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Organisation: Pakistan Agricultural Research Council (PARC)
Author: Umar K. Baloch
Edited by AGSI/FAO: Danilo Mejia (Technical), Beverly Lewis (Language&Style), Carolin Bothe (HTML transfer)

CHAPTER VI WHEAT: Post-harvest Operations


1.1 Economic and Social Impact

1.2 World Trade

1.3 Primary product

1.4 Secondary and Derived Products

1.5 Requirements for export and quality assurance

1.6 Consumer preference


1. Introduction

Wheat, has been the staple food of the major civilisations in Europe, Western Asia, and North Africa for 8,000 years. During the past four decades the crop has undergone historic changes. Asia experienced benefits from the "Green Revolution", started in the mid 1960s. The region made great strides in food production, achieving sufficiency in basic grains. Crop production is dictated by Nature, but post-production operations play an important role in creating a stable food supply. It is estimated that about 25.0 million tons of wheat are lost during post-harvest stages (including storage and post-production). About 46 percentage of this loss is recorded in developing countries.

In Asia wheat, rice and maize are the major food grains contributing over 90 percentage of the total food grains. Regional production data show (see Table 1) an estimated 42 percentage of the world's wheat, rice and maize during 1997 were produced in Asia, followed by 31 percentage in Europe and 16 percentage in North Central America (NC America). Asia contributes about 92 percentage of world's rice production followed by South America and Africa at about 3 percentage each. NC America contributes half of the world's maize production, followed by Asia, Europe and South America who contribute 27 percentage, 11 percentage and 8 percentage, respectively.

Table: 1. World Cereal Production (million tons) - Estimates 1997

 

Wheat

Rice (Paddy)

Course grains

Total

         

Asia

249

520.2

198.6

967.8

Africa

15.5

16.8

78.4

110.6

Central America

3.4

2.1

28.7

34.2

South America

18.8

18

61.2

98

North America

93

8.1

291

392.1

Europe

132.6

2.6

172.6

307.8

CIS

80.1

1.4

67.6

149

Oceania

18.2

1.4

9.6

29.3

World

610.6

570.6

907.6

2088.8

Developing Countries

283.6

544.1

357

1184.7

Developed Countries

327

26.5

550.6

904.1

Source: Food outlook, FAO Rome, No. 1, 1998

The major wheat producing and consuming countries in Asia are China, India, Iran, Pakistan and Turkey. The production of wheat in Asia for the years 1991 - 1997 is shown in Table 2.

Table: 2. Wheat Production in the Asian Developing Countries (000, tons)

   

Country/Year

1,991

1,993

1,995

1,997

   

Afghanistan

1,726

1,700

1,700

1,700

Bangladesh

1,004

1,176

1,245

1,400

China

95,954

106,395

101,964

120,000

India

55,135

57,210

65,767

68,700

Iran

8,793

10,732

11,228

11,200

Iraq

1,476

1,187

1,236

1,063

Jordan

62

57

58

51

Korea DP RP

135

123

125

100

Lebanon

59

55

49

45

Mongolia

538

450

257

198

Myanmar

123

139

89

110

Nepal

836

765

942

1,072

Pakistan

1,457

16,157

17,002

16,667

Saudi Arabia

4,036

3,430

2,453

1,500

Syria

2,140

3,627

4,184

4,300

Turkey

20,419

21,016

18,015

18,700

Yemen

100

160

171

170

Others

28

48

60

63

Source: Food outlook, FAO, Rome, No.1, 1998

Wheat is grown under diverse climate conditions, from dry land with limited moisture for the duration of the growing season (e.g.located in much of the USA, Australia, CIS, West Asia and North Africa); and land with adequate water throughout the season such as the countries of Western Europe. Half of the developing world's wheat growing area comprises large irrigated tracts, mostly found in India, Pakistan and China.

Bread wheat (Triticum aestivum L.) is planted on 93 percentage of the global wheat growing area. The spring-habit and winter-habit crop is durum wheat (T. turgidum var. durum). Two-thirds of the cultivated land devoted to wheat is sown with spring types in the developing world. Winter wheat covers a significant expanse of Turkey, Iran, China, USA and Europe.

