Technology of Cheesemaking

Barry A. Law, Adnan Y. Tamime, Barry A. Law, Adnan Y. Tamime

• Editorial: Wiley-Blackwell
• Año: 2011
• ISBN:
  9781444347890
• Edición: 2
• Categoría: Technology & Engineering
• Categoría: Food Science

Now in a fully-revised new edition, this book covers the science and technology underlying cheesemaking, as practised today in the manufacture of hard, semi-soft and soft cheeses. Emphasis is placed on the technology, and the science and technology are integrated throughout. Authors also cover research developments likely to have a commercial impact on cheesemaking in the foreseeable future within the areas of molecular genetics, advanced sensor / measurement science, chemometrics, enzymology and flavour chemistry. In order to reflect new issues and challenges that have emerged since publication of the first book, the new chapters are included on milk handling prior to cheesemaking; packaging; and major advances in the control of the end user properties of cheese using key manufacturing parameters and variables.

The volume has been structured to flow through the discrete stages of cheese manufacture in the order in which they are executed in cheese plants - from milk process science, through curd process science, to cheese ripening science and quality assessment.

Overall, the volume provides process technologists, product development specialists, ingredients suppliers, research and development scientists and quality assurance personnel with a complete reference to cheese technology, set against the background of its physical, chemical and biological scientific base.

1 The Quality of Milk for Cheese Manufacture

T.P. Guinee and B. O’Brien

1.1 Introduction

World production of milk in 2008 is estimated at ~576 × 10⁶ tonnes (ZMP, 2008), with India/Pakistan, the Americas and Europe being the major producing regions. The proportions of total milk produced by cow, water buffalo, goat, ewe, camel and other are ~84.0, 12.1, 2.0, 1.3, 0.2 and 0.2, respectively (International Dairy Federation – IDF, 2008). Cows’ milk is the major milk used for cheese manufacture; however, significant quantities of cheese are also made from goat, sheep and water buffalo milks in some European Union (EU) countries, such as France, Italy and Spain.

Based on an estimated yield of 1 kg cheese 10 kg⁻¹ milk, the percentage of total milk used for cheese is ~25%, but varies widely from ~70–90% in some European countries (Italy, France, Denmark and Germany) to ~0.5% in China. While cheese-like products are produced in most parts of the world, the principal cheese-producing regions are Europe, North America and Oceania. Cheese production has increased consistently over the last two decades at an annual average rate of ~1.5%. As discussed in Chapter 8, this may be attributed to a number of factors including increases in global population and per capita income, globalisation of eating trends/habits, changing lifestyles, growth in use of cheese as an ingredient in the food service (in pizza-type dishes, cheese burgers and salad dishes) and industrial sectors (cordon bleu entrees, co-extruded products with cheese and gratins).

The increase in consumption has been paralleled by a greater emphasis on improved quality and consistency with respect to the levels of particular nutrients (fat, protein, calcium -Ca²⁺ and sodium -Na⁺), physical properties (texture and cooking attributes), sensory characteristics and processability (size reduction attributes, such as shredability; ability to yield processed cheeses or other cheese products when subjected to secondary processing). Consequently, this has necessitated an increase in the quality and consistency of all inputs (milk composition/quality, enzyme activity/purity, starter cultures characteristics, for example, acid productivity, phage resistance, autolytic properties and flavour-imparting characteristics) and standardisation of the manufacturing process (cf. Chapter 8). In an overall context, milk quality for cheese manufacture may be defined as its suitability for conversion into cheese and deliver cheese of the desired quality and yield. The current chapter examines milk quality for cheese manufacture and the factors affecting it, together with broad-based strategies for improving quality and consistency.

1.2 Overview of milk composition

Milk consists of protein (caseins and whey proteins), lipid, lactose, minerals (soluble and insoluble), minor components (enzymes, free amino acids, peptides) and water (Table 1.1).

