Wheat Flour

162 Pages·2016·44.518 MB·English

by  William A. Atwell, Sean Finnie

Handbook Series
Wheat Flour
SECOND EDITION
Sean Finnie
and
William A. Atwell
Front cover: Counterclockwise from upper left:
colorful rotelle pasta ©An Nguyen/Shutterstock.com;
whole flour in bag with wheat ears ©M. Unal Ozmen/Shutterstock.com;
flakes, breakfast cereal ©Davydenko Yuliia/Shutterstock.com;
shredded wheat ©Michael C. Gray/Shutterstock.com;
jam-filled cream cheese cookies ©Coprid/Shutterstock.com;
bagels courtesy Elaina Espino and Karee Bohman
Library of Congress Control Number: 2015960970
International Standard Book Number: 978-1-891127-90-8
©2016 by AACC International, Inc.
Published 2001. Second Edition 2016
All rights reserved.
No part of this book may be reproduced in any form, including photocopy,
microfilm, information storage and retrieval system, computer database or
software, or by any other means, including electronic or mechanical,
without written permission from the publisher.
Reference in this publication to a trademark, proprietary product,
or company name is intended for explicit description only
and does not imply approval or recommendation of the product
to the exclusion of others that may be suitable.
Printed in the United States of America on acid-free paper
AACC International, Inc.
3340 Pilot Knob Road
St. Paul, Minnesota 55121, U.S.A.
About the AACC International Handbook Series
The AACC International Handbook series was developed for food industry practitio-
ners. It offers a practical approach to understanding the basics of food ingredients, ap-
plications, and processes—whether the reader is a research chemist wanting practical in-
formation complied in a single source or a purchasing agent trying to understand product
specifications. The handbook series is designed to reach a broad readership; the books are
not limited to a single product category but rather serve professionals in all segments of
the food processing industry and their allied suppliers.
In developing this series, AACC International recognized the need to fill the gap be-
tween the highly fragmented, theoretical, and often not readily available information in
the scientific literature and the product-specific information available from suppliers. It
enlisted experts in specific areas to contribute their expertise to the development and
fruition of this series.
The content of the books has been prepared in a rigorous manner, including substan-
tial peer review and editing, and is presented in a user-friendly format, with definitions
of terms, examples, illustrations, and trouble-shooting tips. The result is a set of practical
guides containing information useful to those involved in product development, produc-
tion, testing, ingredient purchasing, engineering, and marketing aspects of the food in-
dustry.
Acknowledgment of Sponsors for Wheat Flour, Second Edition

Buhler Inc. Corbion Caravan
Minneapolis, MN 55440 Lenexa, Kansas 66215
www.buhlergroup.com www.corbion.com

CHOPIN Technologies General Mills, Inc.
Villeneuve-la-Garenne, France Minneapolis, MN 55426-1347
www.chopin.fr www.generalmills.com
AACC International has designed this handbook series as practical guides serving the
interests of the food industry as a whole, rather than the individual interests of any single
company. Nonetheless, corporate sponsorship has allowed these books to be more afford-
able for a wide audience.
Preface
The purpose of Wheat Flour has not changed since the publication
of the first edition in 2001. While the basic understanding of wheat
has changed slowly, there have been rapid advances in knowledge
focused on wheat’s nutritional properties, analysis of its functional
properties, and formulation of wheat in consumer products. This sec-
ond edition supplies more-current information on these topics. It has
also been our intention to update the first edition by supplying cur-
rent information on the types of wheat now produced and numbers
describing current production and consumption around the world.
As with the first edition, we have attempted to make this text un-
derstandable not only to scientists entering the field of grain science,
but also to those working in peripheral areas. To facilitate understand-
ing, terms specific to wheat technology have been defined in a glos-
sary. Since Wheat Flour is intended only as an introduction, references
have been updated and expanded, and a list of currently relevant
websites has been supplied to allow the reader to obtain additional
information on all the topics covered.
