Smit Dairy Processing

Improving Quality
1. Auflage 2003
ISBN: 978-1-85573-707-5
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 536 Seiten

Reihe: Woodhead Publishing Series in Food Science, Technology and Nutrition

The dairy sector continues to be at the forefront of innovation in food processing. With its distinguished editor and international team of contributors, Dairy processing: improving quality reviews key developments and their impact on product safety and quality.The first two chapters of part one provide a foundation for the rest of the book, summarising the latest research on the constituents of milk and reviewing how agricultural practice influences the quality of raw milk. This is followed by three chapters on key aspects of safety: good hygienic practice, improvements in pasteurisation and sterilisation, and the use of modelling to assess the effectiveness of pasteurisation. A final sequence of chapters in part one discuss aspects of product quality, from flavour, texture, shelf-life and authenticity to the increasingly important area of functional dairy products. Part two reviews some of the major technological advances in the sector. The first two chapters discuss developments in on-line control of process efficiency and product quality. They are followed by chapters on new technologies to improve qualities such as shelf-life, including high pressure processing, drying and the production of powdered dairy products, and the use of dissolved carbon dioxide to extend the shelf-life of milk. Part three looks in more detail at key advances in cheese manufacture.Dairy processing: improving quality is a standard reference for the dairy industry in improving process efficiency and product quality. - Reviews key developments in dairy food processing and their impact on product safety and quality - Summarises the latest research on the constituents of milk and reviews how agricultural practice influences the quality of raw milk - Outlines the key aspects of safety: good hygienic practice, improvements in pasteurisation and sterilisation, and the use of modelling to assess the effectiveness of pasteurisation

Autoren/Hrsg.

Smit, G.

