Search

Low-cost electronic noses, i.e. arrays of non-specific gas sensors, have many applications for quality assessment in the food production, storage and retail industries. Classifying properties of natural products by analysing their volatile organic compound (VOC) patterns allows fraudulent and mis-represented goods to be identified and removed, before they enter the consumer market. Early results from a small study performed on olive oils demonstrate that a low cost electronic nose device based on an array of MQ-series SnO2 gas sensors has the potential to correctly classify differing qualities of olive oils, with accuracies in the range 67–77%. Results confirm that use of sinusoidally varying heater voltage cycles on some MQ sensors improves their sensitivity, selectivity and susceptibility to drift. By using discrete Fourier transform analysis of the sensor responses, the unit discriminates between virgin/extra virgin and blended/chemically extracted pomace oils with prediction accuracies in the range 88–91%. There is also evidence that, with refinement, the unit may be capable of distinguishing among certain olive varieties. The unit can be assembled for around 30 euro.

Milk and dairy products are inextricably linked with enzymes; the involvement of enzymes falls into six main areas: 1. Biosynthesis of milk constituents in the mammary gland; 2. Indigenous enzymes in milk, i.e., enzymes which enter milk from mammary tissue, including somatic cells, or the blood; 3. Endogenous enzymes, i.e., enzymes secreted in milk or dairy products by contaminating microorganisms or microorganisms added as cultures; 4. Exogenous enzymes, i.e., enzymes added to milk or dairy products to induce specific changes, 5. Use as analytical agents, which are very sensitive and which avoid the need to purify the target substrate; 6. Enzymes involved in the catabolism of the constituents of milk or dairy products. Aspects 1 and 6 are considered to be outside the scope of this book. In addition, one of the principal proteins in milk, α-lactalbumin, is an enzyme modifier, involved in the biosynthesis of the milk sugar, lactose, but will not be considered. Aspects 2, 3, 4 and 5 will be considered briefly to provide an introduction to the chapters that follow.

The creaming properties of human milk have not been widely studied to date, and a mechanism for this phenomenon is not known. Here, the natural creaming of human milk, as affected by temperature and pre-treatments, was studied using dynamic light-scattering. The creaming rate of human milk increased with temperature in the range 5 °C–40 °C. Freezing human milk at −20 °C and thawing at room temperature had little influence on creaming. Compared with bovine milk, human milk showed a faster creaming rate at 40 °C, but a slower rate at 5 °C, suggesting a lack of cold agglutination; the mechanisms of creaming were also shown to differ in response to heat treatment. This study expands the current knowledge on milk creaming, and may have potential application to storage and handling of human milk in hospitals or homes, therefore supporting optimal nutrition of infants.

Proteins represent one of milk's macroconstituents (along with water, lipids, and carbohydrates), accounting for ~ 3.0%–3.5% of the total composition. In bovine milk, there are two main protein families, namely, casein and whey protein. Caseins are milk-specific proteins that exist as colloidal aggregates dispersed in milk serum. The bovine milk protein system is casein dominant, which enables large quantities of calcium to be delivered to the neonate. The natural function of milk is to supply the neonate of the species with its complete nutritional requirements for a period of time postpartum. Milk proteins (and their peptides) provide essential amino acids and amino groups for the biosynthesis of nonessential amino acids and, when in excess, also supply energy. They also provide many of milk's physiological functions, performed by immunoglobulins, enzymes, enzyme inhibitors, growth factors, hormones, and antibacterial agents. The development of advanced fractionation and processing techniques has led to the production of many milk-derived ingredients that have different functional properties and applications.

Background Cheeses are inherently microbiologically and biochemically dynamic. Numerous biotic and abiotic drivers govern the establishment and assembly of a core microbiota in cheese, which, for internally-ripened cheeses, having an intermediate to long period of ripening, consists of starter and non-starter lactic acid bacteria (SLAB and NSLAB). The management of this dynamic ecosystem has to consider this core as a super-organism, which results from the sums of microbial metabolisms and interactions among individual microbes. Scope and approach This review focuses on all presumptive drivers, raw and pasteurized milk, farming system and house microbiota, and intrinsic and extrinsic factors during cheese manufacture and ripening, which qualitatively and mainly depending on the farm management system and cheese variety may influence the populations of SLAB and NSLAB. The interactions between these two microbial groups are described also. Key findings and conclusions The cheese ecosystem shows a variable flux of its core microbiota from milking through manufacture to ripening. Many and diverse drivers establish and assembly the lactic acid bacteria biota. If such drivers are efficient to guarantee microbial and cheese diversities, on the other hand, their control is the fundamental pre-requisite to synchronize and balance microbiological events. The methodological approaches (e.g., omics techniques and integrated system biology) have markedly improved to concretize this ambitious goal. Facing and improving the knowledge on the main drivers, the current step should focus on a unique puzzle of coexisting species/biotypes likely a super-organism, whose guide has to consider all casehardened microbial elements.

