Brevibacterium linens and Leuconostoc mesenteroides contribute to the unique characteristics of certain cheeses. B. linens, for instance, is known for its role in producing the strong-smelling compounds found in cheeses like Epoisses, Münster, and Limburger. L. mesenteroides is involved in converting citric acid into diacetyl, giving some cheeses a buttery flavour.
The interaction between bacteria, yeast, and mould creates a complex ecosystem within cheese that contributes to its overall character. The presence and balance of these microorganisms influence the aroma, flavour, and texture of the final product. Thus, bacteria play a fundamental role in the ageing and ripening of cheeses, transforming them from simple curds to the diverse and delectable products we know and love.
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Different types of bacteria are used for different types of cheese
Cheese is a dairy product made in a range of flavours, textures, and forms. It is produced by coagulating the milk protein casein and then separating the milk into solid curds and liquid whey. The liquid whey is drained away, and the curds are salted, shaped, and left to ripen in a controlled environment.
Microorganisms are used in each step of this process and determine the flavour and texture of the final cheese. The broad groups of cheese-making microbes include many varieties of bacteria, yeast, and filamentous fungi (moulds).
Lactic acid bacteria are often called "starter cultures" or "starter bacteria" as they play a main role in converting the basic milk sugar, lactose, into lactic acid. This lowers the cheese's pH and makes the cheese inhospitable to spoilage organisms. There are two main families of lactic acid bacteria: lactococci (sphere-shaped, lactic-acid producing bacteria) and lactobacilli (rod-shaped, lactic-acid producing bacteria). Streptococci can also play an important role in initial cheese ripening and are very important in yoghurt-making. Lactobacillus helveticus is an example of a culture commonly used in Swiss and alpine cheeses.
Other bacteria used in cheese-making include Brevibacterium linens, which is one of the most common "smear" bacteria, and Leuconostoc mesenteroides, which is used in Gouda cheese. Propionibacteria are also used in Swiss cheeses such as Emmental, giving them their characteristic "holes".
The type of bacteria used in cheese-making depends on the type of cheese being made. For example, thermophilic bacteria, which thrive at higher temperatures, are used to make sharper cheeses such as Gruyère, Parmesan, and Romano. On the other hand, mesophilic bacteria, which thrive at room temperature but die at higher temperatures, are used to make cheeses such as paneer and cottage cheese.
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Frequently asked questions
Yes, bacteria are used in the production of many cheeses.
There are two main families of bacteria used in cheesemaking: lactococci (sphere-shaped, lactic-acid producing bacteria) and lactobacilli (rod-shaped, lactic-acid producing bacteria).
Bacteria convert milk sugars into lactic acid, which lowers the pH of the milk and creates an environment inhospitable to spoilage organisms. This is the first step in creating the distinctive flavour of each cheese.
Common cheeses that use bacteria in their production include Cheddar, Mozzarella, Camembert, Gouda, Gruyere, Parmesan, Romano, and Emmental.
The types of bacteria used in cheesemaking can determine the flavour and texture of the final product. Different bacteria thrive at different temperatures and produce different compounds, so cheesemakers select bacteria that will create the desired characteristics for each type of cheese.
