Three dimensional (3D) food printing is being widely investigated in food sector recent years due to its multiple advantages such as customized food designs, personalized nutrition, simplifying ...supply chain, and broadening of the available food material.
Currently, 3D printing is being applied in food areas such as military and space food, elderly food, sweets food. An accurate and precise printing is critical to a successful and smooth printing. In this paper, we collect and analyze the information on how to achieve a precise and accurate food printing, and review the application of 3D printing in several food areas, as well as give some proposals and provide a critical insight into the trends and challenges to 3D food printing.
To realize an accurate and precise printing, three main aspects should be investigated considerably: material properties, process parameters, and post-processing methods. We emphasize that the factors below should be given special attention to achieve a successful printing: rheological properties, binding mechanisms, thermodynamic properties, pre-treatment and post-processing methods. In addition, there are three challenges on 3D food printing: 1) printing precision and accuracy 2) process productivity and 3) production of colorful, multi-flavor, multi-structure products. A broad application of this technique is expected once these challenges are addressed.
•Factors affecting 3D food printing precision were discussed.•Applications of 3D printing in food sector were reviewed.•Challenges to 3D food printing were proposed.
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.
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•Thixotropic and thermo-reversible gel system was used as a model in 3D printing.•Ink's rheology and 3D printability was correlated in the whole printing process.•1D, 2D, 3D structures were fabricated and correlated with ink's rheology.
3D printing was used for printing mashed potatoes (MP) constructs with variable internal structures. The dimensional properties, textural and structural qualities of the printed objects were ...investigated as a function of infill levels (10, 40 and 70%), infill patterns (rectilinear, honeycomb and hibert curve), and number of shell perimeters (3, 5 and 7). The printed samples significantly matched the designed geometries. Hardness and gumminess were strongly related to infill levels and perimeters, but the printing paths being performed to fill the samples showed no effect on them. Firmness and Young's modulus were only affected by infill percentage but not by perimeters and printing paths. Further, comparative assessment of 3D printed and cast samples were also conducted on the textural properties and microstructure features. Microstructure analysis indicated a uniform internal structure was obtained for cast sample. In comparison, an obvious layered structure was observed in longitudinal-sectional direction while a porous structure was obtained in cross-sectional view of 3D printed samples regardless of infill levels. 3D printed samples, even at 100% infill, were significantly (p < .05) less hard, by up to 26.75% and 28.36% in terms of hardness and gumminess, compared to cast samples. The results suggest that 3D printing considerably changes the properties of printed samples, possibly offering a new way for tailoring textural properties of printed samples through creating their internal structure.
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•Different internal structure of mashed potatoes was created by 3D printing.•3D printing offers a new way for tailoring textural properties.•Comparative assessment was made between 3D printed and cast samples.
Currently most of food printers apply one printhead to extrude a single or a mixture of multiple materials. Such a printhead cannot control the materials distribution in a drop-on-demand way, while a ...multi-extruder printer enables the fabrication of highly attractive multi-material constructs with higher geometric complexity. In this study, the effects of extruder offset and retraction on the printing behavior were firstly optimized, followed by the preliminary tests of two methods of dual extrusion 3D printing. Method A is to create a multi-part model and assign each of them to one extruder. Method B is to create a single part model and assign different roles to each extruder. Some constructs with different inside shape were created using Method A. Product hardness and gumminess increased linearly with mashed potatoes (MP) percentage but showed no correlation with inside shape. Porous samples with special texture were printed using Method B by varying infill levels. Total printing time, firmness, hardness and gumminess increased with infill levels, and a clear discrimination was observed by principle component analysis (PCA). This suggested that dual extrusion 3D printing enables the fabrication of attractive multi-material constructs and has a potential to tailor textural properties of samples through varying infill percentage.
•A multi-extruder printer was used to print mashed potatoes/strawberry juice gel.•Extruder offset and retraction value of dual extrusion printing were optimized.•Texture modified edible parts were created by varying internal infill level.
This note investigates the stability of switched Boolean networks (SBNs) under arbitrary switching signal by using the tool of semi-tensor product of matrices. First, an algebraic expression is given ...for the SBN via the semi-tensor product. Based on it, a necessary and sufficient condition is presented for the switching point reachability of the system. Second, using the switching point reachability, the pointwise stabilizability is studied, and a necessary and sufficient condition is obtained. Finally, the global stability of SBNs under arbitrary switching signal is investigated, and an easily verifiable necessary and sufficient condition is presented. Two illustrative examples are presented to show that the main results are effective in analyzing the stability of SBNs.
