Rheological & 3D printing properties of potato starch composite gels

Starch based gels can be three-dimensional (3D) printed to fabricate food products. Previously, researchers added sodium alginate to the starch gel to enhance shape retention of corresponding printed products. This inspired us to hypothesize that xanthan gum, which is also a common thickening agent, might play a similar role in structuring starch composite gel in 3D printing experiments. The geometric accuracy of products, as well as their rheological properties, water state distribution, and scanning electron microscopy images, were evaluated with varying amounts of added sodium alginate (4%, 5%, and 6% w/w, dry basis), xanthan gum (4%, 5%, and 6% w/w, dry basis), and sodium alginate/xanthan gum (2%/2%, 2.5%/2.5%, and 3%/3% w/w, dry basis) for extrusionbased 3D printing. Computation fluid dynamic simulation was used to model the printing process. The results showed that pseudoplastic gels with relatively high extrudability and shape retention were formed. The 3D-printed starch gel with an optimized formula with added sodium alginate and xanthan gum (2.5%/2.5% w/w, dry basis) exhibited the best geometric accuracy. The shape was retained with appropriate gel formation characteristics and physical properties. The addition of sodium alginate and xanthan gum at suitable levels contributed to the formation of 3D-printed starch based products with technical feasibility for potential food applications. Mathematical model of the 3D printing process was established. The model explained the nonuniformity of velocity distribution in the flow channel due to the varied diameter, and such non-uniformity led to jet expansion during the 3D printing process.