Wheat: Chemistry and Technology

Khalil Khan

• Editorial: Woodhead Publishing and AACC International Press
• Año: 2016
• ISBN:
  9780128104545
• Edición: 4
• Categoría: Technology & Engineering
• Categoría: Food Science

Wheat science has undergone countless new developments since the previous edition was published. Wheat: Chemistry and Technology, Fourth Edition ushers in a new era in our knowledge of this mainstay grain. This new edition is completely revised, providing the latest information on wheat grain development, structure, and composition including vital peer-reviewed information not readily available online.

It contains a wealth of new information on the structure and functional properties of gluten (Ch. 6), micronutrients and phytochemicals in wheat grain (Ch. 7), and transgenic manipulation of wheat quality (Ch. 12). With the new developments in molecular biology, genomics, and other emerging technologies, this fully updated book is a treasure trove of the latest information for grain science professionals and food technologists alike.

Chapters on the composition of wheat—proteins (Ch. 8), carbohydrates (Ch. 9) lipids (Ch. 10), and enzymes (Ch. 11.), have been completely revised and present new insight into the important building blocks of our knowledge of wheat chemistry and technology. The agronomical importance of the wheat crop and its affect on food industry commerce provide an enhanced understanding of one of the world's largest food crop.

Most chapters are entirely rewritten by new authors to focus on modern developments. This 480-page monograph includes a new large 8.5" x 11" two-column format with color throughout and an easy to read style.

Wheat: Chemistry and Technology, Fourth Edition provides a comprehensive background on wheat science and makes the latest information available to grain science professionals at universities, institutes, and industry including milling and baking companies, and anywhere wheat ingredients are used. This book will also be a useful supplementary text for classes teaching cereal technology, cereal science, cereal chemistry, food science, food chemistry, milling, and nutritional properties of cereals. Cereal and food science graduate students will find Chapter 1 – "Wheat: A Unique Grain for the World" particularly helpful because it provides a succinct summary of wheat chemistry.

CHAPTER 1

Wheat: A Unique Grain for the World

C.W. Wrigley Food Science Australia and Wheat CRC, North Ryde (Sydney), NSW, Australia

Wheat is unique. Of all the seeds in the plant kingdom, the wheat grain alone has the gluten proteins capable of forming the fully elastic dough required to bake leavened bread. These gluten proteins are also needed to make the great variety of foods that are associated with wheat around the world. This unique property is the reason why about 10¹⁴ wheat plants are grown annually on all continents (except Antarctica), producing well over 600 million tonnes (metric tons, t) of grain (Table 1.1) from about 220 million hectares (ha), with an average yield of nearly 3 t/ha. Worldwide, this level of wheat production is equivalent to nearly 300 g of grain per person per day. However, in practice, this theoretical estimate is meaningless, since the regions of wheat production differ from the populations in need of the grain. Furthermore, although human food is the main use of wheat, a significant proportion also goes to animal feed and to industrial uses.

TABLE 1.1

Wheat Production and Yield in 2005 for Countries Producing More Than one Million Tonnes^a

Country	Production (millions of tonnes)	Yield (t/ha)
Algeria	3	1.4
Argentina	16	2.6
Australia	24	2.1
Austria	1	5.0
Bangladesh	1	2.0
Belgium	2	8.3
Brazil	5	2.2
Bulgaria	4	3.2
Canada	26	2.6
Chile	2	4.4
China	96	4.2
Czechoslavakia, former area of	6	5.5
Denmark	5	7.2
Egypt	8	6.5
Ethiopia, former area of	2	1.4
France	37	7.0
Germany	24	7.4
Greece	2	2.1
Hungary	5	4.5
India	72	2.7
Iran	15	2.3
Italy	8	3.5
Mexico	3	5.0
Morocco	3	1.0
Nepal	1	2.1
Netherlands	1	8.7
Pakistan	22	2.6
Poland	9	3.8
Romania	7	2.9
Russian Federation	45	…
Saudi Arabia	2	5.2
South Africa	2	2.5
Spain	38	1.7
Sweden	2	6.3
Syrian Arab Republic	5	2.6
Tunisia	1	1.6
Turkey	21	2.6
UK	15	8.0
USA	57	2.8
USSR, former area of	92	2.0

^aSource: FAOSTAT data (2006), accessed via the web site at www.fao.org.

