DRYING KINETIC OF FRESH AND OSMOTICALLY DEHYDRATED MUSHROOM (AGARICUS BLAZEI)

Abstract

ABSTRACTThe aim of this study was to model the drying kinetics of fresh and osmotically pretreated mushroom slices (Agaricus blazei). Besides the effects of drying air temperature and air velocity, the effect of osmotic pretreatment on drying kinetics and color of dried mushrooms was also determined. The osmotic treatment was carried out at 20C with a 10% (w/w) salt solution, 80 rpm agitation and 60 min immersion time. The fresh and osmosed mushrooms were dried in a vertical bed dryer with forced airflow at different temperatures (40, 60 and 80C) and air velocities (1.0, 1.75 and 2.5 m/s). Drying curves obtained from the experimental data were fitted to the different thin layer‐drying models (Fick's, Page's and logarithmic models). Drying rates of osmosed mushroom decreased due to the presence of infused solids. Increasing the drying temperature and air velocity caused shorter drying times. Osmotically pretreated mushroom presented lower luminosity values (L*) when compared with fresh mushroom, indicating that the osmotic dehydration was not efficient to prevent color loss. Temperature strongly affected the color parameters luminosity L* (or lightness) and chroma C* (or color intensity).PRACTICAL APPLICATIONSBiological materials are highly perishable due to their high moisture content. Therefore, these materials must be processed to improve their shelf life. Among the several methods employed for preservation, drying is a process in which the water activity of the food is reduced by the removal of water, minimizing chemical, enzymatic and microbiological reactions. Several pretreatments are commonly used to minimize adverse changes occurring during drying. Osmotic dehydration is used for the partial removal of water from the food by immersion in a hypertonic solution reducing the physical, chemical and biological changes during drying at higher temperatures. Thus, this study intends to contribute in understanding the behavior of undesirable color quality degradation during the process.