In bovine milk, and the milk from most other species, the caseins represent family of 4 gene products (αs1-, αs2-, β-, and κ-casein) and exhibit significant microheterogeneity due to genetic variation and posttranslational glycosylation and phosphorylation. In milk, the caseins are found predominantly in association colloids called casein micelles, which include micellar calcium phosphate that contributes to the integrity and stability of the micelles. Enzymatic destabilization of casein micelles or adjustment to their isoelectric point (pH 4.6) can result in coagulation or gelation; this is the principle by which cheese or yogurt are produced. In addition, the size of micelles allows their ready recovery from milk using membrane filtration, and caseins, collectively or individually purified, are widely used as ingredients in a wide range of food applications. In this chapter, the properties of the individual caseins, the casein micelles, and properties and applications thereof are reviewed.

Starting from a limited range of raw materials (bovine, ewe, goat, or water buffalo milk, starter cultures, coagulant—rennet or acid—and salt), a large number (perhaps 1500) of cheese varieties are produced. In order to facilitate their study and to help consumers, retailers, and cheese technologists, a number of attempts have been made to classify cheese varieties into meaningful groups or families. Overall, criteria for classification include dairy species, coagulating agent (rennet or acid), texture/moisture content, matured or fresh, and microbiota (internal bacterial, surface/smear bacterial, internal or surface mold, propionic acid bacteria).

In the 1980s, the French historian Michel Aymard (1983) highlighted how cheese was the poor relation in the extensive history of Medieval and Modern European food and farming. Aymard’s observation may also readily be applied to the Italian context. According to Aymard, cheese was studied as a substitute or complementary food. It had a somewhat marginal role, not at all considered in itself worthy of attention.

As described in Chaps. 1 and 2, Italy has a long tradition and cultural heritage on cheeses. Based on the most widespread, official and nonofficial, catalogues and atlas, Italy has documented about 400–450 varieties of cheeses (Assolatte 2016; Atlante Qualivita 2013; Mucchetti and Neviani 2006; Ottogalli 2001). This number of cheeses is certainly incomplete because of the many local varieties that escape any form of cataloguing. A country with such a large tradition and diversity has undoubtedly a cultural/technical heritage and some distinguishing features for cheese manufacture, which deserve worldwide knowledge. This chapter focuses on the main distinguishing traits that characterize the Italian cheese heritage.

More than 80% of 13.65 million tonnes of milk produced in Italy in 2016 was processed into cheeses, 52.6% of milk was used for the manufacture of cheeses with a Protected Designation of Origin (PDO), according to CE Regulation 1151/2012 (EU 2012). Table 6.1 shows the production of the principal Italian cheeses in 2016. Data for other individual cheese varieties are not official or not available due to the fragmentation of their production. In 2016, almost 390.000 tonnes of Italian cheeses were exported, representing an economic value of ca. 2,500,000,000 Euro (72% to the European Union, 13% America, 7% Asia, 5% non-UE European country, 2% Oceania, and 1% Africa) (Assolatte 2016).

Cheese is the generic name for a group of fermented milk-based food products, produced in a wide range of flavors and forms throughout the world. The primary objective of cheesemaking is to conserve the principal constituents of milk, but cheese has evolved to become a highly nutritious food with epicurean qualities. 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). Harbutt (2002, 2009) described 750 cheese varieties, with photographs, and several cheese-based recipes. Barthilemy and Sperat-Czar (2001) described, with photographs, 1200 varieties. A list of 450 Italian cheeses, some with photographs, is given by Rubino et al. (2005) in Wikipedia, but many of these are variants; there are probably 40 distinct varieties of Italian cheese. Thirty-one varieties of Italian cheese were described, with photographs, by Jerry Finzi in Grand Voyage Italy in Wikipedia.

