3D food printing: assessing the printability of dark chocolate

Abstract

3D food printing (3DFP) is an emerging novel technology in food fabrication, capable of creating food constructs with a layer-by-layer technique based on the desired design. The flexibility of this new technology offers the freedom to customise any preferred design. Among various type of 3D printing techniques, extrusion method is favourable to print the majority of fresh and edible foods. This method allows fresh foods in a paste, or liquid form to be extruded through the nozzle. Understanding the food material characteristic is the major factor that needs to be considered in choosing substrates for 3DFP. Dark chocolate was used as the main material in this work. It composed of cocoa butter (fat), cocoa solids, sugar, and lecithin. The important constituent in chocolate is cocoa butter (fat) containing the stable β-crystals in the chocolate matrix. These crystal fats help the chocolate to retain its quality such as glossy appearance, smooth texture and will set even after its being partially melted maintaining the β-crystal nuclei during printing. Extrusion method (auger) was applied in this work as the primary method to print the chocolate in powder form. Also, the addition of additive in auger extrusion is required to act as a flow enhancer, minimising the occurrence of slipeffect. Various physical properties, including analysing the effect of food additives, modification of internal structure, sensorial and potential consumers' perception and acceptance of 3D printed chocolates, were evaluated during this research work. At the beginning of this work, several modifications to a commercial 3D printer were required. The modification included developing a new 3D printer bed, water re-circulating system and the attachment of an air blower. A custom stainless steel printer bed (200 mm x 200 mm x 10 mm) was designed with an in-built water recirculation system (flow rate of 6.3 mL/s and maintain the temperature at ~16 ºC). Also, the printer bed was supported by a custom stabiliser printed by 3D filament printer using a plastic filament (Acrylonitrile Butadiene Styrene ABS). Additionally, an air blower was attached to avoid condensation that may occur on the printer bed due to cooling below room temperature. These modifications were done to ensure that the extruded chocolate solidifies efficiently upon extrusion. The optimisation of printing parameters was executed to determine the nozzle height and printing temperature. A series of comprehensive analysis including thermal properties, flow properties and tribological properties of printed chocolate was conducted. The original chocolate and the printed chocolate had a similar thermal melting profile (average melting peak of 32.9 ± 0.3 °C) as analysed by DSC suggesting that the printed chocolate had similar crystal forms. Food grade additives, magnesium stearate (Mg-ST) and native plant sterol (PS) were investigated for their suitability as a flow enhancer to reduce the slip-effect of the powdered chocolate Financial support This research was supported by a 'Skim Latiha...