Design and characterisation of edible biopolymer mixtures for use in additive manufacturing

Recent interest in personalisation of food through additive manufacturing has identified a need for more information on the formulation and printability of potential ingredients. Fused deposition modelling is a type of additive manufacturing technique which uses a thermal extrusion process in order to create objects in a layer by layer method. Key challenges posed for the creation of formulations using this additive manufacturing technique include the need for the material to be thermoreversible, shear thinning during extrusion, but then have the ability to retain its shape after extrusion. The majority of research of edible manufacturing using this technique have thus far only been investigated at single temperatures and predominately on materials that only maintain their shape due to a yield stress, reducing the amount of available materials. Therefore, the aim of this work was to develop novel edible material feedstocks for the creation of objects through the use of an additive manufacturing process. Initially, the printability of a mixture of two food hydrocolloids, gelatin and kappa-carrageenan, were investigated. Design rules were established in order to determine if the materials fit the requirements of the process. The gelling temperatures of the systems were established, then, the rheological characteristics including: flow profiles, evolution of elastically dominated structures and frequency dependent behaviour were examined. The mixtures were subsequently printed at two temperatures, just above and much greater than, the gelling temperatures. It was observed that the rheological behaviours accompanying the coil-helix transitions of the systems were key to printing in a well-defined way. Printing resolution could be described by the changes in elastic modulus, where rapid formation of an elastic network gave rise to highly defined shapes with the ability to self-support under multiple layers. The printability of the mixtures of gelatin and kappa-carrageenan were then further probed by changing the properties of the printer, including the nozzle diameter, printing temperature and printing speed. Alteration of these properties affected the viscosity of the material during extrusion, which affected the behaviour of the material and altered the printability. The viscosity of the formulations at various speeds and temperatures was established, and these were related to the printability. Further design rules were established in order to deepen the unde