Quality and Sorption Characteristics of Microwave-Vacuum, Air and Freeze dried Button Mushrooms

摘要

Button mushrooms (Agaricus bisporusj were dehydrated by three different drying techniques viz. hot-air, microwave-vacuum and freeze-drying to a moisture content of about 6 %(w.b.). Dehydrated samples were compared on the basis of different quality parameters such as color, texture (hardness), rehydration ratio and sensory evaluation. Statistical analysis of data using Tukey's HSD test revealed significant difference among the drying methods for all the properties at p <= 0.05. Although freeze dryingproduced the best quality dehydrated products having maximum rehydration ratio, highest instrumental color (L-value) and lowest hardness, the microwave-vacuum dried mushrooms were rated as equal to freeze-dried samples by a sensory panel in terms of appearance, color and overall acceptability. Microwave-vacuum dried mushrooms had significantly higher rehydration potential, lower density, better color and softer texture than those obtained by air drying. The effect of drying methods on the water sorptionproperties of dehydrated products was also evaluated at 20, 30 and 40 deg C. It was found that freeze-dried products absorbed maximum water vapour and microwave-vacuum dried products had a higher sorption capacity than conventional hot-air dried products. Four different sorption models proposed in the literature (GAB, Oswin, Iglesias and Chirife, and Peleg) were used to fit the sorption data. Based on the coefficient of determination (R~2), mean relative percent error (E) and standard error (S.E.) values, the Peleg's model gave the best fit to the experimental sorption data of button mushroom.