Bushra Griffith
Blue cheese is made using the fungus Penicillium roqueforti, which is added as a starter culture during production. P. roqueforti is well-suited to dairy environments and thrives in cold temperatures, low oxygen levels, and alkali preservatives. When added to milk, it removes the hairy layer of κ-casein, allowing casein micelles to aggregate and form curds, which are then made into blue cheese. The growth of P. roqueforti gives blue cheese its distinctive flavour and blue-green veins.
Explore related products
What You'll Learn
The role of fungus in blue cheese production
During the cheese-making process, the P. roqueforti inoculum is sprinkled on top of the curds, along with Brevibacterium linens, a type of bacteria responsible for body odor, which contributes to the cheese's unique aroma. The growth of P. roqueforti leads to the production of volatile and non-volatile flavor components and changes in cheese texture due to the metabolic action of the species. The characteristic blue-green veins in the cheese are a result of fungal sporulation.
The blue-green color of the veins is derived from the pigmented spores formed by the fungal growth. Through bioinformatics and gene studies, scientists have discovered that this pigment formation is due to a DHN-melanin biosynthesis pathway. By altering this pathway, different spore colors can be produced, ranging from white to yellow-green to red-pink-brown, offering the potential to create new colored strains of blue cheese.
Additionally, the secondary metabolites of P. roqueforti, known as andrastins A–D, are found in blue cheese. These andrastins have potential health benefits, as they inhibit proteins involved in the efflux of anticancer drugs from multidrug-resistant cancer cells. However, it is important to note that P. roqueforti can also produce harmful secondary metabolites, such as the neurotoxin roquefortine C, and other mycotoxins under certain growth conditions. Nevertheless, the levels of these toxins in cheese are typically too low to cause toxic effects.
Blue Cheese Dip: Creamy, Tangy, and Delicious
You may want to see also
Types of fungus used in blue cheese
Blue cheese is made by mixing spores of the fungus Penicillium roqueforti with milk. This fungus is widespread in nature and can be isolated from soil, decaying organic matter, and plants. It was first described by American mycologist Charles Thom in 1906 and has been used in cheese-making since at least the 15th century. The fungus thrives in cool, moist environments and produces a bluish-green pigment that gives blue cheese its characteristic colour.
Penicillium roqueforti is the most common fungus used in blue cheese production. It is responsible for creating the distinctive blue veins in the cheese and is also known as the 'blue-cheese fungus'. The fungus is added to the cheese curds, either by injecting the spores directly into the curds or adding them to the brine solution in which the cheese is soaked. The mould grows rapidly, spreading throughout the cheese and creating the blue veins. The blue veins are also responsible for the aroma of blue cheese.
While Penicillium roqueforti is the most common fungus used in blue cheese production, other species of Penicillium are also used. For example, Gorgonzola, an Italian blue cheese with a mild flavour and crumbly texture, is made with Penicillium glaucum.
In addition to Penicillium roqueforti, various yeasts are also present in blue cheese, including Debaryomyces hansenii and its non-sporulating form Candida famata, as well as Kluyveromyces lactis and its non-sporulating form Candida sphaerica.
The use of Penicillium roqueforti in blue cheese production has been optimized through domestication, with two independently domesticated populations of the fungus used in cheese-making. The first population, used in Roquefort cheese, exhibits traits beneficial for pre-industrial cheese production, such as slower growth in cheese and greater spore production on bread. The second population, used in all other types of blue cheese, displays phenotypes more suited for industrial cheese production, including high lipolytic activity, efficient cheese cavity colonization ability, and salt tolerance.
Bothwell Cheese: A Local Treasure Made in Wisconsin
You may want to see also
How fungus gives blue cheese its colour
The blue-green veins that characterize blue cheese are the result of fungal growth. Specifically, the colour comes from pigmented spores formed by the Penicillium roqueforti fungus, which is added as a starter culture during cheese production. This fungus, along with other microbes used in food production, has been domesticated by humans, adapting to a human-provided niche and losing unfavourable properties while gaining favourable ones. For example, P. roqueforti can tolerate cold temperatures, low oxygen levels, and alkali and weaker acid preservatives, allowing it to thrive in dairy environments.
