1. Vedpal Yadav, Lecturer in Food Technology, Government Polytechnic, Mandi Adampur, Hisar, Haryana, India-125053.
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Some important crops globally.
India- Targets and Achievements of Production of major crops during 2002-03 to
2006-07 (Million Tonnes)
Crop 2002-03 2003-04 2004-05 2005-06 2006-07
Common Name Vernacular
1 Wheat Gehun Triticum spp.
2 Maize or Corn Makka Zea mays
3 Rice Chaval Oryzae sativa
4 Oats Jai Avena spp.
5 Barley Jau Hordeum vulgare
6 Sorghum Jowar Sorghum vulgare or S. bicolor
7 Pearl Millet Bajra Pennisetum typhoideum or P. Americana
8 Finger Millet Ragi Eleusine coracana
9 Kodo Millet Pakodi Arika Paspalum scrobiculatum
10 Proso Millet Vari or Kutki Panicum miliaceum
11 Little Millet Panicum miliare
12 Foxtail Millet Rala or Kangni Setaria italica
13 Japenese Barnyard Millet Echinochloa colona
14 Gram or Chick Pea Chana Cicer arietinum
15 Peas Mattar Pisum sativum
16 Pigeon Pea Arhar Cajanus spp.
17 Lentil Masur Lens culinaris or L. esculenta
18 Mung Bean Mung Phaseolus aureus
19 Urd Bean or Black Gram Urd Phaseolus mungo
20 Moth Bean Moth Phaseolus aconitifolius
21 Soybean Bhatt or Japan Pea Glycine max
22 Lablab Sem Dolichos lablab
23 Groundnut or Peanut Moongphali Arachis hypogaea
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Rice 93 71.82 93.00 88.53 93.50 83.13 87.80 91.04 80.78 75.74
Wheat 78 65.76 78.00 72.15 79.50 68.64 75.53 69.48 - -
33 26.07 34.00 37.60 36.80 33.46 36.52 34.67 28.69 24.51
Pulses 16 11.13 15.00 14.91 15.30 13.13 15.15 13.11 5.78 4.97
27 14.84 24.70 25.19 26.20 24.35 26.58 27.73 18.12 13.24
# Million Bales of 170 kg. each.
@ Million Bales of 180 kg. each.
Advance Estimates as on 15.07.2006
$ Advance Estimates as on 15.09.2006
4.2: Three Largest Producing States of Important Crops during 2005-06
Production : Million Tonnes
Crop/ Group of Crops States Production
Rice West Bengal 14.51
Andhra Pradesh 11.70
Uttar Pradesh 11.13
Wheat Uttar Pradesh 24.07
Maize Andhra Pradesh 3.09
Total Coarse Cereals Karnataka 6.56
Total Pulses Madhya Pradesh 3.23
Uttar Pradesh 2.23
Total Foodgrains Uttar Pradesh 40.41
Andhra Pradesh 16.95
Groundnut Gujarat 3.39
Andhra Pradesh 1.37
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Tamil Nadu 1.10
Rapeseed & Mustard Rajasthan 4.42
Uttar Pradesh 0.91
Madhya Pradesh 0.85
Soyabean Madhya Pradesh 4.50
Sunflower Karnataka 0.79
Andhra Pradesh 0.30
Total Oilseeds Rajasthan 5.96
Madhya Prd. 5.72
World Crop Production Summary: 2001 to 2006
[In millions of metric tons, (581.08 represents
581,080,000), except as indicated]
Commodity World 1 Asia
Million metric tons Russia China India Pakistan Australia
2004-2005 628.77 45.40 91.95 72.06 19.50 22.60
2005-2006 preliminary 621.86 47.70 97.45 72.00 21.50 24.50
2004-2005 1,014.62 29.60 138.25 34.15 1.98 11.57
2005-2006 preliminary 973.48 27.60 147.47 33.67 1.98 13.96
2004-2005 400.49 0.31 125.36 83.13 4.92 0.23
2005-2006 preliminary 413.11 0.38 126.40 89.88 5.50 0.72
Total Grains 3:
2004-2005 2,043.87 75.31 355.57 189.34 26.40 34.40
2005-2006 preliminary 2,008.45 75.68 371.32 195.55 28.98 39.17
2004-2005 381.17 5.63 57.97 28.64 5.53 2.57
2005-2006 preliminary 390.13 7.44 56.56 29.82 5.01 2.44
TOP WHEAT PRODUCING NATIONS - 1996-2002
updated 2/03 with 1/30/03 International Grains Council
"Grain Market Report" figures
Country **2002 *2001
China 89.0 94.0
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India 71.5 68.8
United States 44.0 53.3
France 39.0 31.4
Russia 50.6 46.9
TOP RICE PRODUCING NATIONS
China, India, Indonesia, and Bangladesh account for nearly 70 percent of global rice production. China
produces both indica (mostly in the south) and japonica (mostly in the north). India, Indonesia, and
Bangladesh grow primarily indica rice. In addition to China, the other major producers of japonica are:
Japan, South Korea, North Korea, Taiwan, the European Union, Australia, Egypt, and the United
States. Other major producers of indica rice are Thailand and Vietnam.
TOP BARLEY PRODUCING NATIONS
No. Barley Production 2003
1 Russian Federation 17,967,900
2 Canada 12,327,600
3 Germany 10,665,700
4 France 9,818,000
5 Spain 8,698,400
source: FAOSTAT data, 2004.
TOP MAIZE PRODUCING NATIONS
The top five producers of maize are the
US 229 million MT,
China 124 m MT,
Brazil 35.5 m MT,
Mexico 19 m MT and
France 16 m MT.
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• 1/5 of all calories consumed by humans
• 30% of world grain production
• 50% of world grain trade
Main wheat exporters- US, Canada, Australia, Argentina, France
Main parts-Germ, Endosperm, Bran
Germ (Embryo)- Germination of wheat seed, all nutrients are present
Endosperm- Store house of wheat, storage as starch mainly
Bran- Outermost covering layer
Some High Yielding Wheat Varieties
1. Sonalika (HD-1553) released in 1967. This is an early maturing variety. It is single gene
dwarf wheat with attractive grains, resembling good quality desi wheats. It is suitable for
timely as well as late sowings in U.P., Haryana, Delhi, Rajasthan, M.P., Maharashtra, A.P.,
Tamil Nadu and Karnataka.
2. Kalyan Sona (HD-1 593) released in 1967. it is a medium late maturing variety. It is high
yielding wheat with widest adaptability. It has been grown in Jammu and Kashmir, Punjab,
Haryana, Delhi, U.P., Rajasthan, M.P., Bihar, Orissa, West Bengal and Maharashtra.
3. Sharbati Sonora released in 1967. Sharbati Sonora is an amber mutant of Sonora-64 with
early maturity and synchronous habit of filleting. It is grown in all wheat growing regions.
4. Shera (HD-1925) released in 1974. It is double dwarf wheat with very good bold amber
grains. It ;s resistant to lodging, shattering and black rust in Central and Western zones of
5. Rai-911 released in 1974. It is a 2-gene dwarf durum. It is high yielding as well as resistant
to rust. It is suitable for the central wheat tract.
6. Malvika (HD-1502). It is a triple dwarf durum. It is suited for peninsular wheat tract.
7. WL 71 1, UP 368 and HD 2177 are recommended for cultivation under timely sown
irrigated high fertility condition of Punjab, Jammu area, Haryana, Delhi, Western Uttar
Pradesh and Rajasthan (except Kota and Udaipur divisions). These varieties are better than
Kalyan Sona and Sonalika in yield and rust- resistance.
8. WL 410 and C 306 are good for cultivation under low fertility rain-fed conditions of north-
9. UP 115 and HP 1209 are good for irrigated high fertility and late sowing conditions of
Bihar, eastern Uttar Pradesh, West Bengal, Assam, Orissa and other eastern states.
10. High yielding and disease resistant CC 464 and HD 2189 are good for -peninsular India
comprising Maharashtra, Karnataka, Andhra Pradesh and the plains of Tamil Nadu.
11. HD (Hybrid Delhi)-2204. It is for the first time that a variety of g wheat combines high
yield and disease resistance. It has been recommended for Large-scale cultivation under
high fertility irrigated conditions in the north-western plain zone comprising the country's
wheat bowl areas of Punjab, Haryana, Rajasthan, Uttar Pradesh, Delhi and Jammu and-
12. IWP-72. It has been recommended for the above-mentioned zone of HD-2204 for rain-
13. HW-657. This highly disease-resistant variety has been recommended for filn-fed
cultivation in the peninsular zone states of Maharashtra, Karnataka and Andhra Pradesh.
14. X-7410 and HUW-12. These two varieties have been re- commended for irrigated areas
in the north-eastern plains.
15. VL-421 (Vivekanand Laboratory, Almora). This variety has been recommended for the
north hill zone.
16. The Punjab Agricultural University released a new variety of wheat called WL-71 1.
A brief account of some of the high yielding varieties of wheat is given below.
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Variety Description Areas of adaptability
Kalyan Sona A double dwarf variety
released jointly by IARI and
the Punjab Agricultural
University. Most widely
grown in India presently.
Suitable for cultivation under
both normal and late
plantings as well as high
and low fertility conditions,
and irrigated and rain fed
areas. Yields range from 60-
70 quintals/ ha. Grains are
amber, medium and
lustrous. Highly resistant to
loose smut and hill bunt
Suitable for cultivation
Sonalika A single dwarf variety next in
popularity to Kalyan Sona in
India. Grains are bold, hard,
lustrous and very attractive.
Sonalika is highly field
resistant to black and brown
rusts. It is suitable for
cultivation under both
normal and late plantings
but particularly suitable for
the later category of
conditions. Yield potential
from 50-65 quintals/ ha.
Suitable for cultivation
Sharbati Sonora An amber grained double
dwarf variety through
irradiation of the red seeded
Sonora-64. It has high
resistance to black rust.
Grains are amber, hard,
lustrous and of medium size.
