Effects of Drying Methods on Microstructure of Juicy Peach

To describe the changes of juicy peach microstructure under different drying methods, microstructure images and cell parameter distribution curves of juicy peach under different moisture ratios were obtained by using paraffin section, micro-imaging and image processing technologies, after treated by five drying methods (i.e. hot-air drying (HAD), vacuum drying (VD), freeze drying (FD), hot-air and vacuum combined drying (HA-VD), freeze and hot-air combined drying (F-HAD)). The effect of drying methods on microstructure parameters (i.e., cell area, cell perimeter, cell roundness, cell wall surface roughness and porosity) were analyzed via cell parameters distribution curves. Fitting equations were built by polynomial fitting to describe the correlation between cell parameters and moisture ratios. The results showed that microstructural parameters of juicy peach primarily changed in the first half process (moisture ratio>0.5) of hot air drying and second half process (moisture ratio<0.5) of vacuum and freeze drying. The changing trend of cell area was FD<HAD<VD<HA-VD<F-HAD. Cell perimeters increasing was HAD<HA-VD<VD<F-HAD<FD. Cell roundness decreasing was HAD<FD<F-HAD<HA-VD<VD. Cell wall surface roughness increasing was F-HAD<VD<FD<HA-VD<HAD. Degree of porosity increase was FD<F-HAD<HAD<HA-VD<VD. Compared with single drying methods, the change of microstructure parameters was significantly inhibited by using corresponding combination drying methods. The results provided an important reference for exploring variation of microstructure parameters and establishing mathematical model of juicy peach with moisture ratios under different drying methods.