Keywords: solar drying, ear-lobe mushrooms, solar tunnel dryers, moisture content, energy efficiency, safe storage, food quality
Design, development and experimental investigation of a solar tunnel dryer for drying mushroom
A solar tunnel dryer was designed and fabricated with locally available materials having the cross sectional area of the entire tunnel 5400 ? 1700 mm. The half of the nearly air tight tunnel base was used as the flat plate air heating solar collector and the remaining half as a dryer. The drying air temperature could be easily raised by some 6-10?C above the ambient temperature at an air velocity of approximately 1.5 m/sec. The moisture content of 12.5 kg freshly harvested mushroom was reduced to 10% (wet-basis) within two days from the initial moisture content of 91.7% (wet-basis). The energy utilisation efficiency of the dryer was about 32.0%. It was possible to reach the moisture content level for safe storage within less than two days with solar tunnel dryer and 3-4 days in open air natural sun drying. The improvement in the quality of ear-lobe mushroom in terms of colour, flavour, and taste and food value was distinctly recognised.