- Email: [email protected]
Cheese | Mechanization of Cheesemaking
Mechanization of Cheesemaking R J Bennett, Massey University, Palmerston North, New Zealand K A Johnston, Fonterra Research Centre, Palmerston North, New Zealand ª 2011 Elsevier Ltd. All rights reserved.
Introduction Cheese manufacture has been carried out for thousands of years and, for the most part, as a cottage industry. Toward the end of the nineteenth century, as industrialization progressed, cheese manufacture moved into the factory. Since then, there has been progressive development of the technology to the situation today, with large, highly automated plants employing minimal staff. A major component of this development can be described under the term cheese mechanization, which may be defined as a process where mechanical devices are used to carry out the manufacturing processes traditionally done manually. The major developments in cheese mechanization occurred during the period from the 1950s to the 1970s. The primary drivers of cheese mechanization include reduced manufacturing cost, elimination of laborious tasks, manufacturing efficiency, labor savings, increased capacity, and improvement in quality. Much of the early development work occurred in Australia and New Zealand, where major expansion of the cheese industry, in particular the manufacture of hard cheese varieties such as Cheddar, necessitated the development of novel approaches to equipment design. Most of this work was done under the auspices of the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia, the New Zealand Dairy Research Institute (NZDRI), and the New Zealand Dairy Board. Both the CSIRO and the NZDRI had research groups dedicated to this task. This article uses the developments associated with hard cheeses, in particular Cheddar, as its framework, with the focus on those developments that have survived. Consideration is then given to other cheese types and likely future directions.
Hard Cheeses – Cheddar Family The mechanization of Cheddar cheesemaking can be reviewed by considering, sequentially, the key steps in the process, using much the same approach as that taken by those undertaking the original mechanization of the cheesemaking process. The steps discussed include milk treatment, starter culture preparation, vat process, texturing (cheddaring), milling, salting,
pressing (block forming), and ripening (including packaging and storage). Milk Treatment Fat standardization of cheese milk has been used as a means of better controlling the composition of the final cheese for some time, but the more recent innovation in this area has been the standardization of the protein content of the cheese milk, especially where the milk composition tends to vary over a dairy season as is the case in New Zealand and Australia. New Zealand was one of the first dairying nations to use this approach to standardize its Cheddar cheese milk in the early 1990s. The protein in skimmed milk is concentrated in a separate retentate stream to a higher level than required and the concentrated skimmed milk is fed back into the whole milk to achieve a consistent proteinto-fat ratio and a consistent protein content of between 3.7 and 4%. Nonconcentrated skimmed milk can also be added if required. The advantages of protein standardization for cheesemaking include increased throughput, improved processing, improved product consistency, less whey handling, and a clean lactose permeate stream. Starter Culture Preparation Neutralization of the starter culture during the growth phase resulted in increased numbers of organisms per milliliter of culture, allowing the cheesemaker to reduce starter addition volumes and to save on bulk starter capacity. Introduced during the 1980s in New Zealand, the one-shot neutralization of mesophilic starter cultures with sodium hydroxide during bulk starter growth doubled starter numbers from 5 108 to 1 109 per milliliter. Once the pH of the starter culture had reached 4.8, a quantity of sodium hydroxide solution was added in one amount (one-shot) and was stirred in to return the pH to 6.7, allowing further starter growth before acid levels again became inhibitory. Later development of a multishot continuous system tripled starter numbers, allowing for a threefold reduction in the starter volume added to each vat. Other systems use internal pH-controlled media (buffered bulk starter media) to achieve a similar increase
607
608 Cheese | Mechanization of Cheesemaking
in starter numbers to that shown for one-shot neutralization.
Vat Process The traditional cheese vat consisted of a long, rectangular vessel of about 4500–10 000 l, in which all the operations up to pressing were carried out. Elimination of the backbreaking labor associated with these vats was one of the main drivers of mechanization. It was recognized early on that further development necessitated retention of the vat stage for the steps associated with primary curd formation and fermentation only. The remaining operations could be transferred to downstream equipment that had yet to be developed. The vat stage became concerned solely with the conversion of liquid milk into a coagulum, followed by cutting, stirring, and cooking, to produce a curd and whey mixture of the appropriate pH, moisture, and mineral composition, by the controlled activity of the starter cultures incorporated at the beginning of the process. The late 1960s saw the introduction of the enclosed vat. The majority of the enclosed vat systems available contain or two revolving knife panels of various designs • one that are used for both cutting and stirring operations,
• • •
depending on their direction of rotation, a fully surrounding or partially surrounding (steam or hot water) heating jacket, whey removal systems for predraw and in-vat curd washing, and automated rennet addition, cleaning-in-place (CIP), and computer-controlled options for cutting/stirring speeds and cooking recipes (later models only).
Another advantage of the fully enclosed cheese vat is the reduced risk of foreign matter and airborne microbiological contamination. The choice of equipment for the vat stage of the cheesemaking process depends on many external factors including type of cheese to be made, downstream curd processing, flexibility, cost, and throughput. Internal vat factors are also important, such as the configuration of the vat and its cutting and stirring mechanism, how the tank is heated and emptied, rennet addition, and CIP configurations. How the curd is cut is of particular significance. The cutting operation, together with the speed of stirring following cutting, influences how large the particles will be at draining and how much of the original milk components (fat and protein) is lost to the whey. A number of vat types are available, including OST, Damrow, Scherping, and APV CurdMaster; a number of cheese types are made using these systems, including Edam, Gouda, St. Paulin, Havarti, Cheddar, Emmental,
Romano, Monterey Jack, Egmont, Mozzarella, Danbo, Raclette, Tilsit, Blue, Feta, Maasdam, Cagliata, Provolone, Norvegia, Manchego, Camembert, Pecorino, Grana, Port Salut, and Parmesan. One of the first and most popular choices of enclosed cheesemaking vat was the Tetra Tebel OST vat. To date, five models have been produced, each model designed with and without predraw capability. Both the Alfa Laval OST I vat and the Alfa Laval OST II vat were upright, single silo-shaped tanks with one (OST I) or two or more (OST II) knife panels that were vertically mounted. The OST III vat was the first horizontally mounted vat of the OST series and its design was driven by a demand to process larger (>20 000 l) volumes of milk. The OST III vat design has been continued in OST IV and OST V models (Figure 1). The vertical Damrow vat was developed in 1972 and has had two updates since then. Easily recognized with its ‘double-O’ configuration, the vertical Damrow vat had two vertical knife arrangements that were used to both cut and stir the curd (Figure 2). The first dual-barreled horizontal cheese vat was developed by Scherping Systems in 1988. Of interest is the unique design of the vat’s ‘counter-rotation’, dual agitator, cutting and stirring system and the staggered design of the knife arrangement of the third generation model (Figure 3). The first APV CurdMaster was produced in 1993 and its design is based on the Protech CurdMaster and the Damrow Double-O vat. Texturing Development of equipment to replace the traditional invat cheddaring process presented one of the more challenging aspects of mechanization. A common device developed for dewheying prior to cheddaring was the static dewheying screen, followed by a short drying belt. Many ingenious devices were developed for texture development, including some that mimicked the process in the vat. However, the development of the cheddaring tower in New Zealand provided a revolutionary system for cheddaring that is still in use today (Figure 4). Another very significant development has been the use of belts for cheddaring, as demonstrated by the Damrow draining and matting conveyor two-belt system, developed in the United States, and the Alfomatic (Figure 5), developed in Australia by Alfa Laval (now Tetra Pak). In this system, the curd is allowed to fuse together on another belt and is then inverted as it drops on to a third belt for further cheddaring. Stretch is induced at the transfer. The belt cheddaring system has been widely adopted by other manufacturers such as APV (Figure 6) and Scherping. The belts are now plastic, rather than the original stainless steel, may be perforated, and may be
Cheese | Mechanization of Cheesemaking
609
Figure 1 OST IV cheese vat. 1, Combined cutting and stirring tools; 2, strainer for whey drainage; 3, frequency-controlled motor drive; 4, jacket for heating; 5, manhole; 6, CIP nozzle. Courtesy of Tetra Pak, Sweden.
