Paper Code and Title: Food and Nutrition

Module Code and Name: F01FS13 Structure of Wheat grain-Classification, Structure,

Conclusion.
Name of the Content Writer: Dr. P.A. Raajeswari

STRUCTURE OF WHEAT

The cereal grains are seeds of the grass family. The word cereal is derived from ceres,
Roman Goddess of Grain. The principal cereal crops are Rice, Wheat, Maize, Jowar, Ragi and
Bajra.

Wheat is a grass widely cultivated for its feed, a cereal grain which is a worldwide staple
food. There are many species of wheat which together make up the genus Triticum, the most
widely grown is common wheat. Wheat grains have either a dark, orange-brown appearance or a
light, yellowish colour. Wheat belongs to the genus Triticum and there are 30,000 species. The
wheat produced in the country belongs to triticumaestivum (95%), Triticum durum (4%) and
triticumdicoccum (1%).

Depending on the soil, climate conditions, quality of seed and farming techniques, wheat
varies widely in its properties. It is grown on more land area than any other food crop.

World trade in wheat is greater than for all other crops combined. In 2016, world
production of wheat was 749 million tones, making it the second most produced cereal after
maize. Since 1960, world production of wheat and other grain crops has tripled and is expected
to grow further through the middle of the 21st century.Globally, wheat is the leading sources of
vegetable protein in human food, having a protein content of about 13%, which is relatively high
compared to other major cereals and staple foods. The ease with which wheat grains produced
and stored, together with relatively low cost and nutritional contributions as resulted in wide
spread use of wheat and wheat is the staple food in the diets of most population groups.

When eaten as the whole grain, wheat is a source of multiple nutrients and dietary
fiber.Regular consumption of wheat fiber is associated with lower risk of several diseases,
including coronary heart disease, stroke, cancer and type 2 diabetes. In a small part of the general
population, gluten – the major part of wheat proteincan trigger celiac disease, non–celiac gluten
sensitivity,glutenstaxia and dermatitis herpetiformis.
Paper Code and Title: Food and Nutrition
Module Code and Name: F01FS13 Structure of Wheat grain-Classification, Structure,
Conclusion.
Name of the Content Writer: Dr. P.A. Raajeswari

There was a time when many countries preferred white seeded wheat’s. Now a days this
preference has gradually disappeared and mainly golden brown colored varieties are grown
nowadays. Wheat is generally classified according to the colour and hardness of grain. Hard
wheat yield flour that is high in good quality protein such has high Water Absorption Power
(WAP) good mixing and fermentation tolerance and has good retention power and is excellent
for bread making. Soft wheat have lower amount of proteins and absorb less water. Such flours
are good for cakes, soft dough, biscuits and cookies but are unsuitable for bread making.

Now let’s see the BOTANICAL CLASSIFICATION OF WHEAT

Kingdom: Plantae

Unranked: Angiosperms

Unranked: Monocots

Unranked: Commelinids

Order : Poales

Family : Poaceae

Subfamily: Pooideae

Tribe : Triticeae

Genus : Triticum

CLASSIFICATION OF INDIAN WHEATS

Wheat is an annual plant of Grammeae family. Although as many as 18 species of wheat have
been described and recognized, only a few are of agricultural importance. They are discussed as
under.
Paper Code and Title: Food and Nutrition
Module Code and Name: F01FS13 Structure of Wheat grain-Classification, Structure,
Conclusion.
Name of the Content Writer: Dr. P.A. Raajeswari

1. EMMER WEHAT – (TriticumdicoccmSehuh): This is reported to be grown in certain

areas of southern India. i.e. Maharastra, Tamilnadu, Karnataka and Andhrapradesh. It is
good for the South Indian dish uppuma.
2. MACRONI WHEAT –Cultivation of macaroni wheat in India is considered to be very
old. It is the best wheat for drought conditions or under restricted irrigation conditions of
Punjab, MP, Karnataka, Tamilnadu, Gujurat, West Bengal and Himachal Pradesh. It is
used for semolina. i.e. suji or rawa, semiya and sphagetti.
3. COMMON BREAD WHEAT (TriticumvulgareHist): It is typical wheat of alluvial soils
of Indo Gangetic plains. i.e. Punjab, UP, Bihar and parts of Rajasthan. The bulk of Indian
crop, therefore, consists of this type. The prominent varieties are K65, K68, C13, Pb591
and C306.
4. INDIAN DWARF WHEAT (TriticumspherococcumMihi): This belongs to the club
wheat of Western countries. This is grown in limited areas of India and Pakistan. These
are characterized by very short and compact heads having shorter grains.
5. MEXICAN DWARF WHEAT (Triticumaestivum): This is presently grown in almost all
the wheat growing zones. This wheat was introduced in India by Dr. NE Borlaug of
Mexico. Nowadays it is the most widely grown wheat species in India. It covers more
than 87% of the total wheat growing of India, followed by durum wheat and dicoccum
wheat. The common wheat (T aestivum) which is good for chapatti making and bakery
products is grown in whole of North India and also in central and South India.

