Abstract: In order to investigate the effects of κ-carrageenan concentration on the printability of gel system, as well as the effects of lyophilization and rehydration on the shape fidelity and the change in volatile organic compounds (VOCs) of 3D printed products, the 3D printing properties of the gel system were analysed by testing rheological properties, moisture status, infrared spectroscopy, printability, textural properties, and microstructure. The physicochemical properties of the gel system were analysed by the shape fidelity of lyophilized product and rehydrated product. The changes of VOCs in blueberry syrup, 3D printed product and rehydrated product were analysed by gas chromatography-ion mobility spectrometry (GC-IMS). The following results were obtained: 1) Rheological analysis, moisture state assessment, and infrared spectroscopy revealed that increasing κ-carrageenan concentration enhanced hydrogen bonding and promoted the formation of a more cross-linked and compact network structure. This structural development reduced the fluidity of the gel system and improved its self-supporting capacity and resistance to deformation, thereby enhancing the molding quality and structural stability of the 3D-printed products. 2) Analysis of print formability, textural properties, and microstructure revealed that increasing κ-carrageenan concentration enhanced the hardness and cohesiveness of the 3D printed products and led to the formation of a denser network structure. At a κ-carrageenan concentration of 2%, the gel system exhibited optimal 3D printing performance, characterized by the lowest print deviation values and the most well-defined print of the ‘FOOD LAB’ design, indicating superior print fidelity. 3) Analysis of the effects of κ-carrageenan concentration on the formability of lyophilized products and rehydrated products revealed that increasing κ-carrageenan concentration enhanced the moisture content and hardness of the lyophilized products. At a concentration of 2%, the surface of both lyophilized and rehydrated products remained smooth and intact, without noticeable wrinkles or cracks, resulting in the highest shape fidelity. The rehydrated products with 2% κ-carrageenan concentration exhibited the best fit to the Peleg model (R²=0.9592), indicating its superior ability to describe rehydration behavior. 4) Changes in volatile organic compounds (VOCs) among the blueberry pulp, 3D printed products, and rehydrated products were analysed using gas chromatography–ion mobility spectrometry (GC–IMS). A total of 44 compounds were identified, including 6 alcohols, 10 aldehydes, 4 ketones, 11 esters, 4 benzenes, 6 terpenes, and 3 miscellaneous compounds. Principal component analysis (PCA) revealed distinct differences in VOCs across the three samples. In both the 3D printed and rehydrated products, most aldehydes exhibited markedly diminished or undetectable signal intensities, resulting in a reduction of greasy and irritating odours and preventing the formation of excessively pungent aldehydic notes. Several VOCs, including (E,Z)-2,6-nonadienol, (E)-2-hexen-1-ol, 2,4-heptadienal, 2-heptanone, propyl acetate, and linalool oxide, exhibited strong signal intensities in rehydrated products, contributing to characteristic blueberry-like fruity aroma and the complex bouquet typical of ripe berries. In summary, the concentration of 2% κ-carrageenan resulted in the gel system exhibiting optimal 3D printing formability, as well as superior surface properties and shape fidelity following lyophilisation and rehydration. The rehydrated product was able to retain the characteristic blueberry-like fruity aroma while reducing the pungent aldehyde odour. This study offers novel insights into the 3D printing applications of blueberries, along with theoretical support and practical guidance for the optimal design of personalized, customized portable foods in the future.