Protein content high (up to
16%) One of the best
wheats today in India for
Yield potential 50-65
Late planting in produced
Punjab, U.P., Rajasthan,
and normal plantings , in
M.P., Bihar, W. Bengal,
Gujarat, Maharashtra, A Pt.,
and Tamil Nadu
The dorsal side of the wheat grain is rounded, and the ventral side has a deep groove or
crease along the entire longitudinal axis. At the apex or small end (stigmatic end) of the grain
is a cluster of short, fine hairs known as brush hairs. The pericarp, or (try fruit coat, consists
of' four layers: epidermis, hypodermis, cross cells, and tube cells. The remaining tissues
of the grain are the inner bran (seed coat and nucellar tissue), endosperm, and embryo
(germ). The aleurone layer consists of' large, rectangular, heavy-walled, starch - free cells.
Botanically, the aleurone is the outer layer of the endosperm, but as it tends to remain
attached to the outer coats during wheat milling.
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The embryo (germ) consists of the plumule and radicle, which are connected by the
mesocotyl. The scutellum serves as an organ for food storage. The outer layer of the
scutellum, the epithelium, may function as either a secretary or an absorption organ. In a
well-filled wheat kernel, the germ comprises 2-3% of the kernel, the bran 13-17%, and the
endosperm the remainder. The inner bran layers (the aleurone) are high in protein, whereas
the outer bran (pericarp, seed coats, and nucellus)-is high in cellulose, hemicelluloses, and
minerals; biologically, the outer bran functions as a protective coating and remains practically
intact when the seed germinates. The germ is high in proteins, lipids, sugars, and minerals;
the endosperm consists of largely of starch granules embedded in a protein matrix.
Some Implications of Kernel Structure
Significance Parameter Effect Commodity
Threshing Germ Damage or
All Cereal Grains
Drying Cracks, Fissures and
Value; Lowered Grade,
Impaired Storability, Dust
Mainly Corn and Rice
Discoloration Reduced Commercial
Value, Lowered Grade
Marketing Breakage Reduced Commercial
Value in Food
Mainly Corn and Rice
General Use High Husk: Caryopsis
Ratio or High
Value as Food and Feed
All Cereal Grains
General Use Kernel Shape and
Proportion of Tissues
in the Kernel;
Nutrients in the
Yield of Food Products;
Nutritional Value of
Cereal (or Cereal
Products) as Food or
All Cereal Grains
Malting Germ Damage,
Milling Uneven Surface,
Deep Crease, or
Reduced Milling Yield Mainly Wheat and
Milling Steely Texture Increased Power
Damage, High Water
Absorption, Difficulty in
Wheat and Malt
Starch Granule Size Uneven Degradation All Cereal Grains
Change in Nutritional
All Cereal Grains
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THE HULL AND BRAN LAYERS
The outer pericarp layers of' wheat (epidermis and hypodermis) have no intercellular spaces
and are closely adhering thick walled cells. The inner layers of the pericarp, on the other
hand, consist of thinned walled cells and often contain intercellular spaces, through which
water can move rapidly and in which molds are commonly found. Molds can also enter
through the large intercellular spaces at the base, of the kernel where the grain was
detached from the plant at harvest and where there is no protective epidermis. The structure
of the pericarp, seed coats, and nucellus also explains how the kernel reacts to water.
Following initial rapid water absorption, the rate decreases significantly. The seed coat offers
more water resistance than the nucellus. The ability of the germ to absorb and hold
considerable amounts of water probably accounts in part for the susceptibility of the germ to
attack by molds.
An intact grain stores much better than damaged or ground grain. Deteriorative changes (i.e.,
rancidity, off-flavors, etc) occur slowly in the whole grain but rapidly after the grain has been
ground. The hull, apparently, prevents the grain from becoming rancid by protecting tile bran
layers from mechanical damage during harvesting and subsequent handling.
The germ is a separate structure that generally can be easily separated from the rest of the
cereal grain. However, the scutellar epithelium (located next to the endosperm) has finger
like cells. The free ends protrude toward the adjacent starch endosperm cells and form all
amorphous cementing layers between the germ and endosperm. If part of the layer projects
into the spaces between the fingerlike cells of the scutellar epithelium and into the folds of
the scutellar structure, it may be difficult to separate the germ from the endosperm unless the
cementing layer is softened. The softening may be accomplished by steeping in corn wet
milling or by conditioning in wheat milling. In rice, a layer of crushed cells separating the
scutellar epithelium from the starchy endosperm provides a line of easy fracture.
Germ separation is also enhanced by the fact that the germ takes up water faster and swells
more readily than the endosperm. The strains resulting from differential swelling contribute to
easy separation in milling.
Like that of other foods of plant origin, the chemical composition of the dry matter of different
cereal grains varies widely. Variations are encountered in the relative amounts of proteins,
lipids, carbohydrates, pigments, vitamins, and ash; mineral elements present also vary
widely. As a food group, cereals-are characterized by relatively low protein and high
carbohydrate contents; the carbohydrates consist, essentially of starch (90% or more),
dextrins, pentosans, and sugars.
Table 4-2 Weight, Ash, Protein, Lipid and Crude Fiber Contents of main anatomical
parts of the wheat kernel and flours of different milling extraction rates.
Wheat Kernel Fractions Milling Extraction (%)
Weight 9 8 80 3 75 83 100
Ash 3 16 0.5 5 0.5 1 1.5
Protein 5 18 10 26 11 12 12
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Lipid 1 9 1 10 1 1.5 2
21 7 >0.5 3 >0.5 0.5 2
The various components are not, uniformly distributed in the different kernel structures. Table
4-2 compares the weights and compositions of the main anatomical parts of the wheat kernel
with the composition of flours, which vary in milling extraction rate. The hulls and pericarp are
high in cellulose, pentosans, and ash; the germ is high in lipid content and rich in proteins,
sugars, and ash constituents. The endosperm contains the starch and is lower in protein
content than the germ and, in some cereals, bran; it is also low in crude fat and ash
constituents is greatly reduced by the milling processes used to prepare refined food. In
these processes, hulls, germ, and bran which are the structures rich in minerals and
vitamins, are more or less completely removed.
All cereal grains contain vitamins of the B group, but all are completely lacking in vitamin C
(unless the grain is sprouted) and vitamin D. Yellow corn differs from white corn and the
other cereal grains in containing carotenoid pigments (principally cryptoxanthin, with smaller
quantities of carotenes), which are convertible in the body to vitamin A. Wheat also contains
yellow pigments, but they are almost entirely xanthophylls, which are not precursors of
vitamin A. The oils of the embryos of cereal grains are rich sources of vitamin E. The relative
distribution of vitamins in kernel structures is not uniform, although the endosperm invariably
contains the least.
Protein contents of wheat and barley are important indexes of their quality for manufacture of
various foods. The bread-making potentialities of bread wheat are largely associated with the
quantity and quality of its protein. The cereal grains contain water-soluble proteins
(albumins), salt-soluble proteins (globulins), alcohol-soluble proteins (prolamins), and acid
and alkali-soluble proteins (glutelins). The prolamins are characteristics of the grass family
and, together with the glutelins, comprise the bulk of the proteins of cereal grain. The
following are names given to prolamins in proteins of the cereal grains: gliadin in wheat,
hordein in barley, zein in maize, avenin in oats, kafferin in grain sorghum, and secalin in rye.
The various proteins are not distributed uniformly in the kernel. Thus, the proteins
fractionated from the inner endosperm of wheat consist chiefly of a prolamin (gliadin) and
glutelin (glutelin), apparently in approximately equal amounts. The embryo proteins consist of
nucleoproteins, an albumin (leucosin), a globulin, and proteoses, whereas in wheat bran a
prolamin predominates with smaller quantities of albumins and globulins. When water is
added, the wheat endosperm proteins, gliadin and glutenin, form a tenacious colloidal
complex, known as gluten (see Figure 4- 1).
Gluten is responsible for the superiority of wheat over the other cereals for the manufacture
of leavened products, since it makes possible the formation of a dough that retains the
carbon dioxide produced by yeast or chemical leavening agents
The gluten proteins collectively contain about 17.55% nitrogen; hence, in estimating the
crude protein content of wheat and wheat products from the determination of total nitrogen,
the factor 5.7 is normally employed rather than the customary value of 6.25, which is based
on the assumption that, on the average proteins contain 16% nitrogen.
As a class, cereal proteins are not so high in biological value as those of certain legumes,
nuts, or animal products. Zein, the prolamin of corn, lacks lysine and is low in tryptophan.
The limiting amino acid in wheat endosperm proteins is lysine. While biological values of the
proteins of entire cereal grains are greater than those of the refined mill products, which
consist chiefly of the endosperm, the American and North European diets normally include
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various cereals, as well as animal products. Under those conditions, different proteins tend to
supplement each other, and the cereals are important and valuable sources of amino acids
for the synthesis of body proteins.
In most cereal grains, as total protein contents increases to about 14% the concentration of
the albumins plus globulins (and consequently of lysine) in the protein decreases.
The main form of carbohydrate is starch, which is the main source of calories provided by the
grains. The major portion of the carbohydrates is in the starchy endosperm.
Fatty acids in cereals occur in three main types-neutral lipids, glycolipids, and phospholipids.
The lipids in cereals are relatively rich in the essential fatty acid, linoleic acid. Saturated fatty
acids (mainly palmitic) represent less than 25% of the total fatty acids for most grains.
In summary, cereal grains are a diversified and primary source of nutrients. Their high starch
contents make them major contributors of calories; they also contribute to our needs for
proteins, lipids, vitamins, and minerals. Vitamins and minerals lost during milling into refined
food products (wheat flour or white rice) can be (and in many countries are) replaced by
nutrient fortification. The composition of cereal grains and their milled products make them
uniquely suited in the production of wholesome, nutritional, and consumer-acceptable foods.
COMPOSITION OF WHEAT
Table 1.2 Range of Major Components in Wheat
Determination Range of Analytical Results, %
Protein (N x 5.7) 7.0 18.0
Mineral Matter (Ash) 1.5 2.0
Lipids (Fat) 1.5 2.0
Starch 60.0 68.0
Cellulose (Crude Fiber) 2.0 2.5
WHEAT FLOUR PROTEINS
-Non Dough Forming
-Soluble, foaming proteins
(25,000 – 1,00,000)
-Soluble in acids, bases,
hydrogen bonding solvents
- Suspendable in acids, bases, hydrogen
-Complexes with lipids
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Moisture 8.0 18.0
Wheat composition can vary considerably from one area to another as well as from year to
year within any given area. A fairly typical range in composition of wheat samples within the
U.S. in one crop year is indicated in Table 1.2. Samples represented many different varieties
of all commercial grades.