Starch based gels can be three-dimensional (3D) printed to fabricate food products. Previously, researchers added sodium alginate to the starch gel to enhance shape retention of corresponding printed ...products. This inspired us to hypothesize that xanthan gum, which is also a common thickening agent, might play a similar role in structuring starch composite gel in 3D printing experiments. The geometric accuracy of products, as well as their rheological properties, water state distribution, and scanning electron microscopy images, were evaluated with varying amounts of added sodium alginate (4%, 5%, and 6% w/w, dry basis), xanthan gum (4%, 5%, and 6% w/w, dry basis), and sodium alginate/xanthan gum (2%/2%, 2.5%/2.5%, and 3%/3% w/w, dry basis) for extrusion-based 3D printing. Computation fluid dynamic simulation was used to model the printing process. The results showed that pseudoplastic gels with relatively high extrudability and shape retention were formed. The 3D-printed starch gel with an optimized formula with added sodium alginate and xanthan gum (2.5%/2.5% w/w, dry basis) exhibited the best geometric accuracy. The shape was retained with appropriate gel formation characteristics and physical properties. The addition of sodium alginate and xanthan gum at suitable levels contributed to the formation of 3D-printed starch based products with technical feasibility for potential food applications. Mathematical model of the 3D printing process was established. The model explained the non-uniformity of velocity distribution in the flow channel due to the varied diameter, and such non-uniformity led to jet expansion during the 3D printing process.
•Starch gel was modified with other polysaccharides for 3D printing.•Physical properties of the printing material were assessed.•The interactions among xanthan gum, alginate, and starch were explored.•The relationship between geometric accuracy and rheological property was studied.•Mathematic model of 3D printing process of extruded starch gel was explored.
An air-fried 3D printed snack was developed to potentially provide consumer an alternative choice of potato snack with reduced oil. One cylindrical shape was firstly 3D printed with variable internal ...structures, followed by air-frying post-printing. The unfried printed samples well matched the designed geometry but with a slight shrinkage after air-frying process. Hardness and fracturability of air-fried potato snack, significantly affected by infill pattern, also significantly decreased when infill level decreased. The 100% infill printed and cast samples were observed with a serious puffing phenomenon during air-frying process. Finally, one kind of a food structure comprised of different parts illustrating multiple textures was developed by varying infill structure. The results suggested that the textural properties of the air-fried 3D printed potato snack could be modified by altering its internal structure, possibly offering a new way of oil reduction for potato-based snacks by creating customized internal structure by applying 3D printing.
Using the semi-tensor product of matrices, this paper investigates the maximum (weight) stable set and vertex coloring problems of graphs with application to the group consensus of multi-agent ...systems, and presents a number of new results and algorithms. Firstly, by defining a characteristic logical vector and using the matrix expression of logical functions, an algebraic description is obtained for the internally stable set problem, based on which a new algorithm to find all the internally stable sets is established for any graph. Secondly, the maximum (weight) stable set problem is considered, and a necessary and sufficient condition is presented, by which an algorithm to find all the maximum (weight) stable sets is obtained. Thirdly, the vertex coloring problem is studied by using the semi-tensor product method, and two necessary and sufficient conditions are proposed for the colorability, based on which a new algorithm to find all the k-coloring schemes and minimum coloring partitions is put forward. Finally, the obtained results are applied to multi-agent systems, and a new protocol design procedure is presented for the group consensus problem. The study of illustrative examples shows that the results/algorithms presented in this paper are very effective.
This paper addresses the disturbance decoupling problem (DDP) of mix-valued logical networks by using both the semi-tensor product of matrices and the matrix expression of logical functions, and ...presents a number of new results on the DDP. First, in order to solve the DDP, a new algorithm is proposed to construct a kind of Y-friendly subspace for the state space of mix-valued logical networks. Second, based on the constructed Y-friendly subspace, several necessary and sufficient conditions are obtained for the existence of decoupling controllers, and a new control design procedure is established to deal with the DDP. Finally, an illustrative example is studied by the new method proposed in this paper, and two kinds of decoupling controllers are designed. The study of the illustrative example shows that the new method is effective in dealing with the DDP of mix-valued logical networks.
•Microwave vacuum drying was used for post-processing of 3D printed samples.•Designed infill structure was created to modify texture properties.•Good structural stability and maintenance of 3D ...information was achieved.
3D printing has the advantage to modify food texture by regulating internal structure. In this study, 3D printing was used to design the infill structure and microwave vacuum drying (MVD) was used to post-process the potato-based snack. Results indicated that MVD was a promising post-processing method with a high drying efficiency and good maintenance of structure information of 3D printed samples. Increased microwave power reduced the drying time, but increased the heating non-uniformity. NaCl addition increased the dielectric loss factor (ε′′), reduced the drying time and hardness of MVD products. Sucrose addition did not affect the dying time, but increased the hardness of products. Infill percentage and infill pattern closely related to the hardness of samples. Increased infill percentage increased the hardness of samples. Cast-made samples and 100% infill 3D printed samples were not suitable for MVD post-processing. Finally, product with various texture within one sample was produced by adjusting the infill structure of each part. This study provides a new aspect to modify food texture by changing infill structure, with MVD as a post-processing method.
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