Figure 2 Damrow Double-O cheese vat. Courtesy of Damrow Inc., USA.
610 Cheese | Mechanization of Cheesemaking
Figure 3 Scherping horizontal cheese vat. Courtesy of Scherping Systems, USA.
Figure 5 Alfomatic cheesemaker. 1, Curd/whey mixture inlet; 2, whey screen; 3, curd stirrer; 4, turnover chute; 5, chip mill; 6, dry salting feed; 7, salt mixing drum; 8, chips drawn to blockformer by vacuum. Courtesy of Tetra Pak, Sweden.
Figure 6 APV Cheddarmaster belt system. Courtesy of Fonterra Cooperative Group, New Zealand.
equipped with stirrers for curd agitation. Some plants, particularly in the United States, make Cheddar without ‘cheddaring’ and continuously dry stir the curd prior to salting.
Milling and Salting
Figure 4 APV cheddaring tower, with guillotine and mill at base. Courtesy of APV, UK.
The purpose of milling is to cut the cheddared curd into fingers (chips) of approximately 1.5 1.5 8 cm, to aid in salt uptake. Mechanical reciprocating chip mills were introduced in the earliest stages of mechanization for open vats and for equipment such as the Australian CheeseMaker 3. In contrast, the milling system developed for the New Zealand Cheddarmaster process consisted of a rotating cutting drum, which cut the curd in two directions at once using a blade and a cutting comb. Rotary
Cheese | Mechanization of Cheesemaking
mills using a similar principle but covering the width of the belt are now used at the end of the cheddaring belts on systems such as the Alfomatic and the Cheddarmaster. A number of techniques have been used to apply and mix dry, granular salt into the curd. The CheeseMaker 3 design incorporated what became known as the trommel salter, in which the milled curd passed over a weighing belt that discharged into a rotating conical mixing drum, with a metered flow of salt being deposited on to the curd as it entered the drum. The early Cheddarmaster design utilized a salting boom that moved backward and forward across the curd on the mellowing conveyor belt. The quantity of salt applied was proportional to the curd flow, determined by a sensing fork that measured the curd depth. Following salting, the curd passed along the mellowing conveyor where peg stirrers would aid salt uptake and moisture expulsion. Interestingly, the systems that have survived to be incorporated into modern plants consist of refined versions of the trommel design (Figure 7), as these give excellent control of the salt content in the final cheese.
Pressing It was recognized early on that the traditional pressing process using metal hoops or molds was very labor intensive. About half the labor force in New Zealand factories was used in this part of the process. Sophisticated systems have been developed to fully mechanize and automate the mold filling and pressing operations, such as the APV Sanipress, but, for dry-salted cheeses, these have been largely superseded by the development of the continuous block former described below. However, the early development of the large hoop system as part of the Cheddarmaster process deserves a mention. These vertical hoops were designed to hold
Figure 7 Trommel salting system. Courtesy of Fonterra Cooperative Group, New Zealand.
611
818 kg of curd. After pressing for approximately 10 h, including a vacuum stage, the large block of curd would be hydraulically pushed from the hoop through a special cutter head, producing 44 blocks of cheese (each 18.1 kg) per hoop. The labor saving with this system was significant, but one major problem with the long pressing time was the lack of curd cooling. Nonstarter lactic acid bacteria could grow to very high numbers during the overnight pressing and this could give rise to problems of flavor and gas production in the final cheese. However, barrels or large forms of cheese are still produced in the United States, normally for rapid use as ingredients in processed cheese. The introduction of Wincanton’s continuous block former in 1980–81 in New Zealand following a 17-year development reduced holding times from 24 h to 30 min and reduced and minimized the floor space and the labor force required to carry out the pressing and block-forming part of the process. Operating principles are shown in Figure 8. The modernization of the ‘hanging plate’ arrangement to a completely welded, perforated, rectangular-shaped, continuous inner skin and the extension of the tower to increase the capacity from 700 to 1600 kg are more recent innovations, shown in Figure 9.
Ripening or Curing (Including Packaging and Storage) The initial reel feed sheet systems for wrapping rindless cheese have now been replaced by laminated barrier bags, such as those provided by Cryovac. This company has also been involved in the development of bag presenters, which automatically place bags on the cheese blocks as they exit the block-forming towers. The bagged cheese blocks are transported through vacuum chambers, where they are heat sealed, and then placed in a carton base and conveyed to a rapid cooling tunnel. The carton format varies from base-only and box and lid to the most popular wraparound style. The cheese exiting the towers can be quite warm (30–33 C). The rapid cooling process reduces the average block temperature to between 16 and 20 C in 12–24 h. This solidifies the fat, firms the block, and, more importantly, dramatically reduces the growth potential of undesirable non-starter lactic acid bacteria, which can cause major problems of flavor and gas production. Fully automated, first-in/first-out, openstacked conveyor systems operating in blast chillers are used to achieve this cooling. An example is shown in Figure 10. Following this initial cooling, the cheese blocks are palletized by a robot and then transferred to controlledtemperature ripening and storage rooms. The operations,
612 Cheese | Mechanization of Cheesemaking
Figure 8 Blockformer operating principles. Courtesy of Tetra Pak, Sweden.
including cardboard packaging, are highly mechanized and automated, with minimal staff involvement.
