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Food additives can be used to enhance processability and/or nutritional properties of food. In this study, two type of additives, magnesium stearate (Mg-ST) powder (as a processing aid) and plant sterol (PS) powder (as a processing and nutritional aids) were added into grated chocolate in order to enhance its flowability during auger type extrusion-based 3D printing. The thermal and rheology data showed that the melting peak of chocolate with additives ranged from 31.4 ± 0.8 °C to 32.1 ± 0.1 °C and a rapid reduction in viscosity began between 31.1 ± 0.7 °C and 33.3 ± 0.2 °C. The addition of additives showed no significant difference (p > .05) in melting peak (Tp) temperature of control chocolate samples and 3D printed chocolate samples suggesting that Mg-ST and PS do not affect the melting behaviour of chocolate. However, the yield stress values of chocolates containing additives were relatively higher than that of control samples indicating the possible effect of particulates. The tribology curve did not represent the typical Stribeck curve with or without the addition of additives. The particles in the additive potentially influenced the lubrication behaviour of 3D printed chocolate as their addition increased the coefficient of friction of the chocolate samples reducing the slippage in auger extrusion.

3D food printing is an emerging technology with a potential to influence the food manufacturing sector. Rheological properties of food inks are critical for their successful 3D printing. However, the relationships between rheological properties and 3D printability have not been clearly defined in food systems. In this work, a gel model system composed of carrageenan-xanthan-starch was prepared for an extrusion-based 3D food printer. The 3D printing process was divided into three stages and the corresponding rheological properties of inks for each stage were determined, namely extrusion stage (yield stress, viscosity and shear-thinning behaviour), recovery stage (shear recovery and temperature recovery properties) and self-supporting stage (complex modulus G* and yield stress at room temperature). Finally, 3D printability of the model inks was systematically studied starting with printing lines/pentagram (one dimensional, 1D structure) to printing lattice scaffold (two dimensional, 2D structure) and finally printing cylinders (three dimensional, 3D structure). Results demonstrated that addition of starch and xanthan gum in k-carrageenan based inks increased inks' gelation temperature (Tgelation), viscosity (within shear rate of 0.01–100 1/s), yield stress, G*, enhanced shear-thinning (thixotropic) behaviour and reduced time-dependence of modulus (temperature recovery). Rheological responses of yield stress (cross-over point where G′ (elastic modulus) equals to G′′ (viscous modulus) in the stress sweep tests) and shear-thinning behaviour (viscosity decreased when shear rate increased) were closely related to ink's extrudability. Inks' gelation temperature (Tgelation) and time-dependent behaviour (gelation time, tgel) significantly affected their printability and shape retention performance. The mechanical strength of the ink is important to be self-supporting, especially for 3D structures. Insights achieved from this study could provide guidance on improving 3D printability of foods that use hydrocolloids as a printing aid.

3D printing is a new promising technology capable of creating intricate food shapes. To stabilize the mechanical properties of the complex printed food it may require support structures. The 3D shape of chocolate was designed with different support structures (cross support, parallel support and no support) and its effect on the snapping properties was investigated. This study also determined the relationship between the physical properties of chocolate used for printing and the quality of the printed 3D constructs. The dimensions (wall thickness, height, and diameter), weight as well as physical properties (melting properties, flow behaviour, snap ability) of the 3D printed chocolate were evaluated. The nozzle temperature before deposition was maintained at 32 °C in order to extrude the melted state of the sample as the flow behaviour curves indicated that the melting of chocolate started between 28 °C to 30 °C. Incorporation of Magnesium Stearate (MgST) in the chocolate formulation aid in material lubrication and increase flow efficiency during deposition. Results showed that there was a minor difference between the predetermined diameter and the actual output diameter for each sample suggesting similarity between the printed 3D structure and the pre-designed 3D model. Wall thickness of printed item varied along the height due to uneven deposition of chocolate as the layer height increased. The breaking strength of the sample was strongly related to the additional support structure, with 3D chocolate with cross support structure requiring the highest force (N) to break the sample. Industrial relevance The development and production of food with 3-Dimensional printing (3DP) technology has potential to create and produce food in a more advanced format that will be a new paradigm shift in the food industry. Through 3D printing, personalised food can be created in terms of shape and nutritional composition. To firmly establish this promising technology as a powerful tool for engineering food it is required a thorough understanding of the supply ingredients and strategies to enhance printability. This study demonstrates the use of flow enhancer and inclusion of support structure in the designed shape were key factors influencing printability capacity of chocolate (edible ink chosen as a model).