In addition to publications on the proximate composition of wheat, which indicate only broad
classes of chemical constituents, a vast amount of analytical data has been assembled on
the amino acid content of wheat proteins, the elements constituting the ash or mineral
matter, enzyme activity, vitamin content, and the properties of wheat starch and other
The uniqueness of wheat among cereal grains depends mostly upon the characteristics of its
protein content. In wheat, as in other plants, protein is developed from simpler substances
extracted from the environment. As a plant develops from a seed, two metabolic processes
take place in the cells--photosynthesis and nitrogen fixation.
Photosynthesis involves formation of carbohydrates from carbon dioxide, water, and energy
while nitrogen fixation is the conversion of nitrogen gas into chemically combined nitrogen
that can readily assimilated by the plant.
Nitrogen fixation can be carried out by legumes, which bear root nodules containing certain
kinds of bacteria, by some algae, by chemical synthesis, or by electrical discharges in the
atmosphere (lightning). Recent research seems to indicate that a minor amount (at least) of
nitrogen fixation may occur in many more plant species than previously recognized but, even
so, almost all the protein made by the wheat plant is based on soluble nitrogen compounds
absorbed through the roots. These relatively simple compounds are transformed into
proteins by enzymic processes and the proteins then used as part of the structural materials
and protective tissues of the seed, and as enzymes and storage proteins. The latter will
ultimately be used in constructing some of the tissues of the new plant, which emerges from
the seed as it sprouts.
The proteins of wheat are complex, and there is no simple explanation of their constitution or
biological function. Neither difference in the amounts of the various classes of proteins nor
differences in the amount or kind of amino acids account for the wide variations in baking
properties of flours.
The storage proteins in wheat kernels are the source of gluten, which is the complex of
nitrogenous compounds that give wheat flour dough its cohesive and elastic properties.
Gluten can be separated from wheat flour by making a stiff dough from a mixture of flour and
water, then washing (manually or mechanically) this dough in an excess of water (as in a
stream of water) until the starch granules and all soluble materials have been removed.
Gluten appears to be a mixture of two major components called glutenin and gliadin. The
gliadin fraction is soluble in neutral 70% aqueous ethanol. It consists mainly of monomeric
proteins that associate by noncovalent hydrogen bonding and by hydrophobic interactions,
but also contains polymeric proteins that are related structurally to some glutenin subunits.
The glutenins are essentially insoluble in 70% ethanol, and appear to consist of proteins or
subunits that are aggregated into high molecular weight polymers by covalent disulfide
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Proteins with enzyme activity are the albumins and globulins located in the embryo,
aleurone, and endosperm.
The protein content of wheat kernels is affected both by the genetic constitution of the plant
and by environmental conditions during growth of the plant and development of the seed.
Typically, hard red spring wheat and durum will analyze about 13 to 17% protein. Hard red
winter wheat will test out at 11 to 15% protein, in most cases. Soft winter wheat and club
wheat would ordinarily fall in the range of 7 to 11% protein. Of course, in the normal course
of events, many samples will be found that fall outside this range because of unusual
weather events, heavy fertilizer applications, disease, or characteristics of a particular
The total protein of the wheat kernel is not a well-balanced nutrient so far as the human diet
is concerned. It has a PER far below that of egg or milk, for example, although its protein
quality is within the same range as most other cereals. The limiting amino acid is lysine,
as is the case with most cereal proteins. Generally speaking, the more refined the product,
the less lysine is present. Germ contains the most. Various attempts have been made to
develop strains of wheat, which have better than average protein quality, particularly by
increasing the content of lysine. Some success has been achieved, but high lysine strains
generally have other defects, such as poor yield, reduced bread making quality, etc.
Starch is the carbohydrate present in the greatest amount in the mature wheat kernel;
in fact, it exceeds all other types of compounds, being several times larger than the next
largest class of substances. It is formed out of carbon dioxide and water by the process of
photosynthesis and is deposited in plant cells as microscopic particles of varying size and
conformation. Many genes are involved in determining the shape, crystalline pattern, and
chemical properties of starch granules. Starch is a polymer of D-glucose, most of the hexose
units being joined together by α-(1-4) bonds. There are varying proportions of amylose and
amylopectin, the former being virtually a straight chain, but with a few branch points, while
the latter contains numerous side chains attached by 4 to 5% α-(1-6)-D-glucosidic linkages
and has a molecular weight greater than about 108
The starch granules grow in the developing endosperm as single entities in amyloplasts. In
wheat starch, they have a bimodal size distribution, with about 3 to 4% (50 to 75% by weight)
being lenticular and 15 to 40 microns in size and the remainder being small, approximately
spherical, granules, ranging in size from about 1 to 10 microns. In spite of the apparent
bimodal distribution, there is actually a continuous gradation in size of granules from smallest
to largest, especially evident during development of the kernel, as would be expected since
the sudden appearance of large granules without any intermediate growth stages would
indeed be a curious phenomenon. In the ripened kernel, though, the intermediate size
granules are not numerous, constituting in many cases only a fractional percentage of the
total weight of starch.
Polysaccharides other than starch are found in cell walls of the parenchymatous and lignified
tissues of the wheat plant. In the cell wall parenchymatous tissues, they are mainly the
arabinoxylans and the soluble β-D- glucans. Small amounts of cellulose and
glucomannans may be present, but pectins and pectic substances are absent. Wheat
endosperm is comparatively rich in arabinoxylan and very low in β-D-glucans. Cell walls of
the lignified bran layers of the kernels contain appreciable amounts of cellulose.
Arabinoxylans are present in the endosperm. Lignin and protein can be found in the isolated
polysaccharide fraction (Lineback and Rasper 1988). ,
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Mono- and disaccharides are present, but in very small amounts. As a percentage of dry
matter, the following values may be considered fairly representative of wheat kernels:
fructose 0.06, glucose, 0.08, galactose 0.02, sucrose 0.54, difructose 0.26, and maltose
0.05. Raffinose has been reported as being present at about 0.19%. Table 1.5 gives
the results of a compilation of numerous analyses performed by several laboratories
investigating the carbohydrate content of wheat kernels.
Table-1.5 Sugars and Polysaccharides in Wheat Kernels
Component Content Component Content
Total Alcohol Soluble Sugars 2.15 - 3.96 Glucose 0.03 - 0.09
Glucofructosans 0.94 - 1.14 Fructose 0.06 - 0.08
Raffinose 0.19 - 0.68 Galactose 0.02
Glucodifructose 0.26 - 0.41 Starch 62.9 - 75.0
Maltose 0.01 - 0.18 Crude Fiber 1.70 - 3.02
Sucrose 0.54 - 1.55 Pentosans 5.57 - 9.00
Among the lipids reported to have been found in wheat kernels are free fatty acids, simple
glycerides, galactosylglycerides, phosphoglycerides, sterol lipids, sphingolipids, diol
lipids, tocopherols, carotenoids, wax esters, and hydrocarbons. In amount, the principal
lipids are acyl lipids containing the fatty acids palmitic, stearic, oleic, linoleic, and α-
linolenic. Reports have indicated minor amounts of many other fatty acids. The principal
glyceride in wheat is triglyceride, with minor amounts of diglyceride and monoglyceride. The
glycolipids consist of glycosylglycerides, sterylglycosides, and glycosylceramides. The
ubiquitous plant phosphoglycerides are present, phosphatidylcholine,
phosphatidylethanolamine, phosphatidylinositol, phosphatidylglycerol, phosphatidic
acid, most of the corresponding monoacyl derivatives of lysophospholipids, and N-acyl
phosphohpids. The principal sterols are the C29 and C28 4-dimethyl sterols sitosterol and
campesterol. Significant amounts of cholesterol have occasionally been reported, but there is
not universal agreement these results are accurate. Most of the sphingolipids consist of
ceramide and a series of ceramide glycosides, containing no phosphorus. Acylated diols
(with C2 to C5) have been reported in wheat (Morrison 1988).
Minerals form a small part of the wheat kernel and an even smaller proportion of the
endosperm-less than 1%. Major constituents of the mineral fraction are the phosphates and
sulfates of potassium, magnesium, and calcium. Some of the phosphate is present in the
form of phytic acid. There are significant quantities of iron, manganese, zinc, and copper as
well as trace amounts of many other elements. One report shows the following ranges, in mg
per kg, for wheat: iron 18-31, zinc 21-63, copper 1.8-6.2, manganese, 24-37, and
selenium 0.04-0.71. Hard wheat generally contains more of these elements than soft wheat.
Potassium is present at about 0.37% in whole soft wheat (air dry basis), magnesium at
0.1.5%, phosphorus at 0.42%, and calcium at 335 ppm (O’Dell et al. 1972). The sodium
content of wheat is quite low.
The results of one extensive set of analyses are reproduced in Table 1.7.
TABLE 1.7 MINERAL AND PHYTATE CONTENT OF WHEAT KERNELS
CONTENT IN KERNEL OR PART
Germ Endosperm Aleurone Hull
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Total P, % 0.42 1.66 0.11 1.39 0.08
Phytate P, % 0.32 1.10 0.001 1.16 0
Zn, ppm 40.4 222 14.1 119 88.7
Fe, ppm 54.6 235 21.5 186 110
Mn, ppm 56.4 402 8.80 130 182
Cu, ppm 4.25 18 2.80 12 22.6
Ca, ppm 335 1760 173 730 2570
Mg, % 0.15 0.54 0.02 0.58 0.13
K, % 0.37 0.91 0.12 1.10 0.24
The kernel was composed of 3.5% germ, 70.5% Endosperm, 23% Aleurone and 3%
All analysis reported on air dry weight.
Bioavailability of the wheat minerals must be considered in any nutritional evaluation of the
grain. Phytate, most of which is found in the aleurone layer, forms insoluble complexes
with some minerals, and these complexes are poorly absorbed from the digestive
tract. Zinc may be rendered totally unavailable by this effect, and the availability of other
essential minerals may be adversely affected. Calcium is said to increase the binding effect
of phytin on zinc.
