Say "Cheese"

Acceleration of Cheese Ripening

2005-11-08T23:19:00.000-05:00

Earlier, the aromas, flavors, and textures of cheese were all explained to develop during the ripening stage of the cheese making process. Numerous enzymes are delivered from the cheese milk, the coagulant, starter and non-starter bacteria. As stated in Biochemistry of Cheese Ripening the ripening stage can take from two weeks to even two years depending on the variety of cheese. However, most cheeses that are noted for its fine texture and rare taste are produced through the long and complete process of ripening. During ripening, microbiological and biochemical changes occur that result in the development of the flavor and texture characteristic of the variety. The changes account for the long and slow process that is characterized as neither predictable nor controllable. This has consequently been an issue of economic concern and thus there are incentives for economic and also for technological reasons to accelerate the ripening of the cheese curd.
There are several methods in which cheese-makers have accelerated ripening: with an elevated ripening temperature, modified starters, exogenous enzymes and cheese slurries.
Rise in temperature accelerates the ripening of the cheese curd for the reason that it speeds up the microbiological and biochemical changes. Modified starters are genetically modified lactic acid bacteria that are capable of producing more of the important substances involved in the chemical process of cheese making and the cheese-ripening process can therefore be accelerated. Lastly cheese slurries affect the timing of release of enzyme activity into the cheese matrix and thereby shortening the times in between each enzyme release.

Fat Content in Cheese

2005-11-08T22:32:00.000-05:00

As stated by the National Dairy Council: "The fat content of cheese is mainly responsible for its flavor and texture, which contribute to consumers' preference for full fat cheeses". Although consumers prefer these fatty cheeses it is not detremental to your health as long as you consume a well balanced diet. The ingredients of the cheese determine the fat and cholesterol content in it. Another option to low fat cheeses is reduced fat cheeses, which are made by different processes that are meant to keep their taste but lower their fat. In order for a cheese to be considered low fat, there must be 3 grams or less of fat per serving, according to the United State’s Food and Drug Administration. Cheese is not just made up of fat, it contains essential nutrients such as calcium, conjugated linoleic acid, sphingolipids, and high quality proteins. Linoleic acid, and sphingolipids have been speculated to reduce the risk of diseases such as heart disease and certain types of cancer. As long as the consumer eats a well balanced diet the fat in cheese should be of no concern to them.

Cheddar Cheese Variation - Tested II

2005-11-08T22:10:00.000-05:00

Earlier, we discussed the consumer acceptability of various kinds of Cheddar cheese but reached no encompassing conclusion on consumer preferences; now, we will discuss a similar study relating consumer acceptability of Cheddar cheese to variation in quality associated with the cheese’s ripening period.

Conducted at the Mississippi Sate University Dairy Plant, the test material consisted of three blocks of Cheddar cheese, one aged for two months of ripening, one aged for four months of ripening and one aged for seven months of ripening. As conducted in the aforementioned experiment, the researchers utilized a panel experienced in cheese categorizing according to a standardized descriptive language. The panel then distinguished the cheeses according to flavor, aroma, and texture. Consumer testing based on preference for the varying cheeses were matched up to the characterization of those cheeses given by the nine-man panel.

Consumer test results depicted the highest rating of “like moderately” for medium ripened cheese (aged for 8 months) which corresponded to “cooked, why, cowy, and buttery flavor.” The two runner-ups included the 6 and 11 month cheese, respectively characterized by “a nutty, pungent flavor” and “a sulfur, earthy, prickle bite flavor.” These scores bear importance to the food industry as the correlation between the compounds and sensory characteristics can be capitalized on – at least for the Mississippi area.

Carbohydrates in Cheese

2005-11-08T21:59:00.000-05:00

Most people are under the impression that lactose intolerant people are unable to eat any dairy products at all, but this may not be the case. According to the National Dairy Council, "Because of their low lactose content, most cheeses, particularly aged cheeses, are well tolerated by individuals who have difficulty digesting lactose." Most cheeses, especially aged cheeses such as cheddar, have low lactose content; lactose being the main carbohydrate in cheese. Most of the lactose is removed in the whey while the cheese is being made, and the rest is converted into acids, such as lactic acid, in the curd during ripening. Within three to four weeks of aging there is basically lactose left in ripened cheeses. Fresh unripened cheeses, such as cottage cheeses, convert fifteen to twenty percent of the lactose into acids in a couple of hours. This means not only lactose intolerant people, but also Atkins diet members can eat as much cheese as they want as long as it is low in lactose. Although there are always the exceptions: processed and cottage cheeses may contain more lactose (and therefore more carbohydrates) because of the optional ingredients that they add such as cheese whey and nonfat milk.

