In this article we will discuss about the methods and processes of cheese production. Learn about:- 1. Principles of Cheese-Making 2. Production of Cheddar Cheese 3. Production of Swiss Cheese 4. Production of Surface-Ripened Cheeses 5. Production of Mold-Ripened Cheeses 6. Production of Process Cheese.
- Principles of Cheese-Making
- Production of Cheddar Cheese
- Production of Swiss Cheese
- Production of Surface-Ripened Cheeses
- Production of Mold-Ripened Cheeses
- Production of Process Cheese
1. Principles of Cheese-Making(With Steps):
The basic steps in cheesemaking, as outlined by Kosikowski (1977), are:
(1) Setting milk (adding starter cultures and coagulant to pre-warmed milk),
(2) Cutting the coagulum,
(3) Cooking the cut coagulum (curd),
(4) Removing whey from the curd,
(5) Allowing curd particles to “knit,”
(6) Salting (this comes at different times in the procedure for different cheeses),
(7) Pressing, and
(8) Ripening of the finished cheese.
The various facets of this general procedure will be considered in the following paragraphs:
Fresh milk obtained from healthy cows (or other animals that may serve as a source of milk) should be cooled rapidly and then promptly delivered to the cheese factory where it should be converted to cheese as soon as possible. The milk should be free from antibiotic residues, other chemical contaminants, and serious off-flavors.
Furthermore, the raw milk should not have supported excessive growth of psychrotrophic bacteria because such growth can cause irregularities in the manufacture of cheese by affecting activity of lactic starter cultures and coagulation of milk by rennet extract. The quality of cheese resulting from such milk also will be inferior4e that of cheese made from milk without excessive growth of psychrotrophic bacteria. The difficulties just mentioned occur because many species of psychrotrophic bacteria produce proteolytic enzymes that partially degrade the casein in milk.
After milk arrives at the factory, it is commonly clarified with a centrifuge to remove small extraneous particles and somatic cells. The milk fat content of the clarified milk may be adjusted, depending on the variety of cheese that is to be made. Some cheese is made from raw milk, but it is more common to use heat-treated (heat treatment less than that of pasteurization) or pasteurized milk.
Heat-treated milk is sometimes preferred because the resultant cheese tends to be more flavorful than that made from pasteurized milk. Tests to determine the microbiological quality, composition, and presence of unwanted chemical contaminants in milk are described in Standard Methods for the Examination of Dairy Products.
One or several species of lactic acid bacteria are commonly added to pre-warmed milk. The small amount of acid produced by these bacteria early in the cheese-making process (fermentation) facilitates subsequent clotting of milk by the coagulant. Furthermore, the starter bacteria become a part of the finished cheese where they contribute to processes that occur in the cheese during ripening.
The kind of cheese to be made determines which microorganisms to add to milk, For example- to make Cheddar cheese one would use Streptococcus cremoris and/or Streptococcus lactis, the so-called mesophilic lactic acid bacteria. In contrast, to make Swiss cheese one would use Lactobacillus bulgaricus and Streptococcus thermophilus, the so-called thermophilic lactic acid bacteria (the definition one chooses for thermophilic bacteria will determine if these bacteria are truly thermophilic). There are still other examples, but these two should suffice to illustrate the point.
Microorganisms other than lactic acid bacteria sometimes are added together with them when cheese is made. Examples are Propionibacterium shermanii for Swiss cheese or molds for blue or Camembert cheese.
Currently, concentrated frozen starter cultures can be purchased and added directly to milk in preparation for cheese-making. Provided that the manufacturer’s instructions are followed, this approach will result in greatest uniformity in culture activity from day to day and also will minimize, if not eliminate, problems caused by bacteriophage infections.
The alternative approach is to transfer the culture from one lot of a suitable medium to another until finally a volume of culture suitable for cheese-making is obtained. When this is done, the problem of bacteriophage infection can be controlled through use of a phosphate-treated medium. Several commercial organizations market such a medium.
Regardless of how the culture is handled before it is added to milk, presence of antibiotics in milk (as a result of administering them to lactating dairy cows) will either retard activity and acid production by the culture or completely stop acid production if the starter culture is inactivated.
Loss of activity by the starter culture will lead to inferior cheese and may cause public health problems. Presence of antibiotics is normally controlled by frequent testing of the raw milk from individual farms according to methods described in Standard Methods for the Examination of Dairy Products.
A suitable coagulant is added to milk; usually a short time (e.g., 30 min) after the starter culture was added. The coagulant is an enzyme that splits colloidal casein into a carbohydrate-rich peptide fraction and the insoluble paracasein that precipitates in the presence of calcium ions.
Traditionally, rennet extract obtained from the fourth stomach of young calves has been used as the coagulant. A worldwide shortage of young calves has led to a shortage of rennet extract. Consequently, replacements such as blends of rennin and pepsin, rennet extracts from mature cows and coagulants of fungal origin have been developed. Fungi which produce coagulants for use in cheese-making include Mucor miehei, Mucor pusillus, and Endothia parasitica. Much of the cheese currently made in the United States and marketed without extended aging is made with a coagulant of fungal origin.
Rectangular frames with thin wires, horizontal on some and vertical on others are used to cut the coagulated milk into cubes. Such cutting increases the surface area of the coagulum which facilitates its loss of whey. Cubes of coagulum also can be heated uniformly during the cooking process. Small cubes (e.g., 1.3 cm3) lead to low-moisture cheese, whereas large cubes (e.g., 4-5 cm3) lead to high-moisture cheese.
