Multivariate evaluation of the printing process on 3D printing of rice protein

The combination of printing parameters appropriately improves the printability of 3D-printed foods. In this regard, the present study aims to evaluate the effect of 3D printing process parameters on protein food generation. Printability of a cylinder 3 cm in diameter and 1 cm in height using a protein mixture of rice water and xanthan gum with a ratio of 30:70:0.5 was evaluated in an extrusion printer with an XYZ system. A ½ fractional factorial design was used with three factors: nozzle diameter (1.2 - 2.2 mm), layer height (1.0 - 2.0 mm), and print speed (20 - 50 mm/s). Each combination of factor levels was performed in triplicate for 12 runs plus three central points. Print time (min), sample weight, change in diameter (%), change in height (%), change in volume (%), mass flow rate (mg/s), appreciation (qualitative variable), and textural and rheology characters were obtained as response variables. The linear effects of the factors and combination factors were evaluated by analysis of variance. Additionally, a principal component analysis was performed to visualize the similarity between the observations and the relationship between the variables. The results showed that the layer height and nozzle diameter affect the printing accuracy concerning surface quality, shape stability, resolution, and layer layout. The nozzle with a diameter of 1.7 mm combined with speeds between 35 and 50 mm/s allowed the effects of overextrusion to be overcome, generating a better flow of the material. Low scores in the printability variable were related to low-speed values (20 mm/s) and a high nozzle diameter (2.2 mm), which generated higher deformations in the printed protein cylinder. Additionally, some printing conditions affected the textural and rheological characteristics, which allowed inferring that the capacity of the protein mass to store and recover energy in compression processes is conditioned by the printing parameters.