Abstracts Category : Other

Extrusion-based 3D Printing and Characterization of Edible Materials

by Chu Yin Huang

3D printing food offers the ability to customize shapes, texture, as well as nutritional content. In addition, it can automate the cooking process to save time and produce meals on-demand to minimize waste. One potential application is to 3D print food for those suffering from dysphagia, a condition that affects ones ability to swallow. Texture modified food products for dysphagia often lose their shape and have limited visual appeal. 3D printing could provide shape to these texture modified food products and ultimately improve nutrient intake. One of the limitations that are currently preventing wider adaption of this technology is the lack of understanding of how food properties affect the 3D printing process and quality of the printed object. In this thesis, room temperature extrusion-based 3D printing was investigated using a desktop 3D printer with a syringe extrusion system. Two hydrocolloids, modified starch and xanthan gum, were used as model material to study room temperature extrusion-based 3D printing. The relationship between the 3D printer settings and the extrusion process variables, extrusion rate and nozzle speed, was obtained by investigating the machine command (G-code). The nozzle speed could be controlled by the extrusion multiplier while the extrusion rate could be controlled by the stepper motor speed. In addition, extrusion tests showed that the syringe extrusion system displayed a lag time around 2 to 5 minutes before stable extrusion rate was reached. The extrusion lag time increased with increased material yield stresses and decreased with increased syringe motor speed. Xanthan gum paste, modified starch pastes, and pured carrot were selected as model inks. Oscillatory rheology measurements including strain and frequency sweep were conducted to study the range of properties suitable for 3D printing. The range of yield stress suitable for extrusion was between 60-730 Pa and around 0.1-0.2 for the loss tangent (tan ). The printable range of complex modulus (G*) was from 320 to 1200 Pa. Furthermore, data from the frequency sweep of xanthan gum and modified starch pastes was fitted to power law models and compared to published data of foods to assess their potential suitability as food inks for 3D printing. Pured carrot had higher G* compared to xanthan gum and modified starch pastes but had lower elasticity. Pured carrot was suitable for 3D printing because of its stiffness and low elasticity. In addition, food texture measurements based on the methods described in the International Dysphagia Diet Standardisation Initiative (IDDSI) were also conducted. Printable inks were able to retain its shape on a fork without dripping through the prongs and slide off a spoon with minimal residue. Two printed objects were considered, a line and a cylinder. The line printing was conducted to find the optimal settings of volumetric extrusion rate, nozzle speed, and layer height. The cylinder printing was conducted to assess the effects of ink rheology and infill levels, the fraction of the