After the coagulum is cut, the cubes of coagulum (curds) suspended in whey are heated to a given temperature in a specific time (e.g., to 37°-38°C in 30 min for Cheddar cheese). This heating is accompanied by stirring of the curd-whey mixture and causes the cubes of curd to contract and thus express free whey. Cooking also serves to control acid production by the lactic starter culture, to suppress growth of some spoilage bacteria, to influence texture of the curd, and to aid in control of the amount of moisture in the finished cheese.
After cooking is completed, whey is removed from the curd. This can be accomplished by draining whey from a vat that contains the whey-curd mixture, using appropriate precautions to prevent loss of curd. An alternative method, designated as dipping, involves scooping the curds from the whey-curd mixture.
During the time needed for removal of curds from whey, some additional lactic acid is produced by the starter bacteria. The curd may be removed from the vat and placed in a form or mold, as in the manufacture of Camembert cheese. Alternatively, the curd may remain in the vat so some knitting of curd particles can occur, as in the manufacture of Cheddar cheese.
This step allows for further production of lactic acid and for modification of the curd particles so they will adhere to each other and form a single mass of cheese. The characteristic texture of a given variety of cheese is partially determined by this process.
Salt (sodium chloride) is applied to curds in one of several ways. Dry salt may be sprinkled on loose curds as in the manufacture of Cheddar cheese or it may be rubbed onto the surface of freshly made cheese. Alternatively, freshly made cheese can be immersed in a nearly saturated aqueous solution of salt. Adding of salt contributes to the flavor, texture, and appearance of cheese; controls production of lactic acid; suppresses growth of spoilage microorganisms; and further reduces the amount of moisture in finished cheese.
This step sometimes comes before salting (as with cheeses that are immersed in brine) or afterward (as with Cheddar cheese). Curds are placed into a form, sometimes called a hoop, and pressure is applied hydraulically or through use of weights. If cheese with an open texture is desired, external pressure may not be applied. Piling of curds in a vat, as in Cheddar cheese manufacture, is a form of pressing although hydraulic pressure is used later in the manufacture of this variety of cheese.
Pressing gives the cheese its characteristic shape and contributes to its compactness. Free whey is expressed and knitting of curd particles is completed during pressing. Use of vacuum chambers during or after pressing- can aid in removing occluded air from cheese and thus give the product a closely knit body.
Ripening of Cheese:
The finished cheese is placed in a room with controlled temperature and relative humidity (e.g., 4°C and 85% for Cheddar cheese) and is held there for several months to several years, depending on the variety of cheese and the extent of ripening that is desired.
Ripening allows for enzymatically-induced changes to occur in the protein and fat fractions of the cheese. These changes transform the freshly made cheese into one with desired and characteristic flavor, texture, aroma, and appearance.
Automation of Cheese-Making:
Making of cheese was and for some cheese-makers continues to be largely a hand operation. However, increases in cost of labor and in amount of cheese a given factory desires to produce prompted development of machines which have automated various portions of the cheese-making process. This also includes preparation of finished cheese for the retail market.
2. Production of Cheddar Cheese(With Steps):
Cheddar is the first of several varieties of cheese to be discussed in some detail. Next to be considered is Swiss cheese and this will be followed with information about surface-ripened and mold-ripened cheeses. Brief comments about process cheese will end the discussion of varieties of cheese.
Cheddar cheese is of English origin, having been developed in a dairying region surrounding the village of Cheddar which is situated at the foot of the Mendip Hills in Somerset. Church records indicate that cheese from this region was provided to King Henry II in 1170, but the procedure for making Cheddar cheese was not published until 1857 when it appeared in a research report of the Ayrshire Agricultural Association.
Cheddar cheese is made in cylindrical and block shapes. The size of these is variable with blocks as large as 290 kg having been made, but this is not common. Some Cheddar cheese is produced by filling curd into large steel barrels; this cheese probably will be used to make process cheese.
The following steps are involved in manufacturing Cheddar cheese:
(1) Whole milk is clarified and pasteurized (71.7°C for 16 sec) or heat- treated (an exposure to heat that is somewhat less than that of pasteurization). Sometimes raw milk is used.
(2) Milk to be made into cheese is warmed to 31°C and then inoculated with 0.5% (or more, depending on circumstances) of an active culture of S. cremoris and/or S. lactis. Annatto cheese color also may be added if a cheese with a yellow-orange color is desired.
(3) Inoculated milk is held at 31°C for 30 min to permit some bacterial activity, and then the coagulant is added. Coagulation of milk is completed in about 25 min.
(4) The coagulum is cut into cubes of curd and the curd-whey mixture with continuous agitation is warmed (cooked) to 38°C in 30 min.
(5) Whey is drained from the curds which remain in the vat, piled against the long sides of the vat, with a trench going down the center of the vat. The trenched curds are allowed to mat for about 15 min after drainage of whey is completed.
(6) The trenched curd is cut into blocks which are triangular in shape and about 10 cm in thickness. These slabs of curd, after resting on one side for 15 min, are turned and again allowed to rest. This may be repeated after which they are piled 2 high and again turned every 15 min. The slabs can be piled 3 high for the last 30 min. This process is called “cheddaring,” and allows for development of acid and textural characteristics in the curd.
(7) The slabs of curd are fed into a curd mill which is suspended over the vat. This device cuts the slabs of curd into smaller pieces of curd which are ready for salting.
(8) Salt is applied and the curds are stirred for about 30 min. The salt is likely to be applied in 3 portions early during the stirring process.
(9) Curd is placed into a metal form or hoop of the desired shape and size. The hoop is outfitted with an appropriate cloth which covers all interior surfaces of the hoop. Hoops filled with curd, are placed on a horizontal hydraulic press and pressure is applied for approximately 18 hr.
