Impact of konjac glucomannan on hot extrusion 3D printability of cake gel

Several foods, including cake gel (CG), have a wide range of applications, but are natively non-printable, restricting their usage in 3D printed products. In this work, for the first time, hot extrusion 3D printing of CG with excellent print quality was achieved. Levels of konjac glucomannan (KG) addition, printing temperature, and other process parameters were optimized. A detailed investigation of rheological properties was performed to understand the underlying mechanisms, assessing small and large amplitude oscillatory shear effects, temperature sweeps, and thixotropy behavior; the loss factor value was found to be less than 1 for all gel formulations. Also, texture, crystallinity and functional group studies were conducted, and results were correlated with improvements in printability; particularly, texture values showed a 2-fold increase with the addition of 8 % KG. Similarly, it was observed that the increased levels of storage modulus (~9000 Pa) and apparent viscosity (91,543 mPas) in the 8 % KG formulation at a CG:KG ratio of 1:1.5 contributed to printability and post-printing stability. With a reduction in KG content, the melting temperature gradient was found to decrease, but crystallinity increased. The highest melting temperature of the gel formulation was for 8 % KG at ~140 °C, based on the thermal analysis results. The findings of this research provide insights into the development of ready-to-eat foods layer-by-layer fabricated using hot extrusion 3D food printing. Specifically, using a similar approach CGs can be conveniently used in 3D-printed bakeries, confectionary other formulations for customized/personalized finishes.