Continuous Hard Cheese Process Any discussion of the mechanization of hard cheeses would be incomplete without mention of the pioneering work of the Australian CSIRO team, who came very close to the successful commercial development of a semicontinuous Cheddar (Sirocurd) process. This was based on ultrafiltration of the milk, the incorporation of whey proteins, and many ingenious inventions such as a barrel system for coagulation. Two commercial plants were commissioned but are no longer in operation.
Semihard Cheeses Developments associated with these cheese types, such as Gouda, Edam, and Tilsit, paralleled those for dry-salted varieties. Three manufacturing differences distinguish these varieties from hard cheeses such as Cheddar – whey drainage and curd washing in the vat, pressing of the curd under whey, and brine salting. Vat Process Similar vats to those developed for Cheddar varieties can be used. An additional feature incorporated into the Tetra Pak OST vat is a whey strainer that can be lowered into the vat, when stirring has been stopped, to remove part of the whey. The whey can then be replaced by hot water to wash the curd and reduce the lactose content.
Other Varieties
Pressing
The same issues of reduction in labor costs and manufacturing costs, increased throughput, and improvement in quality applied to other varieties and similar process developments were undertaken.
Post-vat manufacturing operation is quite different for these cheese types. It is necessary to separate the curd and whey without air incorporation, to allow for anaerobic fermentation during the ripening process. This is
Cheese | Mechanization of Cheesemaking
613
Figure 9 Details of Blockformer 6. Courtesy of Tetra Pak, Sweden.
achieved by first forming the curd into a block (prepressing), followed by further compression into a closely pressed block while further acidification occurs. Early attempts to mechanize the first part of this process resulted in the development of prepressing vats, a modern example of which is shown in Figure 11. In larger plants, the major type of equipment that is used is the Tetra Pak Casomatic (Figure 12). The curd and whey mixture in a 1:4 ratio is pumped to the top of the column, about 3 m in height. The curd settles below the whey to a height of about 2 m. The whey is removed via three whey drainage bands. A controlled rate of removal is essential for the formation of a block of curd at the base of the column. The curd block is formed in a dosing chamber and is then cut by guillotine and discharged into a mold to which a lid is fitted, enabling further pressing. Blocks of various shapes and sizes can be produced with minor modifications, and a multicolumn version is also available. The development of plastic microperforated molds such as the Laude mold (Figure 13) has been a major advance from the traditional wooden or metal cloth-lined molds.
Further pressing of the formed block is necessary to achieve the desired cheese properties and to allow ongoing acid development and whey drainage. Large table systems have been developed; the individual molds are conveyed on to tables that are fitted with individual hydraulic presses for each mold. The pressing regime is computer controlled, for example, 100 kPa for 20 min, followed by 200 kPa for 40 min. Following pressing, the blocks are discharged and the molds are washed and recycled. An example of this type of installation is shown in Figure 14. The APV Sanipress can also be used.
Salting Cheeses that have been formed into blocks under the whey cannot be salted prior to molding and pressing, as further acid development is required. For some varieties, dry salt may be applied to the cheese surface, but, for most, brining is the technique that is used. Brining essentially involves the immersion of the cheese block into a refrigerated brine bath (which also cools the cheese) for the required period
614 Cheese | Mechanization of Cheesemaking
required time, for example, 36 h for a 10 kg block, before unloading, drying, and wrapping. Ripening, Packaging, and Storage Highly mechanized systems have been developed for the material-handling aspects of these steps, including specialized cheese-turning equipment and the use of robots.
Soft Ripened Cheeses
Figure 10 Rapid cooling tunnel. Courtesy of Fonterra Cooperative Group, New Zealand.
to achieve the desired salt uptake. Highly automated systems have been developed, and these often involve the use of the brine solution as a conveyor system for the demolded cheeses, which float in the brine and are directed to a racking system in deep brine tanks that, once loaded, are submerged (Figure 15) for the
Many types of cheese fall into this category, such as Camembert, Brie, and Blue. Their manufacture is characterized by a high rate of syneresis and acid development, followed immediately by molding of the curd to the various final cheese shapes, under gravity, as the whey is drained from the curd. Hence, large-scale vat production is not desirable as the cheeses produced at the start and end of emptying would be quite different, due to composition and pH changes, and consistency of mold filling would be impossible. There have been various attempts to automate and mechanize curd production using a series of mini-vats, followed by automated mold filling and handling. Systems have been developed by companies such as Tecnal and Servi Doryl in France and APV in the United Kingdom, whose Contifiller system is shown in Figure 16. The multimolds used to form the cheese may be in two sections to provide sufficient volume for the initial fill, with the upper layer being removed later. The filled molds can be stacked automatically, conveyed to ripening rooms, turned frequently as required to ensure even block production, brine salted (or surface dry salted), and then conveyed to ripening rooms for mold development.
Figure 11 Prepressing vat. 1, Prepressing vat; 2, curd distributors, or CIP nozzle (2A); 3, unloading device; 4, conveyor. Courtesy of Tetra Pak, Sweden.
Cheese | Mechanization of Cheesemaking
615
Figure 14 Conveyor pressing system, with Casomatics in the foreground. Courtesy of Fonterra Cooperative Group, New Zealand.
Figure 12 Casomatic operating principles. 1, Curd/whey mixture inlet; 2, column with sight glass; 3, perforated whey discharge; 4, interceptor; 5, whey balance tank; 6, cutting and discharge system; 7, mold; 8, pawl conveyor; 9, whey collecting chute.
Figure 15 Deep brining system. Courtesy of Fonterra Cooperative Group, New Zealand.
The same processes of coagulation, cutting, and stirring occur as the mini-vats move along, by the use of tools that are placed alongside the belt. The curd/whey mixture discharges into molds at the end of the belt.
Soft Fresh Cheeses
Figure 13 Laude block mold. Courtesy of Laude bv, The Netherlands.
A very successful process that comes close to a continuous vat stage has been developed by Alpma in Germany. The basis of this system is a continuous flexible belt, which is formed into a trough to hold the milk. The trough is then subdivided into a series of mini-vats by a series of semicircular plates that also move with the belt.
Cottage cheese consists of curd particles that are packed into a container with the appropriate dressing. Specialized equipment, such as the O-Vat from Tetra Pak, has been developed to mechanize and automate production of this popular product. Quark uses a very different process of mechanization, in which the curd is formed in special ripening vats, followed by whey separation using a specially designed centrifugal separator. The product is then blended with components such as cream and is filled directly into the final container.
