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Blue cheese is any
cheese Cheese is a type of dairy product produced in a range of flavors, textures, and forms by coagulation of the milk protein casein. It comprises proteins and fat from milk (usually the milk of cows, buffalo, goats or sheep). During prod ...
made with the addition of
cultures Culture ( ) is a concept that encompasses the social behavior, institutions, and Social norm, norms found in human societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, Attitude (psychology), attitudes ...
of edible molds, which create blue-green spots or veins through the cheese. Blue cheeses vary in flavor from mild to strong and from slightly sweet to salty or sharp; in colour from pale to dark; and in consistency from liquid to hard. They may have a distinctive smell, either from the mold or from various specially cultivated bacteria such as '' Brevibacterium linens''. Some blue cheeses are injected with
spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...
s before the curds form, and others have spores mixed in with the curds after they form. Blue cheeses are typically aged in temperature-controlled environments.


History

Blue cheese is believed to have been discovered by accident when cheeses were stored in caves with naturally controlled temperature and moisture levels which happened to be favorable environments for varieties of harmless mold. Analysis of paleofeces sampled in the salt mines of Hallstatt, Austria showed that miners of the
Hallstatt Period The Hallstatt culture was the predominant Western and Central European archaeological culture of the Late Bronze Age (Hallstatt A, Hallstatt B) from the 12th to 8th centuries BC and Early Iron Age Europe (Hallstatt C, Hallstatt D) from the 8th to ...
(800 to 400 BC) already consumed blue cheese and beer. According to legend, one of the first blue cheeses,
Roquefort Roquefort () is a sheep milk blue cheese from southern France. Though similar cheeses are produced elsewhere, European Union law, EU law dictates that only those cheeses aged in the natural Combalou caves of Roquefort-sur-Soulzon may bear the na ...
, was discovered when a young boy, eating bread and ewes' milk cheese, abandoned his meal in a nearby cave after seeing a beautiful girl in the distance. When he returned months later, the mold (''
Penicillium roqueforti ''Penicillium roqueforti'' is a common saprotrophic fungus in the genus ''Penicillium''. Widespread in nature, it can be isolated from soil, decaying organic matter, and plants. The major industrial use of this fungus is the production of blu ...
'') had transformed his cheese into Roquefort.
Gorgonzola Gorgonzola (, ) is a famously pungent Italian blue cheese made from unskimmed cow's milk; believed to have been created in the 9th century; now with use of its name controlled under the criteria of a Protected Designation of Origin (PDO). Gorg ...
is one of the oldest known blue cheeses, having been created around AD 879, though it is said that it did not contain blue veins until around the 11th century. Stilton is a relatively new addition, becoming popular sometime in the early 1700s. Many varieties of blue cheese originated subsequently, such as the 20th century Danablu and
Cambozola Cambozola is a soft-ripened cheese specialty which is made of cow's milk. The blue cheese veins inside give this creamy cheese its very special flavor. History Cambozola was patented and industrially produced for the global market by the G ...
, were an attempt to fill the demand for Roquefort-style cheeses.


Production

Similarly to other varieties of cheese, the process of making blue cheese consists of six standard steps. However, additional ingredients and processes are required to give this blue-veined cheese its particular properties. To begin with, the commercial scale production of blue cheese consists of two phases: the culturing of suitable spore-rich inocula and fermentation for maximum, typical flavor.Watts, j. C. Jr.. Nelson, J. H. (to Dairyland Food Laboratories, Inc.), U.S. Patent 3,072,488 (8 January 1963).


