Evaluating drying feature differences between ginger slices and splits during microwave-vacuum drying by hyperspectral imaging technique.

• MVD ginger slices showed higher shrinkage rates and hardness than splits. • MVD ginger splits had higher rehydration rates than slices at the beginning. • The surface layer of MVD ginger slices showed more porous than that of splits. • A more uniform moisture distribution was found in MVD original ginger slices. This study aimed to investigate the difference between ginger slices (vertically cut) and splits (horizontally cut) during microwave-vacuum drying (MVD) procedures. MVD ginger slices showed a higher shrinkage rate and a higher hardness value, with a more porous structure of the surface layer. MVD ginger splits had higher rehydration rates at the first 15 min of the rehydration. Nine optimal wavelengths were selected by regression coefficients (RC) from the partial least squares regression (PLSR) model based on the raw data. A simplified PLSR model based on optimal wavelengths showed a good performance with a coefficient of determination in prediction (R p 2) of 0.973 and a root mean square error in prediction (RMSEP) of 4.63%. Texture features of grey level co-occurrence matrix (GLCM) of moisture prediction maps demonstrated a more uniform moisture distribution in MVD ginger slices than that in splits in the original geometry. [ABSTRACT FROM AUTHOR]