P. roqueforti is added to the cheese after the curds have been ladled into containers and drained. The curds are then formed into loaves with a relatively open texture, and whey drainage is continued for 10 to 48 hours. Salt is added to provide flavour and act as a preservative, and the cheese is then aged for 60 to 90 days to develop its characteristic flavour.
The blue-green colour of the veins is due to a DHN-melanin biosynthesis pathway. By systematically deleting pathway genes, scientists have been able to alter the spore colour, resulting in white to yellow-green to red-pink-brown phenotypes. This demonstrates the potential to generate new coloured strains of blue cheese. Interestingly, the use of UV-induced colour mutants does not appear to impact the levels of methyl-ketones associated with blue cheese flavour.
Not all blue cheeses are made with P. roqueforti, however. For example, Gorgonzola blue cheese is made with Penicillium glaucum, and takes its name from the village of Gorgonzola in Italy where it was first made. This fungus also produces the characteristic blue-green veins during the ripening process. Other blue cheeses, such as Bleu de Gex and Rochebaron, also use P. glaucum.
Who Said the Moon Was Made of Cheese?
You may want to see also
Explore related products
How fungus impacts the flavour of blue cheese
The flavour of blue cheese is significantly influenced by fungus, specifically the Penicillium roqueforti fungus, which is added to the cheese curds as a starter culture. This fungus is responsible for the distinct blue-green veins and pigmentation in blue cheese. The blue-green colour is derived from the pigmented spores formed during fungal growth.
The metabolic action of Penicillium roqueforti leads to the production of volatile and non-volatile flavour components, contributing to the overall flavour profile of blue cheese. The fungus breaks down fatty acids, forming ketones that give blue cheese its characteristic rich flavour and aroma. The specific compounds contributing to the odour of blue cheese include 2-nonanone, 1-octen-3-ol, 2-heptanol, ethyl hexanoate, methylanisole, and 2-heptanone.
While Penicillium roqueforti is the most commonly used fungus in blue cheese production, other fungi can also be used. For example, some varieties of blue cheese, like Gorgonzola, are made with Penicillium glaucum, which also contributes to the blue-green veining and flavour development during ripening.
The use of different fungal strains can result in variations in the flavour and appearance of blue cheese. Research has shown that by altering the DHN-melanin biosynthesis pathway, it is possible to change the colour of the spores and, consequently, the colour of the cheese without significantly impacting the levels of methyl-ketones associated with blue cheese flavour. This allows for the development of new coloured strains of blue cheese while preserving the iconic flavour.
In addition to its role in flavour development, the fungus also impacts the texture of blue cheese. The growth of Penicillium roqueforti leads to changes in the cheese's texture due to its metabolic action. The curds in blue cheese are not tightly packed, allowing for air gaps that facilitate the growth of the mould throughout the cheese.
Cheese and Tuna Helper: What's in the Cheese?
You may want to see also
Other uses of the fungus
The fungus Penicillium roqueforti is used in the dairy industry to make blue cheese. However, it has several other uses, including:
Antibiotics
Penicillium roqueforti can be used to produce compounds that can be employed as antibiotics.
Fragrances and Flavours
The microorganism can be placed into cream and aerated to produce a concentrated blue cheese flavouring. A similar flavouring can be produced using other sources of fat, such as coconut oil. Strains of the fungus are also used to create fragrances.
Specialty Chemicals
Penicillium roqueforti can be used to produce specialty chemicals, such as methyl ketones, including 2-heptanone.
Research
Penicillium roqueforti has emerged as an excellent model for studying adaptive divergence.
Cheese Crafting: Skimmed Milk Curds
You may want to see also
Frequently asked questions
Blue cheese is made from milk, usually cow's milk.
The fungus Penicillium roqueforti is used to make blue cheese.
The blue-green colour comes from pigmented spores formed by the growth of the fungus.
Penicillium roqueforti is used to make many blue cheeses, including Roquefort, Stilton, Danish blue, and Cabrales.
First, curds are formed from milk using rennet, an enzyme that removes the "hairy layer" from casein micelles, allowing them to aggregate. The curds are then ladled into containers and sprinkled with Penicillium roqueforti inoculum. The curds are formed into loaves, drained, salted, and finally aged to ripen the cheese.
