###### Abstract  
The objective of this study is to innovatively evaluate the biochemistry performance of \(\alpha\)-chitosan from _Portunus trittuberculatus_ shell and \(\beta\)-chitosan from _Ilex argentitus_ squid gladius by using the weighted composite index method, and provide a theoretical basis for better development and utilization of chitosan biomedical materials. To build a composite evaluation system, seven key indicators, including molecular weight (M\({}_{\text{w}}\)), deacetylation degree (DD), water binding capacity (WBC), fat binding capacity (FBC), thermal stability (TS), primary structure and secondary structure, which significantly affect chitosan biochemical characteristics, were determined and analyzed. The viscosity average M\({}_{\text{v}}\) of chitosan was in the range of 22.5-377.1 kDa, and the DD was 83.4-97.8%. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses of commercial chitosan (CS), crab chitosan (CSC) and squid chitosan (CS) showed a downward trend in TS, while WBC and FBC showed an obvious upward trend. FT-IR had a similar profile in peak shape, but the peak position slightly shifted. CD indicated that chitosan maintained the double helix structure and multiple secondary structural elements. The composite weighted index values of CS, CSC and CSS were 0.85, 0.94 and 1.31 respectively, which indicated that the CSS biochemistry performance was significantly better than CSC, and \(\beta\)-chitosan has great potential in biomedical materials. chitosan; biochemistry; weighted composite index +
Footnote †: journal:\(\beta\)-form, is usually found in squid cartilage and composed of two parallel chains, showing a certain degree of hardness, flexibility, and fluidity, possibly due to the weak intermolecular forces caused by parallel polymer chains. The \(\beta\)-form chitosan in squid cartilage has superior affinity and reactivity under various physical and chemical treatments compared to the \(\alpha\)-form chitosan in crab and shrimp shells, due to the \(\beta\)-form's weaker intermolecular forces than the \(\alpha\)-form [6]. Currently, chitosan is extensively applied in versatile fields, ranging from biomedical to cosmetics, textiles, food industry and agriculture, due to its outstanding properties, including solubility, bioactivity, biocompatibility, biodegradability, non-toxicity and non-immunogenicity [7; 8; 9], etc. Conventional methods to extract chitosan from marine organisms are generally accomplished using three different methods: chemical (hot alkaline), microbial culture and enzyme degradation. The enzymatic degradation mainly uses chitin deacetylase to catalyze the deacetylation of chitin molecules, but the main principle of microbial fermentation is to remove the acetyl group of chitin molecules contained in the cell wall by catalysis of the enzymes produced by the microorganism itself (such as _Aspergillus niger_ and _Rhizopus oryzae_). The yield of chitosan by the enzyme and microbiological methods is superior with no obvious problems of molecular chain degradation or alkaline pollution [10], but the operation is more complex and the cost is higher, so it is difficult to be popularized in the industry. At present, chitosan is produced industrially mainly by the hot alkali method, which has high reaction speed and high DD, but requires hazardous chemical compounds, and is energy intensive [11]. In order to solve this problem, chitosan was prepared by ultrasonic assisted EDTA combined with the high-pressure steam method, and the physiochemical properties and biological structure of chitosan were characterized and analyzed in this study. Under the action of ultrasonic cavitation, most of the minerals can be eliminated in a short time. The hydrogen bond in the molecule can be destroyed due to the thermal energy being converted into mechanical energy under saturated steam and high pressure, and the temperature condition, which can disintegrate the chitosan crystalline structure and make the reaction, protein removal rate and DD greatly improved [12; 13].