Sean Finnie
William Atwell
v
CHAPTER
1
Wheat
A wheat seed warms, and moisture begins to penetrate its outer
In This Chapter
layers. The metabolic processes fostering growth are initiated; a
shoot emerges, as does a root, and the seed becomes a fledgling Historical Perspective
wheat plant. If conditions are favorable, the plant continues to grow,
Wheat Types
resembling its close cousins, the common grasses found in lawns.
The plant continues to grow and, eventually, inside the stem, a head Wheat Breeding
of wheat begins to develop. The stem swells, and then the head Growth Regions
emerges. It flowers, initiating the development of new seeds within
Wheat Consumption
the head, which ripen from a soft “milky” consistency to kernels
and General Uses
that eventually resemble the seed that initiated this entire growth
Kernel Structure
cycle. As the wheat ripens, the plant turns from green to amber and
loses moisture. Germination and
It is now time to harvest the new wheat kernels by mechanically Growth
separating them from the rest of the plant. Perhaps the wheat will be
Wheat Production
transported to elevators, stored, and transported to larger elevators Problems
before the wheat is tempered and milled into flour, or perhaps the
World Wheat
kernels will be milled locally. Regardless of where it is milled, this
Production and
“new crop” flour will eventually be used to produce a seemingly end-
Marketing
less variety of wheat- based products.
Logistics
As the major ingredient in such products, flour exerts a major ef-
fect on their quality. To be able to effectively use flour to make high- Wheat Standards
quality products without encountering processing or end-p roduct
Wheat Storage
quality problems requires a thorough working knowledge of all as-
Factors Important to
pects of wheat and flour. It is the objective of this handbook to be a
the Wheat Producer
broad- based resource to aid the reader in acquiring this knowledge.
Historical Perspective
Clearly, wheat was one of the earliest and most widely grown agri-
cultural crops cultivated by humans. It is generally accepted that
wheat originated in the Tigris and Euphrates River Valley and that the
cultivation of wheat as a food crop probably began between 10,000
and 8000 B.C.E. Egyptian tombs 5,000 years old have been unearthed
that contain hieroglyphics depicting the harvesting and processing
of wheat. Chinese records of wheat date back to 2700 B.C.E. The hardi-
ness of wheat and the variety of food forms that it can take have
made it a truly universal part of the human diet.
1
2 / CHAPTER ONE
Wheat Types
The first type of wheat cultivated was einkorn (Triticum mono­
coccum), a diploid wheat containing seven chromosome pairs. Later a
Diploid—Describing an organ-
28- chromosome tetraploid wheat known as emmer (T. dicoccum)
ism with two sets of chromo-
somes. An early wheat known evolved and was cultivated extensively in the Middle East. Emmer
as einkorn was diploid. and einkorn are still cultivated and are now referred to as ancient
grains. Durum wheat, which is used today to make pasta, is also tetra­
Chromosome—A body com- ploid. Common wheat, which is used to make the wide variety of
posed of DNA and carrying
dough and batter- based products today, is hexaploid, having three
part of the genetic code for the
pairs of each of the seven basic chromosomes.
organism, i.e., the wheat plant.
With respect to biological classification, three species of wheat are
There are seven distinctly differ-
ent chromosomes in wheat. most commonly grown today. The first, T. aestivum, forms the classes
hard red winter, hard red spring, soft red winter, hard white, and soft
Tetraploid—Describing an or- white. T. compactum includes the club wheats. The third species is
ganism with four sets of chro- T. durum, which includes the durum and red durum wheat classes.
mosomes. Durum wheat is
Three sets of terms are used to describe most modern T. aestivum
tetraploid.
