Rehydration of freeze-dried and convective dried boletus edulis mushrooms: effect on some quality parameters.
Quality of rehydrated products is a key aspect linked to rehydration conditions. To assess the effect of rehydration temperature on some quality parameters, experiments at 20 and 70 degrees C were performed with convective dried and freeze-dried Boletus edulis mushrooms. Rehydration characteristics (through Peleg's parameter, k(1), and equilibrium moisture, W(e)), texture (Kramer), and microstructure (Cryo-Scanning Electron Microscopy) were evaluated. Freeze-dried samples absorbed water more quickly and attained higher W(e) values than convective dried ones. Convective dehydrated samples rehydrated at 20 degrees C showed significantly lower textural values (11.9 +/- 3.3 N/g) than those rehydrated at 70 degrees C (15.7 +/- 1.2 N/g). For the freeze-dried Boletus edulis, the textural values also exhibited significant differences, being 8.2 +/- 1.3 and 10.5 +/- 2.3 N/g for 20 and 70 degrees C, respectively. Freeze-dried samples showed a porous structure that allows rehydration to take place mainly at the extracellular level. This explains the fact that, regardless of temperature, freeze-dried mushrooms absorbed water more quickly and reached higher W(e) values than convective dried ones. Whatever the dehydration technique used, rehydration at 70 degrees C produced a structural damage that hindered water absorption; consequently lower W(e) values and higher textural values were attained than when rehydrating at 20 degrees C.
Hernando
I
I
Dept. de Tecnología de Alimentos, Univ. Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain.
Sanjuán
N
N
Pérez-Munuera
I
I
Mulet
A
A
D001487:Basidiomycota / Q000648:ultrastructure; D003890:Desiccation / Q000379:methods*; D005511:Food Handling / Q000379:methods*; D005519:Food Preservation / Q000379:methods*; D005612:Freeze Drying; D008855:Microscopy, Electron, Scanning; D013696:Temperature; D014867:Water
D014867:Water