Measurement of moisture transformation and distribution in Tricholoma matsutake by low field nuclear magnetic resonance during the hot-air drying process

Abstract

This study aims at measuring the moisture transformation and distribution of Tricholoma matsutake (T. matsutake) during the hot-air drying process, to provide theoretical guidance for drying optimization of T. matsutake. Pileus and stipe of T. matsutake were dried at 55 °C for 14 hr. During the hot-air drying, spin-spin relaxation measurements and magnetic resonance image were used to determine the water composition and the moisture transformation, respectively. Results showed that three categories of moisture including free, immobilized, and bound water were presented in T. matsutake. During the drying process, the immobilized water was the major, free and immobilized water were active, while bound water was stable. The measurements of moisture transformation and distribution in T. matsutake by low field nuclear magnetic resonance suggested that hot-air drying was an inhomogeneous drying process. Practical applications T. matsutake is rich of nutritional and bioactive compounds. The fresh T. matsutake contains large amount of water, therefore, the dehydration process is essential for the preservation of T. matsutake. Hot-air drying has been widely used in food preservation. Moisture content and states are key parameters affecting the quality of dehydrated foods. However, no data have shown the dynamics of moisture transformation and distribution of T. matsutake during the hot-air drying process. This study aims at measuring the profiles of moisture during hot-air drying by low field nuclear magnetic resonance (LF-NMR) and NMR proton density imaging, which could help to optimization the drying of T. matsutake or other edible fungi.