wheat types. The first term (i.e., “hard” or “soft”) relates to the physi-
cal hardness of the kernel. Hard wheat requires more energy to mill
Hexaploid—Describing an or-
ganism with three sets of chro- than soft wheat, because each individual kernel requires more force
mosomes. Most common to crush it. The second term (i.e., “red” or “white”) relates to the pres-
wheat is hexaploid. ence or absence of a reddish pigment in the outer layers of the wheat
kernel. A visual examination is all that is required to differentiate
Species—A biological classifica-
these two types of wheat. The third term (i.e., “winter” or “spring”)
tion below genus and above
generally describes the growth “habit” of the wheat. Winter wheat is
variety. Wheat varieties from
planted in the autumn, sprouts in the spring, and is harvested in the
three species of wheat are com-
monly grown. summer. It requires a period of below- freezing temperatures before it
can form the heads that ultimately contain the wheat kernels. This
Class—A type of wheat usually process is known as vernalization (from the Latin for “spring”). Spring
designated by hardness, color, wheat does not require cold weather in order to form heads and is
and growing season. Hard red
generally planted in the spring and harvested in late summer or au-
spring wheat is a class of wheat
tumn. All combinations of growing season, color, and hardness are
that is commonly used to pro-
possible. Consequently, three letters (e.g., HRS for hard red spring,
duce bread. Durum is a class of
wheat used to make pasta SWW for soft white winter, etc.) are used to describe most common
products. wheats.
The wheats making up the two other species commonly grown
Vernalization—A process re- (T. durum and T. compactum) are distinctly different from the com-
quired for a winter wheat to
mon wheat types described above. Durum wheat does not require
create wheat heads. The tem-
vernalization and produces kernels much harder than common hard
perature must drop below
wheats. Additionally, desirable yellow pigments are not concentrated
freezing for this to occur. If win-
ter wheat is not vernalized, the in the outer layers of the durum kernel but are distributed through-
plant will grow but never pro- out the entire endosperm. Club wheats are unique in that they are
duce heads with new seeds. always soft and usually have low protein content. However, both
winter and spring varieties of club wheats exist, as well as red and
Variety—A biological classifica-
white varieties.
tion below species. Many vari-
HRW, HRS, SRW, durum, hard white (HW), and soft white (SW) are
eties of wheat are grown
the major classes of wheat. Club wheat is grown in such small quanti-
throughout the world, and new
varieties are continually being ties that it is often included in the soft white class. Within each class
developed. are a large number of wheat varieties. Each variety is genetically differ-
WHEAT \ 3
ent and is differentiated from others in some observable or measur-
able characteristic such as yield potential, disease resistance, drought
resistance, or some physical attribute of the plant.
Wheat Breeding
Many wheat varieties were initially brought from one area to an-
other with a similar climate. This was the case with the variety Turkey
Red, which was transported from the Ukraine to Kansas. However,
new varieties are always under development. Traditionally, this has
been accomplished with classical breeding programs in which prom-
ising varieties are genetically crossed and their progeny evaluated for
positive and negative characteristics.
A good breeding program must take all aspects of wheat quality
(e.g., yield, climatic tolerance, protein quantity, protein quality, and
baking performance) into account to develop a truly superior variety.
The process of creating a new variety takes several years. Individual
plants of known varieties with desirable traits are first selected. They
are then crossed, and the progeny are grown through several genera-
tions under controlled conditions to produce enough seed for evalu-
ation. Evaluations are first performed on a small scale in a laboratory
to identify any improvements. Varieties exhibiting desirable charac-
teristics in the laboratory are then grown in test plots under field
growing conditions. Wheat varieties from the test plots are evaluated
for growth characteristics (e.g., yield and disease resistance), milling
quality, and baking quality. Those exhibiting superior characteristics
in these field tests are then released to wheat producers for commer-
cial use. Adoption of new varieties by wheat producers is a subjective
process and can also take several years. Since the process of develop-
ing, testing, and releasing new wheat varieties is so time- consuming,
the percentages of each variety grown in a given area change slowly
from year to year. An improved variety may take five years or more
between initial development and acceptance as a commercial variety
for production.
