Fractal structure evolution of moisture-containing porous media under the weak potential difference in cases of garlic stems.

In cases of garlic stems, during ice-temperature storage (0 °C) with precooling air velocities of 1.0 m/s, 1.5 m/s and 2 m/s, the variations of fractal parameters such as pore fractal dimension, porosity, tortuosity and tortuous fractal dimension were studied. The results showed that the selection of precooling air speed plays a major role in maintaining the moisture contained in garlic stems after harvest. Compared with precooling air velocities of 1.5 m/s and 2.0 m/s, the precooling air velocity of 1.0 m/s has more significant impact on the porosity, the tortuosity and the tortuous fractal dimension in the cells microstructure. Cells at the epidermis were more affected than cells at the 1/2 radius and the center. Meanwhile, there is a significant two-dimensional linear correlation among the average tortuosity, porosity and tortuous fractal dimension in the three conditions during ice-temperature storage. The two-dimensional correlation coefficients under the precooling treatment of 1.0 m/s is the largest among the three air velocities.