الفهرس 
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Abstract
SUMMARY AND CONCLUSIONS
Corn (Zea Mays L.) is one of the most important strategic cereal
crops in Egypt. In 2015, about 2259730 faddans were planted with white
and yellow single and three –way crosse and a total production of about
7057735 Mg according to Ministry of Agriculture and land
reclamation (2015). It is widely used in bread making in rural areas of
the country. Recently, maize flour is mixed with wheat flour by 20% in
bread making in order to reduce amount of the imported wheat. Maize
grains are the main component of animal and poultry feed production
since it represents about 70% of components. In addition, it is used in
silage production, and also used in oil extraction and in some other
industrial purpose such as starch and fructose (Field Crops Research
Institute, 2014).
Drying is an excellent way to preserve food. It preserves foods by
removing enough moisture from food to prevent decay and spoilage.
Drying is a process in which water is removed to halt or slow down
the growth of spoilage microorganisms, as well as the occurrence of
chemical reactions (Vega-Mercado et al., 2001). In Egypt, natural sun
drying is one of the most common ways to conserve agricultural products;
the food is dehydrated when it is exposed directly to solar radiation. The
moisture is carried away by wind as it blows above the product. The food
products are placed in polythene sheet, mud or cement floor or on racks.
There are losses may occur during natural sun drying due to various
influences, such as rodents, birds, insects, rain, storms and
microorganisms. The quality of the dried products may also be lowered
significantly.
Solar-drying technology offers an alternative which can process the
vegetables and fruits in clean, hygienic and sanitary conditions to national
and international standards with zero energy costs. It saves energy, time,
occupies less area, improves product quality, makes the process more
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SUMMARY AND CONCLUSIONS
efficient and protects the environment. Solar drying can be used for the
complete drying process or as a supplement to artificial drying systems, in
the latter case reducing the fuel energy required. Solar dryer technology
can be used in small-scale food processing industries to produce hygienic,
good quality food products. (Sharma et al., 2009).
The main object of this study is to study the ability of utilizing
greenhouse solar dryers for drying corn in order to obtain the best quality
of dried grains for using it as seeds with the least drying time, and
comparing with the natural sun drying method. The experiments were
carried out under two different operating conditions of two different
drying methods (solar drying method using greenhouse solar dryer -
natural sun drying method), two different plant conditions (ear cornshelled
corn) and three different air velocities (0.5, 1.0 and 1.5 m/s)
The obtained data of this study can be summarized as following:
Solar radiation:
The values of solar radiation varied from hour to hour due to
climate conditions, variation in solar altitude angle from early morning to
late afternoon and solar incident angle. Solar radiation gradually
increased from sunrise till reaches the maximum average value to
1068.571 W/m2 and 1191.481W/m2 at the time of 12 noon for ear and
shelled corn drying period respectively, then decreases gradually till it
reaches to the minimum values of 121.429 W/m2 and 131.429W/m2 at 6
p.m. for ear and shelled corn drying period respectively. The actual solar
radiation inside the solar dryer was lower than that outside the dryer due
to the reflectivity, absorptivity and transmissivity of the solar dryer
covering material.
Air temperature and relative humidity:
Air temperature and relative humidity inside the solar dryer were
affected by the air velocity inside the dryer. Increasing the air velocity
decreased the air temperature inside the dryers while the relative humidity
63
SUMMARY AND CONCLUSIONS
Gehad A. Abdalgawad (2017), M.Sc., Fac. Agric., Ain Shams Univ.
was increased. When air passes through the dryers atair velocities 0.5,
1.0 and 1.5m/s, the solar dryer increased the air temperature by 11.02,
9.51and 7.11˚C, respectively. The relative humidity also decreased by,
13.09, 12.26 and 10.36 %at air velocities 0.5, 1.0 and 1.5m/s, respectively
Grain bulk temperature:
Bulk temperature of ear and shelled corn was measured at different
positions of the drying bed. The recorded values of bluk temperature of
ear corn were 42.49, 40.56 and 38.63˚C at air velocities 0.5, 1.0 and 1.5
m/s, respectively. The corresponding values for shelled corn were 38.06,
38.32 and 34.39˚C, respectively. The differences in bulk temperatures
could be attributed to the variation in ambient air temperature and dryer
air temperature. The average daily grain bulk temperatures for ear and
shelled corn under natural sun drying method were 31.53 and 28.09˚C
respectively.
In general, the bulk temperature of all conditions of corn steadily
increased with time till approaching the adjusted level of drying air
temperature. During the early stage of drying process, it was decreased
with the drying time due to the higher drying rate and the corresponding
evaporative cooling of corn. Following this stage and near the end of
drying process a noticeable increase of bulk temperature was observed as
the moisture content of seeds decreased and approached the final moisture
content.
Grain moisture content and drying rate:
At the first stage of drying process, the moisture removal rate was
high then it was decreased continuously with the drying time. The drying
rate and the reduction in moisture content of grain were varied with air
velocity, air dryer temperature and corn condition. Grain moisture content
of ear corn decreased from an initial level of 31.73 to final level of
14.07% (d.b.) in 26, 24,28 and 46hours with drying rate of 0.784, 0.853,
0.674 and 0.491 %/h for solar drying at air velocities 0.5, 1.0 , 1.5m/s and
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SUMMARY AND CONCLUSIONS
Gehad A.