Effect of deacetylation of chitosan on the physicochemical, antioxidant and antibacterial properties activities of chitosan–mannose derivatives

Abstract BACKGROUND The present study investigates the physical, chemical, and antibacterial properties of water‐soluble chitosan derivatives. Preparation of the water‐soluble chitosan derivatives was performed by the Maillard reaction (MR) between chitosan [with the degree of deacetylation (DD) being 50%, 70%, and 90%] and mannose. No organic reagent was used in the process. Systematic evaluations of the effects of chitosan DD on the reaction extent, the structure, the composition, as well as the physicochemical properties, antioxidant properties, and bacterial inhibitory properties of the finished chitosan–mannose MR products (Mc‐mrps), were carried out. RESULTS Based on the experimental data obtained from Fourier transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, Pyrolysis‐gas chromatography‐mass spectrometry analysis, and 1 H‐NMR, the Mc‐mrps formed from chitosan with different DDs had different structures and components. An increase in the DD of chitosan led to a significant increase in the degree of reaction, color difference (△ E ), and solubility ( P < 0.05). The zeta potential and particle size of the Mc‐mrps were also influenced by the DD of chitosan. Additionally, the antimicrobial action against Gram‐positive ( Staphylococcus aureus and Bacillus subtilis ) and Gram‐negative bacteria ( Escherichia coli and Salmonella typhimurium ), as well as antioxidant activity, were enhanced by the incorporation of mannose. This was also achieved by the increase of the DD of chitosan. CONCLUSION The results of the present study suggest that chitosan was derived with mannose to yield a novel, water‐soluble polysaccharide with better antioxidant and antimicrobial activities. The DD of chitosan had a significant effect on the properties of the Mc‐mrp, which can serve as a reference point for the subsequent preparation and application of such derivatives. © 2023 Society of Chemical Industry.