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Cheese: Chemistry, Physics and Microbiology 4th Edition



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Author: Paul L. H. McSweeney, Patrick F. Fox

Publisher: Academic Press

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Publish Date: October 9, 2017

ISBN-10: 124170129

Pages: 1302

File Type: PDF

Language: English

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Book Preface

Since its first publication in 1987, Cheese: Chemistry, Physics, and Microbiology has become established as the leading text in cheese science which gives the in-depth coverage needed by graduate students, researchers and industry personnel working in the subject. Since the publication of the third edition of this book in 2004, research on cheese science continues to be active and investigators have developed a substantial corpus of literature, which is summarised in these volumes. In recent years, our understanding of the factors affecting texture, cheese microbiota and the science and technology of local varieties has expanded greatly. The fourth edition of this book retains the two-volume layout of the earlier editions. The first volume, which covers basic aspects of cheese science, retains a number of chapters, which are considerably updated, often by new authors and also new chapters on milk for cheesemaking and cheese microbiota are included. Coverage of rennet coagulation and syneresis is completely revised by new authors while the chapters on cheese ripening have been updated. The second volume (Major Cheese Groups) retains the structure of the previous editions but is expanded to 22 chapters with new chapters on cheese legislation and low-fat cheese while the revised and updated chapters on membrane technology and factors affecting cheese quality are moved to this volume. We wish sincerely to thank the many authors who contributed to the 46 chapters in the two volumes of this book and whose cooperation made our task as editors a pleasure.
Paul L.H. McSweeney Patrick F. Fox Paul D. Cotter David W. Everett

 

Cheese is the generic name for a group of fermented milkbased food products, produced in a wide range of flavors and forms throughout the world. Although the primary objective of cheesemaking is to conserve the principal constituents of milk, cheese has evolved to become a food of haute cuisine with epicurean qualities, as well as being highly nutritious. Sandine and Elliker (1970) suggested that there are more than 1000 varieties of cheese. Walter and Hargrove (1972) described more than 400 varieties and listed the names of a further 400, while Burkhalter (1981) classified 510 varieties (although some are listed more than once). As discussed in detail in Chapter 31, a number of attempts have been made to classify cheese varieties into meaningful groups. The most common criterion for the classification is texture (very hard, hard, semihard, semisoft, soft), which is related mainly to the moisture content of the cheese. Various attempts have been made to improve on this basis of classification, for example, by including the milk-producing species, moisture to protein ratio, method of coagulation, cooking temperature, microbiota. These classification schemes are discussed in Chapter 26. However, no classification scheme developed to date is completely satisfactory; the inclusion of chemical indices of ripening would be useful. It is commonly believed that cheese evolved in a region known as the “Fertile Crescent,” that is, starting from the Tigris and Euphrates rivers, through what is now southern Turkey to the Mediterranean coast, some 8000 years ago. The so-called “Agricultural Revolution” occurred in this region with the domestication of plants and animals. Presumably, humans soon recognized the nutritive value of milk produced by domesticated animals and contrived to share the mother’s milk with her offspring. Apparently, goats and sheep, which are gregarious and docile, were the first dairy animals domesticated, but cattle have become the dominant dairy species in most parts of the world (c. 85% of the total world supply of milk is obtained from cattle, mainly Bos taurus). Milk is also a rich source of nutrients for bacteria, which contaminate the milk, some species of which utilize milk sugar, lactose, as a source of energy, producing lactic acid.

