Environment-friendly utilization of squid pen with water: Production of β-chitin nanofibers and peptides for lowering blood pressure.

Chitin, an abundant biopolymer on Earth, represents a resource for sustainable functional materials. However, traditional β-chitin production methods involve alkaline treatment at approximately 90 °C for its separation from the protein, thus not suitable as a functional peptide, as it is mixed with an alkaline aqueous solution. This study examined the conversion of squid pen into solid β-chitin and water-soluble peptides using only water at temperatures of 150-250 °C for 30-120 min. Solid β-chitin was converted to its nanofiber form and the physicochemical properties of the β-chitin nanofibers were almost the same as those produced by the traditional method. Because this method uses only water, the protein in the squid pen may also be a functional peptide for lowering blood pressure, by inhibiting the Angiotensin-1 converting enzyme. High-temperature water treatment is a promising environment-friendly technique for complete utilization of squid pen components, including β-chitin and protein.