''Penicillium roqueforti'' inoculum

In the first phase of production, a ''Penicillium roqueforti'' inoculum is prepared prior to the actual production of blue cheese. Multiple methods can be used to achieve this. However, all methods involve the use of a freeze-dried ''Penicillium roqueforti'' culture. Although ''Penicillium roqueforti'' can be found naturally, cheese producers nowadays use commercially manufactured ''Penicillium roqueforti.'' First, ''Penicillium roqueforti'' is washed from a pure culture agar plates which is later frozen. Through the freeze drying process, water from the frozen state is evaporated without the transition through the liquid state ( sublimation). This retains the value of the culture and is activated upon the addition of water. Salt, sugar or both are added to autoclaved, homogenized
milk Milk is a white liquid food produced by the mammary glands of lactating mammals. It is the primary source of nutrition for young mammals (including breastfeeding, breastfed human infants) before they are able to digestion, digest solid food. ...
via a sterile solution. This mixture is then inoculated with ''Penicillium roqueforti''. This solution is first incubated for three to four days at . More salt and/or sugar is added and then aerobic incubation is continued for an additional 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. A spore-rich ''Penicillium roqueforti'' culture is then added. Next, modified milk fat is added which consists of milk fat with calf pre-gastric
esterase In biochemistry, an esterase is a class of enzyme that splits esters into an acid and an alcohol in a chemical reaction with water called hydrolysis (and as such, it is a type of hydrolase). A wide range of different esterases exist that differ ...
. This solution is prepared in advance by an enzyme hydrolysis of a milk fat emulsion. The addition of modified milk fat stimulates a progressive release of free fatty acids via lipase action which is essential for rapid flavor development in blue cheese. This inoculum produced by either methods is later added to the cheese curds.


Production and fermentation

First, raw milk (either from cattle, goats or sheep) is mixed and
pasteurized In food processing, pasteurization ( also pasteurisation) is a process of food preservation in which packaged foods (e.g., milk and fruit juices) are treated with mild heat, usually to less than , to eliminate pathogens and extend shelf life ...
at for 15 seconds. Then, acidification occurs: a starter culture, such as '' Streptococcus lactis,'' is added in order to change
lactose Lactose is a disaccharide composed of galactose and glucose and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from (Genitive case, gen. ), the Latin word for milk, plus the suffix ''-o ...
to
lactic acid Lactic acid is an organic acid. It has the molecular formula C3H6O3. It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as wel ...
, thus changing the acidity of the milk and turning it from liquid to solid. The next step is
coagulation Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a thrombus, blood clot. It results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The process of co ...
, where
rennet Rennet () is a complex set of enzymes produced in the stomachs of ruminant mammals. Chymosin, its key component, is a protease, protease enzyme that curdling, curdles the casein in milk. In addition to chymosin, rennet contains other enzymes, su ...
, a mixture of
rennin Chymosin or rennin is a protease found in rennet. It is an aspartic endopeptidase belonging to MEROPS A1 family. It is produced by newborn ruminant animals in the lining of the abomasum to curdle the milk they ingest, allowing a longer resid ...
and other material found in the stomach lining of a calf is added to solidify the milk further. Following this, thick curds are cut typically with a knife to encourage the release of liquid or
whey Whey is the liquid remaining after milk has been curdled and strained. It is a byproduct of the manufacturing of cheese or casein and has several commercial uses. Sweet whey is a byproduct resulting from the manufacture of rennet types of hard c ...
. The smaller the curds are cut, the thicker and harder the resulting cheese will become. After the curds have been ladled into containers in order to be drained and formed into a full wheel of cheese, the ''Penicillium roqueforti'' inoculum is sprinkled on top of the curds along with ''Brevibacterium linens''. Then, the curds granules are knit in molds to form cheese loaves with a relatively open texture. Next, whey drainage continues for 10–48 hours in which no pressure is applied, but the molds are inverted frequently to promote this process.
Salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
is then added to provide flavor as well as to act as a preservative so the cheese does not spoil through the process of brine salting or dry salting for 24–48 hours. The final step is ripening the cheese by aging it. When the cheese is freshly made, there is little to no blue cheese flavor development. Usually, a fermentation period of 60–90 days are needed before the flavor of the cheese is typical and acceptable for marketing. During this ripening period, the temperature and the level of humidity in the room where the cheese is aging is monitored to ensure the cheese does not spoil or lose its optimal flavor and texture. In general, the ripening temperature is around eight to ten degrees Celsius with a relative humidity of 85–95%, but this may differ according to the type of blue cheese being produced. At the beginning of this ripening process, the cheese loaves are punctured to create small openings to allow air to penetrate and support the rich growth of the aerobic ''Penicillium roqueforti'' cultures, thus encouraging the formation of blue veins. Throughout the ripening process, the total ketone content is constantly monitored as the distinctive flavor and aroma of blue cheese arises from methyl
ketones In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...
(including 2-pentanone, 2-heptanone, and 2-nonanone) which are a metabolic product of ''Penicillium roqueforti''.


