J. Habibi Asl; L. Behbahani; A. Azizi
Abstract
Introduction Many vegetables such as mint are highly seasonal in nature. They are available in plenty at a particular period of time in specific regions that many times result in market glut. Due to perishable nature, huge quantity of vegetables is spoiled within a short period. The post-harvest loss ...
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Introduction Many vegetables such as mint are highly seasonal in nature. They are available in plenty at a particular period of time in specific regions that many times result in market glut. Due to perishable nature, huge quantity of vegetables is spoiled within a short period. The post-harvest loss in vegetables has been estimated to be about 30-40% due to inadequate post-harvest handling, lack of infrastructure, processing, marketing and storage facilities. Therefore, the food processing sector can play a vital role in reducing the post-harvest losses and value addition of vegetables which will ensure better remuneration to the growers. Drying is a common technique for preservation of food and other products; including fruits and vegetables. The major advantage of drying food products is the reduction of moisture content to a safe level that allows extending the shelf life of dried products. The removal of water from foods provides microbiological stability and reduces deteriorate chemical reactions. Also, the process allows a substantial reduction in terms of mass, volume, packaging requirement, storage and transportation costs with more convenience. Sun drying is a well known traditional method of drying agricultural products immediately after harvest. However, it is plagued with in-built problems, since the product is unprotected from rain, storm, windborne dirt, dust, and infestation by insects, rodents, and other animals. It may result in physical and structural changes in the product such as shrinkage, case hardening, loss of volatiles and nutrient components and lower water reabsorption during rehydration. Therefore, the quality of sun dried product is degraded and sometimes become not suitable for human consumption. For these reasons, to utilize renewable energy sources, reduce vegetable losses and increase farmers income, the current project has been conducted in the Agricultural Engineering Department of Khuzestan Agricultural Research Center during the years 2011-2013. Materials and Methods In this research an indirect cabinet solar dryer with three trays and grooved collector was constructed. To improve air convection, a chimney was mounted above the dryer. The dryer performance was evaluated by drying mint leaves in three levels of mass density of 2, 3, and 4 kg m-2 at two drying manners of natural and forced convection and compared with drying mint leaves in shade as the traditional method. Results and Discussion The results showed that total drying time required in different solar drier treatments was 3.5 to 15 h, while it was about 5 days in traditional method. Drying time in upper trays was more as the air flow decreased due to increase in mass density. Mean required drying time in forced convection was 29.7% less than that of natural convection. Maximum essences with 0.80% and 0.76% were belonged to "natural convection and 3kg m-2 mass density" and "forced convection and 4 kg m-2 mass density" treatments respectively, while minimum one with 0.30% was for "forced convection and 2 kg m-2 mass density" treatment. Also, the highest and lowest chlorophyll content with 8.51 and 4.18 mg ml-1 were measured in "natural convection and 3 kg m-2 mass density" and "forced convection and 4 kg m-2 mass density" treatments respectively. According to obtained results, 3 and 4 kg m-2 mass density can be suggested for natural and forced convection solar drying of mint leaves in Khuzestan condition respectively. Conclusion In order to reduce vegetable losses and increase Khuzestan vegetable producers income, indirect cabinet solar dryer for drying mint leaves in winter season, could be an appropriate option. For natural and forced convection drying methods, mass density of 3 and 4 kg m-2 is recommended respectively.
J. Habibi Asl; E. Dehghan
Abstract
This study was conducted during two years (2007-2009) in Shawoor Agricultural Research Station on a silty-clay soil. Experiment conducted in split plots in a Randomized Complete Blocks Design in three replications. Main plots were planting methods including centrifugal broadcaster (P1), centrifugal broadcaster ...
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This study was conducted during two years (2007-2009) in Shawoor Agricultural Research Station on a silty-clay soil. Experiment conducted in split plots in a Randomized Complete Blocks Design in three replications. Main plots were planting methods including centrifugal broadcaster (P1), centrifugal broadcaster + furrower (P2), seed drill (P3), seed drill + furrower (P4), three lines bed drilling (P5) and four lines bed drilling (P6). Subplots were included seed rates of 120, 160, 200 and 240 kg.ha-1. The results showed that P2 method with 14.91 litter.ha-1 and P3 method with 5.02 litter.ha-1 had the highest and lowest fuel consumption respectively. P3 method with 1.462 h.ha-1 and P5 method with 0.620 h.ha-1 required maximum and minimum total operation time respectively. P2 method with 0.684 ha.h-1 had minimum field capacity. Field capacity of P5 and P6 with averagely 1.67 ha.h-1 was maximum. Field capacity of all drilling methods (P3, P4, P5 and P6) was significantly more than that of broadcasting methods (P1 and P2). The highest seed spacing uniformity (87.2%) was belonged to P6 method and the lowest value (54.7%) was for P1 method. By using drilling methods of P3 and P5 (or P6) instead of P1 method total cost was reduced 41% and 29% respectively. The results of variance analysis of data showed that the difference between planting methods in case of wheat grain yield and yield components was not significant. However, the seed rate had significant effect on some yield components. Suggestion for cropping of wheat Chamran variety in silty-clay soil in Khuzestan province, used P5, P6 and P3 methods are recommended respectively with seed rate of 120 - 160 kg.ha-1.