Bacterial growth and acid production would have occurred during storage or during attempts to dry milk in the prevailing warm, dry climate to produce a more stable product— air-drying of meat, fruits, and vegetables appears to have been practiced as a primitive form of food preservation at this period. When sufficient acid has been produced, the principal proteins of milk, the caseins, coagulate, that is, at their isoelectric points—pH 4.6, to form a gel in which the fat is entrapped. The rate of acidification by the adventitious microbiota is usually slow, allowing the (unhomogenized) fat globules to form a cream layer. This layer of sour cream could be blended into the lower gelled layer or scooped off for the production of butter. Thus originated three of our classical fermented dairy products: fermented milks, sour cream, and lactic butter, all of which are still produced widely, sometimes depending on the adventitious microbiota for acidification, but now usually through the growth of cultures of lactic acid bacteria. The first fermented dairy foods were produced by a fortuitous combination of events—the ability of a group of bacteria, the lactic acid bacteria (LAB), to grow in milk, and to produce enough acid to reduce the pH of milk to the isoelectric point of the caseins, at which these proteins coagulate. Neither LAB nor the caseins were designed for this outcome. The caseins were “designed” to coagulate following limited proteolysis in the stomach of neonatal mammals, the gastric pH of which is around 6, that is, very much higher than the isoelectric point of the caseins. The ability of Lactococcus lactis to ferment lactose, a sugar specific to milk, is plasmid-encoded, suggesting that this characteristic was acquired relatively recently in the evolution of these bacteria. The natural habitats of LAB are vegetation and/ or the intestine, from which they presumably colonized the teats of dairy animals, contaminated with lactose-containing milk; it is likely that through evolutionary pressure, these bacteria acquired the ability to ferment lactose. When an acid-coagulated milk gel is broken, for example, accidentally by movement of the storage vessel or intentionally by breaking or cutting, it separates into curds and whey. It was probably soon realized that the acid whey is a pleasant, refreshing drink for immediate consumption while the curds could be consumed fresh or stored for future use. In fact, whey was long considered to have medicinal benefits (Hoffmann, 1761). It was probably soon realized that the shelf-life of the curds could be extended by dehydration and/or by adding salt; heavily salted cheese varieties are still widespread throughout the Middle-East and small quantities of a number of dehydrated cheeses are produced in North Africa and the Middle East, for example, Tikammart and Aoules (Algeria), Djamid (Jordan), Ekt (Saudi Arabia), and Madraffarah (Syria) (Phelan et al., 1993). It is presumed that one of the principal families of cheese, the acid cheeses, modern members of which include Cottage cheese, Cream cheese, and Quarg, originated in this way. While lactic acid, produced in situ, is believed to have been the original milk coagulant, an alternative mechanism was also recognized from an early date. Many proteolytic enzymes can modify the casein system in milk, causing it to coagulate under certain circumstances. Enzymes capable of causing this transformation are widespread in nature, for example, bacteria, moulds, plant, and animal tissues, but an obvious source would have been animal stomachs. It was probably observed that the stomach of young mammals after its death contained curds, especially if the animals had suckled shortly before slaughter; curds would also have been observed in the vomitus of human infants. Before the development of pottery (5000 BC), storage of milk in bags made from animal skins was probably common (as it still is in many countries). Stomachs of slaughtered animals provided ready-made, easily sealed containers; under such circumstances, milk would extract enzymes (chymosin and some pepsin) from the stomach tissue, leading to its coagulation during storage. The properties of rennet-coagulated curds are very different from those produced by isoelectric (acid) precipitation, for example, they have better syneretic properties which makes it possible to produce low-moisture cheese curd without hardening. Rennet-coagulated curds can, therefore, be converted to a more stable product than acid curds and rennet coagulation has become predominant in cheese manufacture, being exploited for c. 75% of total world production. Although animal rennets were used from early times, rennets produced from a range of plant species, for example, fig and thistle, also appear to have been common in ancient times. However, plant rennets are not suitable for the manufacture of long-ripened cheese varieties and gastric proteinases from young animals became the standard rennets until a shortage of supply made it necessary to introduce “rennet substitutes.” While the coagulation of milk by the in situ production of lactic acid was, presumably, accidental, the use of rennets to coagulate milk was intentional. It was, in fact, quite an
