Table Of ContentMODERN DAIRY TECHNOLOGY
Volume 2
Advances in Milk Products
Second Edition
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MODERN DAIRY
TECHNOLOGY
Volume 2
Advances in Milk Products
Second Edition
Edited by
R. K. Robinson
Department of Food Science and Technology,
University of Reading, UK
BLACKIE ACADEMIC & PROFESSIONAL
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Second edition 1993
Reprinted 1996
© 1993 Chapman & Hall
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ISBN 978-1-4684-8174-7 ISBN 978-1-4684-8172-3 (eBook)
DOl 10.1007/978-1-4684-8172-3
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8
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Preface to the Second Edition
As with the products and processes described in Volume· I of this book,
many of the technical changes associated with, for example, the
manufacture of cheeses or fermented milks have been subtle rather
than dramatic. Nonetheless, the importance for the dairy industry has
often been profound. The market demand for dairy products
containing 'health-promoting' cultures is a development that was
barely discernible 10 years ago, and yet many manufacturers are now
generating a whole range of bio-yoghurts and similar retail items.
Similarly, the legislation covering food hygiene has been modified to
place additional demands upon manufacturers, a move that has in turn
encouraged the further development of analytical methods for quality
controL
These modifications to manufacturing practices are, along with many
others, reflected in this second edition, and I acknowledge with
gratitude the enthusiastic co-operation of all the authors associated
with this project in bringing their disparate contributions up-to-date.
R. K. ROBINSON
v
Preface to the First Edition
Retail sales of most dairy products are still on the increase world-wide,
and this expansion is, at least in part, a reflection of the fact that prices
have tended to remain at a competitive level. This relative stability has
been achieved either through the introduction of major changes in
technology, as in the case of the territorial cheeses, or by a massive
scale-up of a traditional process like yoghurt making, but whatever the
chosen route, the enhanced productivity has been to the benefit of the
consumer. Improved methods of product control have also been instru
mental in raising the efficiency of the various manufacturing procedures,
and the intention of this second volume is to record the current 'state of
the art' in respect of the major dairy products. Obviously, processes will
continue to become sophisticated, but if this text can provide a back
ground to future developments, then the endeavours of the contributors
will have been worthwhile.
R. K. ROBINSON
vii
Contents
Preface to the Second Edition . v
Preface to the First Edition VIJ
1. Manufacture of Yoghurt and Other Fermented Milks
R. K. Robinson and A. Y. Tamime
2. Modern Cheesemaking: Hard Cheeses 49
A. Y. Tamime
3. Modern Cheesemaking: Soft Cheeses. 221
M. B. Shaw
4. Developments in Frozen-Products Manufacture 281
H. L. Mitten and J. M. Neirinckx
5. Physical Properties of Dairy Products 331
M. J. Lewis
6. Modern Laboratory Practice - 1: Chemical Analyses 381
T. Andersen, N. Brems, M. M. B¢rglum, S. Kold-
Christensen, E. Hansen, 1. H. J¢rgensen and L. Nygaard
7. Modern Laboratory Practice - 2: Microbiological
Analyses 417
G. L. Pettipher
8. Technology for the Developing Countries 455
1. T. Homewood and H. J. Hess
Index 495
ix
list of Contributors
Mr T. Anderson
A/S N. Foss Electric, 69 Slangerupgade, DK 3400, Hillerod, Denmark.
Mr M. M. Borglum
A/S N. Foss Electric, 69 Slangerupgade, DK 3400, Hillerod, Denmark.
Mr N. Brems
A/S N. Foss Electric, 69 Slangerupgade, DK 3400, Hillerod, Denmark.
Mr E. Hansen
A/S N. Foss Electric, 69 Slangerupgade, DK 3400, Hillerod, Denmark.
Dr H. J. Hess
Nestec Ltd, Avenue Nestle 55, 1800 Vevey, Switzerland.
Mr J. T. Homewood
Nestec Ltd, Avenue Nestle 55, 1800 Vevey, Switzerland.
Mr J. H. Jorgensen
A/S N. Foss Electric, 69 Slangerupgade, DK 3400, Hillerod, Denmark.
Mr s. Kold~Christensen
A/S N. Foss Electric, 69 Slangerupgade, DK 3400 Hillerod, Denmark.
Dr M. J. Lewis
Department of Food Science & Technology, University of Reading,
Whiteknights, Reading, Berkshire, UK, RG6 2AP.
Mr H. L. Mitten
Apartment 726, 400 West Butterfield Road, Suite 726, Elmhurst, IL
60126, USA.