(10) Cheese is then covered with wax and moved to storage (2°-16°C, 85% relative humidity) for ripening. Rindless Cheddar, which is not waxed but is covered with a plastic film, also can be made.
(11) Ripening can be for as short a time as 3 months or as long as 1 year or more, depending on the intensity of flavor that is desired and the temperature at which ripening occurs.
(12) Ripened cheese can be cut into consumer-sized portions, packaged, and distributed. Alternatively, it can be used as an ingredient in process cheese or another food. Some ripened Cheddar cheese is grated and dried for use on or in other foods.
Freshly made Cheddar cheese will contain appreciable numbers of the starter culture bacteria, S. lactis and/or S. cremoris. These bacteria begin to die within 2 to 8 weeks as the cheese ripens. During this time the bacteria are likely to produce and/or liberate proteolytic and lipolytic enzymes that play a role in modifying the body and flavor of the cheese.
In contrast to the behavior of the lactic streptococci, lactobacilli in Cheddar cheese begin to grow after the cheese is several weeks old and attain a maximum population in cheese that is 3 to 6 months old. There may be a decrease in numbers after that, but large numbers of viable lactobacilli will survive for long times in Cheddar cheese. That lactobacilli can survive a long time was demonstrated by Minor et al. (1970) when they recovered bacteria similar to Lactobacillus casei from a cheese-like product that had spent 105 years submerged in Lake Michigan.
L. casei most commonly appears in Cheddar cheese although other lactobacilli, including Lactobacillus plantarum, L. brevis, L. bulgaricus, L. hel- veticus, L. lactis, L. fermenti, L. acidophilus, L. arabinosus, L. pentosus, L. leichmannii, and L. delbriickii, have been either isolated from Cheddar cheese or have been added to the cheese in attempts to improve its flavor.
Normally, lactobacilli are not added when Cheddar cheese is made, but these bacteria seem to reside within the cheese factory and so invariably are in the cheese. L. casei produces proteolytic and lipolytic enzymes that contribute to the ripening of cheese. Additionally, L. casei can produce hydrogen sulfide which, in small amounts, is needed for flavorful Cheddar cheese.
As with the lactobacilli, micrococci are not commonly added in the manufacture of Cheddar cheese, but these bacteria constitute a major component of the microflora of the ripening cheese. Purposeful addition of certain micrococci when Cheddar cheese is made has resulted in rapid development of a desirable flavor. Beneficial micrococci have included strains of Micrococcus freudenreichii, M. caseolyticus, and M. conglomerates. The beneficial effects of these bacteria have been attributed to their proteolytic activity.
Other bacteria also have been claimed to contribute to or improve the flavor of Cheddar cheese. Included are Streptococcus faecalis, S. faecalis var. liquefaciens, and S. durans. These bacteria are not commonly added when Cheddar cheese is made, but sometimes they might be in raw milk and thus get into the cheese if it were made from such milk.
As is true of most ripened cheeses, the flavor of Cheddar cheese is the result of the correct blend of numerous compounds, many of which are produced through microbial action when the cheese ripens. Major components of the flavor include carbonyl, nitrogenous, and sulfur compounds; fatty acids; alcohols; salt; water; and unmodified fractions of cheese. The concentration of many of the components changes in the cheese during ripening.
Changes in the microflora and flavor during ripening are accompanied by changes in the body of the cheese. Freshly made Cheddar cheese has a firm and elastic body. A reduction in firmness and elasticity is apparent after 2 to 4 weeks of ripening at 7°C. This continues until a desirable, somewhat soft and smooth body develops. The body of well-aged Cheddar (e.g., more than 1 year old) may be somewhat crumbly.
Abnormal fermentation or errors in the manufacture of Cheddar cheese can lead to defects in the finished product. The defects can be grouped into off-flavors, poor body, and public health concerns.
Marth (1963) and Kosikowski (1977) indicate that the common off-flavors include bitterness, acid, rancid, unclean, fermented, and sulfide stinker. Defects in body and appearance mentioned by these authors include open texture, appearance of gas holes, and discoloration of the surface of cheese. Growth of mold can account for spoilage of this and other varieties of cheese.
Slight variations in the procedure used to make Cheddar cheese have resulted in an assortment of varieties of cheese that resemble Cheddar. In England, such varieties include Cheshire, Derby, Lancashire, Caerphilly, Double Gloucester, and Dunlop. American Variations include granular or stirred curd cheese, washed curd cheese, and Colby cheese.
3. Production of Swiss Cheese(With Steps):
Swiss or Emmentaler cheese is an example of a type of cheese which undergoes two fermentations, the lactic and propionic acid fermentations, and in which production of some gas is desirable because this causes formation of the characteristic holes or “eyes” in the body of the cheese. This kind of cheese is commonly called Emmentaler in Europe, where it originated in the Emme Valley, Canton of Bern, Switzerland, in the 15th century.
Traditionally, this cheese was made from raw milk, and that practice continues in some factories in Europe and elsewhere. The cheese can be made in the form of large wheels or millstones and having a firm rind. Individual wheels of cheese can weigh up to 100 kg. Now large amounts are made from pasteurized milk and in the form of rindless blocks that weigh from 36 to 41 kg. To facilitate cutting and packaging into consumer-sized units, some factories make larger blocks that weigh about 91 kg.
Rindless block Swiss cheese is made by the procedure that follows. The outline is based on descriptions of the process by Reinbold (1972) and Kosikowski (1977).
(1) Fresh whole milk is clarified mechanically and then standardized to contain 3% milk fat. Such standardization can be done by adding an appropriate amount of skim milk to whole milk; the procedure is needed so finished cheese will contain the right amount of milk fat, which is 47 to 48% on a dry basis (e.g., fat in the dry matter).
