Table Of ContentINDUSTRIAL USES OF STARCH
AND ITS DERIVATIVES
INDUSTRIAL USES
OF STARCH AND
ITS DERIVATIVES
Edited by
J. A. RADLEY
M.Sc., C.Chem., F.S.D.C., F.R.I.C.
APPLIED SCIENCE PUBLISHERS LTD
LONDON
APPLIED SCIENCE PUBLISHERS LTD
RIPPLE ROAD, BARKING, ESSEX, ENGLAND
ISBN-13: 978-94-010-1331-4 e-ISBN-13: 978-94-010-1329-1
DOl: 10.1 007/978-94-0 10 -1329-1
© APPLIED SCIENCE PUBLISHERS LTD 1976
Softcover reprint of the hardcover 1st edition 1976
All rights reserved. No part of this publication may be reproduced,
stored in a retrieval system, or transmitted in any form or by any
means, electronic, mechanical, photocopying, recording, or other
wise, without the prior written permission ofthe publisher, Applied
Science Publishers Ltd, Ripple Road, Barking, Essex, England
Preface
The literature of starch has proliferated in the last ten years at an almost
geometric rate and a number of important changes and developments in
the technology of starch and its derivatives have taken place which makes
it highly desirable to review these in some depth.
The immensity ofthe subject determined the writer to seek the assistance
of a number of prominent workers throughout the world.
Where older work contains factual information of present value it has
been retained, generally in the form of Additional References. These are
brief abstracts which will help specialised searchers in a branch of the
subject to complete the information given in the text. Inclusion of dis
jointed information can often lead to the loss of coherence and clarity,
and the device of the Additional References, whilst allowing smooth
presentation, also allows the inclusion of up-to-the-minute material
appearing after the main text has been written.
Apart from the immense amount of important practical and theoretical
detail required to produce and use starch for many applications in a
number of important industries, a thorough knowledge is also required of
a number of aspects for the successful buying and selling of starch. This
book was written and published contemporaneously with two others
entitled Starch Production Technology and Examination and Analysis of
Starch and Starch Products. The three books together provide a wide
coverage of starch technology and chemistry with the self-contained
individual volumes providing precise information for specialist readers.
The writer feels that starch may well play an increasing role in the global
scene. New varieties, e.g. of wheat, maize, sorghum and triticale, with
greatly increased yields per unit area, make it possible that Europe alone
could become a net exporter of cereals and could attain self-sufficiency in
v
vi
PREFACE
total cereal production within the present decade. The extremely large
unutilised agricultural capacity of the world provides the potential for
greatly increased production. An important part of the attainment of
agricultural self-sufficiency will be planned development of existing and
novel applications for starch and cellulose. This book reviews the tra
ditional uses of starch and its derivatives. The conversion of starch into
glucose syrups and isomerised syrups is also reviewed. This will continue
to expand the already major outlets for starch derivatives. These markets
should all increase at a rate comparable with that of industrial growth in
Europe.
It appears highly probable that sophisticated starch derivatives will
gradually replace non-renewable petrochemical products and that
agriculture itself may change in such a way that land will be used not
simply for the maximum production of a crop but for the maximum
production of carbohydrate.
My most sincere thanks are due to the contributors for their most
helpful and ready co-operation in getting out a volume that is as up to date
as humanly possible, and to my secretary, Mrs R. M. Russell, for her
valuable help and care in producing the manuscript. I should also like to
record my thanks for the constructive criticism of many practical details
through the book in its early stages that were made by Mr Jack Seaman
before his tragic and untimely death.
Finally, my thanks are also due to the publishers for their part in the
production of this book.
Contents
Preface. v
1. Adhesives from Starch and Dextrin
2. The Food Industry 51
3. The Role of Starch in Bread Staling by E. M. A. WILLHOFT 117
4. The Textile Industry 149
5. The Paper Industry by A. H. ZIJDERVELD and P. G.
STOUTJESDIJK 199
6. Miscellaneous Uses of Starch 229
7. Utilisation of the By-products of Starch Manufacture 253
Index 259
vii
CHAPTER 1
Adhesives from Starch and Dextrin
The field of adhesives is a very wide one, and to cover it completely from
all points of view, including the theoretical and the manufacturer's, would
be outside the scope of this volume; hence attention will be directed solely
to the adhesives made from starch and dextrin.