Beta-cyclodextrin (&beta, CD) is a cyclic oligosaccharide consisting of seven glucose units and is produced from starch using cyclodextrin glycotransferase enzymes to break the polysaccharide chain and forming a cyclic polysaccharide molecule. The use of &beta, CD in food research for reduction of cholesterol is increasing due to its affinity for non-polar molecules such as cholesterol. The aim of this study was to evaluate the feasibility of using &beta, CD in cholesterol removal from pasteurized ewe&rsquo, s milk Manchego cheese and evaluate the effect on the main components of the milk, lipids, and flavor characteristics. Approximately 97.6% cholesterol reduction was observed in the cheese that was treated using &beta, CD. Physicochemical properties (fat, moisture and protein) were not changed by the &beta, CD treatment, except the soluble nitrogen and non-protein nitrogen that showed slight differences after the treatment. The amount of the different components of the lipid fraction (fatty acids, triglycerides and phospholipids) were similar in cheeses treated and not treated with &beta, CD. Flavor compound and short chain free fatty acids were not mostly significantly influenced by the effect of the &beta, CD. &beta, CD molecules are edible and nontoxic and as a result they can be used safely for cholesterol removal processing in cheese manufacturing. Therefore, the present study suggests that &beta, CD treatment is an effective process for cholesterol removal from Manchego cheese while preserving its properties.

Mesophilic lactobacilli are the most important components of the non-starter lactic acid bacteria (NSLAB) microbiota of cheese. This reviews up-dates the most relevant findings concerning the sources of contamination, energy compounds, diversity, genome features and environmental adaptation responses, which enable their growth in cheese during ripening as the main determinant of secondary proteolysis. The use of NSLAB as adjunct cultures is positively documented but it is not free from drawbacks. Attenuation of adjunct cultures could be achieved through promising treatments. Notwithstanding the agreeable and in some cases standard features of traditional raw milk cheeses, mesophilic lactobacilli should not be considered simply as NSLAB because a number of pros may strengthen their use as secondary/adjunct starters with the potential to better control and improve cheese ripening.

Colostrum is the initial milk secreted by mammals following parturition, the composition and physicochemical properties of which are highly dynamic and variable. The composition and physicochemical properties of colostrum during the initial post-partum period has not been systematically reviewed for many years, although the topic remains of interest both to milk producers and processors. In this article, the current understanding of the composition of colostrum, i.e. carbohydrates, proteins, growth factors, enzymes, enzyme inhibitors, nucleotides and nucleosides, cytokines, fats, vitamins and minerals, is reviewed. In addition, the physicochemical properties, i.e. pH and buffering capacity, colour, density and specific gravity, osmotic pressure, somatic cell count, properties of casein micelles, ethanol stability and rennet coagulation properties are discussed, as well as the effects of heat-treating colostrum.

Cheese is the quintessential convenience food, which can be consumed as it is, without preparation, can be used as a sandwich filler, grated or diced and used as a condiment or as a component of several cooked dishes. An estimated 40% of cheese is used as an ingredient or component of other foods.

Most cheeses contain a very low level of lactose after ripening; most is lost in the whey and the small amount of residual lactose trapped in curd is metabolized by starter or nonstarter lactic acid bacteria during the early stages of ripening. Lactate may be racemized or metabolized during ripening via various pathways including to propionic acid, acetic acid, CO2, and H2O in cheeses with a propionic acid fermentation; oxidatively by the molds in mold-ripened varieties; or anaerobically by Clostridium to butyrate, CO2, and H2 which leads to the serious defect known as late gas blowing. Metabolism of citrate by citrate-positive strains of lactococci or Leuconostoc spp. is of significance in Dutch-type cheeses where it leads to the formation of flavor compounds such as diacetyl and small amounts of gas.

The enzymatic hydrolysis of the casein matrix is a major biochemical event that occurs during cheese ripening. Products of proteolysis are a very large number of peptides, together with free amino acids. The enzymes which mediate proteolysis originate from different sources: the milk, coagulant, starter lactic acid bacteria (LAB), and adjunct organisms, nonstarter bacteria and, rarely, exogenous proteinases and peptidases. The principal indigenous proteinase in milk, plasmin, hydrolyzes β- and αs2-caseins during ripening and is of most significance in high-cook cheeses and varieties in which the pH increases significantly during ripening. Residual coagulant trapped in the curd is the major source of proteinase activity in low to medium cooked cheeses. Residual coagulant and plasmin act directly on the caseins to form a number of large and intermediate-sized peptides. The peptides are then acted upon by the cell envelope-associated proteinase of the starter LAB to produce shorter peptides, which are then degraded by a wide range of peptidases to form free amino acids. Only certain regions of the caseins are degraded extensively, and perhaps 75% of the caseins in mature Cheddar cheese remain intact or are present as large polypeptides. Proteolysis results, however, in the formation of perhaps hundreds of peptides and a complement of free amino acids which can be converted to volatile flavor compounds via amino acid catabolism.

