Milk Quality SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. F. HARDING formerly Technical Director Milk Marketing Board Thames Ditton Surrey UK.

Transcription

1 Milk Quality

2 Milk Quality Edited by formerly Technical Director Milk Marketing Board Thames Ditton Surrey UK mi SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.

3 First edition Springer Science+Business Media Dordrecht Originally published by Chapman & Hall in 1995 Softcover reprint of the hardcover 1 st edition 1995 Typeset in 1O/12pt Times by Acom Bookwork, Salisbury, Wiltshire ISBN ISBN (ebook) DOI / Apart from any fair dealing for the purposes of research or private study, any criticism or review, as permitted under the UK Copyright Designs and Patents Act, 1988, this publication may not be reproduced, stored, or transmitted, in any form or by any means, without the prior permission in writing of the publishers, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of licenses issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries conceming reproduction outside the terms stated here should be sent to the publishers at the Glasgow address printed on this page. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. A catalogue record for this book is available from the British Library Library of Congress Catalog Card Number: Printed on acid-free text paper, manufactured in accordance with ANSI/NISO Z (Permanence of Paper)

4 Preface Milk has played a major contribution to the human diet in many different countries across the world since the dawn of time. The dairy cow was domesticated over 6000 years ago, she was the object of worship in the Middle East 2000 years before Christ, and milk and milk products are mentioned more than 50 times in the Bible. Milk and dairy products have become a major part of the human diet in many countries. It is not surprising therefore, that over many years considerable attention has been paid to improving the quality of milk. We have worked to improve the yield, the compositional quality and the hygienic quality, and have striven to minimise the level of contaminants which can find access to this, perhaps our most natural, unrefined and highly nutritious foodstuff. The chain of people involved in the milk industry extends from milk production-farmers, veterinarians and farm advisors-through transport to processing-quality controllers, manufacturers-and on to retailers, legislators, nutritionists, dairy educators and consumers. All will be interested in the quality parameters of milk which are regularly measured for commercial reasons, for trade, for legal requirements and for reasons of nutrition. This book aims to provide easily understood background knowledge of milk quality problems, and to give help and solutions to those committed to improving milk quality. The book identifies the quality parameters of significance, explains what they are, why they are important and why they are measured-the principle of measurement and how and where milk is sampled and tested. Most important of all, the value of good quality milk and how it can be produced and maintained are stressed. The book is therefore intended as a comprehensive source of information and guidance to all involved through the chain of production, processing and handling of milk from cow to consumer. Acknowledgement I am grateful to my son Jonathan whose self-taught computer skills not only amaze a computerphobe like me but have been absolutely invaluable in the production of this book. F. Harding

5 Note Analytical methods for milk have been standardised by a number of National and International Standardisation Organisations, from whom detailed published procedures can be obtained. Several sampling and analytical methods are specifically referenced in the text and are obtainable from the appropriate organisation. These Standardisation Organisations are: ISO IDF BSI International Standards Organisation PO Box Ag Leusden The Netherlands International Dairy Federation Square Vergote Brussels Belgium British Standards Institute Linford Wood Milton Keynes MK144BLE England

6 Contributors Frank Harding Robert Harmon Walther Heeschen Stephen C. Nickerson Formerly Technical Director, Milk Marketing Board of England and Wales, Thames Ditton, Surrey, UK University of Kentucky, College of Agriculture, Animal Sciences, 414 W.P. Garrigus Building, Lexington, Kentucky, , USA Bundesanstalt fur Milchforschung, Institut fur Hygiene, Hermann-Weigmann-Str. 1, Kie1, D-24121, Germany. Louisiana State University Agricultural Center, Louisiana Agricultural Experimental Station, Hill Farm Research Station, Route 1, Box 10, Homer, Louisiana , USA

7 Contents 1 World milk production 1 2 Milk production: Factors affecting milk composition 3 S.C. NICKERSON 2.1 Introduction Synthetic and secretory tissues of the mammary gland Functional anatomy Role of the milk-producing cell Milk flow within the udder The initiation and establishment of lactation The milk ejection reflex Effect of breed on milk composition and yield Role of genetics in milk production Effect of environment on milk composition and yield Effects of season Effects of thermal stress Dairy cattle nutrition and its influence on milk yield and composition IS Dietary effects on milk fat IS Influence of ration on milk protein The effects of milking management practices on milk quality Milking interval Milking rate Frequency of milking Milking routine Cow preparation and residual milk Influence of age and stage of lactation on milk component yield 22 References and further reading 23 3 Mastitis and milk quality 25 R. HARMON 3.1 Introduction Causative organisms Contagious and environmental pathogens Inflammation Compositional changes Milk losses Impact on dairy products Control of mastitis Measurement Summary 37 Further reading 38