There are considerable variations in published figures for the vitamin content of wheat, but
the grain is considered to be a significant source of the vitamins thiamin, niacin, and Bs.
Davis et al. 1981 reported the vitamin content of 406 wheat cultivars from five market
classes. The mean values, in mg per kg, were 4.6 for thiamin, 1.3 for riboflavin, 55 for
niacin, and 4.6 for pyridoxine. Ranges were 3.3 to 6.5, 1.0 to 1.7, 38 to 93 and 1.6 to 7.9,
respectively. From another source, content in a wheat sample (HRS) of other vitamins in mg
per kg on a dry weight basis were, biotin 0.056, folacin 0.56, and pantothenic acid 9.1.
The content of vitamin A is known to be negligible, but the germ is one of the richest
known sources of vitamin E. In one large sample of wheat, the total tocopherols ranged
from 4.9 to 40.1 mg per kg.
As with all discussions of dietary fiber, quantitative presentations are clouded by the almost
continual changes in definition and concept of this category of substances which have
occurred over the past decade or so, as well as by the lack of standardization in test
conditions which existed until quite recently. Wheat endosperm contains only minor amounts
of substances, which could be called fiber even by the most liberal definition, and this
consideration carries through to white flour. Wheat flour (containing some of the outer layers)
and whole-wheat flour (containing all the fractions in the same proportion as in the kernel)
are somewhat better, but are not superior, sources of dietary fiber. White flour, whole-
wheat flour, and wheat bran contain, on the average, 2.78%, 12.57%, and 42.65% dietary
fiber (dry matter basis) according to Cumming and Englyst (1987).
Ripe wheat grain varies from light buff or yellow to red-brown, according to the amount of red
pigmentation in the seed coat. The color will vary little in true breeding cultivars, allowing
wheat varieties to be reliably classified as red or white. Red pigmentation is controlled by
three genetic loci, with the result that depth of color can vary between varieties classified as
red. The amber color of some durum wheats results from the endosperm pigments showing
through the translucent exterior layers. Nearly all bread wheat grown in the U.S. is red, but
Australia produces white wheat exclusively. Canadian wheat is all, or nearly all, of the red
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type. In some emmer wheats, a purplish kernel color has been observed. Soft, chalky
endosperm increases the paleness of white wheats and decreased the color of red
wheats, while hard, vitreous endosperm has the opposite effect.
The endosperm of wheat has a pale yellow color, which is slightly more intense in hard
wheat, as compared to soft wheat, and durum has even more color. The outer layers of
wheat have a slight red to dark brown color, depending on the cultivar. These pigments are
not desired in white bread, but the yellow color is much less objectionable than the
grayish effect given by bran particles. The yellow color is highly desirable in pasta,
however, and therefore is a quality factor in durum semolina. Bran specks are at least
as objectionable in pasta as in bread, and probably more so.
The yellow pigments are primarily carotenoids, hydroxylated xanthophylls (lutein),
mono- and di-esters of lutein, and flavones (primarily tricin). Very small amounts of
other xanthine compounds and chlorophyll decomposition products have also been
reported. The bleaching agents used on some types of flour oxidize carotene; nutritionally
this is not important since there is not enough provitamin A in flour to be a significant source
for humans. Xanthophylls are easily oxidized to colorless compounds. Both carotenes and
xanthophylls are insoluble in water but readily dissolve in many organic solvents. Tricin is the
major flavone in wheat. The flavone pigments range in color from yellow to brown.
A preparation of the enzyme(s) called hpoxygenase is commercially available for use
as a bleaching agent in bread dough. In a rather complex series of reactions, carotene is
oxidized by this enzyme preparation, so that a lighter-colored breadcrumb is obtained.
There are certainly hundreds, perhaps thousands, of different kinds of enzymes in wheat,
since virtually all of the reactions, which make up the metabolic activities of the plant, are
expedited and guided by these organic catalysts. In the intact, dry, ungerminated grain, the
total enzyme activity appears to be very slight, but this picture changes dramatically when
germination begins. Then, activity becomes pronounced as new enzymes are generated and
preformed but hindered enzymes are released. The enzymes, which have received the most
attention from investigators, are the amylases, or starch-digesting enzymes, primarily
because the effects of these enzymes are so important in baking and, particularly, in malting
Among the carbohydrases; in cereals are α-amylases, β-amylases, debranching
enzymes, cellulases, β-glucanases, and many glucosidases. Alpha-amylase appears to
be the most important carbohydrase. Wheat also contains a large number of proteolytic
enzymes, such as endoproteolytic enzymes (cleaving peptide bonds some distance from
the ends of protein molecules) and exoproteolytic enzymes (attacking either the
carboxyl or amino termination of a protein molecule). The acid carboxypeptidases,
which are exoproteolytic enzymes reacting at the carboxyl termination, are relatively
abundant. Ester hydrolases include enzymes such as lipases, esterases, and
phosphatases; the first two are differentiated by their ability to break ester linkages from
water-insoluble esters and soluble carboxylic acid esters, respectively. Phosphatases act
primarily on esters of orthophosphoric acid.
Phytase catalyzes the hydrolysis of phytic acid to inositol and free orthophosphate.
Lipoxygenase, which catalyzes the peroxidation of certain polyunsaturated fatty acids
by molecular oxygen, is present in relatively high concentration in soybeans and is found in
wheat. Polyphenol oxidases (catechol oxidase, tyrosinase, etc.) oxidize phenols to
quinones and are evidently more concentrated in the bran than in the endosperm; some of
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their reaction products are colored. Peroxidases and catalase are classed as
hydroperoxidases that catalyze the oxidation of certain aromatic amines and phenols by
hydrogen peroxide; they are also more active in bran than in the endosperm.
Over two-thirds of the annual harvest of wheat is processed for food. The limited use for
industrial purposes is due mainly to its high price in relation to other cereal grains. The main
use of wheat for food is the manufacture of flour for making bread, biscuits, pastry products,
and semolina and farina for alimentary pastes. A small portion is converted into breakfast
cereals. Large quantities of flour are not sold in the form in which they come from the mill but
are utilized as blended and prepared flours for restaurants, cafeterias, and schools and as
all-purpose flours for the private household.
Industrial uses of wheat include the manufacture of malt, potable spirits, starch, gluten,
pastes, and core binders. Because of the relatively high price, wheat malt is used little in
the brewing and distilling industries. It is used mainly by the flour milling industry to increase
the alpha-amylase activity of high-grade flours. In the USA, small quantities of wheat flour
(mainly low-grade clears) are used to manufacture wheat starch as a by-product of viable
(functionally in bread making) gluten. The gluten is used to supplement flour proteins in
specialty-baked goods (hamburger buns, hot-dog buns, hearth-type breads, specialty
breads, etc) and as a raw material for the manufacture of monosodium glutamate, which
is used to accentuate the flavors of foods. Some low-grade flours are used in the
manufacture of pastes for bookbinding and paper hanging, in the manufacture of plywood
adhesives, and in iron foundries as a core binder in the preparation of molds for castings. In
Australia, the starch is a by-product of wheat gluten manufacture. Low-grade flours are also
used in Australia as an adjunct in brewing (as a source of fermentable sugars). The high
yields of wheat in western Europe (compared to those of corn) make attractive production of
starch and gluten, provided both products can be marketed economically.
WHEAT AND FLOUR QUALITY
In wheat and flour technology, the term quality denotes the suitability of the material for some
particular end use. It has no reference to nutritional attributes. Thus, the high-protein hard
wheat flour is of good bread making quality but is inferior to soft wheat flours for
chemically leavened products such as biscuits, cakes, and pastry.
The miller desires wheat that mills easily and gives a high flour yield. Wheat kernels should
be plump and uniformly large for ready separation of foreign materials without undue loss of
millable wheat. The wheat should produce a high yield of flour with maximum and clean
separation from the bran and germ without excessive consumption of power. Since the
endosperm is denser than the bran and the germ, high-density wheats produce more flour. In
production of bread flours, the reduction in protein content from wheat to flour should be
minimum (not above 1%). The test weight is affected by kernel shape, moisture content,
wetting and subsequent drying, and even handling, because these characteristics and
operations affect the grain packing. Weathering lowers
the test weight by swelling kernels, but the proportion of the endosperm remains the same.
Some environmental factors influence the ease of milling. Bran of weathered and frosted
wheats tends to pulverize, and it is difficult to secure clean separation of flour from bran.
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Milling grain as food for man has been traced back more than 8,000 years. Flour milling has
advanced from a primitive and laborious household task to a vast and sophisticated, to a
large extent automated industry. In the production of white flour, the objective is to separate,
the starchy endosperm of the grain from the bran and germ. The separated endosperm is
pulverized. A partial separation of the starchy endosperm is possible because its physical
properties differ from those of the fibrous pericarp and oily germ. Bran is tough because of its
high fiber content, but the starchy endosperm is friable. The germ, because of its high oil
content, flakes when passed between smooth rolls. In addition, the particles from various
parts of the wheat kernel differ in density. This makes possible their separation by using air
The differences in friability of the bran and the starchy endosperm are enhanced by wheat
conditioning, which involves adding water before wheat is actually milled. The addition of
water toughens the bran and mellows the endosperm. The actual milling process comprises
a gradual reduction in particle size, first between corrugated break rolls and later between
smooth reduction rolls. The separation is empirical and not quantitative. The milling process
results in the production of many streams of flour and offals that can be combined in different
ways to produce different grades of flour. Still, the offals contain some of the starchy
endosperm particles, and some of the flour streams have little bran and germ particles.
Selection and Blending
The miller must produce a flour of definite characteristics and meet certain specifications for
a particular market. The most critical requirement is maintaining a uniform product from a
product (wheat) that may show a wide range of characteristics and composition.
Consequently, selection of wheats and milling according to quality for proper blending are
essential phases of modern milling. An adequate supply of wheat, binned according to
quality characteristics, makes it possible to build a uniform mix to meet some of the most
stringent specifications. The availability of rapid, nondestructive, near-infrared reflectance
instruments has made this task substantially easier.