A great diversity of cheeses is produced worldwide, and attempts have been made to classify cheese varieties into relatively homogenous groups. A range of such approaches are discussed including those based on textural and compositional parameters of cheese, methods of coagulation of milk, and ripening indices. No one classification scheme is entirely satisfactory, but the method used in this book, based on method of coagulation of the milk and unique technological or microbiological parameters, is discussed. Brief descriptions are given of the major families of cheeses and related products.

This chapter comprehensively reviews the classification, structure, function, catalytic mechanism, and milk-clotting properties of chymosin, pepsin, and other aspartyl proteinases Hydrolysis of the principal bovine milk proteins (β-, αs-, and κ-caseins) by calf chymosin is described in detail, as is the hydrolysis of caseins from the milk of other, nonbovine, species. Rennets, other than chymosin, are discussed and their hydrolysis of caseins is described. Interspecies milk coagulation is reviewed and includes detail on the chymosins of several nonbovine species, including, camel, pig, equine, New World monkies, rat, and seal. The milk-clotting ability of aspartyl proteinases from other sources, for example, plants, fish, and crustaceans is discussed.

Cheese is the generic name for a group of fermented milk-based 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.

Milk is a very complex fluid. It contains four principal constituents, water, lipids, proteins and lactose and perhaps 100 minor constituents, the most important of which from a cheesemaking viewpoint is calcium phosphate. The manufacture and quality of cheese depend, especially, on the properties of one of its protein groups, the caseins, and to a lesser extent on the lipids. Most (~90 %) of the water of milk is removed in the whey, which contains the soluble constituents, i.e., the whey proteins, lactose and some of the inorganic salts. Traditionally, whey was an almost worthless by-product but it is now the source of several very valuable products which are described in Chap. 22.

The coagulation of milk (by proteolysis or acidification) is the key operation in cheesemaking. The enzymatic (rennet-induced) coagulation of milk can be divided into two phases: (1) hydrolysis of the micelle-stabilizing protein, κ-casein, (2) aggregation and gelation of the rennet-altered micelles, with the development of a particulate gel.

The rheology of cheese characterizes its deformation behaviour when subjected to stress or strain. Based on stress/strain behaviour, materials may be generally classified as ideal elastic solids, ideal viscous (Newtonian) liquids, or viscoelastic. Cheeses, like most other solid- and semi-solid foods that contain moisture and solids such as protein, fat and/or carbohydrate, exhibit the characteristics of both an elastic solid and a viscous fluid, and are thus termed viscoelastic. The rheological behaviour of cheese can be measured by an array of tests. Some tests, for example creep and low strain oscillation rheometry, involve application of a low strain (e.g.

The objective of this chapter is to present a very brief description of the principal operations so that the operations described in the following chapters can be seen in an overall context.

This chapter considers the microbiology of cheese ripening and complements the next chapter which considers the biochemistry of cheese ripening and the development of cheese flavour. The important parameters controlling the shelf-life of cheese, viz., water activity, NaCl level, oxidation-reduction level, pH, nitrate and temperature are examined in some detail as is the growth of non-starter lactic acid bacteria, mainly lactobacilli, which grow in all cheeses during ripening. The role of the secondary cultures, e.g., brevibacteria, propionibacteria and moulds, which grow only during ripening, are considered within descriptions of the microbiology of the individual cheese varieties. The cheeses examined in detail from a microbiological view include Cheddar, Swiss-type cheese, Parmigiano Reggiano, Gouda and Edam, bacterial-, e.g., Limburger, Livarot and Tilsit, Reblochon and Gubbeen, and mould surface-ripened cheeses, e.g., Camembert and Brie, and blue cheeses. Microbial spoilage of cheese, e.g., early and late gas formation, open texture, growth of lactobacilli and propionibacteria in Dutch-type cheese, and yeast and moulds, is considered. Finally descriptions of the various genera other than starter and non-starter bacteria found in cheese, e.g., Agrococcus, Arthrobacter, Brachybacterium, Brevibacterium, Corynebacterium, Microbacterium, Propionibacterium, Micrococcus, Kokuria, Kytococcus, Staphylococcus and the various yeasts and moulds are given.

