Dynamics of water mobility and distribution in Sur clam (Mactra chinensis) during dehydration and rehydration processes assessed by low-field NMR and MRI

摘要

Drying method effects on water dynamics in Sur clam during dehydration and rehydration were studied using the non-destructive nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) techniques. Three water populations were observed in Sur clam samples with different migration behavior when they were dried by hot air at 60 °C for 8 h versus sun-dried for 53 h. Good correlation between the A2 parameter of NMR and moisture ratio MR was found, and the Page model exhibited the maximum coefficient R2 value with the minimum root mean squared error. Notably, the NMR and MRI characterization showed that the water release of hot-air dried clams was different from that of the sun-dried samples, and the principal component analysis (PCA) of NMR relaxation data offered a stable classification for the hot-air dried and sun-dried clams. Similarly, the rehydration of hot-air dried and sun-dried clams was also assessed by NMR and MRI revealing that the absorbed water was mainly the immobilized and free water. The proper rehydration time was 180 and 120 min, respectively, for the hot-air and sun dried clams. The rehydrated clams could be distinguished from the boiled samples before dehydration process through the PCA of NMR relaxation data, but undistinguishable between the rehydrated hot-air dried and sun-dried clams.These results demonstrated that NMR and MRI are effective methods for non-destructive analysis of Sur clams during dehydration and rehydration processes.