Introduction, Composition and Storage Strategies of Wheat Grains in Pakistan
Sadia Ismail1*, Touqeer Haider2, Maryam Rafique1, Muhammad Sajid3 and Arshad Ali3.
1 Stress Physiology Lab. Department of Botany, New Science Block, University of Agriculture, Faisalabad
2 Pomology lab, Institute of Horticulture, University of Agriculture, Faisalabad
3 Postgraduate Lab, Department of Agronomy, University of Agriculture, Faisalabad
*Corresponding author’s email: [email protected]
Introduction, Composition and Storage Strategies of Wheat Grains in Pakistan
Importance of Wheat:
Millet, Wheat, rice, and pulses (gram, lentils) are different food grains which are consumed in Pakistan. Among which wheat is the most important food grain crop of our country. Its main importance is due to the fact that its seed can be ground into flour and semolina etc. and thus it offerings the main source of nutrients to the most of the world population.
Wheat-as a Staple Food:
Nutritionally, wheat has enormous important among the few crop species which are grown as staple food sources. Wheat is the main staple food in Pakistan and about 80 to 90 percent of the food consumed by each individual in every meal. Although it is consumed in different forms such as bread (dabal roti), chapati, biscuits, cookies, porridge, macaroni and sweets. It’s most popular and widely use is as ‘chapati’. A bulk of the intake food is made by wheat therefore, it is the chief source of energy and protein requirements especially for those who have not enough money to take protein-rich foods like meat and pulses.
Wheat Grain Introduction:
Wheat belongs to Gramineae family and its fruit botanically recognized as caryopsis. In which fruit wall (pericarp) and seed coat are united and the seed and fruit cannot be separated. The two external layers of pericarp are made up of dead empty cells and inner aleurone layer are filled with living protoplasts.
Wheat grains are generally oval shaped. While different types of wheat have different spherical to long, narrow and flattened shaped grains. The length of wheat grain is usually between 5-9 mm and weight is between 35-50 mg and has a one sided crease down where it was originally connected to the wheat flower.
Composition of Wheat Grain:
The wheat grain encompasses of 2-3% germ, 13-17% bran and 80-85% endosperm. The main part of the grain is covered by several layered and (53%) water insoluble fibers comprising bran. Large amount of vitamin B and minerals are present in bran.
Chemical composition of wheat bran fibre is complex as it contains cellulose and pentosans, polymers based on xylose and arabinose basically, which are closely bound to proteins. These substances are typical polymers present in the cell walls of wheat such as aleurone layer. 1, 6% of total dry matter of bran is represented by proteins and carbohydrates and 7, 2% of mineral contents. Levels of certain amino acids in the aleurone layer and those in flour are largely different such as levels of glutamine and proline are only about one half, while arginine is triple and alanine, asparagine, glycine, histidine and lysine are double those in wheat flour.
The endosperm is nutritive tissue which provides nutrition to the developing embryo. It is rich in energy-yielding starch. Fused pericarp and seed coat are surrounded the endosperm. The aleurone (outer) layer of endosperm, is composed of single layer of cubic shaped cells. The aleurone layer is rich in proteins and enzymes, which play a dynamic role in the germination process. The inner endosperm (without aleurone layer) is denoted as mealy or starchy endosperm. Apart from carbohydrates, 1, 5% fats, 13% proteins albumins, glubulins and the major proteins of the gluten complex- glutenins and gliadins- proteins that will form the gluten at dough making are present in the mealy endosperm. Low mineral contents (ash) and dietary fibers are present 0, 5% and 1, 5%, respectively. The seed lies at one end of the grain. It has 25% proteins, 8-13% lipids and 4, 5% minerals. Wheat seeds are available as a separate thing because it is an important source of vitamin E. Wheat germ has only one half the glutamine and proline of flour, but the levels of alanine, arginine, asparagine, glycine, lysine and threonine are double.
Why Wheat Grains Stored Properly?
Highest protein contents are present in wheat but still not adequate. Over two-fifth of the world’s population faced the most serious nutritious problems and over five hundred million children are show physically stunted growth and development due to protein and other nutrients deficiency. In childhood, lack of protein could weaken development of nervous system and ability of learning. Over three billion people affected by shortage of micronutrients such as iron, zinc, and vitamin A (malnourished) due to dysfunctional food system. Presently preference of traditional nutrients and beneficial compounds containing foods are increasing among consumers. Food systems should be insured that balanced staple food must be provided continuously to all people in adequate and reasonable amounts. For the reduction of micronutrient malnutrition plant breeding strategies are used by which staple foods are enrich by micronutrients.
As population increases, demand for cereals is predicted to be increased. Wheat is the most important food grain crop of our country, and occupies the dominant position with respect to area, production and importance. Subsequently no amount of heat or cold is too severe for the growth of wheat plant and is grown in almost all parts of the country.
