Application of LF-NMR and Its Imaging Technology in the Study of Winter Jujube Storage Process

In order to investigate the water migration of winter jujube during low temperature (4 ℃) storage, LF-NMR and its imaging technology were used to monitor the transverse relaxation time and image the water distribution of the samples stored within 60 days. At the same time, the appearance change, color, weight loss rate, hardness and respiration intensity of the samples were determined. The results showed that with the passing of storage time, the content of free water in the winter jujube decreased greatly, and gradually permeated to the direction of the fruit core, and transformed into water that was not easy to flow and bound water. The fruit epidermis changed from green to dark red at 32 d, and the weight loss rate increased linearly and reached 2.23% at 40 d. Fruits continue to softening, and the hardness value dropped by nearly half. In addition, winter jujube is a respiratory climacteric fruit, and its respiration intensity reached its peak at 40 days under 4 ℃ environment. The results showed that the migration and loss of water in fruits were accompanied by the decline of related quality physical and chemical indexes. In this study, low-field NMR technology was applied to the quality monitoring of fruits and vegetables, which provided a certain degree of reference for the direction of fruit and vegetable preservation.