Cheddar Cheese Variation - Tested

2005-11-08T18:07:00.000-05:00

Previously, we discussed types of Cheddar cheese variation. Yet to be explained, however, is how the public views the variation found in Cheddar cheese – described in a study by the Journal of Diary Science. In the demographic locations of North Carolina and Oregon, Cheddar cheese varying from 1-19 months in age was tested for various consumer attributes, including overall liking. Additionally, descriptive sensory provided a scientific means of assessing the diverse spread of Cheddar cheese.

Descriptive sensory comprised the first, analytical portion of the study. Descriptive sensory profiles of the tested cheeses were engendered by a trained panel of fourteen and an accepted “cheese flavor sensory language.” This language comprised a Cheddar cheese flavor lexicon that described Cheddar cheese flavor attributes and was published by Drake et al. in 2001.

Despite the different geographic position, the average consumer responses, among 100 consumers at each location, were not different. However, the study identified six consumer clusters, the population of each differed between the demographic locations. Furthermore, the consumers described the “young” and “aged” Cheddar cheeses of the spectrum “as exhibiting intense Cheddar cheese flavors.” Despite this, consumers distinguished the difference between the “aged” cheeses versus the “young” cheeses.

Although producing information about specific trends and observations by consumers, the study concluded with the following, “Cheddar cheese acceptancevaries widely among consumers and is related to consumer preferencesfor distinct cheese flavor profiles.” Thus, we end with what we already knew; “to each his own.”

Vitamins and Minerals In Cheese

2005-11-03T23:03:00.000-05:00

The content of vitamins and minerals in cheese is a direct effect of what type of milk is used, and how the cheese is made. Most of the vitamins that are fat-soluble are usually transferred from the milk to the cheese because most of the fat taken from the milk forms the curd. The water soluble vitamins of the milk are mostly located in the whey, and the amount of these is decided by the cheese’s amount of whey in it. According to the National Dairy Council “The share of calcium provided by cheese was more than six times higher in 1999 at 25% than in 1909 at 4%.” This is mostly because of the increase in the consumption of cheese within that time period. The amount of calcium in the cheese is affected by the coagulation acidity and how much whey separates from the curd. The calcium and phosphorous remain in the curd in the coagulating enzyme made, ripened whole milk cheeses. Less calcium is retained in the acid coagulated cheeses. In most cases cheeses that contain other minerals in considerable amounts are also higher in calcium content.

Pasteurization of milk in cheese-making Part II

2005-11-03T19:07:00.000-05:00

In late September, an 11-year ban on the French blue cheese Roquefort was lifted by Australia. How was such a cheese banned in the first place? The key to answering this question lies in Roquefort's origin; it is not made from pasteurized milk. Australia maintains that cheese must be engendered solely from pasteurized milk to avoid infections like listeria.

However, this argument is not completely true. Even after the “botulinum cook," a heat treatment of 121^o C for 3 minutes used on canned products, there exists a microscopic chance (1 can in 10^12) that a Clostridium botulinum spore remains. More important than this minute chance of survival is the probability of recontamination of the milk supply. Cases of food poisoning by cheese made with pasteurized milk, such as the Swiss Vacherin Mont d'Or which killed 34, have been attributed to contamination of the milk after pasteurization. Post-pasteurized contamination of the milk is also more likely than such contamination of unpasteurized milk due to the Jameson Effect, which states that “reduced number of competitive flora allows greater scope for pathogenic bacteria to multiply.” Therefore, pasteurization cannot be argued as a panacea against all forms of infection. In Arthur Cunyngham and John Dennis’s article, they conclude that:

“the safety of cheese depends not on the microbiological quality of milk at a single time point during the manufacturing process but on a careful assessment of the cheesemaking process as a whole, applying Hazard Analysis Critical Control Point (HAACP) principles, to produce a final product which can be consumed with confidence”

Australia agrees with the aforementioned arguments. According to BBC News, "Australian food safety officials decided the risk was slight after seeing the limestone caves in southern France where Roquefort is made." However, Australia still has a long way to go; Christopher Pyne, the parliamentary health secretary stated that of all blue mould cheese, only Roquefort raw milk cheese manufactured under a set of stringent conditions is permitted in Australia.