Wheat received in the mill contains many impurities. Special machines are available to
remove those impurities. Preliminary cleaning involves the use of sieves, air blasts, and disc
separators. This is followed by dry scouring in which the wheat is forced against a perforated
iron casting by beaters fixed to a rapidly revolving drum. This treatment removes foreign
materials in the crease of the kernel and in the brush hairs. Some mills are equipped with
washers in which the wheat is scrubbed under a flowing stream of water. The washed wheat
is then passed through a "whizzer" (centrifuge), which removes free water. In practice, little
wheat is washed today, because the process is relatively ineffective, may actually increase
microbial populations, and creates problems of disposing large amounts of polluted water
with a high biological oxygen demand (BOD).
In this process water is added and allowed to stand for up to 24 hours to secure maximum
toughening of the bran with optimum mellowing of the starchy endosperm. The quantity of
water and the conditioning time are varied with different wheats to bring them to the optimum
conditioning for milling. The quantity of added water increases with decreasing moisture
content of the wheat, with increasing vitreousness, and with increasing plumpness.
Generally, hard wheats are tempered to 15-16% moisture and soft wheats to 14-15%
moisture. In the customary conditioning, the wheat is scoured again, after it has been held in
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the tempering bins for several hours. A second small addition of 0.5% water is made about
20-60 minutes before the wheat goes to the rolls.
The first part of the grinding process is carried out on corrugated rolls (break rolls), usually
24-30 inches long and 9 inches in diameter. Each stand has two pairs of rolls, which turn in
opposite directions at a differential speed of about 2.5: 1. In the first break rolls there are
usually 10-12 corrugations per inch. This number increases to 26-28 corrugations on the fifth
break roll. The corrugations run the length of the roll with a spiral cut, which is augmented
with an increase in the number of corrugations. As the rolls turn rapidly toward each other,
the edges of the corrugations of the fast roll cut across those of the slow roll, producing a
shearing and crushing action on the wheat, which falls in a rapid stream between them. The
first break rolls are spaced so that the wheat is crushed lightly and only a small quantity of
white flour is produced. After sieving, the coarsest material is conveyed to the second break
rolls. The second break rolls are set a little closer together than the first break rolls so that
the material is crushed finer and more endosperm particles are released. This process of
grinding and sifting is repeated up to six times. The material going to each succeeding break
contains less and less endosperm. After the last break, the largest fragments consist of
flakes of the wheat pericarp. They are passed through a wheat bran duster, which removes a
small quantity of low-grade flour.
After each grinding step, the crushed material called stock or chop, is conveyed, to a sifter,
which is a large box fitted with a series of sloping sieves. The break sifters have a relatively
coarse wire sieve at the top and progressively'-finer silk sieves below, and end with a fine
flour silk at the bottom. The sifter is given a gyratory motion so that the finer stock particles
pass through the sieves from the head (top) to the tail (bottom). Particles that are too coarse
to pass through a particular sieve tail over it and are removed from the sifter box. The
process results in separation of three classes of material:, (1) coarse fragments, which are
fed to the next break until only bran remains; (2) flour, or fine particles, which pass through
the finest (flour) sieve; and (3) intermediate granular particles, which are called middlings.
The middlings consist of fragments of endosperm, small pieces of bran, and the released
embryos. Several sizes are separated from each of the break stocks; individual streams of
similar size and degree of refinement result from the sieving of several break stocks and are
combined. Subsequently, the bran-rich material is removed from the middlings. This is
accomplished in purifiers. Purifiers also produce a further classification of middlings
according to size and thereby complete the work of the sifters. In the purifier, the shallow
stream of middlings travels over a large sieve, while shaken rapidly backward and forward.
The sieve consists of a tightly stretched bolting silk or grits gauze, which becomes
progressively coarser from the head to the tail end of the purifier. An upward air current
through the sieve draws off light material to dust collectors and holds bran particles on the
surface of the moving middlings so that they drift over to the tail of the sieve.
The purified and classified middlings are gradually pulverized to flour between smooth
reduction rolls, which revolve at a differential of about 1.5: 1. The space between the rolls is
adjusted to the granulation of the middlings. The endosperm fragments passing through the
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rolls are reduced to finer middlings and flour. The remaining fibrous fragments of bran are
flaked or flattened. After each reduction step, the resulting stock is sifted. Most of the bran
fragments are removed on the top sieve while the flour passes through the finest bottom
sieve. The remaining middlings are separated according to size, are moved to their
respective purifiers, and are then passed to other reduction rolls. These steps are repeated
until most of the endosperm has been converted to flour and most of the bran has been
removed as offal b the reduction sifters. What remains is a mixture of fine middlings and bran
with a little germ; this is called feed middlings. Impact mills have been used in reduction
grinding, especially with soft wheats. Close grinding using clean middlings on reduction rolls,
followed by a pin mill or detacher, increases the yield of flour from a reduction step. This
process has been used more for soft than for hard wheats.
The embryos are largely released by the break 'system and appear as lemon-yellow particles
in some of the coarser middling streams. These streams are called sizings. The embryos are
flattened in reduction of the sizings and are separated as flakes during sieving. Germ may be
separated also without reduction of the sizings by gravity and regular air currents. Previously,
the entire germ was mixed with the shorts as feed. Some special uses of germ in foods and
as a source of pharmaceuticals have been developed.
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How Wheat Becomes Flour
(A simplified diagram)
ELEVATOR - storage
and care of wheat.
PRODUCT CONTROL -
chemists inspect and
classify wheat, blending
is often done at this
SEPARATOR - iron or
steel articles stay here.
remove stones, sticks
and other coarse and
ASPIRATOR - air
currents remove lighter
DISC SEPARATOR -
barley, oats, cockle and
other foreign materials
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SCOURER - beaters in
screen cylinder scour
off inpurities and
TEMPERING MIXER -
TEMPERING - water
toughens outer bran
coats for easier
separation- softens or
BLENDING - types of
wheat are blended to
make specific flours.
IMPACT SCOURER -
impact machine breaks
and removes unsound
FIRST BREAK -
corrugated rolls break
wheat into coarse
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broken wheat is
air currents and
bran and classify
ROLLS - smooth
A series of
rolls and sifter
flour is matured
from the sifter . . .
from the sifter . . .
from bulk storage . . .
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Each grinding and sieving operation produces flour. In addition to the various break and
middlings flours, a small quantity of flour is obtained from dust collectors and bran and shorts
dusters. With each successive reduction, the flour contains more pulverized bran and germ.
The flour from the last reduction, called "red dog," is dark in color and high in components
originating from the bran and germ, such as ash, fiber, pentosans, lipids, sugars, and
vitamins. Such flour bakes into dark-colored, coarse-grained bread but is mostly sold as feed
In a large mill there may be 30 or more streams that vary widely in composition. If all the
streams are combined, the product is called straight flour. A straight flour of 100%, however,
does not mean whole-wheat flour. It means, generally, 75% flour; because wheat milling
yields about 75% white flour and about 25% feed products. Frequently, the more-highly
refined (white) streams are taken off and sold separately as patent flours; the remaining
streams, which contain some bran and germ, are called clear flours. A diagram of flours and
milled feed products is given in Figure 8-2. Some clear flours are dark in color and low in
bread-making quality. Some of the better, lighter, clear flours are used in blends with rye
and/or whole wheat fl6urs in the production of specialty breads. The darker grades of clear
flours are used in the manufacture of gluten, starch, monosodium glutamate, and pet foods.
Yields of Mill Products
The plump wheat grain consists of about 8% endosperm, 14.5% bran, and 2.5% germ.
These three structures are not separated completely, however, in the milling process. The
yield of total flour ranges from 72% to 75%, and the flour contains little bran and germ. In
ordinary milling processes only about 0.25% of the germ is recovered. Bran range from 12%
to 16% of the wheat milled. The remaining by-products are shorts. The low-grade flour and
feed middlings may be sold separately as feed by-products. The objective of efficient milling
is to maximize the monetary value of the total mill products, generally by increasing the yield
Wheat flour produced by conventional roller milling contains particles of different sizes (from
1 to 150 μm), such as large endosperm chunks, small particles of free protein, free starch
granules, and small chunks of protein attached to starch granules. The flour can be ground,
pin milled to avoid excessive starch damage, to fine particles in which the protein is freed
from the starch. The pin-milled flour is then passed through an air classifier A fine fraction,
made up of particles about 40 μm and smaller, is removed and passed through a second air
classifier. Particles of about 20 μm and smaller are separated; they comprise about 10% of
the original flour and contain up to about twice the protein of the unfractionated flour. This
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high-protein flour is used to fortify low-protein bread flours or for enrichment in the production
of specialty baked goods. A comparable fraction containing about half the protein content of
the unfractionated flour is also obtainable.
Air classification has created considerable interest in the milling industry. Its advantages are
numerous, such as manufacture of uniform flours from varying wheats; increase of protein
content of bread flours and decrease of protein content in cake and cookie flours; controlled
particle size and chemical composition and production of special flours for specific uses. A
number of equipment and process patents on fine grinding and separation have been issued.
The technology of the process is well known, yet its benefits and potential have not been fully
utilized mainly because of the availability of low and high-protein wheats and the high-energy
cost involved in air classification. In recent years there has been interest in air-classified low-
protein fractions as a replacement of chlorinated wheat flour in high-ratio cake production.
Soft Wheat Milling
Soft wheats are milled by the method of gradual reduction, similar to the method for milling
hard bread wheats. Patent flours containing 7-9% protein, milled from soft red winter wheats,
are especially suitable for chemically leavened biscuits and hot breads. Special mixtures of
soft wheats are used to make cake flours for use in cookie and cake making; such flours
usually contain 8% protein or less and are milled to very short patents (about 30%).
Treatment with heavy dosages of chlorine lower the pH to about 5.1-5.3, weaken the gluten,
and facilitate the production of short pastry. Cake flours are sieved through silk of finer mesh
than that used for biscuit or bread flours.