The salt content in rennet-curd cheeses ranges from ~0.7 % (w/w) in Swiss to ~5 % (w/w) in Domiati. Salt has three major functions in cheese: it acts as a preservative; it enhances safety and contributes directly to salty flavour. Together with the desired pH, water activity and redox potential, salt assists preservation of cheese by minimization of spoilage and preventing the growth of pathogens in cheese. The dietary intake of sodium in the modern western diet is generally excessive, being two to three times the level recommended for desirable physiological function (2.4 g Na, i.e., ~6 g NaCl per day). However, cheese generally makes a relatively small contribution to dietary Na intake except when large quantities of high salt cheeses, such as Domiati and Feta, are consumed.

The liquid remaining after removal of the fat and casein from milk by isoelectric or rennet-induced coagulation of the casein is called whey. The whey contains about 90 % of the water of milk, ~98 % of the lactose, ~25 % of the protein and ~50 % of the inorganic salts. Traditionally, whey was an essentially worthless by-product of the cheese industry, to be disposed of as cheaply as possible, e.g., as animal feed. However, lactose and the whey proteins have interesting and unique properties. Advances in protein isolation technology have made it possible to isolate and fractionate the whey proteins in undenatured form. Although of minor importance compared with sucrose, lactose has some important applications, especially in the production of infant formulae; in addition, it can be converted to a number of important derivatives. Human milk contains considerable quantities of unique oligosaccharides (OSs) which are believed to be significant for the development of the neonate. Bovine milk contains only low concentrations of OSs but these can be purified and concentrated from whey and there is considerable interest in developing commercially-viable processes.

Following rennet-induced gelation, the coagulum is subjected to a series of treatments (e.g., cutting, cooking, stirring, acidification, whey drainage), the principal objective of which is to encourage syneresis (removal of whey from the gel) and effectively to concentrate the casein and fat to the degree characteristic of the variety. The principal treatments, which are characteristic of the variety of cheese, are described in this chapter. The cheddaring and pasta filata steps, together with moulding, pressing and packaging cheese, are also discussed.

Fresh cheese represents a diverse group of varieties produced by the coagulation of milk, cream or whey via acidification, acidification with a small quantity of rennet, or a combination of acid and heat and which are ready for consumption once manufacturing is complete. The essential steps in the manufacture of acid-coagulated (or acid-curd) and acid/rennet coagulated verities involves slow quiescent acidification of the standardized, pasteurized cheese milk to pH values (4.6–4.8) close to the isoelectric point of casein, cutting or gently braking the gel, and concentration of the gel to a curd using various means including pouring the broken gel onto cheese cloth or perforated moulds, mechanical separation or membrane filtration. The resultant cheese is then packaged cold (

This chapter summarises foodborne illness due to cheese. Since 1980, there have been 53 outbreaks of food poisoning due to the consumption of cheese during which time almost 250,000,000 tonnes of cheese were produced. The most common organisms involved were Listeria monocytogenes, enteropathogenic Escherichia coli, particularly 0157:H7, Salmonella and Staphylococcus aureus. Of these, listeriosis is the most serious since many outbreaks have resulted in fatalities. The factors controlling the growth of pathogens are the same as those controlling the growth of starters and non-starter lactic acid bacteria in cheese (see Chap. 6). Generally, soft cheeses are more likely to be involved in cheese-associated outbreaks of foodborne illness than hard and semi-hard cheese. Generally, no details of the compositional data of the cheese involved in an outbreak are given, e.g., pH, salt and moisture; such information could be important in understanding how outbreaks occurred. Each of the four groups of bacteria involved is considered in some detail regarding their origin, the symptoms of the illness and the experimental evidence for their growth in cheese. Many cheeses are made from raw milk and confounding factors other than the use of raw milk were involved in these outbreaks.

Cheese quality relates to, and depends on, many attributes, including appearance, texture, functionality, flavour, safety and nutritional value, the relative importance of which depend on the application of the cheese. Since cheese is the end-product of a long and complex process, which may last for two or more years, its quality depends on many factors, some of which are generally pertinent but some are variety-specific. The most important are: 1. The milk supply, including its composition, microbial quality, preparation (standardization and heat treatment) and consistency. 2. The bacterial culture(s) used for acidification and which play(s) major roles during ripening. 3. The rennet used to coagulate the milk and which is the principal proteolytic agent during ripening. 4. The non-starter bacteria which are either indigenous to the milk or gain entry to the milk or cheese from the environment during manufacture. 5. Composition of the cheese. 6. Ripening of the cheese curd, including temperature and duration.