Grains Storage Strategies:
Storage is a component within a farming system, a trading enterprise and government policy. For proper grain store requires appropriate care and planning. It releases and absorbs heat and moisture from the surrounding. Insects infesting stored foods can be divided into primary and secondary grain feeders. Insects capable of infesting undamaged grains include moths, weevils, lesser grain borer and grain beetle. Farmers, traders and governments all have motives for storage other than the profitability of the storage enterprise itself.
Major Factors Affecting Storage:
Temperature and moisture are the most important factors as these not only affect the quality but also give rise to insect pests and fungi. The optimum temperature for most insect pests is around 28-32°C. They are able to develop and multiply between 15.5-18.3°C. Many organisms can live long at low temperatures but their activity is reduced very much. These feed on dry materials need certain amount of moisture.
The moisture requirement vary from species to species but practically all of them need more than 10% moisture with 14% optimum. Therefore, grains with less than 10% moisture is safe for storage. Micro-organisms also develop at high moisture content.
If wheat is stored at a moisture content of 14 to 18% at 21.1°C, it will be attacked by Aspergillus restriculus.
Grain in storage also undergoes chemical changes with a change in moisture.
- Increased respiration of stored grain under high temperature increases fatty acids and reduces sugar content.
- Storage of grains above 16 per cent moisture may reduce seed viability to a great extent.
- High moisture content not only deteriorates quality, but also occupies more space as its bulk increases.
- At high moisture level, carbohydrate fermentation may occur with the production of alcohol or acetic acid resulting in a characteristic sour odour.
- At the time of harvest, the grain should be dried until the moisture content is less than nine per cent.
- The storage of grain requires complete knowledge of all things involved.
Is a primary prerequisite for preventing insect damage in stored products? Most of the insects and mites live in empty warehouse or granaries as well as in stored food. Therefore, it is important to destroy them before the granaries are re-filled with grain.
- Prior to storage, all bins, granaries and surrounding area should be thoroughly cleaned to get rid of insects and mites living in cracks and crevices. Floor, ceiling, walls and doors should be thoroughly swept, cleaned and the collected rubbish should be burned or removed far away from the storage area.
- Empty cellar should also be spread with deltamethrin to kill the already available insects.
- All cracks, crevices and holes should be filled with cement plaster and made birds and rodent proof.
- Adequate ventilation is important.
- Storage cellar should be waterproof and gas-tight to protect grain from moisture and leakages during fumigation.
- Walls should be white washed with white or light colored emulsion paint.
- Grains having moisture less than 10% should be stored.
- Bags should never be stored near the walls of cellar.
- Insect free transport should be used for shifting grain from one area to another.
- Already infested grains should never be stored.
Storage Structures at Public Level:
The government has constructed large sheds commonly called house type cellar/warehouse constructed with some variations to suit climatic and other conditions of the area. In Karachi each unit measures 51.21 m x 12.19 m with a storage capacity for about 1,500 tons of wheat grains. Door and ventilation arrangements are made to provide aeration to stored grains. These types do not provide protection from insect infestation and are impossible to make gas-tight for fumigation. Due to poor maintenance, the structures have deteriorated with the passage of time and considerable grain loss takes place in these cellar/warehouse due to insect pests.
These are dome-shaped structures. The height of the dome in the center is about 10 m with floor having diameter of about 32 m. One binishell has the capacity of about 1,500 tons of grains. The structure gets heated up in summer, particularly in Sindh and Punjab resulting in rapid multiplication of insect pests. The structure is also difficult to make gas tight for fumigation.
There are two types of silos, concrete and metal. Each accommodates about 5,000 tons of grains. Most are not fully utilized due to operational difficulties.
Storage at Village Level:
Major proportion of food grains is held in the houses, in villages and towns, in small but numerous types of receptacles for self-consumption. The receptacles may be gunny bags, earthen and metallic bins and pots of various sizes, pallies, kharas, bakharies etc.
Functions during Storage:
During handling and storage considerable quantity of food grain is lost between harvest and consumption. If safe measures are adopted both quantitative and qualitative losses can be avoided at all levels.
- Banishells due to their high leakage rate are difficult to be fumigated. In these cellar, spray with delta methrin as before and thereafter fumigate with phophine tablets using the multiple dose i.e., first dose at the rate of 1.5 tablets per cubic meter, followed by application of one tablet per cubic meter each on 3rd, 5th and 7th, day.
- But after fumigation and spray cellar should be regularly inspected for insects, rodents, molds and heating spots. As insects mostly move at dusk, it is therefore, better to inspect for live insect pests in dim light in the evening with torch, but the damage should be worked out in daylight. Detailed examination of dust, cracks and crevices for sign of insects should be done.
- Do not allow spoilage of grain in the cellar. Always keep the cellar tidy and occasionally give the walls, floor, ledges beam and doors a good brush out, discard rubbish and treat the infested goods promptly. Perform periodic check of roof, gutters, walls, floor and doors.
- Ventilators and doors should be opened during dry weather and closed during the period of excessive humidity. In case if moisture content of grain exceeds 11 per cent, it should be dried at once, because high moisture is conducive for the attack of insects and formation of mold. Wet grains can be dried by spreading in one inch layer on cemented floor on hot sunny days and given 2-3 turnings during a day.