Abstract: This study aims to investigate the effects of the κ-carrageenan concentration on the printability of the gel system. The 3D printing properties of the gel system were also determined to explore the effects of the lyophilization and rehydration on the shape fidelity and the volatile organic compounds (VOCs) in the printed products. A series of tests was then carried out to determine the rheological properties, moisture status, infrared spectroscopy, printability, textural properties, and microstructure. The physicochemical properties of the gel system were evaluated on the shape fidelity of the lyophilized and rehydrated products. The VOCs were also characterized in the blueberry syrup, 3D printed, and rehydrated products by gas chromatography-ion mobility spectrometry (GC-IMS). The results were obtained: 1) The increasing concentration of the κ-carrageenan enhanced the hydrogen bonding for the formation of a more cross-linked and compact network structure. The fluidity of the gel system was reduced to improve the self-supporting capacity for high resistance to deformation. Thereby, there was the high molding quality and structural stability of the 3D-printed products. 2) The concentration of the κ-carrageenan enhanced the hardness and cohesiveness of the 3D printed products. A denser network structure was formed after printing. The optimal performance of 3D printing was achieved in the gel system at a κ-carrageenan concentration of 2%. The lowest deviation and the most well-defined ‘FOOD LAB’ design demonstrated the superior fidelity after printing. 3) The increasing concentration of the κ-carrageenan enhanced the moisture content and hardness of the lyophilized products. There were the smooth and intact surfaces of both lyophilized and rehydrated products at a concentration of 2%. The highest shape fidelity was obtained without wrinkles or cracks. The rehydrated products with the 2% κ-carrageenan concentration exhibited the best fit to the Peleg model (R2=0.9592), indicating the superior rehydration behavior. 4) A total of 44 VOCs compounds were identified among the blueberry pulp, 3D printed and rehydrated products, including 6 alcohols, 10 aldehydes, 4 ketones, 11 esters, 4 benzenes, 6 terpenes, and 3 miscellaneous compounds. Principal component analysis (PCA) revealed that there were distinct differences in the VOCs across the three samples. The most aldehydes were markedly diminished or undetectable signal intensities in both the 3D printed and rehydrated products. The greasy and irritating odors were reduced to prevent the excessively pungent aldehydic notes. Several VOCs exhibited strong signal intensities in the rehydrated products, including (E, Z)-2,6-nonadienol, (E)-2-hexen-1-ol, 2,4-heptadienal, 2-heptanone, propyl acetate, and linalool oxide. These components greatly contributed to the characteristic blueberry-like fruity aroma and the complex bouquet typical of ripe berries. In summary, the concentration of 2% κ-carrageenan in the gel system was recommended for the optimal formability of 3D printing, superior surface properties, and shape fidelity after lyophilization and rehydration. The rehydrated product retained the characteristic blueberry-like fruity aroma while reducing the pungent aldehyde odor. This finding can offer some insights into the 3D printing applications of blueberries. The theoretical support and practical guidance can be gained to optimize the personalized, customized, and portable foods in the future.