Toxins from the production of blue cheese

''Penicillium roqueforti'', responsible for the greenish blue moldy aspect of blue cheese, produces several
mycotoxin A mycotoxin (from the Greek μύκης , "fungus" and τοξικός , "poisonous") is a toxic secondary metabolite produced by fungi and is capable of causing disease and death in both humans and other animals. The term 'mycotoxin' is usually rese ...
s. While mycotoxins like roquefortine, isofumigaclavine A,
mycophenolic acid Mycophenolic acid is an immunosuppressant medication used to prevent rejection following organ transplantation and to treat autoimmune conditions such as Crohn's disease and lupus. Specifically it is used following kidney, heart, and live ...
and ferrichrome are present at low levels, penicillic acid and PR toxin are unstable in the cheese. Because of the instability of PR toxin and lack of optimal environmental conditions (temperature, aeration) for the production of PR toxin and roquefortine, health hazards due to ''Penicillium roqueforti''
metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...
s are considerably reduced. Additionally, mycotoxin contamination occurs at low levels and large quantities of cheese are rarely consumed, suggesting that hazard to human health is unlikely.


Physicochemical properties


Structure

The main structure of the blue cheese comes from the aggregation of the
casein Casein ( , from Latin ''caseus'' "cheese") is a family of related phosphoproteins (CSN1S1, αS1, aS2, CSN2, β, K-casein, κ) that are commonly found in mammalian milk, comprising about 80% of the proteins in cow's milk and between 20% and 60% of ...
. In
milk Milk is a white liquid food produced by the mammary glands of lactating mammals. It is the primary source of nutrition for young mammals (including breastfeeding, breastfed human infants) before they are able to digestion, digest solid food. ...
, casein does not aggregate because of the outer layer of the particle, called the "hairy layer." The hairy layer consists of κ-casein, which are strings of
polypeptide Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Da or more are called proteins. Chains of fewer than twenty ...
s that extend outward from the center of the casein
micelle A micelle () or micella () ( or micellae, respectively) is an aggregate (or supramolecular assembly) of surfactant amphipathic lipid molecules dispersed in a liquid, forming a colloidal suspension (also known as associated colloidal system). ...
. The entanglement of the hairy layer between casein micelles decreases the
entropy Entropy is a scientific concept, most commonly associated with states of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the micros ...
of the system because it constrains the micelles, preventing them from spreading out. Curds form, however, due to the function that the
enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...
, rennet, plays in removing the hairy layer in the casein micelle.
Rennet Rennet () is a complex set of enzymes produced in the stomachs of ruminant mammals. Chymosin, its key component, is a protease, protease enzyme that curdling, curdles the casein in milk. In addition to chymosin, rennet contains other enzymes, su ...
is an enzyme that cleaves the κ-casein off the casein micelle, thus removing the strain that occurs when the hairy layer entangles. The casein micelles are then able to aggregate together when they collide with each other, forming the curds that can then be made into blue cheese.


Mold growth

''Penicillium roqueforti'' and ''Penicillium glaucum'' are both molds that require the presence of oxygen to grow. Therefore, initial fermentation of the cheese is done by
lactic acid bacteria Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical ( cocci) bacteria that share common metabolic and physiological characteristics. These bact ...
. The lactic acid bacteria, however, are killed by the low pH and the secondary fermenters, ''Penicillium roqueforti'', take over and break the lactic acid down, maintaining a pH in the aged cheese above 6.0. As the pH rises again from the loss of
lactic acid Lactic acid is an organic acid. It has the molecular formula C3H6O3. It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as wel ...
, the enzymes in the molds responsible for
lipolysis Lipolysis is the metabolic pathway through which lipid triglycerides are hydrolysis, hydrolyzed into a glycerol and free fatty acids. It is used to mobilize stored energy during fasting or exercise, and usually occurs in Adipose tissue, fat adip ...
and
proteolysis Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Protein degradation is a major regulatory mechanism of gene expression and contributes substantially to shaping mammalian proteomes. Uncatalysed, the hydrolysis o ...
are more active and can continue to ferment the cheese because they are optimal at a pH of 6.0. ''Penicillium roqueforti'' creates the characteristic blue veins in blue cheese after the aged curds have been pierced, forming air tunnels in the cheese. When given oxygen, the mold is able to grow along the surface of the curd-air interface. The veins along the blue cheese are also responsible for the aroma of blue cheese itself. In fact, one type of bacteria in blue cheese, '' Brevibacterium linens'', is the same bacteria responsible for foot and body odor. ''B. linens'' was previously thought to give cheeses their distinct orangish pigmentation, but studies show this not to be the case and blue cheese is an example of the lack of that orange pigmentation. In pressing the cheese, the curds are not tightly packed in order to allow for air gaps between them. After piercing, the mold can also grow in between the curds.


