The preparation and stability of nano/submicrometer-sized Ganoderma tsugae (G. tsugae) was explored. The fruit body of G. tsugae was treated by homogenization and media-milling. Three sizes (0.8, 0.3, and 0.2 mm) of media were employed for consecutive milling. The final product was obtained by centrifugation (10,000 g, 10 min). Particle sizes were determined by using a laser-light particle size analyzer and further examined by using transmission electron microscopy. The removal of large particles resulted in better stability. After being stored at 25°C for 21 days, the volume-average diameter of supernatant III increased from 0.105 to 0.137 μm. Freeze-drying resulted in particle aggregation and an increase in particle size. Twenty percent of the particles in the freeze-dried supernatant III were smaller than 100 nm, with an average diameter greater than 1 μm. Nevertheless, autoclaving did not result in severe instability of supernatant III. After being stored at 25°C for 12 months, about 40% of the particles were smaller than 100 nm, with an average diameter of 373 nm. In addition, the contents of bioactive compounds such as β-(1,3)-D-glucans, crude triterpenoids, total dietary fiber and chitin in media-milled products were much greater than those present in the hot-water extract.

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