Abstract:
BACKGROUND: A large number of shiitake mushrooms are consumed in dried
form around the world. In this work, the changes in water state, water distribution and
microstructure of shiitake mushrooms during hot-air drying (HAD) and far-infrared
radiation drying (FIRD) processes were investigated using low-field nuclear magnetic
resonance (LF-NMR) and scanning electron microscopy (SEM). Quality attributes of
the dried products were compared in terms of drying property, appearance,
rehydration behavior, texture and storage stability.
RESULTS: As compared with HAD, the rate of water diffusion and evaporation of
the shiitake mushrooms dried by FIRD was higher, thus resulting in shorter drying
time (630 min), lower water content (0.07 g/g w.b.) and higher Tg (7.88°C) of dried
products. Moreover, homogenous and porous microstructure with less shrinkage and
case hardening was owned by the FIRD samples, indicating superior texture, for
instance, larger pileus diameter (3.4 cm), higher rehydration ratio (7.31), lower
hardness (37.93 N), and higher crispness (1.41 mm) of the FIRD shiitake mushrooms.
CONCLUSION: High-quality shiitake mushrooms with desirable texture could be
produced by FIRD through enhancing the diffusion of internal water and alleviating
the case hardening during a relatively short drying process.