Flavour

A portion of the distinct flavour comes from
lipolysis Lipolysis is the metabolic pathway through which lipid triglycerides are hydrolysis, hydrolyzed into a glycerol and free fatty acids. It is used to mobilize stored energy during fasting or exercise, and usually occurs in Adipose tissue, fat adip ...
(breakdown of fat). The metabolism of the blue mold further breaks down fatty acids to form ketones to give blue cheese a richer flavour and aroma.


Regulation


European Union

In the
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
, many blue cheeses, such as Cabrales, Danablu,
Gorgonzola Gorgonzola (, ) is a famously pungent Italian blue cheese made from unskimmed cow's milk; believed to have been created in the 9th century; now with use of its name controlled under the criteria of a Protected Designation of Origin (PDO). Gorg ...
,
Roquefort Roquefort () is a sheep milk blue cheese from southern France. Though similar cheeses are produced elsewhere, European Union law, EU law dictates that only those cheeses aged in the natural Combalou caves of Roquefort-sur-Soulzon may bear the na ...
and Blue Stilton, carry a
protected designation of origin The protected designation of origin (PDO) is a type of geographical indication of the European Union aimed at preserving the designations of origin of food-related products. The designation was created in 1992 and its main purpose is to designat ...
, meaning they can bear the name only if they have been made in a particular region. Similarly, individual countries have protections of their own such as France's
Appellation d'Origine Contrôlée In France, the ''appellation d'origine contrôlée'' (, ; abbr. AOC ) is a label that identifies an agricultural product whose stages of production and processing are carried out in a defined geographical area – the ''terroir'' – and using ...
and Italy's Denominazione di Origine Protetta. Blue cheeses with no protected origin name are designated simply "blue cheese".


Canada

Under the regulation of the
Canadian Food Inspection Agency The Canadian Food Inspection Agency (CFIA; ) is a regulatory agency that is dedicated to the safeguarding of food, plants, and animals (FPA) in Canada, thus enhancing the health and well-being of Canada's people, environment and economy. The age ...
, manufacturers can produce blue cheese with a maximum of 47 percent moisture and minimum of 27 percent milk fat. Salt is allowed to be used as a preservative; however, the amount of the salt or combination of salts shall not exceed 200 parts per million of milk and milk products used to make the cheese. The Canadian Food Inspection Agency does not limit the use of bacterial cultures to aid further ripening and flavoring preparations other than cheese flavoring.


United States

The United States
Code of Federal Regulations In the law of the United States, the ''Code of Federal Regulations'' (''CFR'') is the codification of the general and permanent regulatory law, regulations promulgated by the executive departments and agencies of the federal government of the ...
standard for blue cheese specifies a minimum milkfat content of 50 percent, and maximum moisture of 46 percent. Optional ingredients permitted include food coloring to neutralize the yellowish tint of the cheese,
benzoyl peroxide Benzoyl peroxide is a chemical compound (specifically, an organic peroxide) with structural formula , often abbreviated as (BzO)2. In terms of its structure, the molecule can be described as two benzoyl (, Bz) groups connected by a peroxide ...
bleach, and vegetable wax for coating the rind.


Properties

Gorgonzola, Stilton, and Roquefort are considered to be favored blue cheeses in many countries. These cheeses all have a
protected designation of origin The protected designation of origin (PDO) is a type of geographical indication of the European Union aimed at preserving the designations of origin of food-related products. The designation was created in 1992 and its main purpose is to designat ...
in which they may only be called their respective name if produced a certain way in a certain location.