Inhaltsverzeichnis

1;Front Cover;1
2;Dairy Processing: Improving Quality;4
3;Copyright Page;5
4;Table of Contents;6
5;Contributor contact details;14
6;Chapter 1. Introduction;20
7;Part I: Dairy product safety and quality;22
7.1;Chapter 2. The major constituents of milk;24
7.1.1;2.1 Introduction;24
7.1.2;2.2 Lactose;26
7.1.3;2.3 Lipids;31
7.1.4;2.4 Proteins;37
7.1.5;2.5 Minor proteins;45
7.1.6;2.6 Salts;55
7.1.7;2.7 References;57
7.2;Chapter 3. Influences on raw milk quality;61
7.2.1;3.1 Introduction;61
7.2.2;3.2 Breed, genetics and milk quality;64
7.2.3;3.3 Cow diet and milk quality;71
7.2.4;3.4 Other aspects of animal husbandry and milk quality;74
7.2.5;3.5 Future trends;78
7.2.6;3.6 Sources of further information and advice;80
7.2.7;3.7 Acknowledgements;81
7.2.8;3.8 References;81
7.3;Chapter 4. Good hygienic practice in milk processing;87
7.3.1;4.1 Introduction;87
7.3.2;4.2 The principal hazards;88
7.3.3;4.3 Good hygienic practice;91
7.3.4;4.4 Future trends;96
7.3.5;4.5 Sources of further information and advice;98
7.3.6;4.6 Bibliography;98
7.4;Chapter 5. Improvements in the pasteurisation and sterilisation of milk;100
7.4.1;5.1 Introduction;100
7.4.2;5.2 Kinetic parameters in heat inactivation;101
7.4.3;5.3 Thermisation and tyndallisation;102
7.4.4;5.4 Pasteurisation;104
7.4.5;5.5 Factors affecting the effectiveness of pasteurisation;105
7.4.6;5.6 Extended shelf-life milks;111
7.4.7;5.7 Sterilisation;111
7.4.8;5.8 Ultra-high temperature (UHT) sterilisation;114
7.4.9;5.9 Aseptic packaging and storage;119
7.4.10;5.10 References;119
7.5;Chapter 6. Modelling the effectiveness of pasteurisation;123
7.5.1;6.1 Introduction: the role of predictive modelling;123
7.5.2;6.2 The development of thermal models;124
7.5.3;6.3 Key steps in model development;129
7.5.4;6.4 Models for key enzymes and pathogens;134
7.5.5;6.5 Modelling and risk assessment;136
7.5.6;6.6 Risk assessment and pasteurisation;140
7.5.7;6.7 Future trends;143
7.5.8;6.8 Sources of further information and advice;144
7.5.9;6.9 References;145
7.6;Chapter 7. Flavour generation in dairy products;149
7.6.1;7.1 Introduction;149
7.6.2;7.2 Raw and heat-treated milk;153
7.6.3;7.3 Yoghurt and buttermilk;161
7.6.4;7.4 Conclusion and future trends;166
7.6.5;7.5 Acknowledgements;167
7.6.6;7.6 References;167
7.7;Chapter 8. Controlling the texture of fermented dairy products: the case of yoghurt;174
7.7.1;8.1 Introduction;174
7.7.2;8.2 The manufacture of yoghurt;174
7.7.3;8.3 Factors affecting yoghurt texture;179
7.7.4;8.4 Measuring the rheological and textural properties of yoghurt;185
7.7.5;8.5 Future trends;193
7.7.6;8.6 Sources of further information and advice;195
7.7.7;8.7 References;195
7.8;Chapter 9. Factors affecting the shelf-life of milk and milk products;204
7.8.1;9.1 Introduction;204
7.8.2;9.2 Chemical composition and principal reactions of milk;205
7.8.3;9.3 Bacteria in milk and related enzyme activity;209
7.8.4;9.4 Raw milk enzymes;212
7.8.5;9.5 Control of the quality of short shelf-life products;213
7.8.6;9.6 Yoghurt and fermented milk;216
7.8.7;9.7 Factors affecting the stability of long shelf-life products;217
7.8.8;9.8 Control of the stability of long-life milk products;219
7.8.9;9.9 Summary;225
7.8.10;9.10 Acknowledgement;225
7.8.11;9.11 Bibliography;225
7.9;Chapter 10. Testing the authenticity of milk and milk products;227
7.9.1;10.1 Introduction;227
7.9.2;10.2 Detecting and quantifying foreign fats;229
7.9.3;10.3 Detecting milk of different species;233
7.9.4;10.4 Detection of non-milk proteins, watering of milk and alteration of the casein/whey protein ratio;237
7.9.5;10.5 Measuring heat load;239
7.9.6;10.6 Identifying geographical origin;240
7.9.7;10.7 Conclusions;241
7.9.8;10.8 References;242
7.10;Chapter 11. Functional dairy products;248
7.10.1;11.1 Introduction;248
7.10.2;11.2 Composition of milk;248
7.10.3;11.3 Fermented milk products;250
7.10.4;11.4 What do we mean by functional dairy products?;252
7.10.5;11.5 Examples of functional dairy products: gastrointestinal health and general well-being;253
7.10.6;11.6 Examples of functional dairy products: cardiovascular health;257
7.10.7;11.7 Examples of functional dairy products: osteoporosis and other conditions;260
7.10.8;11.8 Future trends;261
7.10.9;11.9 Sources of further information and advice;262
7.10.10;11.10 References;263
7.11;Chapter 12. Developing and approving health claims for functional dairy products;265
7.11.1;12.1 Introduction;265
7.11.2;12.2 The body's defence mechanisms;266
7.11.3;12.3 In vitro studies;268
7.11.4;12.4 Animal studies;270
7.11.5;12.5 Human studies;271
7.11.6;12.6 Making health claims;273
7.11.7;12.7 Future trends;274
7.11.8;12.8 Sources of further information and advice;275
7.11.9;12.9 References;276