WHEAT STRUCTURE

The overall structure of cereal grains is basically simple. The kernel of wheat is usually 1/8-1/4
inch long. In some kinds of wheat, the tip of each kernel is covered by stiff hairs called the brush.
Wheat grains are ovoid in shape, rounded in both ends. Along one side of the grain, there is a
crease, a folding of the aluerone and all covering the layers. The physical structure of wheat
consist of
Paper Code and Title: Food and Nutrition
Module Code and Name: F01FS13 Structure of Wheat grain-Classification, Structure,
Conclusion.
Name of the Content Writer: Dr. P.A. Raajeswari

1) bran: 14.5-15%
2) endosperm: 83%
3) germ: 2.5%

The grains develop from flowers or florets, which are enclosed in a pair of bracts or leaves,
called Gemma and Palea. The ovary and the Ovule with in it, after fertilization by pollen,
develop into the grain. In wheat, the Gemma and palea become free from the grain at threshing
and from chaff. Here it is said to be naked grain called caryopsils. The bracts adhering to the
grain constitute the hull or husk.

Wheat consists of fruit coat (pericarp) and seed. The seed comprises the seed coat, germ and
endosperm. Each of the main parts of the grain, pericarp, seed coat, germ and endosperm is
further divided into various layers, tissues and regions

BRAN (Or) PERICARP

Bran is made up of six layers. The outer layer (epidermis) of the wheatconsists of thin walled,
long, rectangular cells. Next to the epidermis is the hypoderm of varying thickness. The inner
most layer of the pericarp tears during the ripening of the seed and in the mature grain they are
represented by a layer of branching hypha like cells known as tupe cells. The pericarp of wheat is
thin and papery.

SEED COAT

The seed coat or testa, thin single or double layer, is often deeply pigmented which gives grain
with the cellular structure almost obliterated. Next to testa is hyaline layer (nuclear layer) which
is colorless and devoid of any obvious cellular structure.The inner of testa of wheat is often
deeply pigmented which gives grain its characteristic colour.The fourth layer testa contains the
colouring matter which decides the colour of the wheat and also could influence the colour of the
flour. It is rich insterols accounting to 1% of the epicarp.
Paper Code and Title: Food and Nutrition
Module Code and Name: F01FS13 Structure of Wheat grain-Classification, Structure,
Conclusion.
Name of the Content Writer: Dr. P.A. Raajeswari

The outer pericarp constitutes to 3.5% of the pericarp. It is rich in insoluble dietary fibers such as
Xylans, cellulose and lignin.Antioxidants such as phenolic acids are abundantly bound to the cell
walls in the pericarp.

ALEURONE

The endosperm is surrounded by one or more layer of cells known as aluerone which is the sixth
layer which contains protease enzyme, that has softening effect on the flour proteins and
consequently on doughs. In wheat, aluerone a single layer of thick coated cubicle cells and
constitute 7% of grain weight. The cells contain about 20% of each protein, oil, and mineral.

Insoluble dietary fibers and very few soluble fibers such as, xylans and B glucans, phenolic
compounds, lignins, vitamin E, B vitamins and various plant sterols are also present in this
aleuronelayer and 10% of sugar, principally sucrose, neo-ketose and raffinose. The cells are also
rich in nicotinic acid. The aleurone cells also contain tiny grains of phytic acid with some protein
(aleurone grains). The aleuronelayers generally surround only the starchy endosperm. The
aleurone layer and all the covering external to it comprise the ‘bran’. Although bran is
nutritionally rich in vitamin B, but the cellulose material of bran tends to speed up the passage of
food through digestive tract reducing the total nutrient contribution to the body. The sharp edges
of the bran fragments have a cutting action on gluten strands reducing the gas retention power of
dough. Due to these reasons, it is not desirable to have bran contamination in the flour more than
what is absolutely unavoidable in good milling practices.

