Multiscale pore drives mechanical properties and storage stability in peach crisps

Abstract

Multi-scale pore structures are formed during the drying of fruits and vegetables, and the size and distribution of micron- and nanometer-sized pores greatly affect the mechanical properties and storage quality of fruit and vegetable crisps. In this study, we constructed peach crisps with different pore structures using sucrose (SUC) and xylo-oligosaccharide (XOS) impregnation, vacuum freeze-drying (FD), and freeze drying combined with explosion puffing drying (FP). The effects of two-dimensional, three-dimensional, and micro-/nanopore sizes on the mechanical properties and storage quality of peach crisps was analyzed. The size of the pores in the peach crisps ranged from 50 to 300 μm. Notably, FD dried peach crisps exhibited a greater pore distribution in the 1–10 μm range, which FP dried products have no pore distribution in this range. After FP, the proportion of macropores increased significantly. Sugar impregnation led to thicker cell walls, a reduced proportion of micron macropores, a more uniform pore distribution, and an increased fractal dimension. The surface of the XOS-impregnated crunchy flakes became rougher, facilitating the formation of smaller pores and enhancing the pore-throat ratio. In terms of mechanical properties and storage attributes, freeze-dried peach crisps had lower hardness and storage quality. Both sugar impregnation and FP improved the hardness and crispness of peach crisps, while reducing the moisture absorption and vibration breakage rate. Correlation analyses indicated that nanoscale porosity positively influenced hardness and storage quality, whereas micron-sized porosity positively affected the mechanical property index, but negatively affected storage quality. These findings suggest that nanoscale pores can enhance the hardness of crisps and help maintain a better storage quality. Conversely, microscale pores can promote the formation of a crispiness but may compromise storage quality.