Starch adhesives were used by the ancient Egyptians whilst the use of
flour for making papyrus was mentioned by Pliny and ninth-century
112
writing papers of Chinese origin were sized with starch. Decorative wall
hangings appeared in France prior to 1630 and wallpapers stuck on with
flour pastes were a natural development from these. Starch sizes and
adhesives became much more common in the Industrial Revolution and
in the USA John Biddis was granted a patent in 1802 for the manufacture
of starch from potatoes.113 The introduction of postage stamps in 1840
and the subsequent invention of gummed envelopes gave a fillip to the
demand for adhesives whilst, later, further impetus was given by the
development of photography and the introduction of matches. The pro
duction of the tubular cartridge not only accelerated the development
of the shotgun from the muzzle-loader but also laid the foundation of the
cardboard tube industry. The paper bag and high-speed sealing by machines
have developed into the vast packaging industry of today. Until 40 years
ago animal glue was by far the most widely used industrial adhesive. It has
been replaced by vegetable adhesives, nowadays, for many purposes and
these also have special fields of use of their own. They are especially
suitable for labelling and sealing by high-speed, automatic machinery for
manufacturing corrugated boxwood, plywood, envelopes, stamps and
gummed tapes.
They possess the advantages of low price and can be applied cold or at
moderately low temperatures, being reasonably lacking in odour and taste.
1
2 INDUSTRIAL USES OF STARCH AND ITS DERIVATIVES
The latter point makes them especially useful in the food packaging
industry or for any use where the adhesive may make contact with the
tongue, e.g. envelopes and stamps etc.
1.1 PURPOSE AND APPLICABILITyl
One of the most important considerations affecting the manufacture of
adhesives is the particular purpose for which they are intended. It might
appear, for example, that if a starch paste affixes paper to glass firmly, it
would serve in most trades which require to label bottles containing their
products, but more mature consideration will show that it is not so.
Labels may be applied by hand or by machinery, and an adhesive which
works well for the first purpose would not be suited to the latter, e.g. a
tapioca starch paste will work quite well for hand labelling, but on a
machine, although it contains a lot of water, would not feed correctly, as
it is too viscous and does not possess enough 'stick' or 'tack'. If it were to
be thinned down to the required viscosity the large amount of water present
would saturate the label and cause it to pucker on drying, and what 'stick'
or tackiness the paste did possess previously would be seriously impaired.
A very tacky paste is not required in hand labelling, although in the
machine it may be an important point, especially in a pick-up gum machine.
Again, although the adhesive in this case must be tacky, it must not at the
same time 'fibre' or 'spin', i.e. form long fine threads when two surfaces
between which a portion of adhesive has been pressed are pulled apart.
When an adhesive on a fast-working machine starts to spin, thousands of
fine threads are very soon fiying all over the place, which means that time
is lost in stopping and cleaning the machine and replacing the poor batch
of adhesive by a good one.
In this connection the following observation is of interest. A tapioca
dextrin, fairly well converted, or a yellow potato dextrin, will give solutions
in water which can be made to fibre, but if potato and tapioca starches are
mixed in the correct proportions and together converted to dextrin, the
product gives solutions which will not spin.
R. Takahashi and co-workers 157 have examined the spinnability of
starch pastes and have devised an apparatus for its measurement. They
obtained the following results:
1. The length of the threads spun in various unmodified starch pastes
of the same viscosity decreased in order: potato > tapioca > waxy
com > wheat> maize starch.
ADHESIVES FROM STARCH AND DEXTRIN 3
2. The degree of spinnability was related to the relaxation time,
expressed as z' /G' where z' = dynamic viscosity, poise; G' = dynamic
modulus, dyne/cm2 and structural viscosity.
3. The degree of spinnability increased with increasing degree of
gelatinisation and with decrease of gelatinising temperature by
introduction of hydroxy-ethyl, hydroxy-propyl and acryl-amide
groups, etc.
4. They conclude that the spinnability increases with increasing dis
persion of the starch granules.