Durum Wheat Milling
In durum milling, the objective is the production of a maximum yield of highly purified
semolina. Although the same sequence of operations is employed in the production of flour
and semolina, the milling systems differ in design. In semolina manufacture, the cleaning and
purifying systems must remove impurities and the mill offals. Durum wheat milling involves
cleaning and conditioning of the grain, light grinding, and extensive purification. The cleaning,
breaking, sizing, and purifying systems are much more elaborate and extensive than in
flourmills. On the other hand, the reduction system is shorter in durum mills, because the
primary product is removed and finished in the granular condition. For maximum yield of
large endosperm particles, break rolls with U-cut corrugations are employed. The break
system is extensive to permit lighter and more gradual grinding than in flourmills. Durum
wheat of good milling quality normally yields about 62% semolina, 16% clear flour, and 22%
feeds. Particle size distribution and granulation of semolina are highly important in the
production of macaroni.
Flour Bleaching and Maturing
Bleaching of flour was introduced as early as 1879 in Britain and around 1900 in America. In
the earliest days flour was treated with nitrogen peroxide. Subsequently other methods came
into use to make the flour whiter and simultaneously improve the dough handling and bread
characteristics. The treated flour possesses baking properties similar to those of flour that
has been stored and naturally aged. Today, much bread and practically all cake flours in the
United States are bleached. In addition, maturing agents are used to obtain maximum baking
performance. Flour improvers are used in Great Britain, Canada and many other countries.
In West Germany only ascorbic acid may be used legally as a flour improver. In still other
countries no flour improver is allowed. Agents that have maturing action but little or no
bleaching action include bromates, iodates, peroxysulfates, peroxyborates, calcium peroxide,
and ascorbic acid (which is enzymatically converted to dehydroascorbic acid, an oxidizing
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agent). Agents that have both bleaching and maturing effect include oxygen, ozone, chlorine,
and chlorine dioxide. The improvers azodicarbonamide and acetone peroxide have been
approved by the Food and Drug Administration for inclusion with the standards of identity for
flour as bleaching and maturing agents. Acetone peroxide performs a dual function of
bleaching and maturing. Azodicarbonamide H2NCON=NCONH2 is reduced to
hydrazodicarbonamide (biurea), H2NCONHNHCONH2. It has maturing action only. Benzoyl
peroxide is added primarily as a bleaching agent. Additional agents, used less commonly for
bleaching, include nitrogen peroxide, fatty acid peroxides, and certain preparations (e.g.,
from untreated soy flour) containing the enzyme lipoxygenase.
Quantitative requirement for oxidation of flours depends on several factors. Generally, as the
protein content increases, the requirement for oxidants increases. Mixing time and oxidation
levels compensate each other to some extent, even though they are not completely
interchange- able. As the degree of milling refinement or flour grade is lowered, oxidation
requirements increase, because protein sulfhydryl groups susceptible to oxidation are found
in higher concentrations in the aleurone layer and the germ than in the starchy endosperm.
Low-grade flours have more of those tissues than highly refined flours.
It may contain a maximum of 200 ppm ascorbic acid and optimum amounts of the following
bleaching and/or oxidizing (aging) agents (alone or combinations): oxides of nitrogen,
chlorine, nitrosyl chloride, chlorine dioxide, benzoyl peroxide (with carrier), acetone
peroxides, and up to 45 ppm azodicarbonamide. Up to 50 ppm potassium bromate may be
added to flours whose baking qualities are improved by such additions,
Enriched flour contains (mg/lb) 2.9 thiamine, 1.8 riboflavin, 24 niacin, and 13.0-16.5 iron. Its
total calcium content should not exceed 960 mg/lb, and it may contain up to 5% wheat germ
or partly defatted wheat germ.
Instantized flours are prepared by selective grinding or bolting, other milling procedures, or
by agglomerating procedures.
Phosphated flour contains 0.25-0.75% monocalcium phosphate.
Self-raising flour contains a mixture of sodium bicarbonate and one or more acid-reacting
substances added to a maximum level of 4.5 parts per 100 parts of flour to produce at least
0.5% of carbon dioxide.
Cracked wheat is produced by cracking,
Crushed wheat flour by crushing, and
Whole wheat flour by grinding cleaned wheat, other than durum and red durum, to meet
specified granulation requirements. The maximum of potassium bromate in whole-wheat
flour is 75 ppm.
The ash content of farina may not exceed 0.6% and of semolina 0.92%, on a moisture-free
basis, for both. Farina may be enriched to contain (per pound) 2.0-2.5 mg thiamine, 1.2-1.5
mg riboflavin, 16.0-20.0 mg niacin, at least 13.0 mg iron, and 500 mg of the optional
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Hard Wheat Flours
0.35 - 0.40% ash content: 11.0-12.0% protein
Uses: - Danishes, sweet doughs, yeast doughnuts
and smaller volume breads and buns.
0.50 - 0.55%. ash content: 13.0-13.8% protein
Uses: All purpose strong baker's flour, breads,
buns, soft rolls and puff pastry
0.70-0.80% ash content: 15.5-17% protein
Uses: A dark very high protein flour used as a
base for rye bread production; poor color not a
factor in finished product.
Low grade flour, not used in food production.
Constitutes less than 5% of flour produced by a
Soft Wheat Flours
0.36-0.40% ash content: 7.8 - 8.5% protein,
chlorinated to 4.5- 5.0 pH.
Uses: High-ratio cakes (cakes with a high amount
of sugar and liquid in proportion to flour), angel
food cakes and jelly rolls.
0.40-0.45% ash content/8.0-8.8% protein,
chlorinated to 5.0-5.5 pH, (also available
Uses: Cake, pastries and pies.
0.45-0.50% ash content: 9.0 - 10.5% protein
Uses: Cookies and blended flours. For large-scale
manufacturers, flour can be chlorinated to the
Whole Wheat Flour
Various bran coat granulations produce coarse to
Per 100 Parts of Dry Substance
Type & Denomination Maximum Moisture % Maximum Ash Maximum Cellulose Minimum Gluten
Flour Type 00 14.50 .50 NA 7
Flour Type 0 14.50 .65 .20 9
Flour Type 1 14.50 .80 .30 10
Flour Type 2 14.50 .95 .50 10
Flour -Wheat 14.50 1.40 - 1.60 1.6 10
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Longitudinal cross section of rice
Rice is a covered cereal. In the threshed grain (or rough rice), the kernel is enclosed in a
tough siliceous, hull, which renders it unsuitable for human consumption. When this hull is
removed, the kernel or caryopsis, comprising the pericarp (outer bran) and the seed proper
(inner bran, endosperm, and germ), is known as brown rice. Brown rice is little in demand as
a food. It tends to become rancid and is subject to insect infestation. When brown rice is
subjected to further milling processes, the bran, aleurone layer, and germ are removed, and
the purified endosperms are marketed as white rice or polished rice, which is classified
according to size as head rice (at least three-fourths of the whole endosperm) and various
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classes of broken rice, known as second- hand, screenings, and brewers' rice, in decreasing
Types of rice
There are about 20 varieties of rice grown commercially in the U.S. All can be classified as
long, medium or short grain. California grows short and medium grain varieties, while
Louisiana produces medium and long grain varieties. Long grain rice is predominantly grown
in Arkansas, Mississippi, Missouri and Texas, with some production of medium grain
varieties in each state.
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Long and slender, these grains are 4 to 5 times as long as they are wide. Cooked grains
remain separate and fluffy. The perfect choice for side dish, main dish or salad recipes.
Plump, but not round. When cooked, the grains are more moist and tender than long grain
rice. Ideal for dessert, casserole, bread and stir-fry recipes.
Almost round, the cooked grains tend to cling together when cooked. Great for stir-fry recipes
Forms of Rice
Rice from which only the hull as been removed. When cooked, it has a slightly chewy texture
and nut-like flavor. This is a natural source of bran. It cooks in approximately 40-45 minutes.
Unmilled rice is soaked, steamed and dried before milling. Nutrients stay within the grain and
surface starch is reduced, producing a cooked rice that is somewhat more firm in texture and
very separate when cooked. It cooks perfectly in approximately 20 minutes.
Regular-milled White Rice
This rice has been completely milled and polished, removing the bran layer. Vitamins and
minerals are added for enrichment. It takes about 15 minutes to cook.
The objective of rice milling is to remove the hull, bran, and germ with minimum breakage of
the starchy endosperm (White, 1970). The rough rice, or paddy, is cleaned and conveyed to
shelling machines that loosen the hulls. Conventional shelters consist of two steel plates, 4 x
5 feet in diameter, mounted horizontally. The inner surfaces are coated with a mixture of
cement and carborundum. One plate is stationary and the other is rotated. As the plate
revolves, the pressure on the ends of the upturned grains disengages the hulls. The hulls are
removed by aspiration, and the remaining hulled and unhulled grains are separated in a
paddy machine that consists of a large box shaker fitted with vertical, smooth steel plates set
on a slight incline to form zigzag ducts. The plates and the shaking action cause the less
dense paddy grains to move upward while the heavier hulled grains move downward. Rough
rice may also be shelled with rubber rolls or with a rubber- belt operating against a ribbed
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Friction type rice mill
The process causes less mechanical damage and improves stability against rancidity. Hulled
rice is sent to machines that consist of grooved tapering cylinders that revolve rapidly in
stationary, uniformly perforated cylinders. The entire machine is filled with grain, and a blade
that protrudes between the upper and lower halves of the perforated cylinder regulates the
packing force. The outside bran layers and the germ are removed by the scouring action of
the rice grains moving against themselves near the surface or the perforated cylinder. After
passing through a succession of hullers, the rice is practically free from germ and outer bran.
Scouring is usually completed, by polishing in a brush machine. The polished rice contains
whole endosperms and broken particles of various sizes. Grading reels of disc separators
The yield of white rice normally varies between 66% and 70%, based on the weight of rough
rice. As head rice is the most valuable product, its yield determines the milling quality of
rough rice. The price obtained for the various classes of broken rice decreases with size.
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A solvent-extraction process was developed to increase the yield of whole grain rice.
Dehulled brown rice is softened with rice oil, to improve bran removal. Fully milled rice is
sometimes treated with a talc-and-glucose solution to improve its appearance. After the
coating is evenly distributed on the kernels and dried with warm air, the rice emerges from
the equipment with a smooth, glistening luster and is known as coated rice.
The annual production of bran has a potential for 5 million tons of food protein and 6
million tons of edible oil; the husks, for 256,000 billion kcal as fuel; and the straw, for
30,000 billion kcal as metabolizable energy for cattle.