CHEESE Maturation

2005-11-03T12:19:00.000-05:00

The process of cheese making is broken down into the four steps: curdling or coagulation of the milk, shaping of the curds, salting, washing, and seeding, and maturing.
It is the aging of the cheese which gives it its unique flavor – the longer the cheese has been aged, the stronger the flavor. Thus the maturation stage of the cheese making process is an important stage to complete the each cheese cycle in producing its own unique flavor.
According to All about cheese , the environment in which the cheese matures is the main factor that alters the cheese ripening process. The cellars that store the cheese may be either humid and warm, or relatively cool. Most cheeses, however, are stored in drying-rooms to speed up the maturation. The temperature of the cellars can range from 32 to 77 degrees Fahrenheit but the majority of cheeses, once again, is ripened between 46 and 60 degrees Fahrenheit.
The ripening stage is the exchange of gases such as carbon dioxide and ammonia from the cheese and oxygen in the air. This exchange is what leads to the growth of both ‘aerobic surface flora’ and ‘interior flora’.

Carbon dioxide has been recognized as a food preservative. The Dept of Health, during the food and drug regulations act passed an amendment that acknowledged the obtainment of a submission to permit the use of carbon dioxide in a variety of foods. The intention was to provide for the use of carbon dioxide as a ‘pH adjusting agent’ in milk in the production of cheese.

The Dangers of Cheese

2005-10-28T11:34:00.000-04:00

Cheese may be more of a danger to you than just an upset stomach. According to http://www.ucheepines.org/cheese.htm: “Between 1883 and 1947, there were 59 epidemics caused by cheese, with 117 deaths in the U. S. alone.” Cheese is composed of mold’s and bacteria’s waste products, which gives it the unusual flavor; this is usually a sign of danger in foods. Several products are created during the fermenting of cheese including toxic amines such as tryamine, which can cause headaches and migraines. The high salt content of several cheeses increases the likeliness of the consumer of having high blood pressure. There is also the possibility of nitrosamine, a potent cancer causing chemical, being produced within the cheese. Imported cheeses are dangerous because of their ability to transfer food-borne gastroenteritis, which has happened in the U.S. before. As you can see something as seemingly healthy as cheese can actually cause damage to your well being.

Pasteurization of milk in cheese-making

2005-10-27T21:29:00.000-04:00

With the rapidly growing cheese-making technology in late 19th century, food safety was increased. Louis Pasteur, a French microbiologist experimented and proved that harmful organisms in raw milk could be killed if heated to a certain temperature for a certain amount of time. This process came to be known as Pasteurization.
Pasteur concluded from his experiments that raw milk, when heated to 62 oC for 30 minutes or to 71 oC for 15 seconds, will be free of organisms that contaminate the cheese during the ripening process. The standards fro pasteurizing cheese are mainly designed to preserve the phosphatase enzyme which aids in curing the cheese. The enzyme, naturally occurring organism in raw milk, is inactivated when milk is pasteurized. It is stated that there are two widely used methods of milk pasteurization: high temperature/short time (HTST) and ultra-high temperature (UHT). HTST is the most common and is when milk is heated to 72 oC for 16 seconds before it is left to curdle and form cheese while the UHT is the heating of milk to 280 oC for at least two seconds. HTST pasteurization was designed to attain a reduction of viable microorganisms in milk. This process is stated to be adequate for destroying almost all yeasts, mold, and common spoilage bacteria. HTST is more commonly used than UHT because the less severe heat treatment is believed to bring a result of better flavor or cheese because it preserves some of the natural flora.

Cheddar Cheese Variation Part III

2005-10-26T22:59:00.000-04:00

What is nutty flavor? Food Scientist MaryAnne Drake defines, “Nutty flavor is a very elusive flavor that is difficult to pinpoint, but it only occurs in extremely aged Cheddar cheeses,” in the fall ’04 dispatch of the California Dairy Research Foundation. Drake and her colleagues have created a Cheddar cheese “lexicon” in which various Cheddar cheese flavors are described through sensory language. According to the lexicon, nutty flavor is characterized as “nut-like aromatic associated with different nuts.” Finally, scientists have not only isolated the flavor, but also the compounds that precipitate the nutty flavor prevalent in aged Cheddar cheeses.