(2) Milk is heated at about 68° to 70°C for 15 to 25 sec. This serves to destroy unwanted microorganisms that may be in the milk.
(3) Milk at about 32°C is inoculated with Lactobacillus bulgaricus, Streptococcus thermophilus, and Propionibacterium shermanu. Lactobacillus helveticus and L. casei have sometimes been used instead of L bulgaricus. Propionibacteria other than P. shermanu also have been tested with some success. Inoculated milk is held at 32°C to allow for some growth by the added bacteria. Slight acid production that occurs aids in subsequent manufacturing operations.
(4) A suitable coagulant (e.g., rennet extract) is added to milk at 32 U and milk is held at that temperature until a coagulum is formed.
(5) The coagulated milk is cut with a wire knife so small cubes of curd are produced. This allows for expulsion of whey.
(6) The curd, with the aid of an agitator, is slowly moved about in the whey for about 40 min. This further facilitates loss of whey and firms the curd.
(7) The curd is “cooked” by slowly raising the temperature of the curd- whey mixture to 50°-52°C over a 30-40 min period. After the desired temperature has been reached, the curd-whey mixture is stirred for 30-70 min. This process aids the curd in losing moisture and becoming firm, and controls bacterial activity.
(8) Curd and whey are pumped to a cheese-molding vat Air should not be introduced during this process. Whey is drained from the curd.
(9) Curd in the molding vat is covered appropriately and then weights are placed on the curd. This is called “pressing,” continues for 12-18 hr and serves to expel gases and whey from the curd and to facilitate fusing of curd particles into a solid mass of cheese. Air, if present, interferes with this process.
(10) The mass of curd is cut into blocks of suitable size and the blocks are then placed into a solution containing at least 23% sodium chloride Additional salt may be sprinkled on the top of each block of curd as it floats in the brine. Cheese remains in the brine for 1-2 days. During this time a rind develops on the cheese, salt is absorbed by the cheese and bacterial activity is retarded because the cheese cools.
(11) Cheese is removed from the brine, allowed to dry for a day or less and then is wrapped with a flexible, extensible, and fluid-proof wrapping material. Furthermore, the wrapping material should be impermeable to oxygen (to prevent mold growth on the cheese) and permeable to carbon dioxide so it can escape as it is produced during ripening of the cheese.
(12) Wrapped cheese is placed in a cold room at 7°-10°C for up to 10 days. This serves to stabilize the physical-chemical, enzymatic, and microbiological systems operative within the cheese at this time.
(13) Cheese is then moved to the warm room where it is held at 11-24 °C for 2 to 7 weeks. During this time flavor and eyes develop.
(14) Cheese is then refrigerated at 3° to 4°C until it is sold. Refrigerated storage arrests eye development, firms the cheese, inhibits bacterial growth, and controls development of some defects.
Changes during Ripening:
Changes in Swiss cheese during manufacture and ripening have been described in considerable detail by Langsrud and Reinbold (1973B.C). The discussion to follow is based on their extensive review of the subject.
Growth of the starter bacteria begins while milk is being “ripened” and before the coagulant is added. Coagulation of milk serves to concentrate the bacteria in the coagulum, with only a small proportion remaining in whey. Growth of bacteria continues while the curd is being pressed.
Brining and the concurrent drop in temperature of cheese retard further bacterial growth and there may be a reduction in numbers of S. thermophilus and L. bulgaricus during this time. Movement of cheese to the warm room is accompanied by growth of propionibacteria and a further reduction in numbers of S. thermophilus and L. bulgaricus. L. casei can grow during this time and is thought by some to be important in ripening of Swiss cheese.
Proteolysis takes place during ripening and the content of free amino acids in the cheese increases. Propionibacteria do not appreciably affect proteolysis. Most of the characteristic sweet flavor of Swiss cheese has been attributed to its proline content, which is greater than in other varieties of cheese. The ratio of proline to propionic acid is also believed to be important in the flavor of Swiss cheese. Furthermore, volatile carbonyl compounds contribute to the flavor.
The pH of Swiss cheese increases as the cheese progresses from pressing to the cold room, warm room, and final refrigerated storage. Immediately after pressing, cheese has a pH of 5.1 to 5.3. These values increase by 0.05 to 0.1 pH unit in the cold room. After holding in the warm room, the pH of the cheese is about 5.5 and after refrigerated storage, it is from 5.6 to 5.7.
Swiss cheese should contain eyes of proper size and form, and the eyes should be evenly distributed in the cheese. Normal eyes should be 1.3 to 2.5 cm in diameter and should have a distance of 2.5 to 7.6 cm between them.
Lipolysis, probably largely a result of bacterial metabolism, occurs in Swiss cheese and resulting fatty acids also contribute to the flavor of the finished product. Studies with Swiss and Emmentaler cheese have demonstrated that of the fatty acids, propionic and acetic are present in greatest amounts. Appreciable amounts of myristic, palmitic, stearic, and oleic acids also have been observed.
The flavor of Swiss cheese is not the result only of the compounds and processes that have just been mentioned. Instead, many other compounds (alcohols, aldehydes, esters, lactones, methyl ketones, etc.) have been found in Swiss cheese and most are there as a result of microbial activity. These compounds, even though often present in small amounts (ppm or less), contribute to the flavor of the finished cheese. The reader desiring more information on this aspect of Swiss cheese should consult the review by Langsrud and Reinbold (1973C).
