Identification of coexisting low-molecular-weight α- and β-chitin in different anatomical parts of black soldier fly (Hermetia illucens).

Chitin is a natural polysaccharide whose practical value depends strongly on intrinsic physicochemical parameters, including molecular weight, degree of deacetylation, crystalline organization, polymorphic form, thermal behavior, and biological compatibility. In this study, chitin was extracted from different anatomical parts of black soldier fly (BSF, Hermetia illucens), including the head, belly, wing, and cocoon, and its physicochemical properties were systematically characterized. All extracted chitin samples showed relatively low molecular weight, ranging from 78.4 to 108.6 kDa. Combined Raman, FTIR, XRD, and 1H NMR analyses indicated that head- and wing-derived chitin were more consistent with α-chitin, whereas belly- and cocoon-derived chitin were more consistent with β-chitin. Wing-derived chitin showed the lowest crystallinity (35%) and smallest estimated lattice diameter (87 nm), while head-derived chitin exhibited the highest crystallinity (92%). All samples showed similar thermal decomposition regions, although the total mass loss and derivative thermogravimetric profiles varied according to anatomical origin. In L929 fibroblast screening, all samples showed cell viability above 95% under the tested hydrogel condition. These results indicate that BSF anatomical origin influences chitin yield, molecular organization, crystallinity, and preliminary cytocompatibility, supporting the use of BSF by-products as structurally diverse chitin sources for food-related and biomaterial applications.