THIN-LAYER CONVECTION-DRYING OF MUSHROOMS

Dehydration characteristics of the Oyster Pleurotus variety of mushroo m were studied. Both untreated and treated (steam blanching followed b y sulphiting and citric acid pretreatment before drying) mushrooms wer e dried in the thin layer drying experimental equipment at each of the drying air temperatures of 45, 50 and 60 degrees C with air velocitie s of 0.9 and 1.6 m/s. Studies on the equilibrium moisture content (EMC ) of both untreated and treated dehydrated mushrooms were performed at different relative humidities ranging from 11.2 to 86.3% at 30 degree s C. In thin layer drying, mushrooms are dried under a constant-rate p eriod for a short time at the beginning, and subsequently, they are dr ied under a falling-rate period for the rest of the time. Drying equat ions and EMC models for both untreated and treated mushrooms were deve loped. The quality characteristics of dehydrated mushrooms were analys ed. Taking drying time and quality of the dehydrated product into acco unt, a combination of a drying air temperature of 50 degrees C and an air velocity of 0.9 m/s appears to be suitable for drying of both untr eated and treated mushrooms for a good dehydrated product. Copyright ( C) 1996 Elsevier Science Ltd