Selected physical properties of chitin prepared from shiitake stipes

Fungal chitins were prepared from air-dried shiitake stipes by alkaline treatment and three decolorization methods. Yields of chitins A, B and C were 283.2, 367.2 and 250.8 mg/g, respectively. Three chitins were similar in the element profile due to their related N/C ratios. However, it seemed that the nitrogen content in chitin C was the highest (35.4 mg/g). Three chitins showed a melting endothermic peak at 248.65–248.92 °C, higher than stipes at 243.53 °C. The thermal decomposition enthalpies (ΔH) of chitins A and B were the same and higher than ΔH of chitin C and stipes. Under electron microscopic examination, shiitake stipes showed the aggregated flakes with dense and firm structure and without porosity whereas chitins were more compact than stipes. The major crystalline peak for three chitins was at 19.3–19.6° and three WAXD patterns were similar. Generally, three chitins prepared showed similar physical characteristics as evidenced by the element analysis, DSC, SEM and WAXD patterns.