**1. Introduction**

Wheat is one of the most important crops in the world. It is cultivated on an area of about 2 million square kilometers. Its ease of adaptation to the soil has spread to several areas of the world. Wheat is the mainstay of nutrition for many countries in the world. Based on the latest report

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of the Food and Agriculture Organization of the United Nations (FAO), that the global wheat trade in 2017 reached 754.8 million tons; Russia's exports of wheat amounted to 30 million tons, America 26.5 million tons, Europe 25 million tons, Canada 21 million tons, Australia 20 million tons, while exports of Ukraine 15 million tons, Kazakhstan 8.5 million tons, Argentina 8 million tons, the largest countries exporting wheat worldwide (www.fao.org).

Fortunately, global wheat prices have fallen, driven by an increase in global production, which has been affected by good weather and the availability of water to grow in the EU, India, Pakistan, China, and the United States, which was accompanied by a rise in global exports (www.fao.org).

Forecasts indicate that the use of wheat in 2017–2018 will reach 740 million tons. More than 43% of the production is consumed by only six countries: China, India, Russian Federation, the United States of America, and Pakistan. This is because of the population of these countries of nearly three billion people, or half the world's population (www.fao.org).

As many countries in the world do not produce sufficient quantities of wheat for their uses and therefore tend to import this strategic commodity. These wheat-importing countries store large quantities of these grains in storage places called silos. Since ancient times, wheat grains have been stored in huge shipments. Earliest discovery of grain stores dates back to the year 9500 BC [1], and these stores in the settlements of the Neolithic period before the pottery "A" were located in the Jordan Valley, where the first stores were located in places among other buildings. But at the beginning of the 8500 BC, they were moved inside the houses, but with the period of 7500 BC, they were stored in rooms dedicated to it [2]. The area of the first wheat stores was 3 × 3 m from the outside, and had suspended layers in order to protect grain from rodents and insects and provide ventilation [3]. These stores are then located in Mahjara, which is placed in the valley of Sindh since 6000 BC. The ancient Egyptians used to store wheat grains in years of prosperity for use in drought ones. Because Egypt's climate is very drought, Egyptians have been able to store grain in silos without a significant loss of quality. The grain silo, as it is called, is an ideal way to store grains in all lands of the East since time immemorial. In Turkey and Iran, moorings used to buy wheat or barley, which is relatively cheap, and stored it in closed and hidden places in the face of famine. In Malta, relatively large quantities of wheat were stored in hundreds of silos dug into rocks. The silos can store up to 60–80 tons, by taking proper precautions and keeping it in good condition for 4 years or more. By the end of the nineteenth century, stores specifically designed for grain conservation began to spread in Great Britain, but North America was the home for the major stores, called grain levers. There were large-scale climatic obstacles to grain storage in Great Britain on those difficulties significantly. In order to keep the grain in good condition, it should be kept as far away as possible from moisture and heat because new grains tend to release moisture when brought to the store. In this case, microorganisms (mainly fungi) are more active and can heat the grains. If the grain continues to be heated, its quality will be affected. Therefore, effective treatment is to place grains on the ground in the form of non-thick layers, and to keep the place well ventilated. Hence, grain can be configured to store in silos.

staircase on the outer wall. With tremendous advances in engineering technology in the construction of silos, a new generation of forms and possibilities of silos has begun. High-density indoor silos are found in farms, mills, and harbors and can reach a height of 30 m. Largest silos are located in North America at major shipping centers such as Chicago, Kansas city, and Missouri in the United States, and Thunder Bay, Ontario, and Canada. Many cylindrical silos are equipped with a perforated metal floor that allows the air to pass through to keep grain free from moisture. Cylindrical silos are often adjacent, with high mechanical devices nearby. Generally, there are three types of silos, the first type is made of wood, the second type is made of concrete, and the third type is made of metal (steel and galvanized). Wheat is as barley, oat, rye, and so on, used to store suitably both in concrete and metal silos [3] (**Figure 1**). Large silos have many appliances including dryers, detergents, workpieces, cranes, and conveyors. Dryers leave grain free from moisture. The air is heated in the dehydrator and directed over the grains and then used air that has not been heated to cool the grains. The use of detergent ensures grain cleanliness. The absorption of dust, husk, or straw is obtained and screening and vibration leads to the elimination of grains that are not of the appropriate size

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**Figure 1.** Internal structure of a steel silo as in [3].

and density. However, some machines use photovoltaic cells to isolate rotten grains.

