Studies on Water Migration and Microstructure of Areca Brine Based on Low-Field Nuclear Magnetic Resonance and Scanning Electron Microscopy

In order to address rehalogenation and whitening in areca brine during shelf life（60 days）, the water distribution and migration of different areca brine was investigated using low-field nuclear magnetic resonance. Meanwhile, the microstructure of these brine were analyzed by scanning electron microscopy. The results showed that as the proportion of caramel increased in the original halogen, water gradually migrated towards more tightly bound states. Throughout various production stages, LS1 and LS2 areca brine exhibited the similar water migration rules where water existed in a weakly bound state in the original brine stage. In the finished brine stage, water mainly exists in the form of weakly bound water (LS1, 83.12%; LS2, 90.53%). The brine in the core of areca, LS1 mainly existed in the form of strongly bound water (50.88%) and non-mobile water (38.67%), while LS2 mainly existed in the form of strongly bound water (82.43%). The free water content of LS1 was about 3 times higher than that of LS2 during both the brine forming stage and the finished core brine stage. In addition, there was a significant correlation between the water state of brine and brine structure and a higher proportion of bound water corresponded to a more stable brine structure. Furthermore, during the transformation of LS1 areca brine from normal to rehalogen and subsequently to white, the water state mainly migrated from less mobile water to bound water, with a minor portion migrating towards free water. During the transformation of LS2 areca brine from normal to white, water mainly migrated from bound water to free water. This study revealed the water migration patterns in different areca brines and their relationship with brine structure providing important theoretical reference for improving areca brine production processes and product quality.