616 Cheese | Mechanization of Cheesemaking
Figure 16 Process line for soft cheese with Contifiller. 1, Curdmaking; 2, curd draining and filling; 3, stacking of mold batteries (A) and trays (B); 4, turning of mold stacks; 5, acidification lines; 6, destacking; 7, transfer/turning of cheese from mold batteries to trays; 8, transport to climate room (A) and from brining (B); 9, turning/emptying; 10, washing of mold batteries (A) and trays (B). Courtesy of APV, UK.
Pasta Filata cheeses are cheeses for which the curd has been worked or stretched and molded at elevated temperatures before cooling. This process imparts a unique and characteristic fibrous structure that influences both the ripening and the functional profile of the final cheese. Mozzarella is probably the best known of the Pasta Filata cheeses, which are mainly Italian in origin. However, the category also includes such cheeses as Provolone, Scamorza, Caciocavallo, Kashkaval, and Pizza Cheese. Equipment designed to perform the stretching operation incorporates two essential components: cooking and stretching. Stretching describes the mechanical treatment of the curd following cooking. Cooking is the phase in which the Pasta Filata curd is transferred to the hot water section of a cooker/stretcher. At this point, the curd is immersed, heated, and worked by single- or twin-screw augers. Typical water temperatures vary between 60 and 75 C, with cooked curd temperatures varying between 55 and 65 C.
Future Trends The mechanization of the cheesemaking process was the result of an intense amount of activity and development during the 1960s and 1970s. The latter half of the twentieth century saw the refinement of that development – the implementation of specific processes that enhanced
the overall mechanized approach – and these advances guaranteed a more consistent, higher quality, cleaner, and more cost-effective product. Although automation has led to reduced labor costs, improved efficiencies, and higher yields, it has also allowed for greater flexibility in what the plant produces and the ability to store and process large volumes of data that can be used to trend specific characteristics, for example, variability in drain pH, monitoring coagulation devices, temperature and pressure monitoring, and yield data analysis. Rapid and sophisticated in-process analysis techniques, both in-line and at-line, have been developed based on spectrophotometric analyses such as the absorption of infrared energy at specific wavelengths (MilkoScan, FoodScan). The integration of these techniques and the rapid analysis of the data that they can provide have led to almost instant feedback on parameters such as fat, moisture, and salt contents. Calcium contents can now be determined using X-ray fluorescence. Concurrent with the continued development in this area, recent published literature and patent applications would suggest that the next steps in the evolution of cheesemaking in the twenty-first century will be the development of completely new ways of making cheese, together with the continued refinement of the traditional processes that have been seen to date.
Cheese | Mechanization of Cheesemaking
Driven by the same needs that drove the initial mechanization of the traditional processes, these ‘alternative cheesemaking concepts’ will become more common. As an example, in February 2008, the New Zealand dairy industry commercialized a Mozzarella process that is an alternative approach to traditional Mozzarella manufacture. Unique to New Zealand, this process produces a functionally acceptable product directly off the line in a shredded format in less time than the traditional process and at a lower cost. This new process takes a number of ingredients derived from milk and blends and works them in a lowshear environment at an elevated temperature to produce a homogeneous mass that is cooled, shredded, and the shred then chilled or individually quick frozen. It involves processes and equipment that are used in other milk processing operations but have not, to date, been used to make Mozzarella.
Acknowledgments The authors are grateful to Tetra Pak AB, Sweden, specifically Bryce Griffiths (New Zealand), for information supplied and for permission to use illustrations from the Dairy Processing Handbook and other sales literature. The following are also gratefully thanked for the supply and use of technical sales information: APV, UK, Damrow Inc., USA, Laude bv, The Netherlands, Scherping Systems, USA, Stainless Steel Fabricating, Inc., USA. Permission to use photographs from numerous Fonterra sites within New Zealand is gratefully acknowledged, as are the insightful discussions held with Alister Barclay and Craig Honore, Fonterra Co-operative Group. See also: Cheese: Blue Mold Cheese; Camembert, Brie, and Related Varieties; Dutch-Type Cheeses; Hard Italian Cheeses; Membrane Processing in Cheese Manufacture;
617
Pasta-Filata Cheeses: Low-Moisture Part-Skim Mozzarella (Pizza Cheese); Pasta-Filata Cheeses: Traditional Pasta-Filata Cheese; Preparation of Cheese Milk; Raw Milk Cheeses; Salting of Cheese; Secondary Cultures; Starter Cultures: General Aspects; Swiss-Type Cheeses.
Further Reading Bennett RJ and Johnston KA (2004) General aspects of cheese technology. In: Fox PF, McSweeney PLH, Cogan TM, and Guinee TP (eds.) Cheese: Chemistry, Physics and Microbiology, Vol. 2: Major Cheese Groups, 3rd edn., pp. 23–50. London: Elsevier. Bylund G (1995) Dairy Processing Handbook. Lund, Sweden: Tetra Pak Processing Systems. Crawford RJM (1976) Developments in mechanized cheesemaking in the United Kingdom, 1972–1975. Journal of the Society of Dairy Technology 29: 71–85. Jameson GW (1987) Manufacture of Cheddar cheese from milk concentrated by ultrafiltration: The development and evaluation of a process. Food Technology Australia 39: 560–564. Kosikowski FV and Mistry VV (1997) Cheese and Fermented Milk Foods, Vol. 1: Origins and Principles, 3rd edn. Westport, CT: F.V. Kosikowski LLC. Law BA (2001) Cheddar cheese production. In: Tamime AY and Law BA (eds.) Mechanisation and Automation in Dairy Technology, pp. 204–224. Sheffield, UK: Sheffield Academic Press. Olson NF (1975) Mechanized and continuous cheesemaking processes for Cheddar and other ripened cheese. Journal of Dairy Science 58: 1015–1021. Park WJ (1970) Cheese mechanization. Journal of the Society of Dairy Technology 23: 205–210. Pointurier H and Law BA (2001) Soft fresh cheese and soft ripened cheese. In: Tamime AY and Law BA (eds.) Mechanisation and Automation in Dairy Technology, pp. 250–265. Sheffield, UK: Sheffield Academic Press. Robertson PS (1974) The New Zealand system of mechanized cheesemaking. New Zealand Journal of Dairy Science and Technology 9: 40–46. Robertson PS and Bysouth R (1971) The Cheddarmaster cheddaring tower. New Zealand Journal of Dairy Science and Technology 6: 187–189. Scott R, Robinson RK, and Wilbey RA (1998) Cheesemaking Practice, 3rd edn. Gaithersburg, MD: Aspen Publishers. van den Berg G (2001) Semi-hard cheeses. In: Tamime AY and Law BA (eds.) Mechanisation and Automation in Dairy Technology, pp. 225–249. Sheffield, UK: Sheffield Academic Press.