8;Part II: New technologies to improve quality;280
8.1;Chapter 13. On-line measurement of product quality in dairy processing;282
8.1.1;13.1 Introduction;282
8.1.2;13.2 On-line measurement of physical parameters;284
8.1.3;13.3 Measuring product composition;288
8.1.4;13.4 On-line microbiological testing;298
8.1.5;13.5 Monitoring fouling and cleaning-in-place;299
8.1.6;13.6 Future trends;302
8.1.7;13.7 Sources of further information and advice;306
8.1.8;13.8 References;307
8.2;Chapter 14. Rapid on-line analysis to ensure the safety of milk;311
8.2.1;14.1 Introduction;311
8.2.2;14.2 Monitoring contamination during milking: faecal contamination and mycotoxins;313
8.2.3;14.3 Measuring the effectiveness of heat treatment;318
8.2.4;14.4 Future trends;325
8.2.5;14.5 References;325
8.3;Chapter 15. High-pressure processing to improve dairy product quality;329
8.3.1;15.1 Introduction: high-pressure principles and technologies;329
8.3.2;15.2 The effects of high pressure on nutritional and other qualities in milk;330
8.3.3;15.3 The effects of high pressure on bacteria and enzymes;333
8.3.4;15.4 The effects of high pressure on milk proteins;335
8.3.5;15.5 The effects on other properties of milk;336
8.3.6;15.6 The effects on cheese and yoghurt-making properties of milk;338
8.3.7;15.7 High-pressure treatment of cheese;340
8.3.8;15.8 Future trends;344
8.3.9;15.9 Sources of further information and advice;344
8.3.10;15.10 References;345
8.4;Chapter 16. Optimising product quality and process control for powdered dairy products;352
8.4.1;16.1 Introduction: evaporation and drying processes;352
8.4.2;16.2 Quality criteria for dairy-based powders;359
8.4.3;16.3 Modelling quality;366
8.4.4;16.4 Process and product control;372
8.4.5;16.5 Ensuring process safety;378
8.4.6;16.6 Sources of further information and advice;381
8.4.7;16.7 References;382
8.5;Chapter 17. Separation technologies to produce dairy ingredients;385
8.5.1;17.1 Introduction;385
8.5.2;17.2 Separation technologies;387
8.5.3;17.3 Isolation of ingredients;393
8.5.4;17.4 Developments in separation technology;404
8.5.5;17.5 Sources of further information and advice;406
8.5.6;17.6 References;406
8.6;Chapter 18. The use of dissolved carbon dioxide to extend the shelf-life of dairy products;410
8.6.1;18.1 Introduction: factors limiting the shelf-life of dairy products;410
8.6.2;18.2 The effects of CO2 on bacterial growth;410
8.6.3;18.3 The effects of CO2 on raw milk quality;415
8.6.4;18.4 The effects of CO2 on dairy product quality;418
8.6.5;18.5 Bactericidal and sporicidal effects of dissolved CO2 during thermal processing;425
8.6.6;18.6 Conclusions;429
8.6.7;18.7 References;429
9;Part III: Cheese manufacture;436
9.1;Chapter 19. Acceleration of cheese ripening;438
9.1.1;19.1 Introduction;438
9.1.2;19.2 Accelerating cheese ripening: elevated temperature;440
9.1.3;19.3 Addition of exogenous enzymes or attenuated starters;441
9.1.4;19.4 Use of adjunct cultures;450
9.1.5;19.5 Genetic modification of starter bacteria;452
9.1.6;19.6 High-pressure technology;453
9.1.7;19.7 Enzyme-modified cheeses as flavourings;456
9.1.8;19.8 Future trends;459
9.1.9;19.9 Acknowledgement;460
9.1.10;19.10 Sources of further information and advice;460
9.1.11;19.11 References;460
9.2;Chapter 20. Non-starter lactic acid bacteria (NSLAB) and cheese quality;467
9.2.1;20.1 Introduction;467
9.2.2;20.2 Bacteria comprising the NSLAB complex;469
9.2.3;20.3 NSLAB in different cheese varieties;471
9.2.4;20.4 The source of NSLAB in cheese;473
9.2.5;20.5 The growth of NSLAB in cheese;474
9.2.6;20.6 The influence of NSLAB on cheese quality;476
9.2.7;20.7 Selection of NSLAB adjuncts for quality improvement of cheese;480
9.2.8;20.8 Conclusions;482
9.2.9;20.9 References;482
9.3;Chapter 21. The production of smear cheeses;489
9.3.1;21.1 Introduction: smear-ripened cheese varieties;489
9.3.2;21.2 Production and ripening;491
9.3.3;21.3 Developing ripening cultures;496
9.3.4;21.4 Conclusions and future trends;507
9.3.5;21.5 Sources of further information and advice;508
9.3.6;21.6 References;508
9.4;Chapter 22. Flavour formation in cheese;511
9.4.1;22.1 Introduction;511
9.4.2;22.2 Amino acid conversion;512
9.4.3;22.3 Amino acid catabolism;515
9.4.4;22.4 Methionine catabolism;518
9.4.5;22.5 Branched-chain and aromatic amino acid conversion;520
9.4.6;22.6 Conversion of other amino acids;522
9.4.7;22.7 Natural biodiversity and tailor-made starter cultures;523
9.4.8;22.8 Future trends;524
9.4.9;22.9 References;526
10;Part IV: Appendix;532
10.1;Chapter 23. Improving the nutritional quality of milk;534
10.1.1;23.1 Introduction;534
10.1.2;23.2 Factors affecting milk protein content;535
10.1.3;23.3 Factors affecting milk fat content;537
10.1.4;23.4 Future trends;545
10.1.5;23.5 References;546
11;Index;551

