In the beginning, cheese making in the United States was all art, however embracing science and technology was necessary to make progress in producing a higher quality cheese. Traditional cheese making might not keep up with the demand for cheese, and the development of the factory system was necessary. Cheese quality suffered because of poor-quality milk, however 3 major innovations changed that: refrigeration, commercial starters, and the use of pasteurized milk for cheese making. Although by all accounts cold storage improved cheese quality, it was the enhancement of milk quality, pasteurization of milk, and using reputable cultures for fermentation that had the greatest effect. Together with use of purified commercial cultures, pasteurization made it possible for cheese production to be carried out on a fixed time schedule. Fundamental research study on the genes of starter germs considerably increased the reliability of fermentation, which in turn made automation possible. Need for performance, machinability, application in baking, and more emphasis on dietary elements (slim and low sodium) of cheese took us back to the essential principles of cheese making and led to restored vitality for scientific investigations into the chemical, microbiological, and enzymatic modifications that take place throughout cheese making and ripening. As milk production increased, cheese factories required to end up being more effective. Membrane concentration and separation of milk used a service and greatly boosted plant capability. Complete application of membrane processing and use of its complete capacity have yet to be achieved. Execution of brand-new technologies, the science of cheese making, and the advancement of additional advances will require highly trained personnel at both the academic and commercial levels. This will be a fantastic challenge to attend to and overcome.
INTRO: THE ALTERING SCENE OF CHEESE MAKING, EDUCATION, AND RESEARCH
The earliest records of cheese production in the United States, put together by the United States Census (mentioned in Thom and Fisk, 1918), revealed that more than 45 million kilograms of cheese was produced in the United States in 1849. Ladies made most of the cheese, and all of it was made from raw milk. The factory system was the outgrowth of the increased need from England, which required bigger cheeses of more consistent quality than the cheeses produced on the farm.
By 1914 there were 3,520 cheese factories in the United States, mainly in Wisconsin (1,720) followed by New york city (995) and Michigan (196 ), but a considerable quantity of cheese was still produced on the farm (more than 4 million kgs on farms compared with more than 141 million kgs in factories in 1909). Cheese production had moved away from New York to Wisconsin in a really significant method; by 1914, more than 50% of the cheese produced in the United States was made in Wisconsin. New York City and Wisconsin had a similar varieties of cows, and cheese production decreased in New york city because of the huge need for fluid milk in big cities. In 1916, cheese exports were 20 million kilograms and cheese imports were 14 million kgs. Immigrants were asking for the cheeses of their native country, and production of the desired cheeses was becoming more common. Imported cheeses were mostly Parmesan and Gorgonzola from Italy, Emmental from Switzerland, Roquefort and Camembert from France, and Edam from Holland. Much of the research done in the United States on cheese was on the development of making schedules and enhancing quality of these specialty cheeses. In 1916, the typical rate of cheese in the United States was $0.37/ kg, but imported cheeses cost $0.55/ kg. Since US cheese makers achieved success at duplicating the imports, a few of the cheeses were misbranded and offered as though they were imports.
Pasteurization of milk for cheese making was a new technology however was seldom utilized in 1914. There were no prescription antibiotics and no requirements for germs in milk or cheese or even for cheese composition. Major factors for the decline consisted of (1) the presence of bigger factories and increased Cheddar and mozzarella cheese production in California and other western states and (2) the demand for more consistency in the quality of cheese produced in bigger factories.
Overall cheese production in the United States was 5,370 million kilograms in 2015. In 2014, 368 million kgs of cheese was exported and 142 million kgs of cheese was imported, mostly from France and Italy. Mozzarella is currently the most-produced cheese in the United States. Likewise, per capita intake of cheese has increased from about 2.3 kg in 1980 to 15.8 kg in 2015. There is likewise a really active and steadfast group of cheese makers devoted to the manufacture of cheese from raw milk and expensive styles of cheese that were when the mainstay of cheese production in the United States.
Technological developments in cheese making equipment and curd handling permitted for mechanization and automation, which were necessary for this quantum increase in cheese production and resulted in consistent product, lowered bacteriological contamination, and reduced production costs. Execution of advances in engineering of cheese making devices began in the 1960s and has continued quickly considering that.