Since 1950 the world wheat production tripled to 611 million tons in 1997. The growth rate was much faster from 1960-1980 than in the last 18 years. Three quarters of the production is attributed to an increase in yield rather than an increase in area. The most impressive changes have taken place in the large mixed cereal sectors of the developing world such as China. The traditional importers of wheat among the developed countries have also experienced rapid gains in yield. In West Asia and North Africa the yields have been smaller with a slower pace of change. Yields are also low in the tropical belt, which produces less than one percentage of world's wheat. The average wheat yield in developing countries in 1950 was about 700 kg/ha. By 1996 average yield tripled to 2241 kg/ha. This progress stemmed from development of new wheat varieties, which were shorter in stature, high yielding, and earlier to mature. These were supplemented with technologies including methods of sowing, seed rate, irrigation, fertilising, moisture conservation and integrated pest management. Potential yield, particularly in the African and Asian developing countries was not fulfilled as a consequence of inadequate application of improved practices. lack of water, fertilisers, pesticides, improved seeds and socio-economic constraints where the majority of the people below the poverty line are living.

1.1 Economic and Social Impact

Improved wheat production enlarged the demand for agricultural labour. In one study in India, it was estimated that an average increase of 23 man-days per hectare per crop season was needed to accommodate extra fertiliser application, irrigation, weed control, and harvest volume. Assuming an increase of only 10-15 man-days of labour for a given wheat crop, 30 million hectares of modern varieties would require from 300-450 million man-days of additional labour per year, a benefit for employment. These operations promote secondary employment in harvest and post-harvest operations including transportation, storage, manufacturing and merchandising of fertilisers, herbicides and farm tools. Multiple cropping was stimulated by early maturing wheat varieties and the use of fertiliser, further expanding employment.

There has been rapid evolution in the management practices employed for improved high yielding varieties (HYV). In the Indian and Pakistani Punjab, farmers mostly use nitrogenous and phosphate fertilisers and take advantage of improved water management practices. They apply herbicides to control the grassy weeds that have proliferated. Mechanical land preparation and the use of tractors have also been widely adopted. Mechanisation has been increased partly because of the adoption of early-maturing semi-dwarf varieties.

Much of the world's wheat is grown in dry land areas. Even without the introduction of new varieties, substantial gains in productivity have been realised through improved tillage methods to conserve moisture before planting, to execute more timely planting and to maintain better weed control. In Turkey's dry Anatolian Plateau, earlier ploughing, clean fallow and broad-leaf weed control quickly became the norm in the 1970s. The adoption of improved management practices was a major factor in doubling wheat yields and making Turkey self-sufficient.

In the past decade, industrialised countries adopted reduced and zero tillage methods to conserve soil and reduce costs (i.e. energy costs). These techniques are now being tested in less developed countries. One notable example is the direct drilling of wheat in rice stubble. This method has generated tremendous productivity improvement for the eight million hectares of wheat planted in Asia. In industrialised countries yields are high, but these results are costly. This is true for Western Europe where numerous inputs are used. The level of inputs for wheat production is still very low in many developing countries. However fertiliser is widely used on much of the wheat grown on dry land in West Asia and some parts of North America. A combination of more effective research, extension in crop management and appropriate policies to provide inputs is needed to achieve better socio-economic status of the community.

The agricultural advances experienced in the late 1960s in Asia were repeated elsewhere during the 1970s, as semi-dwarf varieties spread to less favourable growing environments. Semi-dwarf wheat varieties were rapidly applied in Mexico during the early 1960s. By 1967 use had expanded to irrigated wheat areas of Northern India and Pakistan. Within a period of 5 years, HYV had been selected by more than half of the wheat growers. The planting of HYV also encouraged the use of fertilisers and provision of improved water supplies. Wheat yields in India, Pakistan and Mexico more than doubled between 1965 and 1985. By 1985, over 50 million-hectares of wheat in the developing countries were cultivated with semi-dwarf wheat. Excluding those from China, most of these varieties incorporated germ plasma from the CIMMYT in Mexico.

Gains in wheat crop productivity created overall benefits for employment, nutrition and income. The expanded wheat production saved hundreds of millions of dollars for India, Pakistan, Iran, Indonesia, Bangladesh, Republic of Korea and Turkey. Otherwise these countries would have been obligated to import food to sustain their large, growing populations.

The consumption of wheat world-wide can be divided into two main categories of countries. These are defined by production and consumption patterns, further dictated by the degree of economic development.

The first group comprises the industrialised counties where wheat is a traditional staple food for all except Japan. Western Europe is a developed market that has historically imported wheat, excluding France. (Japan is not an importer of this grain). The USA, Canada, Argentina, Australia and France have been major exporters of wheat. Centrally planned economies that have traded wheat include the CIS and Eastern Europe.