Leseproben

3

Influences on raw milk quality

M. Boland    Fonterra Research Centre, New Zealand

3.1 Introduction

Milk is produced by all mammalian species for feeding their young, and there is a very large range of milk properties across all the species. Some mammals, such as the Tamar wallaby, can even produce milk of different compositions from adjacent mammary glands of the same individual at the same time (Nicholas, 1988). This chapter focuses exclusively on the range of quality (i.e. composition and related milk characteristics) of raw milk from dairying breeds of cattle (Bos taurus).

Although many people are persuaded that ‘milk is milk’ and that is the end of the matter, not all milks are created equal. There is significant variation in milk composition, which creates both problems and opportunities for the dairy industry. At the simplest level, differences in milk produced by different breeds are well recognised and have been used as a market position by some companies (Canada - Jersey Farm; USA - Promised Land Dairy; UK - ‘Gold Top’ - see Internet URLs at the end of this chapter). Despite thousands of years of domestication and selective breeding of dairy cattle, there is still a wide variation in milk composition from cow to cow. Table 3.1 gives an indication of the scope of variation within the herd of just one country (New Zealand). Much of this variation is evened out by a combination of milk from many animals at the farm level, with further evening out as collections from various farms are accumulated in the milk tanker, and in the silo at the factory, as shown in Fig. 3.1. A major survey of the protein composition of milk at the national level was carried out by the International Dairy Federation in the early 1990s (Higgins et al., 1995). The survey covered 25 milk-producing countries. Annual average protein in the milk varied between countries from 3.00% to 3.55%, with monthly values ranging from 2.75% to 4.09%. Protein as a percentage of the SNF (solids, non-fat) ranged from 32.7% to 46%, and the ratio of casein to whey protein varied from 3.24 to 5.87. Thus, even with national averages, there is considerable variation.

Table 3.1

Range of composition in milks from individual cows in New Zealand. Data were collected from milk samples from 16 000 Friesian cows, 5800 Jersey cows and 340 Ayrshire cows and were analysed using Fourier Transform infrared spectrometry (S. Petch, unpublished, personal communication)

Milkfat %

Friesian

1.4

8.6

Jersey

2.0

10.9

Ayrshire

2.4

6.7

Protein %

Friesian

2.4

5.2

Jersey

2.8

5.7

Ayrshire

2.7

5.0

Lactose %

Friesian

3.7

5.7

Jersey

4.2

5.6

Ayrshire

4.3

5.4

Fig. 3.1 Variation in milk characteristics. Although the example shown relates to butter hardness as measured by solid fat content, the principle is generally applicable. The seasonal range is the variation in milkfat in the silo during a season. Figure courtesy of A.K.H. MacGibbon, Fonterra Research Centre.

Variability in milk composition (and hence quality) extends considerably beyond simple breed characteristics. In this chapter, milk characteristics are addressed according to the source of variation, although they could equally well be divided according to where they impact and have economic or other effect. Milk characteristics have an effect at the processing level, on processability and yield, at the product level, in terms of the overt characteristics of the product, and on the consumer, in terms of nutrition and other physiological activity.

