Abstract: To explore the encapsulation mechanism and performance regulatory effect of a chitosan-starch mixture on the flavor molecule nonanoic acid, this study systematically investigated the effects of different molecular masses (50, 200, 500, and 1 000 kDa) and concentrations (1%, 1.5%, and 2%) of chitosan on the encapsulation capacity and stability of nonanoic acid, as well as the structural and physicochemical properties of the resulting complexes. Texture analysis revealed that changing the molecular mass and concentration of chitosan significantly regulated the textural properties of the composite gels: the hardness and chewiness of the low-to-medium molecular weight groups (50 kDa and 200 kDa) decreased with increasing chitosan mass fraction, whereas those of the 500 kDa group showed an upward trend. Rheological properties indicated that the storage modulus (G′) and loss modulus (G″) increased significantly with chitosan addition. The gelatinization temperature was regulated by the joint action of the molecular mass and addition level of chitosan-50, 200, 500, 1 000 kDa chitosan were most effective in delaying starch gelatinization at 1%, 1.5%, 1.5%, and 2% addition levels, respectively. X-ray diffraction (XRD) analysis showed that the diffraction peaks of the complexes at 7.8°, 13°, and 20° became sharper with increasing amount of chitosan. Short-range order analysis indicated that the peak positions of functional groups shifted without the formation of new characteristic peaks, demonstrating changes in intermolecular forces. The morphology presented a regular honeycomb structure with a smooth surface. X-ray photoelectron spectroscopy (XPS) verified the interaction between starch and chitosan. Thermogravimetric analysis (TGA) results showed that the residual amount of the complex with 200 kDa chitosan at 1.5% was the highest (27.91%). This study provides a theoretical basis for the development of efficient carriers for flavor molecules and the optimization of food flavor stabilization technology.

Key words: chitosan; starch; flavor molecules; encapsulation; composite gel