Frederic Melton
Blue cheese is a variety of cheese characterised by blue or green veins throughout. It is made using a complex process that involves the deliberate introduction of mould spores to milk or curds. The mould, known as Penicillium roqueforti, is the same type of mould that penicillin is derived from. Blue cheese has a strong, distinctive flavour and aroma, which are a result of the metabolic products of Penicillium roqueforti. The question of whether blue cheese is living or non-living is an interesting one, as it involves the concept of what defines something as living.
| Characteristics | Values |
|---|---|
| Living or Nonliving | Nonliving |
| Blue Cheese Varieties | Gorgonzola, Roquefort, Stilton, Danablu, Cambozola, Dana Blu, Bleu d'Auvergne, Danish Blue, Mycella, Gorgonzola Dolce, Picante, Cabrales |
| Blue Cheese Production | Commercial-scale production consists of two phases: culturing of suitable spore-rich inocula and fermentation for maximum flavor |
| Blue Cheese Ingredients | Milk, salt, sugar, Brevibacterium linens, modified milk fat, calf pre-gastric esterase, rennet extract, mesophilic lactic culture |
| Blue Cheese Characteristics | Blue/green veins, soft texture, lower acidity, high pH, strong flavor, pungent, peppery |
| Blue Cheese Microorganisms | Primary (lactic acid bacteria), secondary (Penicillium roqueforti), non-starter lactic acid bacteria, yeasts |
| Blue Cheese Ripening | Temperature: 8-10°C, Humidity: 85-95%, Pierced to allow air to reach spores and promote mold vein development |
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What You'll Learn
Blue cheese is made using a mould called Penicillium roqueforti
Blue cheese is a type of cheese characterised by blue or green veins throughout. It is made using a mould called Penicillium roqueforti. This mould is added to the milk in the cheese vat or to the curds during the cheese-making process. In some cases, it is applied to the finished cheese. The mould is allowed to grow through the piercing of the cheese with needles, creating small openings for air to reach the spores and promote the development of mould veins. This process also contributes to the flavour of the cheese.
Penicillium roqueforti is a type of penicillin, which is a mould that occurs naturally and has been used as an antibiotic. The mould spores are first prepared in an inoculum before being added to the milk or curds. The mixture is then incubated for three to four days at a temperature between 21 and 25 degrees Celsius. More salt and/or sugar is added, and aerobic incubation is continued for an additional one to two days.
The curds are then ladled into containers to be drained and formed into a full wheel of cheese. The curd granules are knit in moulds to form cheese loaves with a relatively open texture to allow the mould to grow. Whey drainage continues for 10 to 48 hours, with no pressure applied, and the moulds are inverted frequently to promote this process. Salt is then added to the cheese to provide flavour and act as a preservative.
The final step in the process is ripening the cheese by ageing it. The temperature and humidity in the room are monitored to ensure the cheese does not spoil and maintains its optimal flavour and texture. The ripening temperature is usually around eight to ten degrees Celsius, with a relative humidity of 85 to 95%. This process can take 60 to 90 days before the flavour of the cheese is typical and acceptable for marketing.
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Blue cheese is characterised by blue/green veins
The distinctive flavour and aroma of blue cheese are a result of the metabolic products of P. roqueforti, specifically methyl ketones (including 2-pentanone, 2-heptanone, and 2-nonanone). Butyric (C4) and caproic (C6) acids, and 2-heptanone are the major compounds responsible for the strong, piquant flavour of blue cheeses. The mould development also contributes significantly to the taste of the cheese, adding a peppery note that should complement the sweet or savoury foundational flavour.
The process of making blue cheese consists of six standard steps, but additional ingredients and processes are required to give it its distinctive properties. Firstly, a Penicillium roqueforti inoculum is prepared. Salt, sugar, or both are then added to autoclaved, homogenised milk via a sterile solution. This mixture is then inoculated with Penicillium roqueforti and incubated for three to four days at 21–25 °C (70–77 °F). More salt and/or sugar is added, and aerobic incubation is continued for an additional one to two days.
Finally, the curds are ladled into containers to drain and form into a full wheel of cheese. The Penicillium roqueforti inoculum is then sprinkled on top of the curds along with Brevibacterium linens. The curd granules are then knit in moulds to form cheese loaves with a relatively open texture. Whey drainage continues for 10–48 hours without applying pressure, but the moulds are inverted frequently to promote this process. Salt is added to provide flavour and act as a preservative, and the cheese is then aged for 60–90 days to allow the flavour to develop.
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Blue cheese has a complex microflora
Blue cheese is a living food product, characterised by a complex microflora of microorganisms that contribute to its unique flavour, texture, and appearance. The primary microorganisms in blue cheese are lactic acid bacteria, specifically mesophilic lactic acid bacteria such as Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris. These bacteria are responsible for the cheese's low acidity and high pH, typically over 6.0 in mature blue cheeses. The lactic acid bacteria are localised in the core of the cheese, and their numbers decrease towards the end of the ripening process.
The secondary microorganisms in blue cheese are strains of the fungus Penicillium roqueforti, which is added to the milk or curds during the cheese-making process. P. roqueforti is an aerobic fungus that requires oxygen to grow, so the texture of blue cheese must be open and airy. This is achieved by not pressing the curds after moulding and by piercing the cheese with needles to create small openings for air to penetrate. P. roqueforti grows in the fissures of the cheese, giving it its distinctive blue-veined appearance and soft texture.