Defects in Swiss cheese can result from incorrect manufacturing procedures, improper gas formation, or growth of unwanted microorganisms that can cause off-flavors and faulty eyes. Details on these defects have been given by Reinbold (1972) and Langsrud and Reinbold (1974).
Defects in eyes relate to distribution, number, size, shape, and interior appearance or condition. Some of these irregularities result from faulty manufacturing practices and others from an unsatisfactory fermentation in the cheese.
Defects also can occur in the body (dry, pasty, weak, brittle), color (bleached, pink ring, colored spots), size and shape (too small or large, bloated, uneven), and finish and appearance (dirty rind, surface splits, dried areas, soft rind, mold, rind rot) of the cheese. Microorganisms can contribute to some of these problems.
Cheeses Similar to Swiss:
Several varieties of cheese that are similar to Swiss or Emmentaler have been developed in different countries.
Some of these will be mentioned in the following paragraphs:
Jarlsberg is made in Norway and derives its name from the Jarlsberg region in southern Norway. The present form of this cheese was developed from 1956 to 1960 at the Norwegian Agricultural College. Milk having 3% milk fat is inoculated with mesophilic (rather than thermophilic) lactic acid bacteria and with propionic acid bacteria. The finished cheese contains about 47% fat in the dry matter.
Samsoe (Samso) is produced in Denmark from milk containing 3.4% milk fat; and using ordinary (mesophilic) lactic starter cultures. Natural contamination serves as the source of propionic acid bacteria. Eyes in Samsoe cheese are limited in number and range in size from that of a pea to that of a cherry.
Iowa-style Swiss is somewhat similar to Samsoe although the starter cultures commonly associated with Swiss cheese are used.
Gruyere is made from raw cows’ milk containing 3.4 to 3.7% milk fats, and using the regular Swiss cheese lactic starters. Propionibacteria are not added intentionally and so this cheese has only a few small eyes. A surface flora develops during ripening; resulting in a cheese that is more flavorful than is Swiss cheese. Gruyere cheese is produced primarily in the French- speaking region of Switzerland and in France.
Alpkase or Bergkase is made largely in the Alpine regions of West Germany, Switzerland, and Austria. Still other names are used for this cheese, particularly in Switzerland. Mesophilic and/or thermophilic lactic acid bacteria but no propionibacteria are added to whole or partially skimmed raw milk. The cheese has fewer eyes but more flavor than does Swiss cheese. Although the manufacturing procedure is similar to that for Emmentaler cheese, numerous local variations seem to exist.
4. Production of Surface-Ripened Cheeses(With Steps):
Some cheeses gain their principal sensory characteristics through the combined efforts of bacteria and yeasts that develop on the surface of the cheese during the ripening process. Examples of this type of cheese include brick and Limburger. Brick cheese will be discussed first and then some other surface-ripened cheeses will be mentioned.
Olson (1969) has described 2 methods that are generally used to make brick cheese.
The following steps are involved in the first method:
(1) Pasteurized whole milk at 32°C is inoculated with Streptococcus thermophilus. Alternatively, a combination of S. thermophilics and S. cremoris or Lactobacillus bulgaricus may be used.
(2) After brief incubation, rennet or another suitable coagulant is added to the milk; the resultant curd is cut into 0.64 cm or 0.95 cm cubes and cooked at 38° to 45°C.
(3) After the curd is sufficiently firm, enough whey is drained so that about 2.5 cm remains above the curd surface.
(4) Curd and whey are dipped or pumped into rectangular hoops held on perforated screens.
(5) Hoops of curd are allowed to drain for 6 to 18 hr and are turned at intervals. Weights can be placed on the cheese during the draining process.
(6) Blocks of cheese are removed from hoops and immersed in brine containing 22% sodium chloride. Alternatively, salt can be applied to the exterior of the cheese.
(7) After 24 to 36 hr in brine, the cheese is removed and placed in a room at 15°C for 4 to 10 days. During this time the “smear” (growth of yeasts and bacteria) develops on the surface of the cheese.
(8) The smear is washed off, the cheese is waxed or packaged in plastic, and it is ripened for 4 to 8 weeks at about 4°C. More flavors can be obtained by leaving the smear intact for the entire ripening period.
The second or “sweet curd” method for making brick cheese employs S. lactis and/or S. cremoris as the starter culture and addition of water to the curd-whey slurry to control development of acid in the cheese. Some other modifications in manufacturing must be made to ensure that the minimum pH is 5.1 to 5.2 in 3-day-old cheese. Salting and ripening proceed as outlined above.
Brick cheese contains not more than 44% moisture and at least 50% of the total dry matter must be milk-fat. A typical brick cheese is about 12 cm wide, 25 cm long and 7.5 cm thick; it weighs about 2.25 kg.
Changes during Ripening:
Yeasts predominate in the surface microflora of brick cheese during the initial stages of ripening. This is because of their ability to grow at the temperature and the relative humidity (approximately 95%) used for ripening as well as the low pH and high concentration of salt at the surface of the cheese. Depending on the water activity of the cheese, yeasts in one or more of the following genera may be present- Debaryomyces, Rhodotorula, Trichosporon, Candida, and Torulopsis.
Growth of yeasts serves to modify the surface of the cheese so that Brevi- bacterium linens and micrococci can grow. Yeasts accomplish this by metabolizing lactic acid and thus raising the pH of cheese at the surface above the minimum for growth of bacteria. Additionally, yeasts produce vitamins which may enhance growth of bacteria. Growth of yeasts also may contribute to the final flavor of brick cheese.
Brevibacterium linens and micrococci (Micrococcus varians, M. caseo- lyticus, and M. freudenreichii) develop after sufficient growth of yeasts has taken place. These bacteria release proteolytic enzymes that are largely responsible for producing the characteristic flavor of brick cheese that has had a surface smear develop during ripening.