Drake and her colleagues determined that the addition of Strecker aldehydes to aged Cheddar cheese samples (over 9 months aged) increased the nutty flavor. The increase in nutty flavor was not as noticeable with those Cheddar cheeses less than 8-months-old. Drake lists three methods of increasing the amount of amino acids required for Strecker aldehyde production: quickening the conversion rate of the amino acids into aroma compounds, adding the amino acids into the pre-curdled milk, and employing starter cultures that produce the required amino acids.

Drake has initiated cheese trials whose purpose is to comprehend the flavor development of Cheddar cheeses inserted with starter culture. She concluded, “We are expecting results in about a year’s time.” According to this time frame, the results should be released in fall of 2005, not a very distant prospect!

The Effect of Salt Content on Cheese

2005-10-21T11:36:00.000-04:00

Salt has more of an effect on cheese than just taste. According to a study posted by A.J. Pastorino’s, C.L. Hansen’s and D.J. McMahon’s Laboratory Results, in the Journal of Dairy Science, the adding of salt to cheese alters the protein interactions, because of the amount of protein that becomes solvent as an effect of the increases the ionic strength. The most significant case of the effect of salt on cheese is from 0% to .5%, during which the addition of the salt increases the solidity, adhesiveness, and the initial rate of cheese flow. Above the .5% range, salt continues to increase the hardness and decrease the consistency. Some results that were expected did not occur: there was no affect of salt on cheese melting, and there was no calcium – sodium exchange, or a change in soluble calcium. It is shown here that something as simple as adding salt to cheese can have a much bigger impact than one would suspect.

Conversion of Amino Acids in Cheese Flavor Variation

2005-10-21T11:12:00.000-04:00

Cheese, as we know, is one of the most nutritious foods made from milk of many mammals including cows, sheep, goats, buffalo, reindeer, camels, yaks, and mares. One of the world’s oldest food products – for thousands of years – cheese has been turned from surplus milk. With many years in cheese’s history, there are also many different varieties of cheese. According to the American Society for Microbiology, there exists more than 400 cheeses that come in hundreds of different flavors, sizes, textures, and aromas.
The article states that enzymatic degradation of amino acids in cheese is believed to produce aroma compounds which are involved in the complex process of cheese flavor variation. Amino acids are found and released from casein, which is encouraged by rennin, by the actions of proteolytic enzymes. They are involved with small peptides responsible for the basic tastes in cheeses; however, amino acids do not directly influence the typical cheese flavors. Because they are precursors of volatile aroma compounds such as aldehydes, acids, alcohols, esters, and thiols that directly contribute to the cheese flavors, amino acids are still able to contribute indirectly to the flavors. The degradation of amino acids occur during the ripening stage of cheesemaking and is due mainly to the action of microbial enzymes. Lactic acid bateria (LAB) is responsible for the generation of amino acids and small peptides and they are existent in all cheeses.

Cheddar Cheese Variation Part II

2005-10-21T01:29:00.000-04:00

Last week, variations on Cheddar cheese were discussed with respect to its meltability and hardness. As an article in the Journal of Dairy Science exemplified, the ratio of chymosin to C. parasitica enzyme dictates both of these qualities as well as the Cheddar cheese’s bitter taste associated with C. parasitica enzyme. This week, a new variation on Cheddar cheese, the reduced-fat Cheddar cheese will be discussed.

Traditionally, reduced-fat Cheddar cheese results from the removal of fat from the milk before coagulation. However, this process results in a diminished “aged” taste and a hard, rubbery consistency undesirable to consumers. In an article by B. K. Nelson and D. M. Barbano published by the Journal of Diary Science, they hypothesized that if fat were removed after the aging of Cheddar cheese, the aged taste would not be lost. This proposition was formulated on previous experiments delineating that cheese flavor comes from the water-soluble portion of the cheese. Therefore, Nelson and Barbano devised certain conditions with which to remove the fat after aging and tested the efficiency of each method. The three factors were temperature, gravitational force, and time applied for each.

They determined that temperature held the highest influence on fat removal; gravitational forces and their duration held less significance at higher temperatures. Indeed, between 20°C to 33°C, they observed a linear relationship between temperature and the amount of fat removed. Fifty percent of the fat in Cheddar cheese was removed at conditions of 30°C and 23,500 x g for five min.

Unfortunately, with most reduced-fat food products, one shortcoming is simply substituted by another (usually a decreased tastiness). However, the article states, “The process of fat removal decreased the grams of saturated fat per serving of cheese from 6.30 to 3.11 g. The flavor intensity of the reduced-fat cheeses were at least as intense as the full-fat cheeses.” Therefore, it seems that Nelson and Barbano succeeded in achieving the best of both worlds. By performing such an experiment, they not only generated healthier but tastier Cheddar cheese as well.

