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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 62 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 64 SUMMARY AND CONCLUSIONS Gehad A. |