Effect of purification method of β-chitin from squid pen on the properties of β-chitin nanofibers

The relationship between purification methods of β-chitin from squid pen and the physicochemical properties of β-chitin nanofibers (NFs) were investigated. Two types of β-chitin were prepared, with β-chitin (a ⿿ b) subjected to acid treatment for decalcification and then base treatment for deproteinization, while β-chitin (b ⿿ a) was treated in the opposite order. These β-chitins were disintegrated into NFs using wet pulverization. The β-chitin (b ⿿ a) NF dispersion has higher transmittance and viscosity than the β-chitin (a ⿿ b) NF dispersion. For the first time, we succeeded in obtaining 3D images of the β-chitin NF dispersion in water by using quick-freeze deep-etch replication with high-angle annular dark field scanning transmission electron microscopy. The β-chitin (b ⿿ a) NF dispersion has a denser and more uniform 3D network structure than the β-chitin (a ⿿ b) NF dispersion. Widths of the β-chitin (a ⿿ b) and (b ⿿ a) NFs were approximately 8⿿25 and 3⿿10 nm, respectively.