Preparation of Nano/Submicron Ganoderma tsugae and Its Stability

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 degrees C for 21 days, the volume-average diameter of supernatant III increased from 0.105 to 0.137 mu m. 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 mu m. Nevertheless, autoclaving did not result in severe instability of supernatant III. After being stored at 25 degrees 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 beta-(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.