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Starch, the major component of rice, is present in the starchy endosperm as compound
granules that are 3-10 pm in size. Protein, the second major component, is present in the
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endosperm in the form of discrete protein bodies that are 1-4 µm in size. The concentration
of nonstarchy carbohydrates is higher in the bran and germ fractions than in the starchy
endosperm. Brown rice contains about 8% protein, 75% carbohydrates, and small
amounts of fat, fiber, and ash. After milling, the protein content of rice is about 7% and the
carbohydrate content (mainly starch) about 78%. Starch is found primarily in the endosperm;
fat, fiber; minerals, and vitamins are concentrated in the aleurone layers and in the germ.
Starch, the main carbohydrate of rice, comprises up to 90% of the rice solids. In common
rice, amylose amounts to 12-35% of the total starch; in waxy (glutinous) rice, the amylose
content is much lower.
Protein composition of milled rice is unique among cereals. The rice proteins are rich (at
least 80%) in glutelins and have a relatively good amino acid balance. Among the protein
fractions, albumin has the highest lysine content, followed by glutelin, globulin, and
prolamin. The high lysine content of rice protein is primarily due to their low prolamin content.
Proteins in milled rice are generally lower in lysine than proteins in brown rice.
The proportions of albumin and globulin and the total protein are highest in the outer layers
of the milled rice kernel and decrease toward the center; proportions of glutelin have an
inverse distribution. In rice, as in other cereal grains, the proteins differ considerably in their
amino acid composition and biological value. The most notable differences are in the high
concentration of lysine in albumins and of cystine in globulins, and in the very low lysine and
cystine concentrations in the prolamines. Rice protein is not ideally balanced; it is relatively
low in lysine concentration when compared with the FAO Reference Pattern;
supplementation with lysine and threonine significantly increases the biological value of rice
The subaleurone region, which is rich in protein, is only several cell layers thick, lies directly
beneath the aleurone, and is removed rather easily during milling. From a nutritional
standpoint, it is therefore desirable to mill rice as lightly as possible and retain some of the
protein in the subaleurone or to breed cultivars that have either an increased, number of
aleurone layers or have the protein more evenly distributed throughout the endosperm.
Protein content of the grain determines the protein distribution between bran polish and
milled rice. Protein distribution is more uniform throughout the grain as the grain increases in
total- protein content. Also, high-protein milled rices usually have more thiamine. The
increase in protein content is related mainly to an increase in the number of protein bodies
and a slight increase in their size.
Brown rice contains 2.4-3.95% lipids. The lipid content depends on
• The variety
• Degree of maturity
• Growth conditions
• Lipid extraction method
The lipid content of bran and polished rice is affected by the degree of milling and the milling
procedure. Polishing gradually removes the pericarp, tegmen, aleurone layer, embryo, and
parts of the endosperm, but parts of the lipid-rich germ may remain attached to the
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endosperm even after advanced polishing and removal of up to 20% of the rice kernel. The
major proportion of the lipid in rice is removed with the bran (containing the germ) and the
• Bran 10.1-23.5%,
• Polish 9.1-11.5%,
• Brown rice 1.5-2.5%,
• Milled rice 0.3-0.7%
In the rice kernel, as in other cereals, lipid content is highest in the embryo and in the
aleurone layer, and the lipid is present as droplets or spherosomes. The spherosomes are
submicroscopic-about 0.5 µm or less in the coleoptile cells. Much higher quantities of lipids
are present outside the aleurone granules than inside them. The testa contains a fatty
material, and a sheath of fat-staining material encloses the aleurone granules. Rice lipids are
mainly triglycerides, with smaller amounts of phospholipids, glycolipids, and waxes. The
three main fatty acids are oleic, linoleic, and palmitic. The main glycolipids are acyl sterol
glycosides and sterol glycosides, and either diglycosyldiglyceride or ceramide,
The distribution of lipid types is not uniform in the rice kernel. Approximate ratios of neutral
and polar lipids are 90:10 in bran, 50:50 in the starchy endosperm, and 33:67 in the
starch. Thus the bran is rich mainly in neutral lipids; the endosperm contains relatively
high concentrations of polar lipids.
There is a considerably higher concentration of ash and of individual minerals in outer layers
of the milled rice kernel than toward the center. P, K, Mg, Fe, and Mn are concentrated in the
aleurone layer; P, K, and Mg are particularly high in the subcellular particles of the aleurone
layer; Ca is abundant in the pericarp. The phytin-P constitutes almost 90% of the total bran-
P and 40% of the milled rice-P.
Rice and its by-products contain little or no vitamin A, ascorbic acid, or vitamin D.
Thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, folic acid, inositol, choline,
and biotin are lower in milled rice than in brown rice and substantially lower than in rice
bran, polish, or germ.
NUTRITIONAL IMPLICATIONS OF PROCESSING
Table 16-2 Composition of Rice (%)
Material Moisture Protein Lipid Fiber Ash Degree of Polishing
Brown Rice 15.5 7.4 2.3 1.0 1.3 0
Rice Bran 13.5 13.2 18.3 7.8 8.9 -----
Polished Rice 15.5 6.2 0.8 0.3 0.6 8 - 10
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Production of brown rice from rough rice increases protein, fat, and starch contents,
since the hulls are low in those constituents. Conversely, there is a decrease in the
crude Fiber and ash contents.
Conversion of brown rice to white or polished rice removes about 15% of the protein,
65% of the fat and fiber, and 55% of the minerals.
Rough rice and brown rice differ little in vitamin content, but conversion of brown rice to white
rice decreases the vitamin values considerably. Thus head rice contains only 20% as much
thiamine, 45% as much riboflavin, and 35% as much niacin as brown rice. The losses have
created much interest in the development of practical methods to retain more of the B
vitamins in the milled rice kernel. Processing the rice before milling to diffuse the vitamins
has approached the problem of improving the vitamin content of milled rice and other water-
soluble nutrients in the outer portion of the grain into the endosperm. Processing of rough
rice to increase vitamin retention involves parboiling or some modification thereof. For
parboiling, rough rice is soaked in water, drained, steamed, and dried. In 1940, a process for
the manufacture of "converted rice" was developed and patented in England. The cleaned
rough rice is exposed to a vacuum, treated with hot water under pressure, and then steamed,
dried, and milled. The converted rice process is particularly effective for the retention of
Parboiling is performed to improve the nutritional and also the storage and cooking attributes
of rice. The main modifications are transfer of some vitamins and minerals from the aleurone
and germ into the, starchy endosperm, dispersion of lipids from the aleurone layer and germ,
inactivation of enzymes, and destruction of molds and insects. Those changes are
accompanied by reduced chalkiness and increased vitreousness and translucence of the
milled rice, and improved digestibility and cooking properties.
Parboiling strengthens the attachment of the germ and aleurone to the starchy endosperm
and prevents the separation of the germ during husking. However, the strengthening of these
attachments and hardening of the endosperm increase the difficulty of milling the husked
grains of parboiled rice. Compared with nonparboiled rices, parboiled rices disintegrate less
during cooking and remain better separated and less sticky after cooking. Parboiling reduces
the amount of solids leached into the cooking water and the extent to which the kernels
solubilize during cooking.
Rice must have acceptable market and eating qualities and good nutritional value. Grain
quality is related mainly to the amylose/amylopectin ratio, which governs water absorption
and volume expansion during cooking, and to cohesiveness, color, gloss, and tenderness of
cooked rice. Long-grain types generally cook to dry, fluffy products that harden on keeping
and are preferred by some. Short-grain types tend to be more cohesive and moist and to
remain relatively tender when kept and consumed cold. Waxy (1-2% amylose) rices, in
contrast to high- amylose (over 25%) rices, are glossy and sticky when cooked. Rices with
intermediate amylose contents and intermediate gelatinization temperatures are preferred in
The modern trend in processed foods is toward convenience items. Precooking in water and
drying under controlled conditions or by application of dry heat may prepare quick-cooking
rices. Other convenience items include canned and frozen cooked rice.
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Parboiling of rice is a term that encompasses quite a variety of different processes, some of
them quite primitive technologically, others quite advanced. The basic or essential features
are that rough rice is first wetted, then heated, and finally dried. Many changes occur in
the rice kernel as a result of this treatment. Of particular importance are the translocation of
some nutrients from the outer layers to inner layers and the gelatinization of the
starch. Subsequently, the rice is milled and, of course, it must be cooked in water before
It is said that parboiling was first developed in India as a method for facilitating removal of
the hulls from the rice kernel. In its earliest forms, parboiling consisted of soaking rough
rice (paddy) in warm water overnight and then drying the grain in the sun. The rice
hulls split open and were easily removed from the kernel. Later, it was learned that
parboiling provides nutritional benefits, since thiamin and other essential nutrients which are
normally present in fairly high concentrations in the bran (but at low concentrations in the
kernel) migrate to the endosperm during the water-soaking step. Since nearly all rice is
milled to remove the bran, parboiling preserves more of the nutritional values contained in
the whole grain. When hot water is used, the starch in the rice endosperm is changed
into a condition that causes the kernel to be more resistant to breakage and thus gives a
greater yield of whole kernels after milling.
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Soaking in water and then pressure-cooking to gelatinize the starch completely can parboil
rough rice. The rice is then dried and milled to remove the outer layers. Conditions used in
the soaking and cooking steps are critical with respect to the properties of the milled product,
particularly for its appearance and the yield of head rice.
The soaking step is carried out in warm water. In one variation, rice is elevated from storage
bins to an automatic scale hopper that weighs and dumps the rice into an accumulating
hopper. When rice sufficient to make a batch has been collected, it is dumped into a steeping
tank. This vessel is connected to a vacuum system, a, water system, and a compressed air
system. When the batch of rice is dropped into it, the tank is evacuated to remove air from
the grain. Then, sufficient water at a temperature of about 200ºF is introduced to cover the
rice. The tank is pressurized to about 100 psi and the rice is steeped about 190 min.