Cranes and conveyors are used to transport grains. Vertical grain movement is obtained by cranes. Among the most used cranes is a crane with a large conveyor belt and a bundle of buckets. Wheat grains in the bucket are transported to high altitude and poured into storage baskets. Tankers move the grains horizontally across the silo, called a grain lift. It is a silage storage place as well. Large quantities of wheat are delivered to the silos. Of course, the huge quantities received by silos are coming directly from farms without any transactions. Wheat is then loaded with all the residues of process of flail, agricultural soil, and contaminants of harvesting tools during the

In Great Britain, small wheat stores were built on mushroom-shaped logs called stone pillars. It was built on a wooden frame and usually has stone roofs. The large ones resemble the open ceiling from the front, but the upper part is closed. The first floor is usually accessed by a stone


**Figure 1.** Internal structure of a steel silo as in [3].

of the Food and Agriculture Organization of the United Nations (FAO), that the global wheat trade in 2017 reached 754.8 million tons; Russia's exports of wheat amounted to 30 million tons, America 26.5 million tons, Europe 25 million tons, Canada 21 million tons, Australia 20 million tons, while exports of Ukraine 15 million tons, Kazakhstan 8.5 million tons, Argentina

Fortunately, global wheat prices have fallen, driven by an increase in global production, which has been affected by good weather and the availability of water to grow in the EU, India, Pakistan, China, and the United States, which was accompanied by a rise in global exports (www.fao.org). Forecasts indicate that the use of wheat in 2017–2018 will reach 740 million tons. More than 43% of the production is consumed by only six countries: China, India, Russian Federation, the United States of America, and Pakistan. This is because of the population of these coun-

As many countries in the world do not produce sufficient quantities of wheat for their uses and therefore tend to import this strategic commodity. These wheat-importing countries store large quantities of these grains in storage places called silos. Since ancient times, wheat grains have been stored in huge shipments. Earliest discovery of grain stores dates back to the year 9500 BC [1], and these stores in the settlements of the Neolithic period before the pottery "A" were located in the Jordan Valley, where the first stores were located in places among other buildings. But at the beginning of the 8500 BC, they were moved inside the houses, but with the period of 7500 BC, they were stored in rooms dedicated to it [2]. The area of the first wheat stores was 3 × 3 m from the outside, and had suspended layers in order to protect grain from rodents and insects and provide ventilation [3]. These stores are then located in Mahjara, which is placed in the valley of Sindh since 6000 BC. The ancient Egyptians used to store wheat grains in years of prosperity for use in drought ones. Because Egypt's climate is very drought, Egyptians have been able to store grain in silos without a significant loss of quality. The grain silo, as it is called, is an ideal way to store grains in all lands of the East since time immemorial. In Turkey and Iran, moorings used to buy wheat or barley, which is relatively cheap, and stored it in closed and hidden places in the face of famine. In Malta, relatively large quantities of wheat were stored in hundreds of silos dug into rocks. The silos can store up to 60–80 tons, by taking proper precautions and keeping it in good condition for 4 years or more. By the end of the nineteenth century, stores specifically designed for grain conservation began to spread in Great Britain, but North America was the home for the major stores, called grain levers. There were large-scale climatic obstacles to grain storage in Great Britain on those difficulties significantly. In order to keep the grain in good condition, it should be kept as far away as possible from moisture and heat because new grains tend to release moisture when brought to the store. In this case, microorganisms (mainly fungi) are more active and can heat the grains. If the grain continues to be heated, its quality will be affected. Therefore, effective treatment is to place grains on the ground in the form of non-thick layers, and to keep the place well ventilated. Hence, grain can

In Great Britain, small wheat stores were built on mushroom-shaped logs called stone pillars. It was built on a wooden frame and usually has stone roofs. The large ones resemble the open ceiling from the front, but the upper part is closed. The first floor is usually accessed by a stone

8 million tons, the largest countries exporting wheat worldwide (www.fao.org).

tries of nearly three billion people, or half the world's population (www.fao.org).

be configured to store in silos.