Introduction Cheese manufacture has been carried out for thousands of years and, for the most part, as a cottage industry. Toward the end of the nineteenth century, as industrialization progressed, cheese manufacture moved into the factory. Since then, there has been progressive development of the technology to the situation today, with large, highly automated plants employing minimal staff. A major component of this development can be described under the term cheese mechanization, which may be defined as a process where mechanical devices are used to carry out the manufacturing processes traditionally done manually. The major developments in cheese mechanization occurred during the period from the 1950s to the 1970s. The primary drivers of cheese mechanization include reduced manufacturing cost, elimination of laborious tasks, manufacturing efficiency, labor savings, increased capacity, and improvement in quality. Much of the early development work occurred in Australia and New Zealand, where major expansion of the cheese industry, in particular the manufacture of hard cheese varieties such as Cheddar, necessitated the development of novel approaches to equipment design. Most of this work was done under the auspices of the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia, the New Zealand Dairy Research Institute (NZDRI), and the New Zealand Dairy Board. Both the CSIRO and the NZDRI had research groups dedicated to this task. This article uses the developments associated with hard cheeses, in particular Cheddar, as its framework, with the focus on those developments that have survived. Consideration is then given to other cheese types and likely future directions.
Hard Cheeses – Cheddar Family The mechanization of Cheddar cheesemaking can be reviewed by considering, sequentially, the key steps in the process, using much the same approach as that taken by those undertaking the original mechanization of the cheesemaking process. The steps discussed include milk treatment, starter culture preparation, vat process, texturing (cheddaring), milling, salting,
pressing (block forming), and ripening (including packaging and storage). Milk Treatment Fat standardization of cheese milk has been used as a means of better controlling the composition of the final cheese for some time, but the more recent innovation in this area has been the standardization of the protein content of the cheese milk, especially where the milk composition tends to vary over a dairy season as is the case in New Zealand and Australia. New Zealand was one of the first dairying nations to use this approach to standardize its Cheddar cheese milk in the early 1990s. The protein in skimmed milk is concentrated in a separate retentate stream to a higher level than required and the concentrated skimmed milk is fed back into the whole milk to achieve a consistent proteinto-fat ratio and a consistent protein content of between 3.7 and 4%. Nonconcentrated skimmed milk can also be added if required. The advantages of protein standardization for cheesemaking include increased throughput, improved processing, improved product consistency, less whey handling, and a clean lactose permeate stream. Starter Culture Preparation Neutralization of the starter culture during the growth phase resulted in increased numbers of organisms per milliliter of culture, allowing the cheesemaker to reduce starter addition volumes and to save on bulk starter capacity. Introduced during the 1980s in New Zealand, the one-shot neutralization of mesophilic starter cultures with sodium hydroxide during bulk starter growth doubled starter numbers from 5 108 to 1 109 per milliliter. Once the pH of the starter culture had reached 4.8, a quantity of sodium hydroxide solution was added in one amount (one-shot) and was stirred in to return the pH to 6.7, allowing further starter growth before acid levels again became inhibitory. Later development of a multishot continuous system tripled starter numbers, allowing for a threefold reduction in the starter volume added to each vat. Other systems use internal pH-controlled media (buffered bulk starter media) to achieve a similar increase
607
608 Cheese | Mechanization of Cheesemaking
in starter numbers to that shown for one-shot neutralization.
Vat Process The traditional cheese vat consisted of a long, rectangular vessel of about 4500–10 000 l, in which all the operations up to pressing were carried out. Elimination of the backbreaking labor associated with these vats was one of the main drivers of mechanization. It was recognized early on that further development necessitated retention of the vat stage for the steps associated with primary curd formation and fermentation only. The remaining operations could be transferred to downstream equipment that had yet to be developed. The vat stage became concerned solely with the conversion of liquid milk into a coagulum, followed by cutting, stirring, and cooking, to produce a curd and whey mixture of the appropriate pH, moisture, and mineral composition, by the controlled activity of the starter cultures incorporated at the beginning of the process. The late 1960s saw the introduction of the enclosed vat. The majority of the enclosed vat systems available contain or two revolving knife panels of various designs • one that are used for both cutting and stirring operations,
• • •
depending on their direction of rotation, a fully surrounding or partially surrounding (steam or hot water) heating jacket, whey removal systems for predraw and in-vat curd washing, and automated rennet addition, cleaning-in-place (CIP), and computer-controlled options for cutting/stirring speeds and cooking recipes (later models only).
Another advantage of the fully enclosed cheese vat is the reduced risk of foreign matter and airborne microbiological contamination. The choice of equipment for the vat stage of the cheesemaking process depends on many external factors including type of cheese to be made, downstream curd processing, flexibility, cost, and throughput. Internal vat factors are also important, such as the configuration of the vat and its cutting and stirring mechanism, how the tank is heated and emptied, rennet addition, and CIP configurations. How the curd is cut is of particular significance. The cutting operation, together with the speed of stirring following cutting, influences how large the particles will be at draining and how much of the original milk components (fat and protein) is lost to the whey. A number of vat types are available, including OST, Damrow, Scherping, and APV CurdMaster; a number of cheese types are made using these systems, including Edam, Gouda, St. Paulin, Havarti, Cheddar, Emmental,
Romano, Monterey Jack, Egmont, Mozzarella, Danbo, Raclette, Tilsit, Blue, Feta, Maasdam, Cagliata, Provolone, Norvegia, Manchego, Camembert, Pecorino, Grana, Port Salut, and Parmesan. One of the first and most popular choices of enclosed cheesemaking vat was the Tetra Tebel OST vat. To date, five models have been produced, each model designed with and without predraw capability. Both the Alfa Laval OST I vat and the Alfa Laval OST II vat were upright, single silo-shaped tanks with one (OST I) or two or more (OST II) knife panels that were vertically mounted. The OST III vat was the first horizontally mounted vat of the OST series and its design was driven by a demand to process larger (>20 000 l) volumes of milk. The OST III vat design has been continued in OST IV and OST V models (Figure 1). The vertical Damrow vat was developed in 1972 and has had two updates since then. Easily recognized with its ‘double-O’ configuration, the vertical Damrow vat had two vertical knife arrangements that were used to both cut and stir the curd (Figure 2). The first dual-barreled horizontal cheese vat was developed by Scherping Systems in 1988. Of interest is the unique design of the vat’s ‘counter-rotation’, dual agitator, cutting and stirring system and the staggered design of the knife arrangement of the third generation model (Figure 3). The first APV CurdMaster was produced in 1993 and its design is based on the Protech CurdMaster and the Damrow Double-O vat. Texturing Development of equipment to replace the traditional invat cheddaring process presented one of the more challenging aspects of mechanization. A common device developed for dewheying prior to cheddaring was the static dewheying screen, followed by a short drying belt. Many ingenious devices were developed for texture development, including some that mimicked the process in the vat. However, the development of the cheddaring tower in New Zealand provided a revolutionary system for cheddaring that is still in use today (Figure 4). Another very significant development has been the use of belts for cheddaring, as demonstrated by the Damrow draining and matting conveyor two-belt system, developed in the United States, and the Alfomatic (Figure 5), developed in Australia by Alfa Laval (now Tetra Pak). In this system, the curd is allowed to fuse together on another belt and is then inverted as it drops on to a third belt for further cheddaring. Stretch is induced at the transfer. The belt cheddaring system has been widely adopted by other manufacturers such as APV (Figure 6) and Scherping. The belts are now plastic, rather than the original stainless steel, may be perforated, and may be
Cheese | Mechanization of Cheesemaking
609
Figure 1 OST IV cheese vat. 1, Combined cutting and stirring tools; 2, strainer for whey drainage; 3, frequency-controlled motor drive; 4, jacket for heating; 5, manhole; 6, CIP nozzle. Courtesy of Tetra Pak, Sweden.