Calcium Concentration and pH's Affect on Mozzarella Cheese

2005-10-14T11:48:00.000-04:00

Calcium concentration and pH are not what most people think of when they are eating their mozzarella cheese yet it may have a large impact on just how watery the cheese is. According to a study published on the Journal of Dairy Science by the American Dairy Science Association, during the storage period of mozzarella cheese the moisture content and the degree of proteolysis, proteins decomposing into simpler peptides and amino acids, is affected drastically by the pH and calcium content. This study was conducted using low-moisture mozzarella cheeses. By lowering the calcium/casein ratio by 7 mg/g of protein, both primary and secondary proteolysis and moisture content showed a noticeable increase. They noticed that their observations agree with that of Fox (1970), whose research lead to their conclusion that reducing this ratio leads to increased rennet-induced proteolysis. Also by increasing the pH by .4, and sustaining the calcium/casein ratio, primary proteolysis in the cheese decreases, however secondary proteolysis stays the same.

History of CHEESE

2005-10-14T11:17:00.000-04:00

Americans consume over half pound of cheese each week. This may be because cheese takes up a large portion of many ingredients for foods or simply because people love to eat cheese. In looking at the history of cheese, it is realized that people’s love for cheese was not a recent founding. Mesopotamia, today’s Iraq, was where the extracting and crafting of milk into cheese started. It holds the oldest traditions involving the process and is believed to have started even before 3000 years before the birth of Christ. As stated in French Cheese the first production of cheese came about in much similar ways as do most discoveries are made in today’s labs: on accident. The fact that milk curdles under the sun or when it is heated for too long was discovered from an observation that lead to the start of experimentation. The first cheese factory to make cheese from scratch was in Rome, New York in 1851. Jesse Williams, the founder of this factory had his own dairy herd; he mixed his milk with others from local herdsman and because of this he was able to make large variety of cheeses with different tastes and textures.
In the 19th century, the development of railway gave way for people to access French cheese varieties. At the time, French companies had developed new ways to make soft cheese and the discovery from Louis Pasteur that microorganisms were what caused the maturity process in cheese further developed the French cheese assortment.
Today, over 500 types and more than 1000 different brand cheeses are made in France, making it one of the biggest cheese producers of the world.

Cheddar Cheese Variation

2005-10-13T18:36:00.000-04:00

The final product, cheese, can be altered by slight modifications during its production. As quoted from the Vegetarian Society of the UK, the “milk used may be full fat, semi-skimmed or fully skimmed… affecting the fat content of the cheese.” The article goes on to say that not only does the animal’s breed determine the ultimate taste of the cheese, but that milk from each specific animal can affect the taste as well. Such miniscule variations result in a changed product. More specifically, in an article from the Journal of Dairy Science, the combined use of chymosin and protease from Cryphonectria parasitica, yielded a correlation between the amount of protease and the meltability, hardness, and bitterness of the end product.

In this experiment, chymosin and Cryphonectria parasitica protease were taken in ratios of 1:0, 0:1, 33:67, and 67:33 in an attempt to dictate Cheddar cheese’s firmness and meltability while keeping the bitter taste of the cheese minimal (bitterness associated with high amounts of C. parasitica enzyme). This attempt actuated from previous evidence that proteolysis, the breakdown of proteins into simpler peptides and amino acids, is the primary mode of changes in “functional properties” of Cheddar cheeses. While both the chymosin and Cryphonectria parasitica serve to facilitate proteolysis, the function of the protease was to engender a Cheddar cheese whose meltability and hardness were dictated by the ratio of chymosin to C. parasitica—the higher the amount of C. parasitica, the greater the meltability and hardness of cheese. Unfortunately, C. parasitica could produce an undesirable bitter taste when used in high enough levels.

The experiment was successful in producing ratios that satisfied the aforementioned criterion. As could be expected, the meltability and hardness of cheese made with only C. parasitica was the highest of all cheeses; however, the level of bitterness was not favorable. The two ratios, 33:67 and 67:33, yielded favorable Cheddar cheese. Both were able to independently dictate Cheddar cheese meltability and hardness without the accompanying bitterness.

