JWSS - Journal of Water and Soil Science

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The application of solar energy for drying cereals and other agricultural commodities has been increasing lately. This is due to the fact that solar energy is free, renewable, inexhaustible and environmentally friendly. This research is a new approach for employing solar energy as the main energy source for drying purposes. The drying test rig was designed, fabricated and evaluated. The grain solar dryer is an active mixed mode type with a semi-continuous discharge system. The rig consists of six solar air collectors, a heating channel, a drying chamber and an air distributing system. Rough rice was selected as cereal grain to be dried in the dryer to evaluate the system of the drying rig. In this research the effect of mass flow rate and time of crop discharge, on the rate of crop drying were evaluated. The experiment was conducted as a factorial experiment on the basis of a completely randomized design with three replications. The first factor was mass flow rate at three levels of 0.011, 0.0066 and 0.0048 kg/m²s and the second factor was the time of crop discharge at two levels of 15 and 30 min. The dryer capacity, the amount of energy consumed (electrical and solar) during drying process, and the efficiency of collectors were also evaluated. According to Duncan's multiples range test, the effects of mass flow rate of drying air, and the interval time of discharge, were highly significant on the moisture content of discharged rough rice. The maximum efficiency of the collectors was 37.13% and the fraction of energy consumed by heating channel during the drying process, compared with solar energy, was 6-8 percent. The maximum capacity of the dryer was about 132 kg of rough rice from 11 AM to 2 PM reducing the initial moisture content from 27% to 13%. On the whole, the evaluation results indicated that the dryer could reduce the moisture content of the crop to the storage safe moisture content during appropriate time with highenergy efficiency.

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To determine the preheating effect on frozen French - fries quality, four potato cultivars: Agria, Marfona, Auozonia & Auola were selected from Faridan region in Isfahan province & transferred to cold storage at temp.=5+0.5°C and RH=85-90%. At first, some physico – chemical characteristics of potato tubers such as specific gravity and dry matter content were measured by A.O.A.C methods. Also reducing sugar contents were analyzed by “High Performance Liquid Chromatography” (HPLC). The potato strips were blanched in hot water at different condition: 70°C - 4 min, 70 °C 10 min, 95 °C - 2min and then deep - fat fried at temperature 175°C for 2 minutes. Product quality properties such as texture, color and oil absorption were determined by standard methods. The data were analyzed using a factorial experiment in a completely randomized design, and average comparisons were made by by Duncan's multiple range test (p < 0.01). The results showed that blanching at 70 °C for 10 minutes markedly improved the quality parameters. Treatment at 95 °C – 2 min did not have any significant effect on Hunter Lab color parameters compared with 70 °C – 10 min. treatment, but the texture was significantly different. The oil absorption increased in strips blanched at 95 °C for 2 minutes. The samples blanched at 70 °C – 4 min had no significant effect on the product quality. In conculsion, Agria &Auola cultivars were more suitable for manufacturing French - fries than the other two varieties.

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Usually, dry soil readily absorbs water .However, not all soils display such characteristics. Some soils (hydrophobic soils) show resistance to wetting. Because of the importance of this subject and lack of research, we evaluated the effect of heating on water repellency and some of soil physical and chemical characteristics. So soil was combined with compost and heated at deferent temperatures, 100, 200, 300, 400 and 500 °C for 30 minutes in an oven or muffle furnace. The results showed that control treatment and heated soil at 300 °C had WDPT and MED 45 (s), 17% and 80 (s), 23% respectively. So, little water repellency was present prior to heating the soil. When soil was heated up to 300°C, intense water repellency resulted, but it was abruptly eliminated by increasing the heating. The soil texture was changed from loam to sandy loam at high temperatures (400 & 500 °C) and the sand percentage was increased. Organic matter decreased by increasing the temperature. Amount of pH decreased up to 200 °C and then increased at 500°C because of increasing ash in soils. Diminution of mineral and organic matter caused EC to decline in all the heated soils.