The second group incorporates the developing countries. Among them, North Africa, West Asia and the southern portion of South America represent traditional wheat consuming countries. Next are the large mixed cereal systems of India, China, Mexico and Brazil where wheat has been a major crop only in selected regions. Tropical countries between latitudes 23°N and 23°S are territories where wheat has not commonly been produced or consumed.

The nutritional impact of the new varieties was higher when measured in actual calories, protein and essential amino acids. The enhanced productivity of the HYV led to a rise in total protein and energy supply of at least 20 percentage. The earlier maturity of some new varieties made multiple cropping possible, which augmented the nutritional balance.

Throughout the developing world the use of wheat per capita has rapidly grown. In the large mixed-cereal economies of India, China and Mexico, higher levels of consumption have been met from greater domestic production and self-sufficiency. Other countries, such as the traditional wheat consumers of North Africa and West Asia have used imports to meet increased consumption. The substitution of wheat for maize, roots, tubers and other foods has accelerated in many countries in conjunction with rising income; urbanisation plus government subsidies to ensure low bread prices for consumers. Wheat consumption has risen more slowly in the developed nations partially due to stable population growth. The utilisation of wheat is highest in Eastern Europe and CIS, where 40 percentage is used as animal feed. In many richer countries, the per capita consumption of wheat is declining as high-energy animal products replace it.

1.2 World Trade

Actual production and consumption patterns have sharply altered the world trade in wheat. Western Europe is a net exporter and India and Pakistan (excluding border leakage) are self-sufficient (Exception: Pakistan during 1997 imported about 4.0 million tons to offset Afghan and Kashmir refugee food requirements and leakage. During 1998 the imports are expected to be less than one million tons). The largest importers are CIS, West Asia, North African countries and the tropical belt.

The developing world's share of all wheat imports is currently around 60 percentage. At the same time imports have risen and wheat has assumed greater importance in the local diet. There is a global surplus of wheat. Prices have declined by 46 percentage terms since 1950. Stocks have reached record levels over the past decade.

The forecast for world trade is significantly below levels reached in the early 1990s. In 1997-98 production was down more than 10 percentage exceeding 17 million tons from 1996-97 levels among the traditional exporting countries Argentina, Australia, Canada and the European Union. The loss is only partially offset by a 6.6 million-ton increase in the projected production in the United States. Nevertheless, supply available for export has become a lesser concern because of record production. Coupled with the absence of large purchases from China and CIS, the gradual upward trend of the past 25 years is expected to continue unabated.

1.3 Primary product

The wheat grain consists of four major parts. Their weight is expressed as a percentage of the total seed as follows:

-Seed Coat (Bran): 10 percentage

-Aleuron layer (Bran):2 percentage

-Endosperm:83 percentage

-Germ:5 percentage

Total100 percentage

The endosperm contains starch granule cells, fixed in the protein matrix, and is coated with cellulose wall. The endosperm is surrounded with aleuron cell layer. The grain has a protective covering called the seed coat. Scutulum separates the germ from the endosperm. The germ embodies the rudimentary root and shoot of the future plant (Figure 1).

In the industrialised world, wheat milling yields flour and mill feed. Before milling, the grain is cleaned and the moisture content of the grain is increased to easily separate the bran (the outer portion of the kernel called seed coat plus the aleuron layer) and the germ from the endosperm. The milling process yields generally 72 to 74 percentage flour. The rest is mill feed. The percentage of flour is multiplied in developing countries, particularly when a given country is trying to diminish wheat imports. If only excessively coarse bran is removed to produce whole-wheat flour, recovery runs as high as 90 percentage (called small milling process). In South Asia, the whole grain is milled and the flour recovery is 99 percentage or more.

The composition of proteins and carbohydrates are considerably different in various food grains. Protein content of durum wheat is low, while whole wheat measures as high as 14.6 percentage. The nutritional composition of commonly used food-grains is listed in Table 3.

Table: 3. Nutritional Composition (%) of Various Food Grains

             
 

Food-grain

Protein

Fat

Carbohydrate

Crude fibre

Ash

             
 

Wheat

10.6 - 14.6

1.6 - 2.1

66.9 - 75.9

1.7 - 2.3

1.3 - 2.2

 

Barley

8.3 - 11.8

1.8 - 2.1

68.0 - 72.0

4.3 - 5.7

2.3 - 2.7

 

Rice

8.4 - 12.0

0.9 - 1.3

70.5 - 76.3

0.9 - 1.3

9.6 - 13.4

 

Maize

9.5 - 11.5

4.0 - 5.0

68.0 - 75.0

1.7 - 2.0

1.2 - 1.6

 

Sorghum

8.0 - 9.5

1.9 - 2.0

70.0 - 74.2

2.0 - 2.5

1.7 - 2.0

 

Millet

9.4 - 10.5

3.2 - 3.8

68.5 - 71.5

1.5 - 1.8

1.8 - 2.2

 

Gram

16.3 - 17.9

0.17 - 0.19

60.2 - 62.3

1.9 - 2.7

2.1 - 2.6

Source:Derived from materials cited in 6. References

The major primary wheat products of Asia, particularly South Asia is flour, Suji and Maida, which are widely marketed. The Suji and Maida are commonly used for cookies and desserts. The nutritional composition of these products is given in Table 4.