Recently, biotechnological methods have been applied to improve
wheat and create new varieties (i.e., genetically modified organisms
[GMOs]). These techniques often shorten the time needed for devel-
opment of a new variety. For example, if a gene is known to have an
improving effect from earlier testing, it can be incorporated into the
target wheat plant and monitored through subsequent generations to
ensure that the improvement is retained. Incorporation of a new gene
using biotechnology does not eliminate the laboratory testing de-
scribed above for the traditional procedures, but biotechnology elimi-
nates some traditional selection processes required to ensure that de-
sirable traits are maintained. Of course, varieties developed with these
techniques are subjected to field tests and must also meet the other
requirements described above. At the time of this publication, GMO GMO—Genetically modified
wheats have been developed but have not been released. These in- organisms.
4 / CHAPTER ONE
clude wheat varieties resistant to the broad- spectrum herbicide
glyphosate similar to those that have been in production for soy-
beans and corn for many years.
Waxy and partial waxy wheats are examples of wheats that have
been developed. In normal wheat, about 75% of the starch is in the
form of the branched polymer amylopectin and 25% is in the form of
the linear polymer amylose. Three genes regulate the amount of amy-
lopectin in wheat. By controlling these genes, wheat breeders have
been able to develop waxy wheat, in which essentially all of the starch
is in the form of amylopectin. In partial waxy wheat, not all of the
genes are controlled, and an amylopectin amount intermediate be-
tween normal and waxy wheat occurs. Waxy and partial waxy wheats
are now being evaluated with respect to end- use qualities.
More recently, advances have been made in adjusting kernel hard-
ness. A durum, the hardest of all wheat types, has been developed
with soft- kernel characteristics but with all other attributes main-
tained. This is accomplished by controlling the genes that code for
friabilin, a protein found in high amounts on the surface of soft
wheat starch granules, in moderate amounts on hard wheat starch
granules, and absent on durum starch granules. By expressing friabi-
lin in the durum system, it is possible to achieve a kernel hardness
equivalent to that of soft wheat (1,2).
Advances are also being made toward increasing the nutritional
value of wheat. For example, crossing standard wheat varieties with
their wild wheat relatives (e.g., spelt) appears to be a promising ave-
nue for developing wheat varieties with enhanced zinc and iron lev-
els (3). Enhanced health benefits in wheat focused on protein quality
(e.g., lysine content) and increased dietary fiber levels are also being
explored (4).
Growth Regions
Wheat is a hardy crop and can be grown under a wide range of
environmental conditions. Renowned wheat-g rowing regions in the
world include the Ukraine, Buenos Aires province in Argentina, the
lowlands of Europe, the southeastern and southwestern states of
Australia, and the Great Plains of the United States and Canada.
Because it is grown in so many places in the world, wheat is being
sown and harvested at some location at any given time during the
Amylopectin—A branched year. Table 1.1 shows the production of the countries producing the
polysaccharide composed en- most wheat.
tirely of glucose units. It is one However, not all wheats are grown in all environments. The United
of the two major components States may be unique in that every class of wheat is grown within its
of starch.
boundaries (Fig. 1.1). HRW wheat is grown in a wide belt extending
from Texas to South Dakota and Montana. HRS wheat and durum
Amylose—A linear polysaccha-
wheat are grown in the Dakotas, Minnesota, and Montana. SRW
ride composed entirely of glu-
cose units. It is one of the two wheat cultivation extends through the Ohio and southern Mississippi
major components of starch. River valleys as well as the southeastern states from Virginia to
WHEAT \ 5
TABLE 1.1. Major Wheat-Producing Countriesa
Wheat Production 2013/14,
(1,000 metric tons) 2009/10 2010/11 2011/12 2012/13 Jun
Argentina 12,000 17,200 15,500 11,000 13,000
Australia 21,834 27,410 29,923 22,077 24,500
Canada 26,950 23,300 25,288 27,200 29,000
China 115,120 115,180 117,400 120,600 121,000
Egypt 8,523 7,200 8,400 8,500 8,800
EU-27 138,816 136,017 137,331 132,064 137,443
India 80,680 80,800 86,870 94,880 92,000
Iran 13,485 15,030 13,500 14,000 15,500
Kazakhstan 17,051 9,638 22,732 9,841 15,000
Morocco 6,400 4,887 5,800 3,870 6,800
Pakistan 24,000 23,900 25,000 23,300 24,000
Russia 61,770 41,508 56,240 37,720 54,000
Turkey 18,450 17,000 18,800 15,500 17,600
Ukraine 20,866 16,844 22,324 15,761 19,500
United States 60,366 60,062 54,413 61,755 56,613
Uzbekistan 6,200 6,500 6,300 6,700 6,700
Others 54,232 49,809 51,352 50,824 54,400
a From (5).