The casein fraction coexists with the insoluble minerals as a calcium phosphate–casein complex. The water and its soluble constituents (lactose, native whey proteins, some minerals, citric acid and minor components) are referred to as serum. During cheese manufacture, the milk is subjected to a partial dehydration, involving controlled expulsion of serum and concentration of fat, caseins (and in some cases denatured, aggregated whey proteins) and some of the minerals. The methods engaged to affect the dehydration include limited destabilisation and aggregation of the calcium phosphate casein in the form of a gel network which

Table 1.1 Compositional and gelation characteristics of cows’ milks.

Source: Compiled from O’Brien et al. (1999b–d), Mehra et al. (1999) and Hickey et al. (2006b) for manufacturing milks.

Characteristic	Mean	Range
Gross composition
Dry matter (g 100 g^−1)	12.04	11.52–12.44
Fat (g 100 g^−1)	3.55	3.24–3.90
Lactose (g 100 g^−1)	4.42	4.21–4.56
Total protein (g 100 g^−1 )	3.25	2.99–3.71
True protein (g 100 g^−1 )	3.06	2.77–3.47
Casein (g 100 g^−1)	2.51	2.29–2.93
Whey protein (g 100 g^−1)	0.54	0.48–0.64
Non-protein nitrogen (N) (g 100 g^−1 N)	5.33	4.79–6.16
Urea (mg 100 g^−1)	27.60	22.00–37.50
Ash (g 100 g^−1)	0.74	0.71–0.77
Calcium (mg 100 mL^−1)	118	108–137
Iron (mg 100 mL^−1)	976	460–1490
Magnesium (mg 100 mL^−1)	107	96–117
Chloride (mg 100 mL^−1)	100	95–116
Vitamins/vitamin components
β-Carotene (μg g^−1 fat)	3.18	0.48–8.37
Thiamine (μg mL^−1)	0.18	0.09–0.35
Riboflavin (μg mL^−1)	0.88	0.19–1.85
Vitamin A (μg g^−1 fat)	9.41	2.18–27.85
Vitamin E (μg g^−1 fat)	25.56	6.84–42.15
Iodine (I) (μg mL^−1)	0.28	0.20–0.51
Cobalt (Co) (μg mL^−1)	0.96	0.44–1.70
Gelation properties^a
RCT (min)	6.15	4.50–7.44
A30 (mm)	46.80	43.00–51.38
1/k20 (mm^−1)	0.23	0.3–0.19
Other components
Total free fatty acids (mg kg^−1 fat)	3769	2629–5108

^aBased on the analysis using the Formagraph (Type 1170, Foss Electric, Denmark) on milks at pH 6.55 and rennet-treated at a level corresponding to ~0.18 mL L⁻¹ (Chymax Plus, Pfizer Inc., Milwaukee, WI); RCT is an index of rennet coagulation (gelation) time, A30 of the curd firmness after 30 min, and 1/k20 of gel firming rate.

encloses the fat and serum via specific enzymatic hydrolysis of the casein, acidification (by fermentation of milk lactose to lactic acid by added bacterial cultures), elevated temperature and various mechanical operations as discussed in Chapter 8. Amongst others, the degrees of casein aggregation and dehydration are critical parameters controlling the properties and quality of the final cheese.

Although manufacturing procedures for most cheese types are very defined (at least in large modern cheesemaking facilities) in terms of technology applied and the type and levels of operations imposed on the milk (cf. Chapter 8), variations in cheese quality do occur. Seasonal variation in the composition and quality of milk are considered to be crucial factors contributing to the inconsistency in quality. Consequently, an overview of milk composition in terms of its relevance to cheese manufacture is presented below. The main focus of this chapter is on cows’ milk, which accounts for an estimated 95% of total milk used in cheese manufacture; the characteristics of other milks are discussed elsewhere (Anifantakis, 1986; Juárez, 1986; Remeuf & Lenoir, 1986; Muir et al., 1993a,b; Garcia-Ruiz et al., 2000; Bramanti et al., 2003; Huppertz et al., 2006; Kuchtik et al., 2008; Caravaca et al., 2009).

