Plasma-assisted extraction of high-purity chitin from crab shells: Eliminating the need for chemical decolorization

Chitin, a high-value biopolymer derived from crustacean shells, generally requires harsh chemical decolorization to achieve acceptable purity and appearance. Herein, we developed a green extraction method for chitin using atmospheric pressure plasma jet pretreatment combined with acid-base processing. Chinese mitten crab shells were subjected to different sequences and concentrations of hydrochloric acid (HCl) and sodium hydroxide (NaOH) treatments, with and without plasma pretreatment. Structural and physicochemical characterizations were performed via FTIR, SEM-EDS, AFM, XPS, NMR, XRD, TGA, and molecular weight analysis. The results indicated that when the acid-base concentrations were ≥2-M HCl and ≥1-M NaOH, plasma pretreatment (PJ-HN) enabled the release of high-purity chitin without the need for chemical decolorization. The chitin obtained exhibited comparable crystallinity (64.58 %), thermal stability (DTG max = 402.9 °C), and molecular weight (6.89 × 10⁵ g/mol) to commercial chitin. Moreover, the PJ-HN samples retained high acetylation degrees and showed enhanced surface roughness, indicating improved functional potential. The antibacterial test confirmed that it possesses broad-spectrum antibacterial activity. The present study demonstrates that plasma-assisted extraction can serve as an eco-friendly and efficient alternative to conventional chemical methods in crustacean chitin processing.