Abstract: Low-temperature energy-focusing ultrasound was used to break down the cell wall of buckwheat bee pollen and the process was analyzed using scanning electron microscope (SEM). In the microscopic field, the bee pollen cells were spited, ruptured along the germ ditch, and broken into pieces successively, which allows the establishment of an accurate method for calculating the efficiency of cell wall disruption. Based on SEM observation, the optimum experimental conditions that provided the maximum efficiency of cell wall disruption (98.33%) were determined as follows: initial temperature 0 ℃, ultrasound power 400 W, pulse duty factor 1:2, sonication time 30 min, and ratio of solid to solvent 1:30 (g/mL). Further study showed that the efficiency of cell wall disruption displayed a linear relationship with the release percentage of total flavonoids from the pollen when incubated in simulated gastric and intestinal fluid, which was fitted into the following equation was y = 0.363 8x + 27.172 with a correlation coefficient (R2) of 0.999 7.

Key words: buckwheat bee pollen, low-temperature energy-focusing ultrasound, wall breakdown, scanning electron microscope, simulated gastrointestinal release, total flavonoids