Figure 2 Damrow Double-O cheese vat. Courtesy of Damrow Inc., USA.
610 Cheese | Mechanization of Cheesemaking
Figure 3 Scherping horizontal cheese vat. Courtesy of Scherping Systems, USA.
Figure 5 Alfomatic cheesemaker. 1, Curd/whey mixture inlet; 2, whey screen; 3, curd stirrer; 4, turnover chute; 5, chip mill; 6, dry salting feed; 7, salt mixing drum; 8, chips drawn to blockformer by vacuum. Courtesy of Tetra Pak, Sweden.
Figure 6 APV Cheddarmaster belt system. Courtesy of Fonterra Cooperative Group, New Zealand.
equipped with stirrers for curd agitation. Some plants, particularly in the United States, make Cheddar without ‘cheddaring’ and continuously dry stir the curd prior to salting.
Milling and Salting
Figure 4 APV cheddaring tower, with guillotine and mill at base. Courtesy of APV, UK.
The purpose of milling is to cut the cheddared curd into fingers (chips) of approximately 1.5 1.5 8 cm, to aid in salt uptake. Mechanical reciprocating chip mills were introduced in the earliest stages of mechanization for open vats and for equipment such as the Australian CheeseMaker 3. In contrast, the milling system developed for the New Zealand Cheddarmaster process consisted of a rotating cutting drum, which cut the curd in two directions at once using a blade and a cutting comb. Rotary
Cheese | Mechanization of Cheesemaking
mills using a similar principle but covering the width of the belt are now used at the end of the cheddaring belts on systems such as the Alfomatic and the Cheddarmaster. A number of techniques have been used to apply and mix dry, granular salt into the curd. The CheeseMaker 3 design incorporated what became known as the trommel salter, in which the milled curd passed over a weighing belt that discharged into a rotating conical mixing drum, with a metered flow of salt being deposited on to the curd as it entered the drum. The early Cheddarmaster design utilized a salting boom that moved backward and forward across the curd on the mellowing conveyor belt. The quantity of salt applied was proportional to the curd flow, determined by a sensing fork that measured the curd depth. Following salting, the curd passed along the mellowing conveyor where peg stirrers would aid salt uptake and moisture expulsion. Interestingly, the systems that have survived to be incorporated into modern plants consist of refined versions of the trommel design (Figure 7), as these give excellent control of the salt content in the final cheese.
Pressing It was recognized early on that the traditional pressing process using metal hoops or molds was very labor intensive. About half the labor force in New Zealand factories was used in this part of the process. Sophisticated systems have been developed to fully mechanize and automate the mold filling and pressing operations, such as the APV Sanipress, but, for dry-salted cheeses, these have been largely superseded by the development of the continuous block former described below. However, the early development of the large hoop system as part of the Cheddarmaster process deserves a mention. These vertical hoops were designed to hold
Figure 7 Trommel salting system. Courtesy of Fonterra Cooperative Group, New Zealand.
611
818 kg of curd. After pressing for approximately 10 h, including a vacuum stage, the large block of curd would be hydraulically pushed from the hoop through a special cutter head, producing 44 blocks of cheese (each 18.1 kg) per hoop. The labor saving with this system was significant, but one major problem with the long pressing time was the lack of curd cooling. Nonstarter lactic acid bacteria could grow to very high numbers during the overnight pressing and this could give rise to problems of flavor and gas production in the final cheese. However, barrels or large forms of cheese are still produced in the United States, normally for rapid use as ingredients in processed cheese. The introduction of Wincanton’s continuous block former in 1980–81 in New Zealand following a 17-year development reduced holding times from 24 h to 30 min and reduced and minimized the floor space and the labor force required to carry out the pressing and block-forming part of the process. Operating principles are shown in Figure 8. The modernization of the ‘hanging plate’ arrangement to a completely welded, perforated, rectangular-shaped, continuous inner skin and the extension of the tower to increase the capacity from 700 to 1600 kg are more recent innovations, shown in Figure 9.
Ripening or Curing (Including Packaging and Storage) The initial reel feed sheet systems for wrapping rindless cheese have now been replaced by laminated barrier bags, such as those provided by Cryovac. This company has also been involved in the development of bag presenters, which automatically place bags on the cheese blocks as they exit the block-forming towers. The bagged cheese blocks are transported through vacuum chambers, where they are heat sealed, and then placed in a carton base and conveyed to a rapid cooling tunnel. The carton format varies from base-only and box and lid to the most popular wraparound style. The cheese exiting the towers can be quite warm (30–33 C). The rapid cooling process reduces the average block temperature to between 16 and 20 C in 12–24 h. This solidifies the fat, firms the block, and, more importantly, dramatically reduces the growth potential of undesirable non-starter lactic acid bacteria, which can cause major problems of flavor and gas production. Fully automated, first-in/first-out, openstacked conveyor systems operating in blast chillers are used to achieve this cooling. An example is shown in Figure 10. Following this initial cooling, the cheese blocks are palletized by a robot and then transferred to controlledtemperature ripening and storage rooms. The operations,
612 Cheese | Mechanization of Cheesemaking
Figure 8 Blockformer operating principles. Courtesy of Tetra Pak, Sweden.
including cardboard packaging, are highly mechanized and automated, with minimal staff involvement.