8 x CONTENTS 4 Hygienic quality Milk production, plant cleaning, on-farm storage and collection of milk Milk production Plant cleaning and sterilisation Effect of storage time and temperature on bacterial count Types of bacteria Cooling and storage of milk on the farm Collection, delivery and reception of milk Churn collection Bulk collection Delivery and storage prior to processing Storage of milk prior to processing Importance of hygienic quality of milk Measurement of the hygienic quality of milk Simple, rapid tests for mesophiles Tests for cooled milk Staining and counting bacteria Measurement of metabolic products of microbial cells Measurement of metabolic activity The future Sampling, storage, preservation and transportation of samples Sample transport and preservation 57 References and further reading 59 5 Adulteration of milk Introduction Extraneous water Vieth ratio Nitrates as an indication of extraneous water Freezing point test for detecting adulteration Basis of the test Freezing point depression and how it is controlled Measurement units How constant is the freezing point of milk? Freezing point of goat's, buffalo's and ewe's milk Factors affecting freezing point of milk Test method Calculation of amount of extraneous water in milk Sources of contamination by extraneous water How to avoid getting water into milk at the farm Control of extraneous water through payment schemes Other sources of adulteration Salt Sugar Skim-milk powder Detergent sterilants Preservatives Colostrum Blood Taints 73 References and further reading 73

9 CONTENTS Xl 6 Compositional quality 6.1 Composition of milk 6.2 Measurement of total solids in milk 6.3 Measurement of the solids-not-fat (SNF) of milk 6.4 Major constituents Fat Proteins Lactose 6.5 The use of instruments in assessing compositional quality Assessing compositional quality using infrared 6.6 Dairy herd improvement (DHI) and quality payment laboratories 6.7 Quality payment systems for milk Compositional quality References and further reading Milk from sheep and goats 7.1 Introduction 7.2 Milking practices 7.3 Compositional quality 7.4 Measuring cow's milk in sheep's or goat's milk products Differences in lipids Differences in protein Immunological techniques General differences 7.5 Instrumental methods of analysis References and further reading The impact of raw milk quality on product quality Introduction Compositional quality Opportunities for manipulation of compositional quality Fat Protein The effect of raw milk hygienic quality on product quality Animal health Mastitis Physical handling of milk Taints and contaminants Pasteurised milk and cream Summary of action to limit problems in pasteurised products UHT products Cheese Impact of milk quality 109 Further reading 110

10 xu CONTENTS 9 Processed milk 9.1 Introduction Raw milk Frozen milk Concentrated milks Homogenised milk Immune milk 9.2 Heat treatments Pasteurisation Sterilisation UHT treatment Factors affecting the shelf-life of heat-treated milk 9.3 Quality control of heat-treated milks Pasteurised milk UHT milk Sterilised milk 9.4 Milks of modified compositional quality Fat-reduced milks Lactose-reduced milks 9.5 Compositional quality of fluid milk products References and further reading Contaminants W. HEESCH EN and 10.1 Introduction 10.2 Veterinary drugs Importance of drugs Test methods 10.3 Keeping antibiotics out of milk Correct and clear identification of treated cows Record all treatments Withholding time Dry cow therapy Other treatments Milking plant contamination 10.4 Hormones (BST) 10.5 Disinfectants 10.6 Nitrates, nitrites and nitrosamines 10.7 Pesticides Incidence Significance of residues Limiting residues in milk 10.8 PCBs 10.9 Motoxins Toxic metals Lead Cadmium Mercury Dioxins Radionuclides in milk What is radioactivity? Radioactive decay Our exposure to radiation

11 CONTENTS How do we measure radiation levels? Access to milk The risk in perspective Partition of radionuclides in dairy products Irradiation Further reading 11 Nutritional aspects Index 11.1 Introduction 11.2 Milk fat 11.3 Dietary cholesterol 11.4 Proteins 11.5 Milk allergy and intolerance Lactose intolerance Milk allergy 11.6 Cultured or fermented milks 11.7 Immune milk 11.8 Minerals Calcium Trace elements 11.9 Vitamins Further reading Xlll ISO 151 lsi ISS