EFFECT OF PRETREATMENTS AND DRYING TEMPERATURES ON THE QUALITY OF DRIED PLEUROTUS MUSHROOM SPP.

Abstract

Among various methods employed for preservation of mushrooms , drying is the most common technique but it affects the colour and texture of the product which are of prime importance to the consumer as product quality criteria. However, pre-drying treatments also affect the quality of dried products. Dehydration of button mushrooms (Agaricus bis-porus) slices were carried out with various pre-treatments like blanching, soaking in 0.5% potassium metabisulphite (KMS), soaking in 0.5% citric acid +0.5% ascorbic acid and soaking in 0.75% EDTA. Drying was done in a tray dryer at drying air temperatures of 50 o and 70 o C and the drying characteristic curves were drawn. The total drying time required for drying of white button mushrooms slices pretreated with various chemicals and dehydrated at different temperature of drying air was determined. The qualities of dehydrated slices were evaluated on the basis of rehydration characteristics and colour. Evolution 600 UV/VIS Spectrophotometer equi-ped with DRA-EV-600 diffuse Reflectance Accessory was used to determine optical properties. Drying air temperature of 50 o C was better as it resulted in dried products having better rehydration characteristics and lighter color. Pre-drying treatments had a significant effect on the whiteness and colour change of dried mushroom slices. Whiteness of blanched mushrooms was very high compared to other samples but the rehydration ratio was very low. Among the four treatments, soaking in 0.5% citric acid and 0.5% ascorbic acid has produced comparatively more acceptable product taking into account all the quality parameters.