Dairy Processing

Improving Quality

G Smit

• Publisher: Woodhead Publishing
• Year: 2003
• Print ISBN: 9781855736764
• eBook ISBN: 9781855737075
• Topic: Technologie et ingénierie
• Subtopic: Sciences de l'alimentation

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

1

Introduction

G. Smit    NIZO Food Research, The Netherlands

Milk and the range of dairy products derived from milk have long been central to diet in both developed and developing countries. Some dairy processing technologies such as fermentation have been used for thousands of years. Building on this long lasting foundation, the dairy processing industry continues to be at the forefront of innovation in the food industry. This important new collection sums up some of the most important recent developments.

Part I considers key aspects of safety and quality. Chapter 2 provides a foundation by summarising current knowledge about the major constituents of milk. The following chapter discusses how factors such as breed and husbandry practices on the farm influence milk composition. The next three chapters focus on safety, covering hygienic practices on the farm, developments in pasteurisation and sterilisation technologies, and the growing use of modelling to improve these techniques whilst retaining milk quality. A final group of chapters in Part I consider key aspects of dairy product quality. There are discussions of the latest research on the control of flavour in milk and other dairy products, improving texture in fermented dairy products, controlling stability and shelf-life, and testing the authenticity of milk and milk products. Building on the traditional nutritional importance of milk, the final two chapters consider the new generation of functional dairy products.

The second part of the book reviews the range of new technologies that have emerged recently to improve dairy product quality. The first two chapters look at on-line techniques to monitor and control various aspects of milk safety and quality. They are then followed by chapters on extending the shelf-life of dairy products through such techniques as high pressure processing, the production of powdered dairy products and the use of carbon dioxide. There is also a chapter on developments in separation techniques to maximise returns by producing a wide range of dairy ingredients. The final part of the book considers key developments in improving flavour and other qualities in cheese manufacture.

The quality of dairy products, e.g. taste, texture, health and safety, as perceived by the consumer should be the prime and ultimate driver for the dairy industry. The new developments described in this book will certainly add to their achievement.

Part I

Dairy product safety and quality

2

The major constituents of milk

P.F. Fox University College Cork, Ireland

2.1 Introduction

Milk and dairy products are major components of the human diet in Western countries, providing about 30% of dietary proteins and lipids and about 80% of dietary calcium. Current annual production of milk is ≈ 600 x 10⁶ tonnes, of which ≈ 85%, 11%, 2% and 2% are bovine, buffalo, caprine and ovine, respectively. Although some raw milk is still consumed, the vast majority of milk is processed to at least some extent. Liquid (beverage) milk is a major food item in all developed dairying countries, representing ≈ 40% of total milk production. The remainder is processed into one of several thousand products - the dairy industry is probably the most diverse and flexible sector of the food industry. The flexibility of milk as a raw material resides in the chemical and physico-chemical properties of its constituents, many of which are unique. The principal constituents of milk can be modified by enzymatic, chemical and/or physical methods, permitting the production of new products. However, the concentrations and properties of milk constituents are variable and hence the processability of milk and the properties of dairy products are inconsistent, although much of this variability can be eliminated by modern technology, which exploits certain features of milk constituents. Today, most milk is processed in large, highly mechanized and automated factories, where consistency in processing properties is essential. The resulting products are distributed through large wholesale and retail outlets, where consistency is, again, paramount. Consumers expect consistency also. The consistency expected by the processor, distributor and consumer can be achieved only if the properties of milk constituents are understood at the molecular level. This chapter will describe the principal chemical and physico-chemical properties of the major constituents of milk, i.e., lactose, lipids, proteins and salts, and variations in the concentrations and properties of these constituents.

The natural function of milk is to supply the neonatal mammal, of which there are ≈ 4500 species, with its complete nutritional and some of its physiological requirements. Because the nutritional requirements are species-specific and change as the neonate matures, the composition of milk shows very large inter- species differences, e.g., the concentrations of fat, protein and lactose range from 1 to 50%, 1 to 20% and 0 to 10%, respectively, and the concentration of each changes during lactation. Inter-species differences in the concentrations of many of the minor constituents are even greater than those of the macro-constituents.

Milk from domesticated animals has been used by humans since at least 8000 BC. Although sheep and goats were the first domesticated dairy animals, because they are more easily managed than cattle, the latter, especially certain breeds of Bos taurus, are now the dominant dairy animals. Total recorded world milk production is ≈ 600 x 10⁶ tonnes per annum, of which ≈ 85% is bovine, 11% is buffalo and 2% each is from sheep and goats. Small amounts of milk are produced from camels, mares, reindeer and yaks in certain regions with specific cultural and/or climatic conditions. This chapter will concentrate on the constituents and properties of bovine milk. Although the constituents of the milk of the other main dairy species are generally similar to those of bovine milk, they differ in detail and the technological properties of the milk of these species differ significantly.

Milk is a very flexible raw material from which several thousand types of dairy products are produced around the world in a great diversity of flavours and forms, including ≈ 1000 varieties of cheese. The proportions of total world milk production used for the principal dairy products are: liquid (beverage) milk, ≈ 39%; cheese, ≈ 33%; butter, ≈ 32%; whole milk powder, ≈ 6%; skimmed milk powder, ≈ 9%; concentrated milk products, ≈ 2%; fermented milk products, ≈ 2%; casein, ≈ 2%; and infant formulae, ≈ 0.3%. (The sum value exceeds 100%; this is due to ‘double accounting’, e.g., butter and skim milk powder, and the standardization of fat content, e.g., for liquid milk, cheese, etc.) This flexibility and diversity are a result of the properties, many of them unique, of the constituents of milk, the principal of which are easily isolated from milk, permitting the production of valuable food ingredients. Milk is free of off- flavours, pigments and toxins, which is a very important feature of milk as a raw material for food ingredients.

The processability and functionality of milk and milk products are determined by the properties and concentrations of its principal constituents: proteins, lipids, lactose and salts. Many of the principal problems encountered during the processing of milk are caused by variability in the concentrations and properties of these constituents arising from several factors, including breed, individuality of the animal, stage of lactation, health of the animal, especially mastitis, and nutritional status. Synchronized calving, as practised in New Zealand, Australia and Irela...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Contributor contact details
• 1: Introduction
• Part I: Dairy product safety and quality
• Part II: New technologies to improve quality
• Part III: Cheese manufacture
• Part IV: Appendix
• Index