To mask the astringent taste of tannic acid, improve its acceptability, and enhance the stability of its biological activity, the tannic acid microcapsules were prepared with konjac glucomannan as wall material and combined with freeze-drying technology.The tannic acid embedding rate was used as the evaluation index to optimize the embedding process, and the microscopic morphology, structure, thermodynamic properties, slow-release effects, antioxidant and antibacterial activity of the microcapsules were comprehensively analyzed.Results showed that the optimum preparation technology of tannic acid microcapsules was as follows:core-to-wall ratio of 1∶15, wall material concentration of 20 g/L, reaction temperature of 45 ℃, and stirring time of 2.0 h.Under these conditions, the tannic acid embedding rate was 75.33%, it was irregularly shaped with slight cracks on the surface.Infrared spectroscopy and differential scanning calorimetry showed that tannic acid was successfully encapsulated in capsules and had good thermal properties.Compared with untreated tannic acid, the microencapsulated tannic acid had a slow-release effect.and the concentrations of the tannic acid group and microencapsulated group in the oral digestion stage were 0.98 mg/mL and 0.57 mg/mL, respectively, which effectively solved the palatability problem of tannic acid.After embedding, the antioxidant and antibacterial activities of tannic acid were not affected.The IC50 values of tannic acid for DPPH free radical and ABTS cationic radical scavenging were 9.20 μg/mL and 9.58 μg/mL, while the IC50 values of tannic acid microcapsules were 9.08 μg/mL and 8.99 μg/mL, respectively.Tannic acid had certain bacteriostasis on four kinds of intestinal pathogenic bacteria before and after microencapsulation, among which the inhibitory effect on Staphylococcus aureus and Escherichia coli was stronger, the inhibitory rate of tannic acid on S. aureus and E. coli was (87.06±2.28)%, (84.44±6.85)%.The bacteriostatic rates of microcapsules were (96.02±3.11)% and (79.34±3.97)%, respectively.Tannic acid could damage the cell membrane of bacteria and affect the growth and reproduction of bacteria, which had a good bacteriostatic effect.Therefore, tannic acid microencapsulation provides useful ideas for the application of tannic acid in different fields.
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