Genetic variations, many of which are breed linked, are the predominant source of variation in milk protein (Ng-Kwai-Hang and Grosclaude, 1992) and have a significant effect on milkfat composition and the amount of water in the milk. These are covered in Section 3.2. The second major influence on milk characteristics is the diet of the cow. This has a much greater effect on milkfat than on protein. It is covered in Section 3.3. In Section 3.4, the effects of other aspects of animal husbandry are dealt with. Section 3.5 gives a speculative view of what might happen in the future of milk production.

3.1.1 Economic importance of milk composition

Before discussing variations in milk composition in detail, it is worth considering the importance to the dairy industry of some of the compositional variables. This area has recently been reviewed by Williams (2002) and Hillbrick and Augustin (2002).

The first component of importance is water. water is not usually directly cited as a compositional variable, but is implicit in the way other components are expressed, as water makes up the bulk volume of milk. water is important in milk for consumption in its liquid form, as it affects the nutritional value per unit volume; however, in milk for processing, it has other important consequences. In dried products such as milk powders, water must be removed, and there is an energy cost for that removal; in the manufacture of cheese, water creates the bulk of the whey and has either a disposal cost, or a removal cost when other products are created from the whey. Further, water has a cost in transport, storage prior to processing, and size of processing plants in manufacturing. Thus, the ideal milk for most manufacturing purposes would have the highest possible solids content consistent with being able to be expressed from the mammary gland.

Protein is the most valuable component of milk. within the major proteins, the most important split is between the caseins and the whey proteins. The ratio of casein to total protein is often known as the casein number (Ng-Kwai-Hang and Grosclaude, 1992) and is usually expressed as a percentage. This number defines the amount of cheese or casein that can be made from the protein in the milk, and is usually around 80. If the casein number gets too low (i.e. not enough casein relative to total protein), it can be difficult to make cheese.

Within the casein proteins, the only casein that seems to have a major concentration-dependent effect on processing is ?-casein. The ratio of?-casein to total casein is an indicator of micelle size (Anema and Creamer, 1993) and relates in turn to curd formation during renneting (Puhan and Jakob, 1994) and stability during milk powder manufacture (Singh and Creamer, 1992).

The composition of milkfat is a very important variable (Hillbrick and Augustin, 2002). In today’s consumer environment, low fat products are valued, and milkfat is often the component that must be removed, for example, in producing half fat and low fat drinking milks. However, fat has a value in its own right, being an essential component in cheese, butter and a range of milkfat based ingredients. As well as the amount of fat in milk being important, the properties of the fat need consideration. Proper functional behaviour of butter, and to some extent of cheese, depends on the appropriate melting behaviour of the fat. Butter needs sufficient solid fat to maintain shape at room temperature, but sufficient liquid phase to allow it to spread from the refrigerator. In all fats, the consumer requirement is for low levels of saturated fats and higher levels of mono- and polyunsaturated fatty acids. Finally, some specific fat components, such as omega-3 fatty acids and conjugated linoleic acid (CLA), are becoming recognised for their possible health benefits (Gurr, 1995; Hillbrick and Augustin, 2002). CLA is of particular interest because milkfat is one of the main dietary sources of this fatty acid.

Lactose has importance as the bulk phase of milk powders. In most countries, lactose is not considered to be a valued component of milk, although recent changes in the Codex Alimentarius of FAO/WHO, allowing standardisation of the level of protein in milk powders by adding lactose, may change this.

Minerals are not generally considered to be valuable components in milk, with the possible exception of calcium. Milk is an important dietary source of calcium, which is important for bone health and the prevention of osteoporosis. In practice, milk calcium is tightly regulated and the calcium level does not vary greatly, with a calcium to protein ratio in the range from 0.7 to 1.0 mmol/g (Davis et al., 2001). It is a relatively simple matter to fortify drinking milks with calcium from other sources.

3.2 Breed, genetics and milk quality

Differences in composition between milks from different breeds are apparent even at the simplest levels of analysis, and are well known to dairy farmers and the processing industry alike. The Jersey breed, once dominant for commercial milk production in some countries, is known for high levels of fat and protein, and higher overall levels of solids in the milk (i.e. less water); however, it produces more fat relative to the amount of protein. It has been observed that Jersey milk performs...