Gorgonzola

Gorgonzola blue cheese takes its name from the village of
Gorgonzola Gorgonzola (, ) is a famously pungent Italian blue cheese made from unskimmed cow's milk; believed to have been created in the 9th century; now with use of its name controlled under the criteria of a Protected Designation of Origin (PDO). Gorg ...
in Italy where it was first made. Belonging to the family of
Stracchino Stracchino (), also known as ''crescenza'' (), is an Italian cow's milk cheese typical of the regions of Lombardy, Tuscany, Veneto, Friuli-Venezia Giulia, and Liguria. It is eaten very young, has no rind and has a very soft, creamy texture an ...
cheeses, Gorgonzola is a whole milk, white, and "uncooked" cheese. This blue cheese is inoculated with '' Penicillium glaucum'' which, during ripening, produces the characteristic of blue-green veins. The odor of Gorgonzola varies between natural and creamy Gorgonzola. 63 components in natural Gorgonzola cheese and 52 components in creamy Gorgonzola cheese contribute to odor with 2- nonanone,
1-octen-3-ol 1-Octen-3-ol, octenol for short and also known as mushroom alcohol, is a chemical that attracts biting insects such as mosquitoes. It is contained in human breath and sweat, and it is believed that insect repellent DEET works by blocking the i ...
, 2-heptanol, ethyl hexanoate, methylanisole and 2-heptanone being the prominent compounds for odor in both cheeses.


Stilton

Stilton blue cheese was first sold in the village of Stilton in England but there is little evidence it was ever made there. Different from Stichelton, which is made from raw milk, Stilton cheese is made from pasteurized milk. In addition to being inoculated with ''Penicillium roqueforti'' to give it the blue vein characteristic, research has shown that other microbiota which are relatives of '' Lactococcus lactis'', ''
Enterococcus faecalis ''Enterococcus faecalis'' – formerly classified as part of the group D '' Streptococcus,'' is a Gram-positive, commensal bacterium naturally inhabiting the gastrointestinal tracts of humans. Like other species in the genus '' Enterococcus'', ' ...
'', '' Lactobacillus plantarum'', '' Lactobacillus curvatus'', '' Leuconostoc mesenteroides'', ''
Staphylococcus equorum ''Staphylococcus equorum'' is a gram-positive, coagulase-negative member of the bacterial genus ''Staphylococcus ''Staphylococcus'', from Ancient Greek σταφυλή (''staphulḗ''), meaning "bunch of grapes", and (''kókkos''), meaning " ...
'', and ''Staphylococcus'' sp. can also be found in Stilton cheese. Some important microbiota contribute to the aromatic profile such as those of the ''
Lactobacillus ''Lactobacillus'' is a genus of gram-positive, aerotolerant anaerobes or microaerophilic, rod-shaped, non-spore-forming bacteria. Until 2020, the genus ''Lactobacillus'' comprised over 260 phylogenetically, ecologically, and metabolically div ...
'' genus due to their production of volatile compounds. During ripening,
free fatty acids In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...
increase in amount which contribute to the characteristic flavor of blue cheeses due to fat breakdown by ''Penicillium roqueforti''.


Roquefort

Roquefort blue cheese originates from the village of
Roquefort-sur-Soulzon Roquefort-sur-Soulzon (; , ) is a commune in the Aveyron department, in the region of Occitania, southern France. Roquefort is located on the Causse du Larzac and is famous for its ewe derived products including milk, wool, and meat. Much ...
, France. Its flavors come from the use of unpasteurized
sheep's milk Sheep milk is the milk of Sheep, domestic sheep. It is commonly used to make cultured Dairy product, dairy products, such as cheese. Some of the most popular sheep cheeses include feta (Greece), pecorino romano (Italy), Roquefort (France) and Ma ...
, inoculation with ''Penicillium roqueforti'', and the special conditions of the natural caves of Roquefort-sur-Soulzon in which they are ripened. ''Penicillium roqueforti'' is the cause of the blue veins in Roquefort cheese. In addition to ''Penicillium roqueforti'', various yeasts are present, namely '' Debaryomyces hansenii'' and its non-sporulating form '' Candida famata'', and '' Kluyveromyces lactis'' and its non-sporulating form ''Candida sphaerica.'' Similarly to other kinds of blue cheeses, Roquefort's flavor and odor can be attributed to the particular mixture of methyl ketones such as 2-heptanone, 2-pentanone, and 2-nonanone.


See also

* List of blue cheeses * Blue cheese dressing


Gallery

File:A Plate of Blue Cheese at Lighthouse Cafe.jpg File:A Blue Cheese from Holiday Inn Goldmile.jpg File:A Danish Blue Cheese with Fig from The Astor.jpg File:Blue Stilton 01.jpg File:Stichleton.jpg File:15-01 Blackstick Blue Lokal K 01.jpg File:Aura juusto.jpg


Notes


References

{{Blue cheeses