The History of Rennet

2005-10-06T08:05:00.000-04:00

Up until the 1960’s rennet, the lining of a calf’s fourth stomach has been used for the chymosin it contains that reacts with milk to make it curd. An interesting bit of information from the EUFIC is “In ancient times, in eastern Europe and western Asia, the practice of carrying milk in bags made of animal's stomachs probably resulted in the first cheeses being made more or less by accident.” The first description on how to make cheese was recorded by the Romans who were also critical to the spreading of this skill of cheese making throughout Europe. The Roman method of forming rennet was taking an extract from the stomach lining from animals such as goats, lambs, or even hares and mixing it with milk (Popular milks during that time were from goats and sheep). The chymosin reacts with the milk proteins and causes them to clump together and form a solid. This solid is cut and drained of the whey, protein and lactose, that is trapped inside. The solid part is called the curd, which is composed mainly of calcium and protein. The pieces of curd are gathered and pressed together to form the cheese, which after maturation is finished. During the 1800’s the selling of rennet extracts started. A laboratory was opened in 1874 in Copenhagen and calf rennet extract was produced from the stomachs taken from the calves killed for veal.

DNA Technology: Genetically-Modified Chymosin

2005-10-05T12:02:00.000-04:00

As a result of the lack of calf rennet needed for the production of cheese, many scientists have strived to come up with ways to compensate for the shortage of rennet. During the 1960s, scientists introduced the procedure of pumping milk through a matrix of chicken bones in an attempt to curdle the milk; this, however, was faded out as the “anion exchange chromatography”, a technique that separated pure chymosin from the stomach extracts of older animals, was exhibited. The latter, nevertheless, did not make it through for its complication and costliness. Before long, another discovery was made; a certain fungi, Mucor miehei, were capable of producing enzymes much like chymosin. Although this breakthrough attended to the production of cheese and the needs of vegetarians, it was dismissed for its tastelessness.
After many attempts, a final discovery was made that ensured the continuity of cheese making without the calf rennet: DNA cloning. Genetic engineering introduced the process of cloning DNA that gave instructions for the formation of chymosin in calf cells. Chymosin was then able to be derived from genetically modified microbes after the cloned genes were inserted into Escherichia coli, Kluyveromyces lactis and Aspergillus niger as exhibited in NCBE: Genetically-Modified Food. These microorganisms that had been genetically modified produced chymosin that is identical to enzymes obtained from animals. In 1988, it became the first genetically-modified source to gain approval for the use in food and in 1990, it was approved by the US Food and Drug Administration.
This process begins when DNA, instructing the protein chymosin from calf cells, is isolated and a copy of this DNA is made. It is then inserted into bacteria, yeast, and/or fungi cells in plasmids. The plasmid is then copied within these cells. Each microbe is then cultivated in a contained environment and chymosin that is identical to the animal protein is then made.
With the recombinant DNA technology, calf stomach shortage no longer worries cheese-makers. Today, about 90% of hard cheese in the UK and over 80% of all cheese in North America is made with chymosin from genetically-modified microbes.

The Traditional Manufacture of Cheese with Rennet

2005-10-03T21:32:00.000-04:00

The production of cheese essentially entails the curdling of milk by an enzyme called chymosin, found in rennet. As described in The Fly in the Ointment, rennet is found in the fourth stomach of calves; however, as calves mature, the amount of chymosin content within their rennet decreases. Therefore, newborn calves offer the prime source of rennet with cheese making potential. However, chymosin’s role manifests itself after the first standard steps of cheese making, as illustrated by the Vegetarian Society of the UK.
First, cheese producers pasteurize the milk at 72°C for 15 seconds to destroy unwelcome bacteria. After cooling the milk to 30°C, they sour the milk by inserting a starter culture of lactic acid. The purpose of such an addition is the conversion of lactose to lactic acid that assists in the milk’s coagulation and improves the cheese’s future quality, texture, and taste. Some cheeses form completely from coagulation by such starter cultures, but others include introduction of rennet.
Rennet contains chymosin, the active ingredient that eventually coagulates milk into cheese. Cheese producers obtain chymosin by cleaning and desiccating a calf’s fourth stomach. The stomach is then divided into small pieces and chymosin is isolated by soaking the pieces in a solution of boric acid or brine at 30°C for 4-5 days.
After the coagulation, the milk divides into curds and whey in a process called curdling. The curds undergo several processes before the final product is achieved – namely: cutting, draining, pressing in vats, and finally maturation. This final process typically takes from 4 weeks to 2-3 years, resulting in a variety of cheeses.