ingenious invention—if the conversion of milk to cheese by the use of rennets was discovered today, it would be hailed as a major biotechnological discovery! The advantages accruing from the ability to convert the principal constituents of milk to cheese would have been apparent from the viewpoints of storage stability, ease of transport and, presumably, as a means of diversifying the human diet, and cheese manufacture became well established in the ancient civilizations of the Middle-East, Egypt, Greece, and Rome. There are numerous references to cheese and other foods in the Bible (MacAlister, 1904). Milk and dairy products formed an important part of the diet of peoples of the Near East during Biblical times; indeed Palestine was “a land flowing with milk and honey” (Exodus, 3.8). Animals herded during Biblical times for milk production included goats (e.g., Proverbs 27.27), sheep (e.g., Deuteronomy 14.4), and possibly camels (Genesis 32.15). Bovine milk is rarely specified in the Old Testament, presumably because of the unsuitability of the terrain of the Holy Land for cow pasture; ancient cattle were larger and less docile than modern breeds. In addition to milk, other foods of dairy origin mentioned in the Bible include curds (perhaps fermented milk: Genesis 18.8; Isaiah 7.22) and butter (Psalms 55.21). There are several clear references in the Old Testament to cheese, for example, Job (1520 BC, where Job remarks to God “did Thou not pour me out like milk and curdle me like cheese”; Job 10.10) and Samuel (1170–1017 BC; as a delicacy sent by Jesse to his sons (I Samuel 17.18) and as a gift presented to David (II Samuel 17.29)). Cheese is represented in the tomb art of Ancient Egypt and in Greek literature. Vegetable rennets are mentioned by Homer (c. 8th century BC) who implies the use of fig rennet in the Iliad (“… as when fig juice is added to white milk and rapidly coagulates, and the milk quickly curdles as it is stirred, so speedy was his healing of raging Ares.” Iliad 5) and describes the Cyclops, Polyphemus, making ewes’ milk cheese in the Odyssey (Book 9) using “well-made dairy vessels” and “pails swimming with whey.” Other Greek authors who mentioned cheese include the Father of History, Herodotus (484–408 BC), who referred to “Scythian cheese” and the philosopher, Aristotle (384–322 BC), who noted that “Phrygian” cheese was made from the milk of mares and asses. Apparently, cheese was prescribed in the diet for Spartan wrestlers in training. Cheese manufacture was well established in the Roman Empire and was a standard item in the rations issued to Roman soldiers (28 g/day). Cheese must have been popular with Roman civilians also and demand exceeded supply, forcing an emperor, Diocletian (284–305 AD), to fix a maximum price for cheese. Many Roman writers, for example, Cato the Elder (234–149 BC), Varro (c 116–27 BC), Columella (AD 4–70), Pliny the Elder (AD 23–79) and Palladius (AD 400–470), described cheese manufacture and quality and the culinary uses of cheese. Pliny the Elder (23–79 AD) mentioned cheese in his encyclopedia, Historia Naturalis (Book 28) and described its uses in the diet and in medicinal applications. Varro (c. 116–27 BC; De Agricultura 2.3–2.6) distinguished between “soft and new cheese” and that which is “old and dry” and described the Roman cheesemaking season in the spring and summer. Varro briefly described cheese manufacture: to about 2 congii (c. 5.7 L) of milk was added a piece of rennet from the hare or kid (in preference to that from the lamb). Varro described the quantity of rennet to be added as “the size of an olive,” implying that the rennet was solid, perhaps a piece of stomach tissue. Fig latex and vinegar were mentioned by Varro as alternative rennets and vinegar is also mentioned as a means for coagulating milk (as practiced today in the manufacture of some forms of Queso Blanco and Ricotta). The most complete ancient description of cheesemaking is that of Lucius Junius Moderatus Columella, a Roman soldier and author from Gades (modern Cadiz), in his treatise on agriculture, De Re Rustica (c. AD 50). A manufacturing procedure for Roman cheese, based on the description of Columella, is given in Fig. 1.1, which includes many observations and practices recognizable by modern cheesemakers. He recommended that the (raw) milk be held at “some degree of heat” but warns against over-heating by placing the pail on the flames of a fire. Columella distinguished between cheese with a “thin consistency” (soft) which