Wheat and bread are integral to human life as well as to human food. Wheat and bread have entered our vocabulary as symbols of food and of social interaction. It is an Eastern European custom to offer a loaf of bread as a symbol of welcome to a guest. Biblical mentions of wheat and bread, such as “Man shall not live by bread alone,” “Cast thy bread upon the waters,” and “Give us this day our daily bread” have entered common usage. The motto of the United Nations’ Food and Agriculture Organization is “Fiat panis,” meaning “Let there be bread.” On the other hand, hunger has traditionally been depicted as the absence of wheat and bread. The dilemma of the world’s “have-nots” is depicted graphically on an old German platter by wheat heads and slices of bread and the words “Altes Brot ist nicht hart – kein Brot, das ist hart!” (“Old bread is not hard—no bread, that is hard”) (Fig. 1.1).

Fig. 1.1 Old German platter, depicting the plight of the world’s hungry. (Reproduced, with permission, from Bushuk 1992)

WHEAT AND PEOPLE

Wheat and Human Origins

Wheat is among the oldest and most extensively grown of all grain crops. The period over which people have influenced the cultivation of wheat is, however, short in terms of human existence on earth. It is widely accepted that wheat was first grown as a food crop about 10,000–8,000 b.c.e. Presumably, wheat’s unique dough-forming property was seized upon by early people, so that wheat grain was treasured above other grain species for baking. Along with other cereal grains, wheat became a major reason for the transition from the hunter-gatherer nomad to the settled agriculturalist. The cultivation of storable grains meant that the family or tribe did not need to keep moving in search of whatever plant and animal food could be found. Instead, it was able to settle in one place, growing crops that could be stored safely for the long period after harvest. This major change in attitude led to a changed life style, leaving time for the development of cultural exploits beyond the day-to-day necessity of seeking food (Diamond 1997).

DEITIES OF WHEAT

The ancient civilizations of Babylonia, Egypt, Crete, Greece, and Rome were based on wheat as a principal food plant. The Egyptians believed wheat to have been a gift of the god Osiris (Buller 1919). The Greeks attributed the provision of wheat to Demeter (Fig. 1.2), the “goddess of the earth and its fruits, a deity presiding over or representing the generative powers of nature” (Fowler 1908). Demeter may have been adopted by the Romans under the name Ceres, but there is evidence that in her earliest form, Ceres was strictly of Roman origin. The first temple to Ceres was built at the foot of the Aventine, one of the seven hills of Rome, and dedicated to Ceres on (our equivalent of) April 19, 493 b.c.e. (Fowler 1908). According to tradition, the temple to Ceres was a consequence of a famine in the year 496 b.c.e. that limited the supply of grain. A divine source of help was sought, and Ceres was the obvious source.

Fig. 1.2 The Greek goddess, Demeter, the goddess of wheat. Awned wheat heads and stalks form her headdress, the sheaf in her arm, and the contents of the basket at her feet. Drawn from a painting found in Pompeii, Naples. (Reproduced from Buller 1919)

The name “Ceres” came from the verb creare, to create, but the meaning became narrowed to relate to agriculture and subsequently to grains, especially wheat. The blessing of Ceres was invoked to bring to maturity the seed sown in the autumn, by preserving it from all pests and hurtful events. The time of autumn sowing extended from the equinox to the winter solstice, but there was also a spring sowing, which began on (our equivalent of) February 7 (Fowler 1908). The festival of Cerealia at the end of the Roman summer involved the offering of ripe ears of wheat to Ceres (Fowler 1908). Today, the term cereals refers to the family of grains derived from the monocotyledonous grasses. The main cereal species are listed in the upper half of Table 1.2, where they are contrasted with the dicotyledonous grains—oilseeds and legumes.

TABLE 1.2

The Main Grain Species, Showing Their Significance in Terms of Annual Production in 2005

Family or Tribe	Genus and Species	Common Names	World Production^a (millions of tonnes)
Monocotyledonous plants
Triticeae	Triticum aestivum	Common (bread) wheat		626 (all wheat)
Triticeae	Triticum durum	Durum (macaroni) wheat
Triticeae	xTriticosecale sp.	Triticale		13
Triticeae	Secale cereale	Cereal rye		15
Triticeae	Hordeum vulgare	Barley		138
Aveneae	Avena sativa	Oats		25
Andropogoneae	Sorghum bicolor	Sorghum		57
Andropogoneae	Zea mays	Corn, maize		692
Oryzeae	Oryza sativa	Rice		615 (as paddy)
Oryzeae	Zizania aquatica	Wild rice
Eragrostideae and Paniceae	Several genera a...