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The objective of this experimental study was to evaluate the effect of twin layer solar tunnel drying on physicochemical quality of tomato slices. The novelty of this dryer is that it has two layers of trays unlike Hohenheim solar tunnel dryer which makes it to have drying capacity of more than two times compare to type hohenheim solar tunnel dryer with equal collector area. The experiment consists of two (tray position and drying position) factors with two levels of tray position (upper tray (samples exposed to direct solar radiation) and lower tray (samples are exposed to only heated air)) and three levels of drying position (collector out let,middle of the dryer and dryer out let) with three replications. During the experiment 180 kg of Tomato slices of Galilea variety with 5mm thickness were dried in the twin layer solar tunnel dryer. Data on physicochemical quality of tomato were collected and analyzed using SAS (version 9.2). software. From the experimental result; an increase in lycopene and phenolic content retention along the length of the dryer was observed while Vitamin C retention showed a decreasing trend. Large retention of total phenol, lycopene and beta carotene content were observed for the lower tray dried tomato slices compared to the upper tray dried ones. The water activity and PH values of the solar tunnel dried tomatoes were within the safe range from microbial growth, enzymatic and non-enzymatic browning. Compared to sun drying; solar tunnel dried tomatoes showed a much better nutrient retention for all quality parameters which is comparable with the data reported for energy intensive mechanical dryers.

In tomato drying, degradation in final quality may occur based on the drying method used and predrying preparation. Hence, this research was conducted to evaluate the effect of different predrying treatments on physicochemical quality and drying kinetics of twin-layer-solar-tunnel-dried tomato slices. During the experimental work, tomato slices of var. Galilea were used. As predrying treatments, 0.5% calcium chloride (CaCl2), 0.5% ascorbic acid (C6H8O6), 0.5% citric acid (C6H8O7), and 0.5% sodium chloride (NaCl) were used. The tomato samples were sliced to 5 mm thickness, socked in the pretreatments for ten minutes, and dried in a twin layer solar tunnel dryer under the weather conditions of Jimma, Ethiopia. Untreated samples were used as control. The moisture losses from the samples were monitored by weighing samples at 2 h interval from each treatment. SAS statistical software version 9.2 was used for analyzing data on the physicochemical quality of tomato slices in CRD with three replications. From the experimental result, it was observed that dried tomato slices pretreated with 0.5% ascorbic acid gave the best retention of vitamin C and total phenolic content with a high sugar/acid ratio. Better retention of lycopene and fast drying were observed in dried tomato slices pretreated with 0.5% sodium chloride, and pretreating tomatoes with 0.5% citric acid resulted in better color values than the other treatments. Compared to the control, pretreating significantly preserved the overall quality of dried tomato slices and increased the moisture removal rate in the twin layer solar tunnel dryer.

Maize is the second most widely grown cereal and gaining importance as a highly nutritious crop in Ethiopia. However, it is severely destroyed by storage insect pests and needs further research to minimize losses. In line with this, research was initiated to evaluate the efficacy of two botanical plant powders (Eucalyptus globulus Labill leaf and Chenopodium ambrosioides L. whole plant) against storage insect pests of maize grains of two maize varieties (BH-661 and Limu) in polypropylene sacks storage conditions at Jimma Zone, Sokoru district. The plant powders were compared with untreated control, and completely randomized design was used in the experiment with three replications for each treatment. Germination capacity, thousand grain weights, percent of insect damage, and weight loss of the stored grains were evaluated and reported in the range of 69.67–94.33%, 318.7–339.3 g, 3.67–50%, and 0.2843–5.22%, respectively, after five months of storage for grains treated with botanicals. However, germination capacity of 10% and 65.33%, percent insect damage of 80.33% and 48%, and weight loss of 23.53% and 5.89% were observed for BH-661 and Limu varieties, respectively, after five months of storage for untreated control. The result indicated that both tested botanicals were effective in protecting the storage insect pests and maintaining the quality of the grains tested in comparison with control and Chenopodium ambrosioides L. whole plant powder is more effective. Although there was significant protective effect compared to untreated control, their effectiveness was decreased drastically after five and three months of storage for Chenopodium ambrosioides L. whole plant powder and Eucalyptus globulus Labill leaf powder, respectively. It is recommended that further research should be done to check if the increasing rate of application increases protection duration of these botanicals and the toxicity of Chenopodium ambrosioides L. should be further studied to use it as a storage insect protectant of maize grains intended for food purpose.