Olson (1969) described the major defects that can appear in brick and other surface-ripened cheeses. Included are defects in flavor, body and texture, and surface microflora.
Flavor Defects Include:
(1) Sour or acid—caused by excessive fermentation of lactose or inadequate washing of curd, or both. Too much acid retards development of surface microflora and too little acid results in fruity and gassy cheese.
(2) Bitterness—caused by abnormal protein degradation when the starter culture contains undesirable lactic acid bacteria such as Streptococcus faecalis var. liquifaciens.
(3) Flat—caused by insufficient growth of surface miroflora.
(4) Fruity and fermented—caused when the pH of cheese is high and the salt content is low so that anaerobic spore-forming bacteria can grow.
Defects in Body and Texture Include:
(1) Corky—caused by inadequate acid development or excessive washing of curd, or both.
(2) Weak or pasty—caused by a combination of excessive moisture, too much or too little acid and inadequate salt.
(3) Mealy—too much acid.
(4) Openness—caused by whey being trapped between firm cubes of curd; openings remain when whey drains from cheese.
(5) Gassiness—caused by growth of coliform bacteria, yeasts, certain strains of lactic acid bacteria, Bacillus polymyxa, or anaerobic spore- forming bacteria.
(6) Split cheese—caused by gas from anaerobic sporeformers.
Defects in the surface microflora include:
(1) Lack of growth—caused by low temperatures during ripening, too much salt in cheese, or drying of the surface of cheese.
(2) Mold growth—results when the surface smear fails to develop because the surface of the cheese is too dry.
Limburger cheese has up to 50% moisture and is made by the procedures used for brick cheese. The initial ripening at 16°C and at a high relative humidity is longer than for brick cheese, thus allowing extensive growth of B linens Surface growth is not removed when the cheese is wrapped and moved to storage at 4° to 10°C.
Extensive growth of B. linens on relatively small pieces of cheese accounts for the strong, pungent flavor and aroma of portdu Salut, Trappist, and Oka are wheel-shaped cheeses developed by Trappist monks and made by procedures somewhat similar to those for brick cheese. Geotrichum may appear in the surface microflora and contribute a distinctive flavor to the cheese.
Other varieties of surface-ripened cheese that is more common in Europe than in the United States include Saint Paulin, Bel Paese, Konigkase, Bella Alpina, Vittoria, Fleur des Alpes, Butter, and Tilsit. Liederkranz is a trade name for a surface-ripened cheese made in the United States by procedures similar to those for Limburger.
5. Production of Mold-Ripened Cheeses(With Steps):
Certain molds are used as the major ripening agents of some cheeses. In some instances mold growth occurs throughout the cheese (e.g., blue cheese), whereas other times growth of mold appears only on the surface of the cheese (e.g., Camembert cheese).
This cheese is ripened primarily by growth and activity of mold throughout the cheese mass. Blue cheese was not made successfully in the United States until about 1918; information on appropriate procedures for making this cheese was not available earlier (Walter and Hargrove 1969). A blue cheese is about 19 cm in diameter and weighs about 2 to 2.3 kg; it is round with a flat top and bottom.
The following steps are involved in producing blue cheese:
(1) Whole milk from cows is separated into cream and skim milk fractions, and the skim milk is pasteurized.
(2) Cream is bleached by adding benzoyl peroxide (maximum 0.002% of the weight of milk), pasteurized, and homogenized. Bleaching is done so that the finished cheese is white (except for mold growth) in color and homogenization increases the surface area of milk fat globules which facilitates lipolytic action that occurs during ripening of the cheese.
(3) Cream and skim milk are combined and 0.5% of an active lactic (Streptococcus lactis and/or Streptococcus cremoris) starter culture is added.
(4) Inoculated milk is held at 30°C for 1 hr to allow some acid production.
(5) A suitable coagulant is added, milk is allowed to coagulate, and the resultant curd is cut into cubes with 1.6 cm wire knives.
(6) Curds are allowed to remain in whey for about 1 hr while additional acid develops. Curds and whey are then heated to 33°C, held briefly, and whey is drained from the curds.
(7) Curd is trenched and inoculated with spores of Penicillium roqueforti; salt is also added and then the curd is stirred. Spores can be obtained in powdered form from commercial culture firms.
(8) Curd is placed into stainless steel blue cheese hoops.
(9) Hoops of curd are turned once every 15 min for 2 hr and then are allowed to drain overnight at 22°C.
(10) The next day curd is removed from the hoop and salt is applied to the surfaces of the cheese. Cheese is then stored at 16°C and 85% relative humidity and is salted once daily for 4 more days.
(11) After salting is completed, each flat surface of the cheese is pierced about 50 times with a suitable needle-like steel rod. This facilitates escape of carbon dioxide from the cheese and entrance of air so that growth of the mold is encouraged.
(12) Pierced cheese is then stored at 10° to 13°C and 95% relative humidity.
(13) After 1 month, surfaces of cheese are cleaned; cheese is wrapped in foil and then stored at about 2°C for 3 to 4 months to allow additional ripening.
Changes during Ripening:
The high acidity and the increasing amount of salt in the cheese cause a rapid demise of the lactic starter bacteria so that only a few viable cells remain in cheese that is 2 to 3 weeks old. Growth of P. roqueforti inside cheese becomes evident about 8 to 10 days after the cheese is pierced. Development of mold is maximal in 30 to 90 days; by then the mold has grown throughout the spaces between curd particles and along holes made when the cheese was pierced.