Another technological improvement in cheese making, membrane processing of milk, also had its roots in the 1960s, however it was not carried out routinely up until the last 20 yr. Membrane processing of milk describes the separation and concentration of milk with membranes. It enables the elimination of a portion of the water, lactose, minerals, and whey proteins depending upon the pore size of the membranes. As a result, CN and fat are concentrated. Making use of membrane-filtered milk permits the cheese maker to acquire higher cheese yields. Membrane processing has actually likewise been applied to whey and is used to focus whey proteins. Significant advances in membrane technology have shown that it has still not reached its potential, however execution of these advances in the United States is slow due to regulatory restrictions. Mechanization and automation reduced labor costs, and the cost of milk is now the biggest expense in cheese making. The yield of cheese per volume or weight of milk is based on fat and CN contents of milk, the recovery of each as cheese, the moisture material of the cheese, and the contribution of included salt. Concentrating milk elements utilizing membrane processes, using equipment and innovations that make the most of healing of fat and CN, and implementing standardized, fixed, timed production schedules have actually considerably enhanced cheese yield and cheese making effectiveness however have actually likewise introduced many difficulties. Two of the challenges are acquiring experienced workers to operate the equipment correctly and adapting a manufacturing schedule to produce cheeses that meet the altering demands of the client. Research study and the education of staff members that arises from its implementation are still at the heart of correct cheese making.
In 1890, the University of Wisconsin’s Agricultural Experiment Station started its Wisconsin Dairy School, the very first of its kind in the United States. Technical training for cheese makers was at least a semester-long endeavor and was not always connected to an academic degree (i.e., 4-yr college degree). Out of desperation and an absence of what he noted as an appropriate book on cheese making, John Decker, a trainer at the school, released his own book on cheese making in 1893. He kept in mind that his book was required because the advances in science (microbiology) and innovation (refrigeration) altered our views on health and offered the potential to enhance cheese quality.
THE JOURNAL OF DAIRY SCIENCE: CHEESE FROM THE BEGINNING
Almost all the research on cheese making released in the United States before 1917 remained in the form of technical bulletins by farming research stations (situated particularly in New york city, Vermont, Ohio, Connecticut, Wisconsin, and Iowa) and the USDA (Appendix Table A1). This trend would continue for a number of decades. A lot of the technical bulletins were on the general approach of manufacture of a particular kind of cheese, mainly cheeses that were imported due to their high need. Research studies on the microbiology and chemistry associated with the cheese making practice were consisted of in these bulletins.
The first paper on cheese published in the journal was on eyes of Swiss cheese (Clark, 1917), followed 2 year later on by a paper on the usage of buttermilk (spin-off of butter making) in making a skim milk cheese for sale to recent immigrants (Rudnick, 1919), who required an inexpensive source of protein and were prepared to compromise quality for nutrition. Subsequent papers on cheese focused on fancy cheeses such as brick, Limburger, blue-veined, Swiss, and home cheeses but not Cheddar, the most typical cheese produced.
Most preliminary papers on cheese making in the journal in the 1920s focused on improving cheese quality. Pasteurized milk for cheese making was being promoted as a sort of remedy to treat the significant problem of the day: gassy cheese caused by coliforms. Milk processing before cheese making, particularly that including membrane technology and problems associated with it, has played a significant role in the numbers of documents released in the journal in the past 2 years (Appendix Table A1).
MODIFICATIONS IN MILK PROCUREMENT AND MILK QUALITY FOR CHEESE MAKING
What was it like to produce cheese in 1917? Probably not unlike when the first cheese factories were built. Milk was delivered daily in metal cans. Milk was cooled by placing the cans in cold sparkling water– approximately 12 ° C was the norm. This was typically a poor methods for cooling milk quickly and led to really high germs numbers in the raw milk. Germs counts surpassing 1 million/mL of milk were common. Cooling was in some cases supplemented by the addition of ice to the water, which facilitated more quick cooling. Hlynka et al. (1943) demonstrated that a fast boost in rancidity and unclean flavors in cheese often accompanied more energetic stirring and when the milk was warmer. They recommended cooling milk with no or very little agitation. New methods to cool milk were eventually established, which helped with the production of more milk at the farm, made it possible for get every other day, and led to modifications in the policies on milk handling. Rancidity in cheese is now really unusual and, when it does take place, it is often attributable to extreme agitation of milk collected from animals with mastitis.