must be sold quickly “while it is still fresh and retains its moisture” and that with a “rich and thick consistency” (hard) which may be held for a long period. Since the concept of pH and the existence of bacteria were unknown in antiquity, no mention is made of starter; the cheese curd was acidified using the adventitious microbiota of the raw milk. However, Columella did discuss different types of rennet in some detail. He recommended coagulation using rennet from lamb or kid but states that milk can also be coagulated using flowers of certain thistles (perhaps Cynara cardunculus), seeds of the safflower (Carthamus tinctorius), or sap from the fig tree. Interestingly, Columella recommended that the smallest amount of rennet possible should be used to ensure high quality cheese. This may be related to the excessive proteolytic activity of plant proteinases used as rennets, which often produce bitter cheese. Whey drainage was through wicker baskets, perhaps analogous to the drainage of whey through moulds in the manufacture of certain soft cheeses (e.g., Camembert). No mention was made by Columella of cooking the curds/whey mixture prior to whey drainage; moisture control seems to have been by pressing the curds during whey drainage or pressing the cheese after salting. Salting was by means of the repeated application of dry salt to the cheese surface (which is still practiced, e.g., in the manufacture of Blue cheese), which encouraged
further loss of moisture (acid liquid). However, Columella also mentioned brine salting as a method of “hardening” cheese. The cheeses were washed with water, allowed to form a rind and placed on shelves in an enclosed place “so that the cheese may remain more tender.” Interestingly, the comparative form of the adjective used in the Latin text (tenerior) can also be translated as “more soft”; if this is the intended meaning, it is the first recorded mention of the changes which occur in cheese during ripening. Columella also discussed defects which may occur in cheese, including being “full of holes” (mechanical openings, as the remedy recommended is increased pressing), too salty or too dry. According to Columella, cheeses were flavored with herbs and colored with smoke, practices which persist to a certain extent today. He also described briefly the manufacture of “hand-pressed” (manu pressum) cheese in which the
hot water is poured over the curds which are then shaped by hand, a practice perhaps related to the kneading and stretching steps for pasta filata varieties. Thus, cheesemaking practice appears to have changed little from the time of Columella until the 19th century! In his work, Opus Agriculturae, Palladius provided a brief description of cheesemaking, generally similar to, but less detailed, Columella, with whose work he was familiar. Kindstedt (2012) traces the development and spread of cheese throughout the Middle East and into Europe: Mesopotamia (6000–4000 BC), Egypt (about 5000 BC), Indus valley (from 3000 BC), Hittite Empire in Anatolia (from 2000 BC), Minoan civilization, Crete (from 2000 BC), Mycenaean civilization, Greek mainland (from about 1500 BC) and into Europe. In many of these civilizations, cheese and butter were high-value products, given as gifts to the Gods, for example, the Goddess, Inana, the Goddess of fertility and erotic love in the Mesopotamian city-state of Uruk. The great migrations of peoples throughout Europe immediately before and after the fall of the Western Roman Empire must have promoted the further spread of cheese manufacture, as did the Crusaders and other pilgrims of the Middle Ages. Probably, the most important agents contributing to the development of cheese “technology” and to the evolution of cheese varieties were monasteries, the manor and feudal estates. The role of the manor farms and estates and their break-up, are described by Kindstedt (2012). In addition to their roles in the spread of Christianity and in the preservation and expansion of knowledge during the Dark Ages, the monasteries made considerable contributions to the advancement of agriculture in Europe and to the development and improvement of food commodities, notably wine, beer, and cheese. Many of our current well-known cheese varieties were developed in monasteries, for example, Wenslydale (Rievaulx Abbey, Yorkshire), Port du Salut or Saint Paulin (Monastery de Notre Dame du Port du Salut, Laval, France), Fromage de Tamie (Abbey of Tamie Lac d’Annecy, Geneva), Maroilles (Abbey Moroilles, Avesnes, France), and Trappist (Maria Stern Monastery, Banja Luka, Bosnia). The inter-monastery movement of monks would have contributed to the spread of cheese varieties and probably to the development of new hybrid varieties. The great feudal estates of the Middle Ages were selfcontained communities. The conservation of surplus food produced in summer for use during winter was a major activity on such estates and undoubtedly cheese represented one of the more important of these conserved products, along with cereals, dried and salted meats, dried fruits, dried and fermented vegetables, beer, and wine. Cheese probably represented an item of trade when amounts surplus to local requirements were available. Within these estates, individuals acquired special skills, which were passed on to succeeding generations. The feudal estates evolved into villages and some into larger communities. Because monasteries
