Comparative extraction and physicochemical profiling of chitosan from Litopenaeus vannamei shrimp shell waste

Chitosan, a biopolymer derived from chitin, is widely used in industrial and biomedical applications, and its physicochemical properties are strongly influenced by extraction conditions and the degree of deacetylation (DD). Although chitosan extraction from Litopenaeus vannamei has been previously reported, many studies rely on single-step deacetylation with limited physicochemical characterization, resulting in variable functional performance. In this study, we evaluate a two-step deacetylation sequence as an intensified modification of conventional alkaline processing, aiming to improve acetyl-group removal, increase amino-group availability, and enable clearer structure-function correlations. Shrimp shell waste was processed under six chemically controlled treatments that varied in demineralization, deproteinization, and deacetylation conditions. The resulting chitosan samples were characterized for yield, molecular weight (MW), ash content, solubility, water and fat binding capacities, DD (via ATR-FTIR), nanoparticle size, and zeta potential, using commercial chitosan as a reference. Yields ranged from 19.16% to 21.17%, DD from 80.29% to 84.72%, and MW from approximately 145 to 481 kDa. The two-step treatment (T₆) produced chitosan with the highest DD (84.72%), improved solubility (87.81%), enhanced water/fat binding capacities (≈715%/543%), and smaller, more stable nanoparticles (152 nm, +24 mV), showing performance comparable to the commercial standard. ATR-FTIR analysis confirmed structural integrity and deacetylation efficiency. The study acknowledges methodological limitations that should be addressed in future work. Overall, the findings indicate that sequential deacetylation can serve as a refined variation of established chemical extraction, providing a reproducible framework for linking processing intensity to functional and colloidal properties and supporting valorization of shrimp shell waste into useful biopolymers.