Temperature and time may be varied somewhat depending on the specific characteristics of
the rice used, its moisture content, time in storage, etc. During the steeping operation, water-
soluble B-vitamin components and minerals are infused into the endosperm from the bran,
Soak in water at RT to 70º C to
saturation (about 30% moisture,
Moisten or Partially
Soak (18-20% Moisture)
Cook by conduction heating
(with hot air and sand )
(With hot air and
Flow chart of steps for making dfferent kinds of parboiled rice and expanded and flaked
rice. RT= Room Temperature
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germ, and hull. At the end of this step, water is drained off and the rice is discharged into a
jacketed rotating vacuum drier equipped with steam tubes.
Variations in properties of different lots of rough rice may affect their response to soaking
conditions, although acceptable products may be obtained over a wide range of conditions.
Poor results are obtained at soaking temperatures above the gelatinization temperature of
the starch. Incomplete soaking or tempering is reflected in excessive breakage of kernels
when the rice is cooked, dried, and milled. For example, Calrose rice soaked at 150ºF for
two hours followed by one hour of tempering before it was cooked and dried yielded more
than 30% broken kernels in the standard milling test.
In the drier, the soaked rice is vacuumized and heated with steam to remove excess
moisture. Dry steam is then injected to gelatinize the starch in the grains, after which the
vessel is vented and evacuated until the moisture of the rice becomes low enough to permit it
to be milled successfully. The dried rice is conveyed to bins where it is cooled by drawing air
through it, and tempered to equalize the moisture content of the batch. Finally, the rice is
milled to remove the bull, bran, and germ. Examples of conditions that have proved to be
successful for cooking are steam pressures of 20 psi for 5 to 8 minutes. Then, drying could
be conducted at 120ºF in a cross flow air drier.
In another process, cleaned rice is steeped in two parts of water at 130º to 150ºF in open
steel tanks for 9 to 12 hr until the rice has absorbed 30 to 35% moisture on the wet basis.
The soaked rice is transferred continuously to a vertical pressure vessel equipped with rotary
valves on the inlet and discharge openings. There it is steamed at 230º to 245º F for 8 to 20
minutes, depending on the degree of parboiling and the cooking quality and color desired in
the end product. Shorter cooking times result in rice of lighter color. Little additional water is
absorbed in the steaming process, and the rice is discharged with moisture content of about
35%. It is dried in a steam tube drier and a series of hot air driers to 11 to 13% moisture, and
then milled in conventional equipment. Yields are from 66 to 71 lb of total milled rice and 58
to 67 lb of whole grains per 100 lb of the original rough rice. The product is said to contain
2.0 mg of thiamin, 0.40 mg of riboflavin, and 44.0 mg of niacin per kg of dry material. Its
useful storage life is about 2 to 3 years. Milling by-products are disposed of in regular
commercial channels for these materials. The wastewater from the steeping process is
generally not utilized; although it could be dried to yield a material having some nutritional
value, for feed, this would not be an economically viable operation.
A third process is similar to the second in general principles, except that both the soaking
and steaming steps are performed in rotating cylinders.
Another variant of the parboiling process consists of the following steps. Rice is tempered in
hot or cold water, depending on the variety, and is then conveyed to soaking tanks each of
which hold 15,000 lb of rice. Hot (100º to 200ºF) water is added and the rice is allowed to
soak for 1 to 10 hr, depending on the variety. After soaking, the rice is transferred through a
rotary valve to a screw conveyor passing through a pressure vessel. Here the grain is
cooked at 15 to 100 psi steam pressure for 10 see to 3 min. Cooked kernels exit through
another valve, and are cooled and dried before milling.
Modern commercial parboiling processes generally include the steps of
1 Soaking the rough rice in 50º to 70º C water for 3 to 4 hours to yield rough rice
having 30% moisture content;
2 Draining the free water from the soaked rough rice;
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3 Applying steam heat under pressure for 15 to 20 minutes to gelatinize the
starch and to raise the water content to about 35%; and
4 Drying the steamed rice with hot air to reduce its moisture content to about
14%. The dried rice is then milled.
Milling yield is higher after parboiling and there are fewer broken grains, i.e., there is a
greater percentage of head rice. The grain structure becomes compact, translucent, and
shiny. Germination is no longer possible, so some storage problems are alleviated. The
endosperm is denser, making it more resistant to insect attack, and the grains remain firmer
during cooking and are less sticky.
According to Luh and Mickus (1980), the most important changes occurring in parboiling
(1) The water-soluble vitamins and mineral salts are spread throughout the grain, thus
altering their distribution and concentration among its various parts. The riboflavin and
thiamin contents are four times higher and the niacin level is eight times greater in parboiled
rice than in whole rice. Thiamin is more evenly distributed in the parboiled rice.
(2) Moisture content is reduced to 10 to 11%.
(3) The starch grains imbedded in a proteinaceous matrix are gelatinized and
expanded until they fill up the surrounding air spaces.
(4) The protein substances are separated and sink into the compact mass of
gelatinized starch, becoming less susceptible to extraction.
(5) Enzymes present in the kernel are partially or entirely inactivated.
(6) Microorganisms and insect forms are either killed or greatly reduced in number.
Parboiled rice has a somewhat elastic texture, and for that reason resists breakage when it is
milled. The better head rice yields obtained from the milling of parboiled rice, as compared to
raw rice, defrays to a considerable extent the cost of parboiling so that the parboiled product
generally does not sell for much more than white rice.
Although parboiled rice is not quick cooking, it has certain advantages over raw rice. It is
more resistant to insect infestations and it does not break up as much when used in canned
formulations such as soups and puddings. When overcooked, it does not become as mushy
as raw rice. Parboiled rice is darker than raw milled rice and has a slightly different flavor, but
it is widely accepted and is often preferred to white rice. in some rice-eating areas of the
world, however, attempts to introduce it have not been successful. Its color, which is usually
a light tan, is probably an adverse factor for consumers who look upon extreme whiteness as
a indication of high quality.
Advantages of parboiling
Parboiling of paddy has following advantages:
1. Dehusking of parboiled rice becomes easy.
2. The germ becomes tougher resulting in reduced losses during milling.
3. Milling parboiled rice has greater resistance to insect and fungus infection.
4. The nutritive value of the rice increases after parboiling because the water dissolves
the vitamins and minerals present in the hull & bran coat and carries them into the
endosperm resulting in no loss of valuable nutrients.
5. The milling and polishing of raw rice result in losses of 75% of Vitamin B1, 56% of
Riboflavin and 63% of Niacin whereas after parboiling these losses are reduced by
58%, 35% and 11% respectively.
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6. The parboiled rice will not turn into a gluten mass when cooked.
Disadvantages of parboiling
1. Parboiling changes the colour of the grain.
2. Sometimes unpleasant smell of parboiled rice is not preferred.
These changes are due to defective steeping while parboiling. During steeping
fermentative changes result in yellowish colour and off flavours of rice.
Section 1 : Definitions of rice
The meaning of the terminology in this Rice Standards is as follows:
1. Rice Standards means the minimum specifications of rice of each type and grade for
domestic and international trade.
2. Rice means non-glutinous and glutinous rice (Oryzae sativa L.) in whatever form.
3. Paddy means rice that is not yet dehusked.
4. Cargo rice (Loonzain rice, Brown rice, Husked rice) means rice that is dehusked only.
5. White rice means rice that is obtained by removing bran from Cargo non-glutinous rice.
6. White glutinous rice means rice that is obtained by removing bran from Cargo glutinous
7. Parboiled rice means non-glutinous rice that has passed through the parboiling process
and has its bran removed.
8. Rice classification means rice kernels of various lengths as specified, which are the
mixture of rice kernels of each class in accordance with the specified proportion.
9. Classes of rice kernels mean classes of rice kernels that are classified in accordance
with the length of the whole kernel.
10. Parts of rice kernels mean each part of the whole kernel that is divided lengthwise into
10 equal parts.
11. Whole kernels mean rice kernels that are in whole condition without any broken part,
including the kernels that have length as from 9 parts onward.
12. Head rice means broken kernels whose lengths are more than those of Brokens but
have not reached the length of the whole kernel. This includes split kernels that retain the
area as from 80% of the whole kernel.
13. Brokens mean broken kernels that have the length as from 2.5 parts but have not
reached the length of Head rice. This includes split kernels that retain the area less than 80%
of the whole kernel.
14. Small brokens C1 mean small broken kernels that pass through round hole metal sieve
45. Vedpal Yadav, Lecturer in Food Technology, Government Polytechnic, Mandi Adampur, Hisar, Haryana, India-125053.
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15. Undermilled kernels mean milled rice kernels that have the milling degree below that
specified for each grade of rice.
16. Red kernels mean rice kernels that have red bran covering the kernels wholly or partly.
17. Yellow kernels mean rice kernels that have some parts of the kernels turn yellow
obviously. This includes parboiled rice kernels that are light brown partly or wholly.
18. Black kernels mean parboiled rice kernels that are black for the whole kernels, including
kernels that are dark brown for the whole kernels.
19. Partly black kernels mean parboiled rice kernels that have black or dark brown area on
the kernels as from 2.5 parts onward but not reaching the whole kernels.
20. Peck kernels mean parboiled rice kernels that have obviously black or dark brown area
on the kernels not reaching 2.5 parts.
21. Chalky kernels mean non-glutinous rice kernels that have an opaque area like chalk
covering the kernels from 50% onward.
22. Damaged kernels mean kernels that are obviously damaged as can be seen by the
naked eyes due to moisture, heat, fungi, insects or other.
23. Undeveloped kernels mean kernels that do not develop normally as should be, and are
flat without starch.
24. Immature kernels mean rice kernels that are light green, obtained from immature paddy.
25. Other seeds mean seeds of other plants than rice kernels.
26. Foreign matter means other matter than rice. This includes rice husk and bran detached
from rice kernels.
27. Milling degree means the degree to which the rice is milled.
28. Sieve means round hole metal sieve No.7, that is 0.79mm. (0.031 inch) thick and with
hole diameter of 1.75mm 0.069 inch).
29. The unit "per cent" means percentage by weight except for per cent of grain
classification which is percentage by quantity.
Thai Jasmine White Rice, also called fragrant rice or "Hom Mali" rice, is
recognized world wide as Thailand's specialty.
Thai Jasmine Rice belongs to the Indica (long-grain) category and could be
divided into 3 main categories as A, B and C according to their quality; Prime
Quality, Superb Quality and Premium Quality.