Water status and distribution in shiitake mushroom and the effects of drying on water dynamics assessed by LF-NMR and MRI

Water status and distribution in shiitake mushroom and the effects of drying temperature on water migration were investigated by low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) technique. Three water components assigned to bound, immobilized water and free water were observed in fresh shiitake mushroom by LF-NMR, and higher moisture content was found in the lamella and outer layer of stalk by MRI. During drying, the transverse relaxation time and peak area of immobilized and free water in pileus significantly decreased. Higher drying temperature could promote the changes in water mobility and population. MRI results revealed the water evaporated from external surface of shiitake mushroom, then the water in inner region migrated to the surface during the drying. The drying properties, color and shrinkage of shiitake mushroom were also measured. The strong correlation between moisture content and total peak area of water with a coefficient of 0.9792 revealed the potential of LF-NMR as a rapid and nondestructive method to monitor drying degree of shiitake mushroom.