Fig. 1.1. U.S. growth regions for the different classes of wheat. 1 = hard red winter, 2 = hard red spring, 3 =
soft red winter, 4 = durum, 5 = hard white, 6 = soft white. (Adapted from [6])
6 / CHAPTER ONE
Kernel—An individual seed of a Alabama. Soft white and club wheats are grown primarily in the
cereal grain. Pacific northwestern states of Washington, Oregon, and Idaho. Hard
white wheat is now gaining more prominence in Kansas and other
Bran—The outer protective lay-
HRW- producing areas. Within any given region, many varieties of
ers of a wheat kernel. Bran can
wheat may be grown, but a relatively small number of varieties make
be pigmented, as in the red
wheats, and is high in fiber up the bulk of the acres planted.
content.
Wheat Consumption and General Uses
Fiber—Carbohydrates that can-
not be digested in the human
gut. Pentosans and β-glucans Wheat is consumed all over the world, and a wide variety of prod-
are fibers found in wheat. ucts are made from it. Amounts for the countries consuming the most
wheat are shown in Table 1.2.
Ash—Material, composed pri- Not all wheat types are suitable for all products. HRW, HW, and
marily of minerals, surviving
HRS wheats are generally used in the production of breads and re-
very high temperature treat-
lated yeast- leavened, dough- based products. This is due in large part
ment of flour or wheat.
to the ability of doughs made from these types of wheat flour to re-
Germ—The potential wheat tain leavening gases and subsequently yield breadlike structures and
plant within the wheat kernel. textures. SRW and SW are commonly used in the production of cakes
It is high in oil content and and other batter- based products as well as in crackers, breakfast cere-
many nutrients. als, and cookies. Flour from this type of wheat generally does not
produce highly elastic intermediate or final products. As a result, the
Endosperm—The major por-
textures of products made with soft wheat are generally not very
tion of the wheat kernel by
chewy. Soft white and club wheats are used in products such as noo-
weight. It is the primary con-
stituent of flour and contains dles, where the presence of pigmented bran specks in the product
starch and gluten.
TABLE 1.2. Major Wheat-Consuming Countriesa
Wheat Consumption 2013/14,
(1,000 metric tons) 2009/10 2010/11 2011/12 2012/13 Jun
Algeria 8,550 8,750 8,950 9,250 9,450
Brazil 11,000 10,800 11,200 10,900 11,200
Canada 7,213 7,552 9,852 9,900 9,700
China 107,000 110,500 122,500 120,000 120,500
Egypt 18,100 17,700 18,600 18,700 18,700
EU-27 125,000 122,250 126,250 120,000 122,750
India 78,150 81,760 81,406 84,140 88,010
Iran 16,800 16,200 15,500 16,100 16,600
Kazakhstan 7,600 6,200 7,400 6,800 7,200
Morocco 7,800 7,850 8,500 8,200 8,400
Pakistan 23,000 23,000 23,100 23,400 23,500
Russia 39,600 38,600 38,000 33,150 36,500
Turkey 17,100 17,300 18,100 17,500 17,600
Ukraine 12,300 11,600 14,950 12,000 11,500
United States 30,978 30,710 32,155 37,586 35,979
Uzbekistan 7,500 7,700 8,000 7,975 7,950
Others 132,781 135,187 143,343 144,102 145,655
aFrom (5).