Mr J. Neirinckx
APV Pasilac AS, Pasteurvej, DK 8600 Silkeborg, Denmark.
Mr L. Nygaard
A/S N. Foss Electric, 69 Slangerupgade, DK 3400, Hillerad, Denmark.
xi
List of contributors
Dr G. L. Pettipher
Reading Scientific Services Ltd, The Lord Zuckerman Research Centre,
University of Reading, Whiteknights, Reading, Berkshire, UK, RG6
2LA.
Dr R. K. Robinson
Department of Food Science & Technology, University of Reading,
Whiteknights, Reading, Berkshire, UK, RG6 2AP.
Mr M. B. Shaw
Dairy Crest Ltd, Portsmouth Road, Surbiton, Surrey, UK, KT6 5QL.
Dr A. Y. Tamime
SAC - Auchincruive, The National College of Food, Land and Envi
ronmental Studies, Food Science & Technology Department, Auchin
cruive, Ayr, UK.
xii
Chapter 1
Manufacture of Yoghurt and Other
Fermented Milks
R. K. Robinson
Department of Food Science & Technology, Univeristy of Reading, UK
and
A. Y.Tamime
SAC-Auchincruive, The National College for Food,
Land and Environmental Studies, Food Science & Technology Department,
Ayr, UK
INTRODUCTION
Although yoghurt and other fermented milks can be manufactured on a
small scale, and with modest levels of technology, the growing demand
for products within the industrialised countries has lead to the installa
tion of plants capable of handling thousands of litres of milk per day. As
a result, sophisticated, automated systems of manufacture are now
commonplace, and yet the basic approach to production is still reminis
cent of the traditional procedures that have been associated with the
peoples of the Middle East for hundreds of years. The reason for this
linkage lies in the fact that success with any fermented product lies with
the microflora and, in many cases, the microorganisms employed in a
modern factory are basically derived from traditional cultures. Obviously,
the manufacturers of starter cultures have become heavily involved with
the selection of strains with special attributes, but at generic or species
level, many of the bacteria enjoy a long association with the dairy
industry (Tamime, 1990). Although historical in origin, the association of
certain cultures with specific products is now well established, and the
link is maintained either by
(a) custom, e.g. the characteristic flavour of yoghurt depends, in the
main, on the presence of detectable levels of acetaldehyde, a
compound released in quantity during the synergistic growth of
2 R. K. Robinson and A. Y. Tamime
Lactobacillus delbrueckii subsp. bulgaricus (Lac. bulgaricus) and
Streptococcus salivarius subsp. thermophilus (Str. thermophilus); or
by
(b) legal or non-legal requirements. In most countries, it is usual to
insist that yoghurt contains at least a small percentage of Lac.
bulgaricus, and similarly that the retail product must contain an
'abundant and viable microflora of starter origin'; products that do
not meet these requirements should not be called 'yoghurt'.
It is against this background that modern systems for fermented milks
have been derived, and as yoghurt remains the most popular item in the
group, it is appropriate that its method of production should serve to
exemplify the associated industrial processes.
PREPARATION OF THE BASIC MIX
The overall procedure for the manufacture of yoghurt is shown in Fig. 1,
and the first step is the production of the basic mix. Most factories
employ liquid milk as the main ingredient, and this material will be
delivered, in bulk, employing road tankers. The reception tests applied to
such milk, and the standards of hygiene expected in the unloading bays,
are similar to those associated with any milk-processing plant (Luck and
Gavron, 1990), and assuming that the normal criteria are met, the milk
will be transferred to storage silos at < 5°C. Beyond this stage, however,
the processing of the milk for yoghurt follows a distinctive pattern of its
own. Although there is a definite market for full-fat yoghurts - both
natural and fruit yoghurts - the major share of the market is taken with
low-fat yoghurts. This trend, while driven in the main by the diet
conscious consumer, does allow the manufacturer to market the cream as
a separate entity. The next step in manufacture usually involves, there
fore, passage of the milk through a centrifugal separator to give a stream
of skim-milk (0·5-0·7% fat) and cream. If the manufacturer wishes to
produce a medium-fat yoghurt, then some of the separated cream will be
fed back into the skim-milk, and automatic monitoring will ensure the
constant composition of the final process stream (see Fig. 2). Once the fat
content has been standardised, the next stage is to raise the level of
milk-solids-non-fat (MSNF), for without this additional protein, the 'gel'
produced during the fermentation stage will be thin and 'watery', and
prone to syneresis, i.e. separation of free whey from the coagulum