ENDOSPERM

The endosperm itself consists of cells of various sizes, shapes and different composition. The
endosperm cells consist mainly of starch and protein, the starch being in the form of spherical
granules which are single granules or tightly packed together, and embedded in a matrix of
protein. The size and shape of the starch granules in the endosperm cells vary from one cereal to
another. Starchy endosperm, accounts for about 80-85% of the grains. Endosperm is the floury
Paper Code and Title: Food and Nutrition
Module Code and Name: F01FS13 Structure of Wheat grain-Classification, Structure,
Conclusion.
Name of the Content Writer: Dr. P.A. Raajeswari

portion of wheat kernel and flour for bakery/ biscuit industry is produced from this part of the
grain.The endosperm is the potential white flour within the centre of the wheat grain. When
milled, the endosperm fractures along the cell and separates from the bran layers.The ease of
separating the endosperm from the bran layers is determined by the wheat’s characteristics. Hard
wheat’s (used for bread making) will allow easily separation, while the endosperm of soft
wheat’s (used for biscuit flours) does not separate as cleanly from the bran layers.

EMBRYO

The wheat germ is the embryo that would eventually develop into the wheat plant.The germ (or)
embryo consists of many parts and account for 3%. It is separated from endosperm, by scutellum
which has the function of mobilizing the stored food in the endosperm and transmitting them to
the embryo when the grain germinated. The germ and scutellum are rich in protein and fat while
most of the B vitamins in the grain are present in the scutellum. Various other nutrients such as
lipids, plant sterols, vitamin E and other antioxidants are also present in germ. Germ contains oil
which reduces the keeping quality of flour hence it is desirable to remove germ during milling
process.It is rich in certain vitamins, protein and oil. Consequently, it is often used in health
foods, such as fortified bread and whole meal flour.

CLASSIFICATION OF WHEAT TYPES ACCORDING TO KERNAL TEXTURE

PROPOSED SKCS T. aestivum T. TOTAL

CLASSIFICATION SCORE durum*
Varieties Germplasm
Very Soft 34 or less 2 (1.8) 2 (1.1) - 4 (1.2)
Paper Code and Title: Food and Nutrition
Module Code and Name: F01FS13 Structure of Wheat grain-Classification, Structure,
Conclusion.
Name of the Content Writer: Dr. P.A. Raajeswari

Soft 35 – 54 5 (4.5) 7 (4.0) - 12 (3.8)

Medium Hard 55 – 74 25 (22.5) 16 (9.2) - 41 (12.8)
Hard 75 – 89 58 (52.3) 74 (42.6) 11 (31.4) 143 (44.7)
Very Hard 90 or more 21 (18.9) 75 (43.1) 24 (68.6) 120 (37.5)
TOTAL 111 174 35 320

Value is parenthesis is the % figure. Includes both released cultivars and genetic sources.

After milling of wheat, the various byproducts are obtained as follows.

Whole wheat flour: It contains the finely ground bran, germ and endosperm of the whole
kernel. Whole wheat products have a distinctive flavor and coarser texture than those made from
white flour. Because of the higher fat content of the germ, whole wheat flour is more difficult to
keep and sometimes becomes rancid in storage under poor conditions.

Wheat flour is fortified with defatted soya flour maximum upto 10%. This not only improves
quantity and quality of protein but also improves functional characteristics such as moisture
retention and less oil absorption in the end product.

Iron fortified wheat flour has been successfully used to prevent iron deficiency anemia in some
western countries.

Maida: The bran and germ are separated in making white flour or maida. Maida bakes more
uniformly into a loof of a greater volume and it is more bland in taste and more easily digested. It
can be stored in an air tight container in a refrigerator.

Semolina: It is coarsely ground endosperm and its chemical composition is similar to that of
white flour. It is used in the manufacture of macaroni products. It is roasted before storing to
save it from insects and worms.
Paper Code and Title: Food and Nutrition
Module Code and Name: F01FS13 Structure of Wheat grain-Classification, Structure,
Conclusion.
Name of the Content Writer: Dr. P.A. Raajeswari

Macaroni products: These products are also called pasta or elimentary pastes. These products
include macaroni, sphagetti, vermicelli and noodles. The main ingredient in the macaroni group
of products is a special durum flour of high gluten content. Macaroni is a tube form, sphagetti
may be either tube or rod, vermicelli is a tiny rod and noodles are flat strips. Pasta products are
also available in the shapes of shell and alphabets.

Glutamic acid: It is derived from wheat. A familiar compound of glutamic acid is monosodium
glutamate, a salt like product generally available and used to bring out flavor of other foods or
seasonings.

Wheat germ: Wheat germ is about 2-3% of wheat grain. It has a high nutritional quality
compared to animal proteins. Wheat germ can be used in bakery products and weaning foods.

Wheat bran: It increases the stool weight by increasing the water holding capacity of the bran.
Wheat bran prevents constipation and may lower the risk of colon cancer.

CONCLUSION

To conclude, wheat is the commonly grown cereal and widely used by different population
groups across the world. Due to improvement in food processing technology, the outcome of
byproducts of wheat has increased a lot. Extrusion technology supports the wheat processing
industry in bringing out new innovative products duly attracted by customers.