Table 4: Average Composition (%) of Wheat and Wheat Products in South Asia

               
 

Commodity

Moisture

Protein

Total Ash

Crude Fibre

Fatty Acid
(mg)

Gluten

           

(mg)

 
 

Wheat

13.3

12.7

1.4

2.4

20.5

8

 

Flour

12.4

11.8

1.3

2

77

7

 

Suji

13.4

10

0.7

0.4

31.9

5.6

 

Maida

12.9

7.9

0.6

0.07

48.2

6.8

Source: Pingale, S. V. 1978. Handling and storage of food grains. ICAR, New Delhi India.

The roller milling process was developed to get the best possible separation of endosperm from the bran. The flour extraction rate depends upon the type and design of the mill. Milling losses are highest in the older mills. In South Asia small stone mills driven by a one horsepower motor have been developed as a cottage industry. The mill grinds wheat into coarse flour (called atta) and has eliminated the drudgery of hand pounding the grain in most villages.

Industrialised countries have systems for grading flours based upon texture, protein, ash content and other physical and chemical measurements. Automated commercial bakeries demand detailed grading systems, as they need precise and consistent flour characteristics to manufacture wheat products. Such exacting standards are not necessary in most developing countries, with the exception of large bakeries in big cities that seek standardised flour.

1.4 Secondary and Derived Products

The advanced milling process yields wheat bran, semolina, wheat germ and wheat germ oil as the main secondary and derived products. Wheat is a valuable ingredient of feed given to milk and beef livestock and poultry because it contains more nutrients than the traditional feed grains such as maize, sorghum and barley. In developing countries, whole-grain wheat is usually fed to animals only when the grain has sprouted, shrivelled, or become damaged.

Mill feed, the by-product of wheat milling (about 25-30 percentage), is an advantageous raw material for mixed feeds. The mill feed percentage is lower in some countries because millers seek to maximise the output of flour. Mill feeds contrast in nutritional value, but typically contain 13 to 14 percentage protein and 2.5 to 3.0 percentage fat (both higher than whole wheat), and 9 to 12 percentage fibre, having feeding value only for ruminants. Mill feeds are more vulnerable to severe storage losses than whole grain because of their high oil content. Mill feed must be safeguarded against birds, rodents and insects. It must be protected from moulds induced by excess moisture.

1.5 Requirements for export and quality assurance

Half to three fourths of the wheat produced in developing countries does not enter marketing channels. The families who grow it periodically bring a sack of wheat to town for grinding at a small mill and carry the flour back home for family use.

The farmers sell the rest of their wheat (25 to 50 percentage of production) to a local grain merchant or to a government agency. This wheat enters the marketing process of storage for a few months to a year, followed by milling into flour, then distribution to commercial bakeries or food shops where the urban consumer buys flour for home baking.

Wheat from most developing countries is unlikely to reach the export market as they export only 10-13 million tons (1997) per year; nearly all of which originates in just three countries-Argentina, Turkey, and occasionally India. On the other hand, over 70 million tons of wheat a year was imported by over 100 developing countries in recent years.

1.6 Consumer preference

To identify desirable qualities in wheat, farmers prefer the ability to resist diseases, mature at the proper time, not lodge or shatter before harvest and yield good plump grain. The miller prefers uniform grain free of foreign matter, with low moisture content, higher protein and yield of flour. The baker looks for flour that produces dough that can hold gas bubbles and make a large loaf of bread with good internal texture and colour. The consumer has a strong preference for appearance, texture, aroma and flavour of bread, biscuits, cakes and other products-characteristics that may be traced partly to the wheat kernel. Scientists who develop new wheat varieties and production standards must consider all these specifications of the farmer, miller, baker and consumer for wheat production.

Sixty-five to seventy percentage of the world's wheat flour is consumed as bread. In European countries the demand for semolina products is much higher than for wheat flour products. Over 90 percentage of wheat is consumed as flour in the developing nations of South and West Asia.

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