NMR study of hydration of navy bean during cooking

MRI and NMR relaxometry were used to monitor the water uptake at macroscopic and microscopic levels during cooking of navy beans. MRI images showed that water gradually penetrated into the center of the bean, and full hydration was achieved after 80 min. A biphasic model, which consists of an exponential phase and a linear phase, was applied to the water uptake data of the navy bean during cooking. The exponential stage finished after 80 min. The NMR relaxometry results indicated there are three water proton components in navy beans. The percentage of bound water decreased gradually as a function of cooking time. The population of the intracellular water reached its maximum at 80 min. A dramatic increase in the population of extracellular water was observed at 150 min. These results suggest that water was incorporated primarily with the intracellular content in navy beans during the initial exponential stage of water uptake. Further water uptake during the linear stage contributed to the increase in the water content in extracellular space. Optical microscopy of the navy bean provided more evidence for the changes in the water distribution at the microscopic level.