100 Global Wheat Production

staircase on the outer wall. With tremendous advances in engineering technology in the construction of silos, a new generation of forms and possibilities of silos has begun. High-density indoor silos are found in farms, mills, and harbors and can reach a height of 30 m. Largest silos are located in North America at major shipping centers such as Chicago, Kansas city, and Missouri in the United States, and Thunder Bay, Ontario, and Canada. Many cylindrical silos are equipped with a perforated metal floor that allows the air to pass through to keep grain free from moisture. Cylindrical silos are often adjacent, with high mechanical devices nearby.

Generally, there are three types of silos, the first type is made of wood, the second type is made of concrete, and the third type is made of metal (steel and galvanized). Wheat is as barley, oat, rye, and so on, used to store suitably both in concrete and metal silos [3] (**Figure 1**).

Large silos have many appliances including dryers, detergents, workpieces, cranes, and conveyors. Dryers leave grain free from moisture. The air is heated in the dehydrator and directed over the grains and then used air that has not been heated to cool the grains. The use of detergent ensures grain cleanliness. The absorption of dust, husk, or straw is obtained and screening and vibration leads to the elimination of grains that are not of the appropriate size and density. However, some machines use photovoltaic cells to isolate rotten grains.

Cranes and conveyors are used to transport grains. Vertical grain movement is obtained by cranes. Among the most used cranes is a crane with a large conveyor belt and a bundle of buckets. Wheat grains in the bucket are transported to high altitude and poured into storage baskets. Tankers move the grains horizontally across the silo, called a grain lift. It is a silage storage place as well.

Large quantities of wheat are delivered to the silos. Of course, the huge quantities received by silos are coming directly from farms without any transactions. Wheat is then loaded with all the residues of process of flail, agricultural soil, and contaminants of harvesting tools during the separation of grains from the ears. It is perhaps of standard importance to prepare wheat grains for the flour process to explain how grinding of wheat grains is done by the following procedures. The grain of wheat consists of three main parts: grain coats, embryos, and endosperm. The purpose of the milling process is to separate as much of the endosperm content as possible from the wrappers. The ratio of flour produced to the percentage of grain used in production is known as extraction. The weight of flour produced from 100 g of grain, and depends on this percentage on several factors, the most important; extraction method used, type of mills used, nature, and specific weight of wheat grains. In general, extraction rate is between 70 and 72% in excellent white flour, and this percentage is 90–95% in brown flour. What is left behind from milling, so-called bran, is used to feed animals. Wheat milling is done by the following subsequent serial steps [4]:

**1.3. White cleaning**

and conidia?

and silica gel.

This unit consists of a peeler and stalker.

**A.** The peeler consists of a cylinder with rough internal surfaces or coated with a precision metal bed that scrapes centrifugal grains. Shells are separated and pulled by an air stream

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**B.** The asset consists of a rectangular basin with a nozzle to feed it with grains, as well as an appropriate water source that can be controlled as needed, and ends with a drainage basin topped by an appropriate filter. Inside cylinder with two helical separators working in opposite directions that wash the grains and push them forward and the light impurities on the surface of the water. With the rush of grain forward, it passes over a vibrator strainer that has been removed from the water and then to a rotary roller dryer to complete removing water droplets from the grain. The question now arises: Is the process of drying wheat grains sufficient to remove all moisture from the grain mass? Can wheat grains be washed before entering the silos? What is the cost for this? What are possible risks of increasing humidity and possibility of conditions for infection of fungal spores

• Presence of units within silos for washing and drying of grains by successive processes of passage of warm air currents, and the source of energy units of solar cells installed one way

• Putting desiccant materials that absorb air moisture inside silos such as sodium chloride

• Exposure of wheat mass to ultraviolet rays for superficial sterilization with constant flip-

