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In current work, pulsed vacuum drying was employed to dry the bananas and the effect of ripeness on drying kinetics and physicochemical properties was explored and related mechanism was understood through the analysis of sugar and the microstructural changes. Results showed that, with the increase in the ripeness of banana, the drying time decreased from 6.0 to 5.0 h, the rehydration ratio increased from 1.76 ± 0.09 to 2.98 ± 0.11. Fourier transform infrared spectroscopic analysis illustrated ripening and pulsed vacuum drying hardly affects the chemical composition of starch molecules. Regardless of fresh or dried samples, the reducing sugar and total sugar content both increased with increase in ripeness. Compared to the dried ripeness III samples, total color difference of samples with ripeness I and II decreased by 25.03% and 25.49%, respectively. As ripeness increased, the total phenolics and DPPH assay of fresh samples decreased, whereas in pulsed vacuum dried samples it significantly increased. The overall findings indicate that the decrease of starch and the increase of sugar with the increase in ripeness have a significant impact on the pulsed vacuum drying kinetics, microstructure and physicochemical properties of the banana samples.
Zhou et al. (Sat,) studied this question.