Water Diffusion Characteristics and Microstrcture of Blueberry During Hot-air Drying

The objective of this study was to investigate water diffusion characteristics and microstructure of blueberry at different temperatures during hot-air drying process, which was respectively 50, 65, 80℃. Using nuclear magnetic resonance (NMR) and microscopic electron microscopy (SEM) techniques, water transport and micro-structural changes in the inner pericarp of blueberries during drying were analyzed. Results showed that moisture distribution was changed in drying process and the moisture with high degree of freedom moved to the moisture with low degree of freedom. Temperature and time were two main aspects during hot-air drying. Drying rate was accelerated with the rise of drying temperature. Drying time at 50, 65 and 80℃ were 50, 18 and 7.5 h, respectively.Water contents in dry base and nuclear magnetic resonance signal amplitude were followed significant linear regression (y=113.99x+5728.6, R²=0.9901, p<0.01).With loss of moisture during hot-air drying process, shrinkage of blueberry occurred and microstructure changed. Microscopically, cell wall microfilaments were arranged from tightly ordered to loosely disordered. This study provided data reference for the changes of water migration and microstructure in the drying process of blueberry fruit.