This study aimed to assess the preferences and perceptions of texture-modified 3D printed chocolate through three measures, two tasting tests and one survey. In the first test, 30 semi-trained panellists ranked their overall preference from among the three samples of chocolate printed in a honeycomb pattern with infill percentages of 25%, 50% and 100%. The panellists ranked the samples based on appearance and hardness. In the second test, the same panellists nominated one preference between a 3D printed sample (100% infill percentage) and a cast commercial chocolate sample. Friedman test indicated that there was no significant difference in overall preferences for hardness although the panellists significantly preferred the appearance of samples with 25% and 50% over the 100% infill. Further, there was no significant difference in preference between the cast and 100% infill samples. The texture data of the chocolate samples showed that a higher force was required to break the chocolate samples as the infill percentage increased from 25% (20.4 ± 1.1 N) to 100% (54.4 ± 1.5 N). Also, the 3D printed chocolate (printed in 100% infill percentage) was found to be less hard than that of casted chocolate. In the survey of consumer perceptions, a total of 244 participated and assessed the samples for their intricate design and novel technology concept through a questionnaire. While there was a general awareness of 3D printing technology among these participants, many were impressed with the application of 3D printing to chocolate, as this was the first time they had seen this. The results obtained from the sensory tests and consumer survey provided a useful insight into consumers' perception of 3D food printing and the 3D products design. This awareness will be beneficial to promote this technology in the food industry. This article is protected by copyright. All rights reserved.

The 3D printing technology has been applied to directly to construct physical model from 3D modelling without any aid of mold. Several industries such as automobile, aerospace including and recently food industry has utilize this technology to manufacture a complicated and intricate part required in the industry. It is foreseeable that 3D food printing (3DP) are possible to produce complex food model with unique internal pattern. A 3D food printing technique is composed of an extrusion-based printing, selective laser sintering and inkjet (liquid binding) printing. The food materials such as sugar, gelatin-based chocolate, and are used to create designed shape based on layer-by-layer method. This paper presents a review of 3D food printing techniques. This review is to categorize, printability, productivity, properties of printable material and mechanism of 3D food printing techniques, as well as to propose the future direction of this novel technology.

This study aimed to create an intricate internal structure of 3D printed chocolate by varying the infill construction. Three intricate infill patterns designed were star, Hilbert curve and honeycomb with infill percentage of 5%, 30%, 60% and 100%. Cadbury dark chocolate (Choc-1) and Callebaut bittersweet dark chocolate (Choc-2) powders were used by incorporating magnesium stearate (Mg-ST) and plant sterol (PS) powders as food additives. Printing parameters were set up with an extrusion temperature of 32 °C, nozzle size of 0.78 mm and printing speed of 70 mm/s. The results showed that voids in printed samples of all three pattern with 5% infill density ranged from 60.8 ± 2.1% to 72.2 ± 1.8%. Voids in samples with 30% infill density ranged from 20.9 ± 2.1% to 49.2 ± 3.6% while with 60% infill density it ranged from 11.6 ± 2.3% to 19.4 ± 4.2%. Additionally, star and honeycomb infill pattern produced the most stable and tough structure at 60% infill as indicated by a higher normal force (N) to break the printed sample. Moreover, even at 100% infill percentage, 3D printed chocolate were found less hard (ranged from 82.2 ± 2.2 N to 92.2 ± 1.3 N) as compared to cast samples (>110 N) in the snap test. The results obtained in this study provide a useful insight in creating various internal structures of 3D printed dark chocolate with different textural characteristic and physical stability.