Microscopic and Macroscopic Analysis of Purple Sweet Potato Dried Products Following Vacuum Steam Pulsation Blanching Pretreatment

Abstract

To improve the drying efficiency and quality of purple sweet potatoes after blanching pretreatment, this study employed three methods: hot water blanching (HWB), microwave blanching (MB), and vacuum steam pulsed blanching (VSPB). The impact of different blanching methods on the microstructural parameters and macroscopic performance of purple sweet potatoes was investigated using techniques such as paraffin sectioning, microscopic observation, and image processing. The results indicated that, at the microscopic level, the proportion of large cells after VSPB was significantly higher than that after hot water and MB, being 15.81%, 5.15%, and 25.68%, respectively. At the macroscopic level, samples pretreated with VSPB had the shortest drying time (210 min), the highest rehydration ratio (RR) (3.988), and the best chewiness (2095.44 g). Further studies explored the effects of blanching vacuum degree, blanching time, and blanching frequency on the distribution of various microstructural parameters of purple sweet potato tissue cells. Through nonlinear polynomial fitting, a fitting equation was established between the microstructural parameters after VSPB and the macroscopic RR and browning index. The determination coeffi cients R² of the established mathematical models and the predicted results were all greater than 0.8. The findings of this study provide an important reference for exploring the mechanism of the impact of VSPB pretreatment on the microstructural parameters and macroscopic performance of purple sweet potatoes and offer a theoretical basis for the design of drying equipment.