Cheese is a very diverse group of foods (perhaps as many as 1500 varieties). To help consumers, retailers and cheese technologists, several schemes for the classification of cheese have been proposed and used. Criteria for classification include: coagulating agent (rennet or acid); texture/moisture content (very hard, hard, semi-hard, semi-soft, soft); matured or fresh; microflora (internal bacterial, surface/smear bacterial, internal or surface mould, propionic acid bacteria).

The development of pasteurised processed (also called process) cheese products (PCPs) in the early 1900s was motivated by the need to develop cheese-like products that were stable (i.e., did not leak fat, ‘sweat’ or become greasy) at ambient temperatures (≤40 °C) and could be stored for a long time without a change in quality. Today, PCPs are used mainly as ingredient cheese products with customized functionalities, and to a lesser extent as table cheese products (e.g., processed cheese spreads and slices). They are produced by comminuting, melting and emulsifying, into a smooth homogeneous molten blend, one or more varieties of natural cheese and optional ingredients using heat, mechanical shear and (usually) emulsifying salts (ES). The optional ingredients permitted are determined by the type of PCP, as defined by national legislation. Manufacture involves formulation, size reduction of cheese and blending of ingredients, heating to 75–85 °C while continuously shearing until a hot uniform molten mass is obtained, hot-filling into packages and cooling. While the ES are not emulsifying agents per se, they solubilise the cheese protein which binds the free water and emulsifies the free fat released during processing (heating and shearing). The ES, usually sodium citrates or sodium phosphates, mediate protein solubilisation by upward adjustment of the pH and sequestering calcium from the cheese protein. PCPs are packaged in varying formats, for example retail products are available as foil-covered blocks or triangle portions, individually wrapped- or stacked-slices or tubs of spread, while products for the catering trade are available as sliceable blocks, slabs, sausage form or spreadable products filled into drums or buckets. The texture, cooking attributes and overall quality of PCPs are influenced by many parameters including characteristics of the cheese and optional ingredients used in formulation, processing conditions (heat, shear) and composition.

While most natural cheeses are consumed directly as table cheese, which can be eaten directly or with crackers or bread, they are also used extensively as ingredients in culinary dishes. Nevertheless, cheeses are in many cases manufactured specifically for use as an ingredient rather than as table cheese. The manufacture of ingredient cheeses involves protocols which impart specific functionalities, such as controlled textural/rheological properties (e.g., sliceability, shreddability or crumbliness) and cooking properties (e.g., Mozzarella with customized flow and stringiness suited to specific pizza brands). Ingredient cheeses are used in an array of culinary dishes, formulated food products and ready-prepared meals. The types and level of functional attributes required from ingredient cheeses depend on the application in which they are used. The functionalities of the unheated and heated cheese are key quality determinants of ingredient cheese. These are strongly influenced by micro- and macrostructure. At a microstructural level, rennet-curd cheese is a matrix comprised of a calcium phosphate para-casein network, which imbibes the cheese serum (moisture and dissolved solids) and encases the fat phase. The network may be viewed as a polymer network, in which the casein polymers are cross-linked mainly by calcium and calcium phosphate. The degree of polymer cross-linking and the relative proportion of fat in the network control the response of the unheated cheese matrix to stresses and strains encountered during the size-reduction processes involved in shredding, grating or eating, and the response of the heated cheese during baking and grilling. At the macrostructural level, cheese is an assembly of fused curd particles (microstructures), with the extent of fusion depending on both the microstructure of the curd particles and the processes to which the curd particles are subjected such as salting, moulding, texturizing and pressing. Hence, a key approach in designing ingredient cheeses with target functionalities is the control of cheesemaking operations that affect the microstructure and macrostructure.

Agriculture dates from about 6000 bc, when certain plants and animals were domesticated in Mesopotamia. Among the domesticated animals were goats, sheep and cattle, the milk of which was consumed by Man as a high-quality nutrient. Milk is also a very good growth substrate for bacteria, some of which produce lactic acid, which causes the milk to gel. The acidified milk was consumed as cultured milk or converted to acid-curd cheese. It was also discovered that milk could be coagulated by certain proteolytic enzymes, e.g., chymosin from the stomach of neonatal mammals; the coagulum was converted to rennet-curd cheese. Cheese has been produced since the earliest civilizations, e.g., Sumer and Egypt and was well established in Classical Rome. Cheese production spread throughout Europe and the Middle East and later to North and South America and Oceania and evolved as at least 1000 varieties. Cheese production was a farm-based operation until the mid-nineteenth century, and much cheese is still produced at an artisanal level. However, the principal varieties are now produced in very large highly mechanized factories by highly developed technology.