Continuous Hard Cheese Process Any discussion of the mechanization of hard cheeses would be incomplete without mention of the pioneering work of the Australian CSIRO team, who came very close to the successful commercial development of a semicontinuous Cheddar (Sirocurd) process. This was based on ultrafiltration of the milk, the incorporation of whey proteins, and many ingenious inventions such as a barrel system for coagulation. Two commercial plants were commissioned but are no longer in operation.
Semihard Cheeses Developments associated with these cheese types, such as Gouda, Edam, and Tilsit, paralleled those for dry-salted varieties. Three manufacturing differences distinguish these varieties from hard cheeses such as Cheddar – whey drainage and curd washing in the vat, pressing of the curd under whey, and brine salting. Vat Process Similar vats to those developed for Cheddar varieties can be used. An additional feature incorporated into the Tetra Pak OST vat is a whey strainer that can be lowered into the vat, when stirring has been stopped, to remove part of the whey. The whey can then be replaced by hot water to wash the curd and reduce the lactose content.
Other Varieties
Pressing
The same issues of reduction in labor costs and manufacturing costs, increased throughput, and improvement in quality applied to other varieties and similar process developments were undertaken.
Post-vat manufacturing operation is quite different for these cheese types. It is necessary to separate the curd and whey without air incorporation, to allow for anaerobic fermentation during the ripening process. This is
Cheese | Mechanization of Cheesemaking
613
Figure 9 Details of Blockformer 6. Courtesy of Tetra Pak, Sweden.
achieved by first forming the curd into a block (prepressing), followed by further compression into a closely pressed block while further acidification occurs. Early attempts to mechanize the first part of this process resulted in the development of prepressing vats, a modern example of which is shown in Figure 11. In larger plants, the major type of equipment that is used is the Tetra Pak Casomatic (Figure 12). The curd and whey mixture in a 1:4 ratio is pumped to the top of the column, about 3 m in height. The curd settles below the whey to a height of about 2 m. The whey is removed via three whey drainage bands. A controlled rate of removal is essential for the formation of a block of curd at the base of the column. The curd block is formed in a dosing chamber and is then cut by guillotine and discharged into a mold to which a lid is fitted, enabling further pressing. Blocks of various shapes and sizes can be produced with minor modifications, and a multicolumn version is also available. The development of plastic microperforated molds such as the Laude mold (Figure 13) has been a major advance from the traditional wooden or metal cloth-lined molds.
Further pressing of the formed block is necessary to achieve the desired cheese properties and to allow ongoing acid development and whey drainage. Large table systems have been developed; the individual molds are conveyed on to tables that are fitted with individual hydraulic presses for each mold. The pressing regime is computer controlled, for example, 100 kPa for 20 min, followed by 200 kPa for 40 min. Following pressing, the blocks are discharged and the molds are washed and recycled. An example of this type of installation is shown in Figure 14. The APV Sanipress can also be used.
Salting Cheeses that have been formed into blocks under the whey cannot be salted prior to molding and pressing, as further acid development is required. For some varieties, dry salt may be applied to the cheese surface, but, for most, brining is the technique that is used. Brining essentially involves the immersion of the cheese block into a refrigerated brine bath (which also cools the cheese) for the required period
614 Cheese | Mechanization of Cheesemaking
required time, for example, 36 h for a 10 kg block, before unloading, drying, and wrapping. Ripening, Packaging, and Storage Highly mechanized systems have been developed for the material-handling aspects of these steps, including specialized cheese-turning equipment and the use of robots.
Soft Ripened Cheeses
Figure 10 Rapid cooling tunnel. Courtesy of Fonterra Cooperative Group, New Zealand.
to achieve the desired salt uptake. Highly automated systems have been developed, and these often involve the use of the brine solution as a conveyor system for the demolded cheeses, which float in the brine and are directed to a racking system in deep brine tanks that, once loaded, are submerged (Figure 15) for the
Many types of cheese fall into this category, such as Camembert, Brie, and Blue. Their manufacture is characterized by a high rate of syneresis and acid development, followed immediately by molding of the curd to the various final cheese shapes, under gravity, as the whey is drained from the curd. Hence, large-scale vat production is not desirable as the cheeses produced at the start and end of emptying would be quite different, due to composition and pH changes, and consistency of mold filling would be impossible. There have been various attempts to automate and mechanize curd production using a series of mini-vats, followed by automated mold filling and handling. Systems have been developed by companies such as Tecnal and Servi Doryl in France and APV in the United Kingdom, whose Contifiller system is shown in Figure 16. The multimolds used to form the cheese may be in two sections to provide sufficient volume for the initial fill, with the upper layer being removed later. The filled molds can be stacked automatically, conveyed to ripening rooms, turned frequently as required to ensure even block production, brine salted (or surface dry salted), and then conveyed to ripening rooms for mold development.
Figure 11 Prepressing vat. 1, Prepressing vat; 2, curd distributors, or CIP nozzle (2A); 3, unloading device; 4, conveyor. Courtesy of Tetra Pak, Sweden.
Cheese | Mechanization of Cheesemaking
615
Figure 14 Conveyor pressing system, with Casomatics in the foreground. Courtesy of Fonterra Cooperative Group, New Zealand.
Figure 12 Casomatic operating principles. 1, Curd/whey mixture inlet; 2, column with sight glass; 3, perforated whey discharge; 4, interceptor; 5, whey balance tank; 6, cutting and discharge system; 7, mold; 8, pawl conveyor; 9, whey collecting chute.
Figure 15 Deep brining system. Courtesy of Fonterra Cooperative Group, New Zealand.
The same processes of coagulation, cutting, and stirring occur as the mini-vats move along, by the use of tools that are placed alongside the belt. The curd/whey mixture discharges into molds at the end of the belt.
Soft Fresh Cheeses
Figure 13 Laude block mold. Courtesy of Laude bv, The Netherlands.
A very successful process that comes close to a continuous vat stage has been developed by Alpma in Germany. The basis of this system is a continuous flexible belt, which is formed into a trough to hold the milk. The trough is then subdivided into a series of mini-vats by a series of semicircular plates that also move with the belt.
Cottage cheese consists of curd particles that are packed into a container with the appropriate dressing. Specialized equipment, such as the O-Vat from Tetra Pak, has been developed to mechanize and automate production of this popular product. Quark uses a very different process of mechanization, in which the curd is formed in special ripening vats, followed by whey separation using a specially designed centrifugal separator. The product is then blended with components such as cream and is filled directly into the final container.