Penicillium roqueforti is primarily responsible for ripening blue cheese. Proteolytic enzymes from the mold act to soften the curd and thus to produce the desired body in the cheese. Some components of blue cheese flavor may result from this proteolytic action. Perhaps more important, the mold produces water-soluble lipases which hydrolyze milkfat to free fatty acids.
Included are caproic, caprylic, and capric acids which together with their salts are responsible forthe sharp peppery flavor of blue cheese. Penicillium roqueforti forms hepta- none-2 from caprylic acid and this ketone is an important component of blue cheese flavor. Other ketones (pentanone-2 and nonanone-2) have been recovered from blue cheese and probably contribute to its flavor.
Additionally, P. roqueforti reduces methyl ketones to form secondary alcohols (pentanol-2, heptanol-2, and nonanol-2) which also contribute to the flavor of the cheese. The pH of blue cheese initially is at 4.5 to 4.7 and increases to 6.0 to 6.25 after 2 to 3 months of ripening.
Growth of microorganisms can occur on blue cheese after 2 to 3 weeks of ripening. This growth consists of yeasts, micrococci, and Brevibacterium spp. and contributes to the final flavor of the cheese. If cheese is waxed, microorganisms will not grow to produce the surface slime.
Improper development of P. roqueforti can cause an assortment of defects. Too much growth can result in a musty, unclean flavor or in loss of the typical flavor, whereas too little growth is accompanied by defects in color, a body that is too firm, and insufficient flavor. Growth of unwanted molds can cause defects on the surface of blue cheese.
Cheeses Similar to Blue:
Roquefort is the original blue cheese. The designation “Roquefort” is applicable only to cheese made from ewes’ milk in the Roquefort area of France. A similar product made elsewhere in France is called bleu cheese. A peculiarity of Roquefort cheese is the fact that it ripens in a network of caves and grottoes where cool moist air moves briskly, temperature never exceeds 10°C, and relative humidity remains at about 95% throughout the year.
Gorgonzola is the principal blue-mold cheese of Italy where it is claimed to have been made in the Po Valley since 879 A.D. The English blue-mold cheese is Stilton, which has been made since about 1750. Stilton is milder than Roquefort or Gorgonzola. The texture of Stilton is sufficiently open so that the cheese usually does not need piercing to facilitate mold growth.
Camembert is an example of cheese that is made with a mold developing only on the surface rather than throughout the mass of cheese as happens with blue cheese. Apparently cheese ripened through the action of mold growth on the surface has been produced in France for centuries. According to Kosikowski (1966), it was in 1791 that Marie Harel, who lived in the village of Camembert in Normandy, developed a product similar to the present Camembert cheese.
The typical Camembert cheese is about 11 cm in diameter, 2.5 to 3.8 cm thick, and weighs 225 to 250 g. The interior is light yellow and waxy, and creamy or almost fluid in consistency, depending on the degree of ripening. The rind is a thin felt-like layer of mold mycelium and dried cheese. The mold is gray-white in color- sometimes bacterial growth occurs on the surface of the cheese and results in development of areas that are reddish-yellow in color.
The basic procedure for the manufacture of Camembert cheese employs the following steps:
(1) Pasteurized whole milk with about 3.5% milk fat is adjusted to about 32°C and ‘is inoculated with 2% of an active lactic starter culture (S. lactis and/or S. cremoris) plus a sporulated culture of Penicillium camemberti (alternatively, spores of the mold can be applied to the surface of the cheese later in the manufacturing process).
(2) Annatto (yellow coloring) may be added to the milk.
(3) Inoculated milk is allowed to “ripen” for 15 to 30 min so that a titratable acid of 0.22% develops. Rennet extract (or other suitable coagulant) is added and the milk is stirred and then held quiescently until a firm curd develops.
(4) Curd is cut into cubes with 1.6 cm knives. Alternatively, uncut curd can be ladled into hoops.
(5) Curd is not cooked but is placed into open-ended, round, perforated, stainless steel molds or hoops. Filled hoops are allowed to drain for about 3 hr at about 22°C; no pressure is applied to the cheese during draining.
(6) Hoops of cheese are turned and draining continues. The turning process is repeated 3 to 4 times at 30 min intervals.
(7) Both flat sides of curd in hoops may now be inoculated by spraying the surface with a fine mist of P. camemberti spores suspended in water.
(8) After an hour, cheese is removed from hoops, placed on a drain table, and held at 22°C for 5 to 6 hr. Weights are generally not placed on the cheese.
(9) Dry salt is applied to the surface of the cheese which is then held overnight at about 22°C.
(10) Cheese is held for 1 or 2 weeks at 10° to 15°C and 95 to 98% relative humidity. It may be turned once during storage to facilitate uniform development of mold on the surface.
(11) Cheese is moved to storage at 4° to 10°C after being wrapped in foil. Storage under these conditions may be for several weeks before the cheese is packaged and moved into distribution channels. Final ripening occurs during distribution.
Camembert cheese should be consumed within 6 to 7 weeks after it is made. The process used to make Camembert cheese has been mechanized in the United States and Europe.
Changes during Ripening:
Foster et al. (1957) have outlined the major changes that occur when Camembert cheese ripens. Normally film yeasts and Geotrichum appear on the surface of the cheese within 3 to 4 days after it is placed in the “warm” room. Growth of P. camemberti is evident a few days later and becomes maximal when the cheese is 10 to 12 days old. Development of mold is followed by appearance of a reddish growth comprised of Brevibacterium linens and related pigmented, rod-shaped bacteria.