Can milk was common into the 1960s and was still used up until the early 1970s. With the development of electrification on the farm, it became possible to utilize mechanical cooling to cool milk faster and to a much colder temperature level. It also led to expansion of dairy herds and assisted in the hauling of milk from the farm in specialized refrigerated milk trucks ran or contracted by the cheese plant. These trucks might transport as much as 23,000 kg of milk. Milk was now gathered from numerous farms by a single truck driver, which freed the farmer from making their own deliveries and the backbreaking lifting of 45-kg cans filled with milk.
2 significant modifications in guidelines resulted in the switch from can milk to bulk milk. Because it was now possible to quickly cool milk to below 7 ° C, by the 1940s regulations were put in place needing that milk be cooled within 2 h of milking to below 7 ° C and that blended milk (milk currently in the bulk tank mixed with freshly obtained milk) not surpass 10 ° C. The second regulation assisted set limitations on the optimum germs numbers in raw milk for cheese making, which decreased from 1 million cfu of bacteria/mL of milk to 300,000 cfu of bacteria/mL of milk. With the advancement of much better cleaning, sanitation, and cooling practices from the cow through shipment of the milk to the cheese factory, the numbers reached today by numerous manufacturers are listed below 20,000 cfu of bacteria/mL of raw milk. Currently, the majority of milk for cheese making includes less than 20,000 cfu of bacteria/mL of milk, and with numbers of germs in between 5,000 and 10,000 cfu/mL of milk being extremely common, it might eventually become the standard.
Due to the fact that of the high bacterial numbers in raw milk used in cheese making 100 yr ago and the unfavorable effect it could have on cheese quality, technologists looked for methods to deal with poor-quality milk. Cheese makers had little control over milking practices and handling at the farm, and there were no real financial rewards for the producer to improve milk quality, nor was it simple for the cheese maker to check raw milk quality.
Due to disease related to drinking raw milk infected with pathogens, by 1917 lots of municipalities required the pasteurization of milk– however not milk for cheese making. The belief was that the acidic conditions in cheese would most likely kill or considerably decrease the development of pathogens in cheese. There was likewise no genuine panic that consuming cheese would cause disease. This frame of mind culminated in the 1940s with the requirement of using pasteurization for cheeses that were consumed young (less than 60 d) because of the perception that it would take that long under acidic conditions to eliminate pathogens present in cheese made from raw milk. Pasteurization of milk for cheese making, started to improve cheese quality, did not necessarily produce a cheese devoid of pathogens. Regardless of the heat treatment provided the milk for cheese making, if the cheeses were infected with pathogens and the cheeses were of low acidity and high water activity, pathogens could grow or a minimum of not die. Reports of pathogens that could impact the safety of cheese have been released (Pearson and Marth, 1990; el-Gazzar and Marth, 1992; Bachmann and Spahr, 1995; Ramsaran et al., 1998; Lundén et al., 2004; Stephan et al., 2008).
Pasteurization of milk for cheese making prevailed in New Zealand by 1923 but was hardly ever practiced in the United States at that time. Sammis and Bruhn (1912) summed up the benefits of using pasteurized milk for cheese making. These benefits included improvement in cheese quality, more uniform quality, and greater cheese yield, and the cheese making process could be systematized to such a degree that cheese production could be on a fixed time schedule. Cost (1927 ), Phillips (1928 ), and Wilson et al. (1945) confirmed their conclusions. As a result, the industry significantly utilized pasteurized milk for cheese making, even though it took more than 50 yr since it was first presented to become commonplace. Milk quality at the time was poor by today’s standard. Bacteria numbers as determined in lab were normally greater than 500,000 cfu/mL of milk and as high as numerous million. An example of the times and milk quality, Kelly (1939) reported numbers of germs in raw milk for the manufacture of cheese ranging from 1.8 million to 5 billion cfu/mL of milk. To control gas formation brought on by coliforms in Limburger cheese, which was a common problem in raw milk cheese regardless of variety, Kelly (1939) advocated using pasteurized milk rather than the common practice of using raw milk for cheese making. There was terrific unwillingness to use pasteurization since of a viewed decline in the development of cheese flavor and the cost and availability of equipment. Pasteurization was typically done with the holder approach– what we now call low temperature level, long time pasteurization. Today just small-volume cheese makers utilize it, and all others use an HTST method (flash approach, as it was called). The HTST