Despite all precautions taken in modern silos, many studies have shown that fungi are flourishing on wheat grains and in the air of these reservoirs [5]. Several research findings have confirmed the presence of harmful and toxic fungi in many silos, not only on stored grains but also on wheat flour derived from those silos. Wheat grains are harvested in agricultural fields so they are subjected to contamination with soil particles as well as germs adhered on wheat plant itself. For these reasons, the mass of wheat stored in silos contains large quantities of dust packed with fungal spores. It is worth mentioning that any defect in the system of grain conservation inside silos is followed by the growth of fungal spores among wheat grains, and these molds may be not visible to the eye, which ultimately leads to the arrival of consumers. The problem seems more complicated if wheat is stored in poor conditions, due to the ability of wheat to imbibe the air humidity of the silos. A study conducted in Zimbabwe indicated that the storage of red wheat in many silos led to a decline in the commercial level of this com-

ping, taking into account the non-exposure of direct workers to those rays.

• Air fumigation of silos with volatile oils that have the potential to sterilize the air.

generated by an electric fan installed at the top of the peeler.

Perhaps, it is possible in this book to put forward some ideas as follows:

or another on sides of the silo exposed to sunlight.

modity and an increase in the level of fungal toxins [6].

#### **1.1. Receiving**

Grain coming from fields or silos is received in the mill after sampling and examined to ensure that it meets specifications set by the mill. Grains are received and emptied in conical tanks, each of which can reach 10 tons. Of which is covered with a fixed metal mesh for impurities when unloading grain. The crane and aspirator pull the grain out of the tanks for delivery to the cleaning equipment.

#### **1.2. Cleaning**

The cleaning equipment consists of two main units: dry-cleaning unit known as black cleaning unit and the wet-cleaning unit known as the white cleaning unit.

#### *1.2.1. Black cleaning*

This unit consists of the following equipment:


#### **1.3. White cleaning**

separation of grains from the ears. It is perhaps of standard importance to prepare wheat grains for the flour process to explain how grinding of wheat grains is done by the following procedures. The grain of wheat consists of three main parts: grain coats, embryos, and endosperm. The purpose of the milling process is to separate as much of the endosperm content as possible from the wrappers. The ratio of flour produced to the percentage of grain used in production is known as extraction. The weight of flour produced from 100 g of grain, and depends on this percentage on several factors, the most important; extraction method used, type of mills used, nature, and specific weight of wheat grains. In general, extraction rate is between 70 and 72% in excellent white flour, and this percentage is 90–95% in brown flour. What is left behind from milling, so-called bran, is used to feed animals. Wheat milling is done by the following subsequent serial steps [4]:

Grain coming from fields or silos is received in the mill after sampling and examined to ensure that it meets specifications set by the mill. Grains are received and emptied in conical tanks, each of which can reach 10 tons. Of which is covered with a fixed metal mesh for impurities when unloading grain. The crane and aspirator pull the grain out of the tanks for delivery to

The cleaning equipment consists of two main units: dry-cleaning unit known as black clean-

**A.** Compound separation device: It is composed of three wire screens installed and portable on a metal frame suspended by pulley rods spring to generate vibration movement. Sieves are arranged on top of each other so that they have wide holes at the top followed by center holes and small holes. As a result, impurities can be eliminated according to their size. The device is fitted with a fan mounted at the top of the frame to generate a

**B.** Separation device according to the specific weight: This device consists of a metal box revolving inside the fan and a strong aspirator and sieve mounted 12% slope from the horizontal level, working on the suction of grain and the deposition of heavy impurities

**C.** Magnetic separation device: It is a death pass inside the grain, and is equipped with magnetic plates electric work to attract pieces of iron nails and clumps which are collected in

**D.** Vibrating machine for the separation of impurities: It is a composite of a serrated cylinder from the inside to be grooves or round pockets to settle round impurities similar to the diameter of the grain and different in terms of form, where they gather in special ditches.

ing unit and the wet-cleaning unit known as the white cleaning unit.

stream of air that helps to breakdown light impurities.

This unit consists of the following equipment:

such as stones and pieces of glass.

a special drawer.