In addition to the primary and secondary microorganisms, blue cheese also contains other microorganisms, including non-starter lactic acid bacteria, yeasts, enterococci, and micrococci. These microorganisms contribute to the complex flavour and aroma of blue cheese, which is dominated by methyl ketones and other compounds generated through the β-oxidation of free fatty acids. The distinctive peppery note of blue cheese is a result of the breakdown of milk fats by the mould and bacteria.
The growth of lactic acid bacteria may be inhibited by P. roqueforti, which can synthesise penicillin as an inhibitory substance. This negative interaction between the microorganisms contributes to the unique characteristics of blue cheese. The production of blue cheese involves carefully controlling the temperature and humidity to promote the growth of the desired microorganisms and prevent the cheese from spoiling.
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Blue cheese is made from cows' milk
Blue cheese is a type of cheese characterised by blue or green veins throughout. It is made from cow's milk, as well as from sheep's milk in some cases. The process of making blue cheese is complex and involves six standard steps, with additional ingredients and processes to give the cheese its distinctive properties. The production of blue cheese consists of two phases: the culturing of suitable spore-rich inocula and fermentation for maximum, typical flavour.
The first phase of production involves preparing a Penicillium roqueforti inoculum. This is done by adding salt, sugar, or both to autoclaved, homogenised milk via a sterile solution. This mixture is then inoculated with Penicillium roqueforti and incubated for three to four days at a controlled temperature. More salt and/or sugar is added, and aerobic incubation is continued for an additional one to two days. Alternatively, a fermentation medium can be created by mixing sterilised, homogenised milk and reconstituted non-fat solids or whey solids with sterile salt. A spore-rich Penicillium roqueforti culture is then added, along with modified milk fat, which consists of milk fat with calf pre-gastric esterase. This solution is prepared in advance through enzyme hydrolysis of a milk fat emulsion.
The second phase of production involves ladling the curds into containers to be drained and formed into a full wheel of cheese. The Penicillium roqueforti inoculum is then sprinkled on top of the curds, along with Brevibacterium linens. The curd granules are then knit in moulds to form cheese loaves with a relatively open texture. Whey drainage continues for 10-48 hours without applying pressure, but the moulds are inverted frequently to promote drainage. Salt is added to provide flavour and act as a preservative, and the cheese is brine-salted or dry-salted for 24-48 hours.
The final step is ripening the cheese by ageing it. The temperature and humidity in the ageing room are carefully monitored to ensure the cheese does not spoil and maintains its optimal flavour and texture. The ripening temperature is usually around eight to ten degrees Celsius, with a relative humidity of 85-95%. The cheese loaves are punctured to create small openings for air to penetrate and support the growth of aerobic Penicillium roqueforti cultures, encouraging the formation of blue veins. The total ketone content is constantly monitored during the ripening process, as the distinctive flavour and aroma of blue cheese come from methyl ketones, which are metabolic products of Penicillium roqueforti.
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Blue cheese is safe to eat despite the mould
Blue cheese is a type of cheese that is created using mould cultures of Penicillium, specifically Penicillium roqueforti. This type of mould is responsible for blue cheese's distinct taste, smell, and appearance. While mould is often a sign of food spoilage, the type of mould used to make blue cheese does not produce toxins and is safe for human consumption.
The process of making blue cheese is similar to that of other varieties of cheese but requires additional ingredients and processes to achieve its characteristic properties. Firstly, salt, sugar, or both are added to autoclaved, homogenized milk. This mixture is then inoculated with Penicillium roqueforti and incubated for three to four days. More salt and/or sugar is added, and aerobic incubation is continued for another one to two days. Alternatively, sterilized, homogenized milk and reconstituted non-fat solids or whey solids are mixed with sterile salt to create a fermentation medium, to which a spore-rich Penicillium roqueforti culture is added.
After the curds have formed, they are ladled into containers to drain and form into cheese wheels. At this stage, the Penicillium roqueforti inoculum is sprinkled on top of the curds, along with Brevibacterium linens. The curds are then knit in moulds to form cheese loaves with a relatively open texture. Whey drainage is continued for 10 to 48 hours without applying pressure, and the moulds are inverted frequently to promote drainage. Salt is then added to the cheese to act as a flavour enhancer and preservative through brine salting or dry salting for 24 to 48 hours.
The final step in the process is ripening the cheese by ageing it in a controlled environment. The temperature and humidity of the room are carefully monitored to ensure optimal flavour and texture development. The ripening temperature is typically around eight to ten degrees Celsius with a relative humidity of 85-95%. During ripening, the cheese loaves are punctured to create small openings that allow air to penetrate and support the growth of Penicillium roqueforti cultures, resulting in the formation of blue veins. The total ketone content is constantly monitored as the distinctive flavour and aroma of blue cheese are a result of methyl ketones produced by the metabolic activity of Penicillium roqueforti.
While blue cheese is made with mould, the specific type of mould used, Penicillium roqueforti, does not produce harmful toxins and is safe for human consumption. This mould is naturally found in the damp limestone caves of southern France and is related to the mould from which the antibiotic Penicillin is derived. The controlled use of this mould in the cheesemaking process ensures that the final product is safe to eat, contributing to the unique flavour, texture, and appearance of blue cheese without posing any health risks.
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Frequently asked questions
Blue cheese is a living thing as it contains microorganisms, including lactic acid bacteria, Penicillium roqueforti, non-starter lactic acid bacteria, and yeasts.
Mold spores are introduced deliberately to the milk in the cheese vat, or to the curds during the cheese-making process. Sometimes mold is applied to the finished cheese.
The mold development contributes to the flavor of the cheese. The peppery note of a good blue is crucial to the overall impression, but it needs to be in balance.