616 Cheese | Mechanization of Cheesemaking
Figure 16 Process line for soft cheese with Contifiller. 1, Curdmaking; 2, curd draining and filling; 3, stacking of mold batteries (A) and trays (B); 4, turning of mold stacks; 5, acidification lines; 6, destacking; 7, transfer/turning of cheese from mold batteries to trays; 8, transport to climate room (A) and from brining (B); 9, turning/emptying; 10, washing of mold batteries (A) and trays (B). Courtesy of APV, UK.
Pasta Filata cheeses are cheeses for which the curd has been worked or stretched and molded at elevated temperatures before cooling. This process imparts a unique and characteristic fibrous structure that influences both the ripening and the functional profile of the final cheese. Mozzarella is probably the best known of the Pasta Filata cheeses, which are mainly Italian in origin. However, the category also includes such cheeses as Provolone, Scamorza, Caciocavallo, Kashkaval, and Pizza Cheese. Equipment designed to perform the stretching operation incorporates two essential components: cooking and stretching. Stretching describes the mechanical treatment of the curd following cooking. Cooking is the phase in which the Pasta Filata curd is transferred to the hot water section of a cooker/stretcher. At this point, the curd is immersed, heated, and worked by single- or twin-screw augers. Typical water temperatures vary between 60 and 75 C, with cooked curd temperatures varying between 55 and 65 C.
Future Trends The mechanization of the cheesemaking process was the result of an intense amount of activity and development during the 1960s and 1970s. The latter half of the twentieth century saw the refinement of that development – the implementation of specific processes that enhanced
the overall mechanized approach – and these advances guaranteed a more consistent, higher quality, cleaner, and more cost-effective product. Although automation has led to reduced labor costs, improved efficiencies, and higher yields, it has also allowed for greater flexibility in what the plant produces and the ability to store and process large volumes of data that can be used to trend specific characteristics, for example, variability in drain pH, monitoring coagulation devices, temperature and pressure monitoring, and yield data analysis. Rapid and sophisticated in-process analysis techniques, both in-line and at-line, have been developed based on spectrophotometric analyses such as the absorption of infrared energy at specific wavelengths (MilkoScan, FoodScan). The integration of these techniques and the rapid analysis of the data that they can provide have led to almost instant feedback on parameters such as fat, moisture, and salt contents. Calcium contents can now be determined using X-ray fluorescence. Concurrent with the continued development in this area, recent published literature and patent applications would suggest that the next steps in the evolution of cheesemaking in the twenty-first century will be the development of completely new ways of making cheese, together with the continued refinement of the traditional processes that have been seen to date.
Cheese | Mechanization of Cheesemaking
Driven by the same needs that drove the initial mechanization of the traditional processes, these ‘alternative cheesemaking concepts’ will become more common. As an example, in February 2008, the New Zealand dairy industry commercialized a Mozzarella process that is an alternative approach to traditional Mozzarella manufacture. Unique to New Zealand, this process produces a functionally acceptable product directly off the line in a shredded format in less time than the traditional process and at a lower cost. This new process takes a number of ingredients derived from milk and blends and works them in a lowshear environment at an elevated temperature to produce a homogeneous mass that is cooled, shredded, and the shred then chilled or individually quick frozen. It involves processes and equipment that are used in other milk processing operations but have not, to date, been used to make Mozzarella.
Acknowledgments The authors are grateful to Tetra Pak AB, Sweden, specifically Bryce Griffiths (New Zealand), for information supplied and for permission to use illustrations from the Dairy Processing Handbook and other sales literature. The following are also gratefully thanked for the supply and use of technical sales information: APV, UK, Damrow Inc., USA, Laude bv, The Netherlands, Scherping Systems, USA, Stainless Steel Fabricating, Inc., USA. Permission to use photographs from numerous Fonterra sites within New Zealand is gratefully acknowledged, as are the insightful discussions held with Alister Barclay and Craig Honore, Fonterra Co-operative Group. See also: Cheese: Blue Mold Cheese; Camembert, Brie, and Related Varieties; Dutch-Type Cheeses; Hard Italian Cheeses; Membrane Processing in Cheese Manufacture;
617
Pasta-Filata Cheeses: Low-Moisture Part-Skim Mozzarella (Pizza Cheese); Pasta-Filata Cheeses: Traditional Pasta-Filata Cheese; Preparation of Cheese Milk; Raw Milk Cheeses; Salting of Cheese; Secondary Cultures; Starter Cultures: General Aspects; Swiss-Type Cheeses.
Further Reading Bennett RJ and Johnston KA (2004) General aspects of cheese technology. In: Fox PF, McSweeney PLH, Cogan TM, and Guinee TP (eds.) Cheese: Chemistry, Physics and Microbiology, Vol. 2: Major Cheese Groups, 3rd edn., pp. 23–50. London: Elsevier. Bylund G (1995) Dairy Processing Handbook. Lund, Sweden: Tetra Pak Processing Systems. Crawford RJM (1976) Developments in mechanized cheesemaking in the United Kingdom, 1972–1975. Journal of the Society of Dairy Technology 29: 71–85. Jameson GW (1987) Manufacture of Cheddar cheese from milk concentrated by ultrafiltration: The development and evaluation of a process. Food Technology Australia 39: 560–564. Kosikowski FV and Mistry VV (1997) Cheese and Fermented Milk Foods, Vol. 1: Origins and Principles, 3rd edn. Westport, CT: F.V. Kosikowski LLC. Law BA (2001) Cheddar cheese production. In: Tamime AY and Law BA (eds.) Mechanisation and Automation in Dairy Technology, pp. 204–224. Sheffield, UK: Sheffield Academic Press. Olson NF (1975) Mechanized and continuous cheesemaking processes for Cheddar and other ripened cheese. Journal of Dairy Science 58: 1015–1021. Park WJ (1970) Cheese mechanization. Journal of the Society of Dairy Technology 23: 205–210. Pointurier H and Law BA (2001) Soft fresh cheese and soft ripened cheese. In: Tamime AY and Law BA (eds.) Mechanisation and Automation in Dairy Technology, pp. 250–265. Sheffield, UK: Sheffield Academic Press. Robertson PS (1974) The New Zealand system of mechanized cheesemaking. New Zealand Journal of Dairy Science and Technology 9: 40–46. Robertson PS and Bysouth R (1971) The Cheddarmaster cheddaring tower. New Zealand Journal of Dairy Science and Technology 6: 187–189. Scott R, Robinson RK, and Wilbey RA (1998) Cheesemaking Practice, 3rd edn. Gaithersburg, MD: Aspen Publishers. van den Berg G (2001) Semi-hard cheeses. In: Tamime AY and Law BA (eds.) Mechanisation and Automation in Dairy Technology, pp. 225–249. Sheffield, UK: Sheffield Academic Press.