Film yeasts and Geotrichum are believed to ferment residual lactose at the surface of the cheese and also are thought to reduce acidity, thereby facilitating later growth of other organisms. Yeasts and Geotrichum do contribute to the flavor of Camembert cheese; however, excessive growth of these fungi leads to excessive softening of the rind and undesirably strong flavors in the cheese.
Development of P. camemberti is essential for production of the normal body and flavor of Camembert cheese. Pigmented bacteria (Brevibacterium) develop after fungi have reduced the acidity of the cheese at its surface. These bacteria also contribute to the flavor of the ripened cheese.
Common defects associated with Camembert cheese include- (a) early gas production during drainage of the cheese, and (b) growth of undesirable “wild” molds on the surface. The first defect can be minimized or eliminated by adequate sanitation and use of high quality milk. The second can be controlled by maintaining adequate humidity in the room where cheese is ripening; wild molds tend to develop on cheese when its surface becomes too dry for normal development of P. camemberti.
Late in 1971 at least 227 persons in 8 states of the United States became ill with acute gastroenteritis about 24 hr after consuming French Camembert or Brie cheese. The illness was attributed to the presence in cheese of enteropatho- genic Escherichia coli.
Cheeses Similar to Camembert:
Walter and Hargrove (1969) and Weigmann (1933) describe several kinds of cheese other than Camembert that are ripened largely through the activity of surface mold. Brie is probably the best known of these Camembert-like cheeses.
Brie is made in 3 sizes:
(a) Large—about 40 cm in diameter and 3.8 to 4.2 cm thick, about 2.7 kg;
(b) Medium—about 30 cm in diameter and somewhat thinner than the large size, about 1.6 kg; and
(c) Small—14 to 20 cm in diameter and 3.2 cm thick, 0.45 kg.
The difference in size between Brie and Camembert causes differences in the ripening process of the two cheeses. This, together with variations in the manufacturing process, causes the flavor and aroma of Brie to differ from Camembert.
Coulommiers is a cheese similar to the small Brie but is ripened for less time. Another cheese similar to Brie is Monthery, which is made in two sizes roughly equivalent to the large-sized and medium-sized Brie. Monthery can be made from whole or partially skimmed milk.
Melum is similar to the small brie but has a firmer body and sharper flavor. This cheese also is designated as Brie de Melum. Other cheeses similar to Camembert and primarily produced in France include Olivet and Vendorne. The latter is sometimes buried in ashes in a cool, moist cellar during ripening.
6. Production of Process Cheese:
James L. Kraft working by himself and Elmer E. Eldredge working for the Phenix Cheese Company were largely responsible for developing process cheese in the United States. Kraft worked with Cheddar cheese and used sodium phosphate as the emulsifying salt, whereas Eldredge worked with Cheddar, Swiss, and Camembert cheese and used sodium citrate rather than phosphate.
Eventually the Kraft and Phenix companies shared their patent rights; the initial patents were issued to Kraft in 1916 and to Eldredge in 1921. Today more than 50 % of the cheese produced in the United States is converted to process cheese or a related product. Development of this industry has been described in detail by Price and Bush (1974A.B).
1. Process Cheese:
This product is made from a mixture of natural cheese, color, salt, and emulsifiers. The mixture is heated to 71°-80°C; the finished product is at pH 5.6-5.8 and contains about as much milkfat and moisture as does the original natural cheese.
2. Process Cheese Food:
This product is made from the same ingredients as process cheese, except that one or more of the following may be added: skim milk, whey, milk, cream, albumin, skim milk, and organic acids. The mixture is heated to 79°-85°C; the finished product is at pH 5.2-5.6 and contains not more than 44% water or less than 23% milk fat.
3. Process Cheese Spread:
This product contains the same ingredients as process cheese food, except that gums may be added to retain water. The mixture is heated to 88°-91°C; the finished product is at pH 5.2 or lower and contains between 44 and 60% water and not less than 20% milk fat.
Manufacture of process cheese begins with selection of the natural cheese to be used. An attempt is made to select cheese so that the finished product will be similar in flavor and other characteristics from day to day. A process cheese with desirable characteristics can be made by blending together 55% non-aged cheese, 35% medium-aged cheese and 10% fully-aged cheese.
After cheese has been selected, the surfaces are cleaned and trimmed and the cheese is ground with a grinder or other suitable device. The freshly ground cheese is mixed with the emulsifier and other ingredients, as appropriate. Emulsifiers are used to regulate the pH and produce a stable product which maintains its integrity during storage. Commonly used emulsifiers include sodium citrate, disodium phosphate, trisodium phosphate, sodium hexa-metaphosphate, and tetrasodium diphosphate.
The mixture of cheese and ingredients is then heated (“pasteurized”) to the desired temperature in a suitable device. After heating (or “cooking”), the smooth molten cheese mass is packaged in suitable containers and cooled. Sometimes ribbons of process cheese are made which are then cut so that sliced process cheese is produced.
Process cheese and related products receive a heat treatment sufficient to inactivate vegetative cells of bacteria and molds, mold spores, and yeasts. Bacterial spores may survive the heat treatment. Sometimes spores of Clostridium tyrobutyricum or Clostridium sporogenes have germinated, grown, and produced gas in process cheese. This defect may occur after the product has been distributed to retail stores.
The problem can be controlled by:
(1) Using natural cheese with few anaerobic spores,
(2) Ensuring that the pH is not above 5.8,
(3) Ensuring that the sodium chloride content of the serum is 6-7%, and
(4) Holding process cheese, including its display in the store, at temperatures below 20°C.
Contamination of sliced process cheese with mold spores during packaging is possible and such contamination can result in mold growth on the product before it reaches the consumer. Appropriate hygienic measures can minimize or eliminate this problem.