pasteurization method helps with high-volume milk throughput, which is important in quickly processing substantial amounts of milk. Milk high in bacterial numbers would contain stress efficient in fermenting lactose and could hinder the wanted rate of acidification throughout cheese making. The cheese maker would not have strict control over the rate and level of acidification during cheese making, which is one of the essential components of successful cheese making. Pasteurization eliminates most germs efficient in fermenting lactose and therefore demands making use of included starter culture for proper fermentation. Pasteurization resulted in much tighter control of acidification during cheese making, and this in turn assisted help with better process control over cheese quality. In 1917, numbers of bacteria remaining in milk after pasteurization were in the thousands per milliliter of milk. Today, bacteria numbers in pasteurized milk are usually less than 100 bacteria/mL of milk. These lower numbers are attributable to the initial low numbers in raw milk, which is assisted in by more efficient overall cleaning and sanitation practices and cooling of milk on the farm and in bulk-milk carrying trucks used today. By 1943, a number of states embraced the pasteurization requirement for milk for cheese making. Universal adoption of pasteurization of milk for cheese making has actually met resistance from numerous artisanal and grange cheese makers, whose customers demand cheeses made from raw milk. Regulatory agencies today are demanding a greater level of examination of the cleanliness and sanitation of milk production on the farm and in the cheese making facility than in the past. The United States federal government has adopted a no tolerance policy for the occurrence of pathogens in cheese. Pasteurization of milk is only one hurdle in the effort to keep pathogens out of cheese. Cheese is not made in a sterile environment, and appropriate cleansing and sanitation of the cheese making facility to prevent contamination is needed. The Food and Drug Administration is mandating efforts to implement guidelines to prevent contamination (i.e., Food Safety and Modernization Act). The growth and survival of pathogens in cheese as the result of contamination throughout manufacture, ripening, or product packaging depends on water activity, competitiveness with other bacteria, and pH history of the cheese. Mold-ripened cheeses (e.g., Camembert or Brie) and soft, surface-ripened cheeses (e.g., Limburger) do not offer adequate protection against the growth of pathogens since they do not satisfy the criteria needed to keep pathogens from growing. These cheeses have high water activity, and throughout ripening they lose level of acidity and thus end up being conducive to the development of impurities. Health problem due to the intake of cheese is really rare, but when it does happen it contributes to the argument for adoption of preventative procedures, such as those explained by the Food Security and Modernization Act.
Cheese making might now be carried out on a fixed time schedule, a significant event that makes massive cheese making feasible today. Biofilms are of concern in cheese plants and other dairy processing facilities since they are the significant source of postpasteurization contamination of milk by bacteria (Wong, 1998; Somers et al., 2001). At times, Streptococcus thermophilus are so numerous in pasteurized milk that their acidification of milk eclipses the acid produced by the added beginners; this avoids stringent control over the rate and degree of acidification required for correct cheese making.
Antibiotics in milk became a major problem in the late 1940s (Katznelson and Hood, 1949; Johns, 1953) through the 1960s (Albright et al., 1961; Kosikowski, 1961), and how to prevent antibiotics from getting into the milk supply stayed a subject for manufacturers (McEwen et al., 1991). There was substantial argument on the overuse of antibiotics for treatment of mastitis. The arguments against the overuse of prescription antibiotics included the capacity that pathogens might end up being resistant to the antibiotic and the truth that if the antibiotic got into the milk it could inhibit lactose fermentation by the starter bacteria or cause an allergenic action in delicate people who consumed the cheese. Although under federal law it was illegal to sell milk which contained prescription antibiotics, it was not till the 1960s that routine screening of raw milk end up being mandatory.
Extraneous matter in milk was common, and it was correlated with cheese quality. Clarification of milk for cheese making was promoted by Combs et al. (1924) to eliminate extraneous matter (sediment, consisting of dirt and hair), and the result was an enhancement in cheese quality. With the introduction of electric motors in the 1930s, mechanical separation ended up being typical. The sediment test for raw milk, which measured the amount of extraneous matter in milk, was developed as an index of the quality of milking practices. A high sediment test meant that the teats were not cleaned effectively before milking.