and feudal estates were essentially self-contained communities, it is apparent how several hundred distinct varieties of cheese evolved from essentially the same raw material, milk, or rennet-coagulated curds, especially under conditions of limited communication. Traditionally, many cheese varieties were produced in quite limited geographical regions, especially in mountainous areas, where communities are isolated. The localized production of certain varieties is still apparent and indeed is preserved for those varieties with protected designations of origin. Regionalization of certain cheese varieties is particularly marked in Spain, Portugal, and Italy, where the production of many varieties is restricted to a very limited region. Almost certainly, most cheese varieties evolved by accident because of a particular set of local circumstances, for example, a peculiarity of the local milk supply, either with respect to chemical composition or microbiota, an “accident” during storage of the cheese, for example, growth of mould or other microorganisms. Presumably, those accidents that led to desirable changes in the quality of the cheese were incorporated into the manufacturing protocol; each variety thus underwent a series of evolutionary changes and refinements. The final chapter in the spread of cheese throughout the world resulted from the colonization of North and South America, Oceania, and Africa by European settlers who carried their cheesemaking skills with them. Cheese has become an item of major economic importance in some of these “new” countries, notably the United States, Canada, Australia, and New Zealand, but the varieties produced are mainly of European origin, modified in some cases to meet local requirements. Cheese was not manufactured in these regions before colonization by Europeans; in fact, there were no cattle, sheep, or goats in Australia, North or South America and there were no mammals in New Zealand before the arrival of the Europeans. For further information on the history of cheese, the reader is referred to Cheke (1959), Davis (1965), Kindstedt (2012), Kosikowski (1977), Kosikowski and Mistry (1997), Robinson and Wilbey (1998), Scott (1986), and Squire (1937). For references on Roman agriculture, see White (1970). Cheesemaking remained an art rather than a science until relatively recently. With the gradual acquisition of knowledge on the chemistry and microbiology of milk and cheese, it became possible to direct the changes involved in cheesemaking in a more controlled fashion. Although few new varieties have evolved as a result of this improved knowledge, the existing varieties have become better defined and their quality more consistent. Considering the long history of cheesemaking, one might be inclined to the idea that what have come to be regarded, as standard varieties have been so for a long time. However, although the names of many current varieties were introduced several hundred years ago (Table 1.1), hese cheeses were not standardized; for example, the first attempt to standardize the well-known English varieties, Cheddar and Cheshire, was made by Joseph Harding in the mid-nineteenth century. Prior to that, “Cheddar cheese” was that produced in a particular area in England around the village of Cheddar, Somerset, and probably varied considerably depending on the manufacturer and other factors. Cheese manufacture was a farmstead enterprise until the mid-nineteenth century—the first cheese factory in the US was established near Rome, NY, in 1851 and the first in Britain at Langford, Derbyshire, in 1870. Thus, there were thousands of cheese manufacturers and there must have been great variation within any one general type. This situation persists in a modified form today in Switzerland and Italy where there are a large number of small cheese factories, often grouped together into consortia for the purposes of marketing and quality control. When one considers the very considerable inter-factory, and indeed intra-factory, variations in quality and characteristics which occur today in well-defined varieties, for example, Cheddar, in spite of the very considerable scientific and technological advances, one can readily appreciate the variations that must have existed in earlier times.


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