**1.1. Receiving**

102 Global Wheat Production

**1.2. Cleaning**

*1.2.1. Black cleaning*

the cleaning equipment.

This unit consists of a peeler and stalker.


Perhaps, it is possible in this book to put forward some ideas as follows:


Despite all precautions taken in modern silos, many studies have shown that fungi are flourishing on wheat grains and in the air of these reservoirs [5]. Several research findings have confirmed the presence of harmful and toxic fungi in many silos, not only on stored grains but also on wheat flour derived from those silos. Wheat grains are harvested in agricultural fields so they are subjected to contamination with soil particles as well as germs adhered on wheat plant itself. For these reasons, the mass of wheat stored in silos contains large quantities of dust packed with fungal spores. It is worth mentioning that any defect in the system of grain conservation inside silos is followed by the growth of fungal spores among wheat grains, and these molds may be not visible to the eye, which ultimately leads to the arrival of consumers.

The problem seems more complicated if wheat is stored in poor conditions, due to the ability of wheat to imbibe the air humidity of the silos. A study conducted in Zimbabwe indicated that the storage of red wheat in many silos led to a decline in the commercial level of this commodity and an increase in the level of fungal toxins [6].

In one of the literatures of the previous research, presence of fungi was tested in 34 samples collected from 3 silos. Results of this experiment proved that presence of fungi produced aflatoxins in majority of tested samples [5]. It is worth mentioning that fungi represent the main factors of starchy grain contamination (mycotoxigenic). Therefore, it has been found logical to review a study conducted by the authors on presence of fungi that have serious precedents as causes of diseases of respiratory system in humans. We will discuss the danger of these fungi to people dealing with wheat grains from the beginning of harvest until the entry into silos.

**3. Results and discussion**

**4. Fungal identification**

lence of each fungus.

Fungi of *Aspergillus flavus*, *A. niger*, *Circinella umbellata*, *Gliocladium* sp., *Penicillium frequentans*, *P. islandicum*, and *Ulocladium atrum* were isolated from wheat samples. **Table 1** shows preva-

**NCl OR TC (%)**

O, number of cases of isolation (NCl;

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It is worth mentioning that all fungi isolated from wheat surfaces stored in the silo, produces huge amounts of spores and conidia. For example, *Aspergillus flavus* is a fungus of a bad reputation which produces the most dangerous toxin called aflatoxin (AFs). This instinct fungus is famous for corruption and damage of many seeds, grains, and nuts [12]. *A. flavus* produces large quantities of conidia bearing on biseriate sterigmata. *A. niger* produces large quantities of conidia that are carried on two-row stregmata; these conidia are black, in long chains. Conidia of *A. niger* cause respiratory problem in people exposed to inhalation of such germs, such as people working in poultry farms, and so on. *Circinella umbellate* is a fungus belonging to zygomycotina that has huge amounts of spores in many sporangia (**Figures 2**–**8**). Previous

**Table 1.** Gross counts of fungal genera and species derived from 20 samples of wheat grains collected from the main silo,

OR = Occurrence remarks; H = 60% -100.0%, M = 33 - 59.0%, L = 20–32%, and R = 7–19%.

*Aspergillus* 145 20H 38.3 *A. flavus* 73 20H 19.3 *A. niger* 72 20H 19.0 *Circinella umbellata* 28 5 L 7.4 *Gliocladium* sp. 8 4 L 2.1 *Penicillium* 138 18H 36.5 *P. frequentans* 70 18H 18.5 *P. islandicum* 68 17H 18.0 *Ulocladium atrum* 59 3 L 15.7

**Genera and species Wheat grains**

Gross total counts 378 No. of genera 5 No. of species 7

Sakaka, Al-Jouf, Saudi Arabia by germs came from soaked grains in sterilized H<sup>2</sup>

out of 20 cases), occurrence remarks (OR), percentage of total counts (TC%) on PDA agar at 28°C.

This part of the book will present results of a study conducted in one of the giant silos in Sakaka city, Al-Jouf region, Saudi Arabia, in the autumn of 2015. Our results will be discussed with results of previous studies in some countries in order to highlight some of the challenges facing safe storage of wheat grains inside silos.