1.2.1 Casein

The nitrogenous fraction of cows’ milk typically consists of casein, whey protein and non-protein nitrogen (urea, proteose-peptones, peptides) at levels of ~78, 18 and 4 g 100 g⁻¹, respectively, of total nitrogen (Table 1.1).

Casein, which is typically present at a level of 2.5 g 100 g⁻¹ in cows’ milk, is the main structural protein of both rennet- and acid-induced milk gels (Table 1.1). The casein is heterogeneous, comprising four main types: α_s1, α_s2, β and κ, which represent ~38, 10, 35 and 15 g 100 g⁻¹ of the total casein, respectively (Fox & McSweeney, 1998; Fox, 2003; Swaisgood, 2003). Model studies in dilute dispersions indicate that the individual caseins vary in the content and distribution of phosphate (Table 1.2); the respective number of (serine) phosphate residues per mole of casein are ~8, 10–13, 5 and 1 for α_s1-, α_s2- β- and κ-caseins, respectively. The serine phosphates bind calcium and calcium phosphate, and consequently, different caseins have different calcium-binding properties. Generally, α_s1-, α_s2- and β-caseins bind calcium strongly and precipitate at relatively low calcium concentrations (~0.005–0.1 M CaCl₂ solutions), inclusive of the calcium level in milk (30 mM); in contrast κ-casein is not sensitive to these calcium concentrations and can, in fact, stabilise up to 10 times its mass of the calcium-sensitive caseins.

Casein in milk exists in the form of spherical-shaped colloid particles (~40–300 nm diameter), known as casein micelles (Fox & Brodkorb, 2008; McMahon & Oommen, 2008). Different models have been proposed for the structure of the casein micelle on the basis of the location of individual caseins (in response to their calcium sensitivity) and the calcium phosphate. These include:

• sub-micelle model (Schmidt, 1982), in which sub-micelles are ‘cemented’ together by colloidal calcium phosphate (CCP) and κ-casein-rich sub-micelles are mainly concentrated at the surface of the micelle; the hydrophilic C-terminal region of the κ-casein orient into the serum as a highly hydrated ‘hairy layer’ that is in a state of constant flux and confers stability to the micelle by steric repulsion;

Table 1.2 Characteristics of cows’ milk proteins of relevance to cheese manufacture.

Source: Compiled from Mulvihill & Donovan (1987), Fox & McSweeney (1998), Fox (2003) and Swaisgood (2003).

• dual bonding model (Horne, 1998), in which the interior of the micelle is composed of α_s- and β-caseins which form a lattice through interactions between hydrophobic regions (hydrophobic-induced) and between hydrophilic regions containing phosphoserine clusters (that attach to CCP clusters), while κ-casein molecules located at the surface interact hydrophobically with the other caseins (α_s- or β-) and orient their highly hydrophilic regions (hairs) into the serum;
• tangled, cross-linked web model (Holt & Horne, 1996), comprising a ‘tangled’ mass of rheomorphic casein chains cross-linked by calcium phosphate nanoclusters, similar in casein composition throughout but with the chains becoming more diffuse at the micelle periphery (on moving outwards from the dense centre); and
• interlocked lattice model (McMahon & Oomen, 2008), featuring a system of interlocking sites composed of anchoring calcium phosphate nanoclusters (several hundred per micelle), which bind the phosphoserine domains of α_s- and β-caseins; the hydrophobic ends of these caseins orientate away from the calcium phosphate nanocluster and interact hydrophobically with other α- and β-caseins, while κ-casein is predominantly surface located because of its lack of phosphoserine domains (to bind to the calcium phosphate nanoclusters) and its highly charged C-terminal regions (which prevents strong electrostatic interactions).

In all of the above models, the arrangement of casein within the micelle is such that the interior is mainly occupied by the calcium-sensitive caseins (α_s- and β- and κ-casein is principally located at the surface, with its hydrophilic C-terminal region (caseinomacropeptide) oriented outwards toward the serum phase in the form of protruding negatively charged hairs, which create an ...