Realization of an indirect solar dryer: With a plan sensor for fruits and vegetables
With 2200 kW/year/m2 of sunshine (National Office of Meteorology — Algeria), Algeria enjoys favorable climatic conditions to use the sun as a source of thermal energy for drying agricultural products. Indeed drying offers the possibility of recovery of surplus fruits and vegetables by their conservation for future consumption. Indirect drying gives better results (nutritional and taste viewpoint) compared to direct drying (traditional), taking into account the quality of dried products. An indirect solar dryer, conducted at the National Institute of Agronomy, gave satisfactory results.
A comprehensive review of the solar dryer
ABSTRACT Drying of agricultural products is an energy-demanding process. High costs, scarcities in fossil fuels and environmental threats attract the use of solar energy as an alternate source, especially in developing countries. Increasing environmental concerns led to the use of clean and green energy resources in the field of drying agricultural products. A solar dryer integrated with a thermal energy storage system is reasonably efficient for continuous and uniform drying of agricultural produce in the temperature range of 40–75°C which is the requisite for drying most of the products. Such dryers have become a natural choice to replace drying systems based on fossil fuels. Many studies have been performed till date by a number of researchers for the last few decades for drying agriculture and food products by a solar dryer. This review paper primarily presents an appraisal of the significant contributions made so far in the field of solar drying systems, with the latest updates in drying technology. Solar dryers which offer drying during off-sunshine hours have been specially mentioned. Some novel ideas like use of phase change materials and desiccant materials which enhance the performance and effectiveness of the dryer have also been attempted.
Effect of moisture content and temperature on some aspects of nonenzymatic browning in dehydrated apple
Dehydrated apple was heat-damaged at various constant moisture contents and constant temperatures and the optical density at 282 nm (OD282) of its methanol-water extracts subsequently determined. Moisture and temperature ranges studied simulate the conditions that usually would prevail during air dehydration of apple. It was found that the rate of increase of OD282 which is associated with the presence of 5-hydroxy-methyl-furfural—followed a zero order reaction kinetics m the range of variables studied. The rates of OD282 increase were determined and correlated with moisture content and temperature. The effect of temperature on the rates is reported as apparent activation energies. It was found that the apparent energy of activation increased with decreasing moisture content.