Sometimes the product has to resist water, as when used for affixing
labels on champagne or wine bottles. For this purpose the glues made by
the cold dispersion of starches in alkali (Perkin glues) at high concentration
(generally 18-25 %) and afterwards neutralised with a mineral acid such
as nitric or sulphuric acid are suitably water resistant. Other methods of
imparting water resistance to starch, e.g. urea formaldehyde resins,
glyoxal, etc. have also been tried with effect. In other cases the addition of
calcium or barium hydroxide confers some water-resisting power, but the
effect is slight.
If a firm will accept returned empty bottles, the labels must be easily
detachable when immersed in warm water or in the cleaning liquid of the
washing machine; straight starch pastes serve very well here. Similarly with
biscuit-tin labels.
So far we have only mentioned adhesives for use between a non
absorbing and polished body and one that absorbs some of the adhesive,
but when we come to deal with rough surfaces, such as a wood-to-wood
joint, different requirements are met. In ajoint between two rough surfaces
all interspaces must be filled with adhesive, which must also firmly unite
those portions that are in contact, the area of which is very much less than
the surface area of the interspaces.
Thus the efficiency of an adhesive to bind together two rough surfaces
will depend very largely on its viscosity; it must be sufficiently fluid to
penetrate the interspaces, and yet have enough body to give a thin but
strong layer of adhesive when the joint is dry. With a comparatively rough
surface the adhesive can 'key' itself into the material, and a rough parallel
ism between the strength of the joint and the strength of a thin film of the
adhesive should exist as long as the adhesive is not stronger than the
material it is joining. When other factors, such as rate of loading and
relative humidity, elasticity, deformability, flexibility, stress and strain
relations, are taken into account the determination of the tensile strength
4 INDUSTRIAL USES OF STARCH AND ITS DERIVATIVES
of a thin film of adhesive does give a good indication of its value in
practice.2
F. Camps-Campins106 has measured the pore size of a number of
papers, and he points out that paper adhesives have to be formulated so
that the penetrative properties have to counterbalance the pore size of the
paper. Thus papers with small pore size require penetrative adhesives but
those with large pores require a filming type of adhesive. Further, according
to this worker, the pore size affects the rate at which the glue sets and also
the behaviour of the wet glue films under pressure. The adhesive must be
formulated, therefore, so that its properties compensate for these factors
and for unequal porosities in the surfaces to be glued. Singleterry's114
observations are of interest in this respect as this worker has found that the
adhesive is keyed to the paper by filling the undercut regions about the
surface fibres giving mechanical keying.
The term 'deformability' is used to define the property of an adhesive
to adapt itself readily to stresses and strains, slow or sharp, which may be
set up in a joint after it has been made. While the adhesive is drying and
setting, strains are set up in the joint by swelling, shrinking, warping,
alteration either in humidity or temperature, and it is the deformability of
a good adhesive which allows it to accommodate itself to new conditions
as they occur and yet maintain a firm bond between the surfaces joined.
In some adhesives the internal strains set up on drying are so great that the
film flies to pieces; an example of this kind is gum-arabic or gum senegal.
If, however, glycerine, glucose or some similar agent is added to the gum
it acts as a plasticiser and confers deformability on the film, which then
dries without disintegrating.
So important is this property that when measuring the tensile strength
of an adhesive film it is quite as necessary to note its deformability as its
strength, if the figures are to be of value in the practical evaluation of the
substance as an adhesive. Colloids in general show this property to a
greater extent than pure substances and are generally superior to them as
adhesives. The following figures illustrate this point: Isinglass, tensile
strength, 13 000 Ib/in2 (90 N/mm2) tough; starch, 7000 Ib/in2 (48 N/mm2),
ductile; sodium silicate, 600 Ib/in2 (4 N/mm2), very brittle; gum-arabic,
no value obtainable, very brittle. Gum-arabic cracks spontaneously on
drying and dextrin pastes which crack on the surface should not be used
to make adhesives for first-class work. If gum-arabic is plasticised, how
ever, its strength immediately increases.
Rate of loading and humidity are important, and it has been found that
long-continued stress on a joint, made between metals with recognised
