Hot extrusion 3D printing technologies based on starchy food: A review

Heat moisture treatment and ultrasound-induced hydrothermal wheat starch modification: Techno-functional, microstructural and quality 3D printed characteristics

In this study, the effect of hydrothermal process, ultrasound and combined freezing-ultrasound process on the physical and structural characteristics of wheat starch (Triticum aestivum) was investigated. Two heat-moisture treatments for 2 h (HMT2) and 4 h (HMT4), high-intensity, high-frequency ultrasound under two treatment times (10 to 20 min) (UT10 and UT20) as pre-treatment and sonication after freezing as post-treatment (FUT) on wheat starch suspension was applied. The modifications of starch crystallinity, chemical bonds of starch treated, morphology, thermal, swelling, pasting, and physicochemical characteristics were evaluated. Finally, the starches treated under these conditions were used as ink for a 3D printer, and the characteristics of the printed product were evaluated. The results demonstrate that heat-moisture modified starch increased swelling and size of granules and lowered syneresis values. Sonication promoted molecular depolymerization and reduction of starch swelling and crystallinity. Combined treatment (Sonication and freezing) showed higher peak apparent viscosity during gelatinization and pasting, and the FUT starch-based hydrogels showed the best printability (better ability to stack layers on top of each other and build the desired 3D shape), indicating better reproducibility of this ink. These results showed that FUT is a suitable process for improving the synergy and properties of wheat starch-based hydrogels, which are suitable as inks for use in 3D printers.

Novel strategy for optimizing of corn starch-based ink food 3D printing process: Printability prediction based on BP-ANN model

Although starch has been intensively studied as a raw material for 3D printing, the relationship between several important process parameters in the preparation of starch gels and the printing results is unclear. In this study, the relationship between different processing conditions and the gel printing performance of corn starch was evaluated by printing tests, rheological tests and low-field nuclear magnetic resonance (LF-NMR) tests, and a back-propagation artificial neural network (BP-ANN) model for predicting gel printing performance was developed. The results revealed that starch gels exhibited favorable printing performance when the gelatinization temperature ranged from 75 °C to 85 °C, and the starch content was maintained between 15 % and 20 %. The R2adj of the BP-ANN models were all reached 0.894, which indicated good predictive ability. The results of the study not only provide theoretical support for the application of corn starch gels in 3D food printing, but also present a novel approach for predicting the printing performance of related materials. This method contributes to the optimization of printing parameters, thereby enhancing printing efficiency and quality.

Effect of plasma-activated water on the quality of wheat starch gel-forming 3D printed samples

In this study, a new method for preparing gels suitable for 3D printing of food structures using wheat starch and plasma activated water (PAW) is presented. The investigation focused on the effect of PAW on starch pasting and the final 3D printed product. It was found that the use of PAW for 15 min in the preparation of wheat starch gels optimized carrier stability and improved height retention in the printed constructs, showing significant shape retention even after prolonged storage. This durability can be attributed to the hindrance of polymerization between starch molecules and the promotion of intermolecular starch polymerization when reactive groups and ions are integrated into the starch structure. The incorporation of PAW with soluble reactive groups, ions and acidity not only accelerates the breakdown of the starch molecules but also facilitates additional hydrogen bonding within the double helix, which strengthens the structure of the gel. This interaction accelerates the retrogradation of the starch, thereby enhancing its overall stability. This study provides a new green approach to modify the 3D printing properties of starch gels.

Characterization of Antioxidant Bioactive Compounds and Rheological, Color and Sensory Properties in 3D-Printed Fruit Snacks

The influence of wheat starch (6%, 8% and 10%, w/w) and a 3D printing program (program 1 vs. program 2) on the content of bioactive compounds, antioxidant capacity, color parameters and rheological and sensory properties was investigated in 3D strawberry and strawberry tree fruit snacks. Increasing the starch content led to a decrease in the content of almost all the bioactive compounds, while it had no effect on the antioxidant capacity. The printing program had no significant effect on the bioactive compounds (except hydroxycinnamic acids), antioxidant capacity and color parameters. A higher starch content improved the strength of the sample but had no effect on the mechanical properties. Smaller particles with a higher starch content improved the stability of the sample. In contrast to the programs, varying the starch content had a significant effect on all the color parameters except the a* values. Eight different sweeteners in two different concentrations were used for the sensory evaluation of the 3D-printed snacks. The variations in sweetener content only affected the sweet and harmonious taste. In summary, this study confirms the great potential of fruit bases for the production of 3D-printed snacks with excellent biological and rheological properties, which can be a step toward personalized food with the addition of sweeteners.

Investigation of the structure, rheology and 3D printing characteristics of corn starch regulated by glycyrrhizic acid

This study aimed to construct a novel corn starch-glycyrrhizic acid (CS-GA) ink and systematically investigate the effects of GA on the water distribution, microstructure, rheology and 3D printing properties of CS hydrogels. The results showed that the CS chains could form strong hydrogen bonds with GA molecules, inhibit the formation of short-range ordered structure of CS and reduce the content of B-type starch. The low-field nuclear magnetic results showed that the introduction of GA could increase bound water content in CS-GA hydrogels. With the increase of GA content, the CS-GA hydrogel changed from CS-dominated to a GA-dominated gel network system. Rheological results showed that all samples exhibited typical shear thinning behavior. High GA concentration was beneficial to increasing the self-supporting properties and thixotropic recovery of CS-GA hydrogels. Compared with the pure CS hydrogel, the 3D printing characteristics of CS-GA hydrogels were significantly enhanced due to the increased bound water content and the enhancement of rheological properties. At 40 % GA content, CS-GA hydrogel showed the highest printing accuracy of 96.4 % ± 0.30 %. The printed product could perfectly replicate the preset model. Therefore, this study provided a theoretical basis for regulating starch's rheology and 3D printing characteristics and developing novel food-grade 3D printing inks.

Effect of protein-polysaccharide hybrid gelator system on the material properties and 3D extrusion printability of mashed potatoes

Mashed potatoes (MP) are famous as ready-to-eat products due to their excellent taste and texture. Problems such as complex injection occur when MP is used as a 3D printing material. To improve the smoothness of MP loading into a 3D syringe barrel and its 3D extrusion printability, the effects of the protein-polysaccharide hybrid gelator developed with different gelatin-B (GB, 2%, 4%, 6%) and κ-carrageenan (KG, 1%) on the rheology and 3D extrusion printability of MP were studied. The rheological results showed that the MP developed a glass transition temperature by adding the hybrid gelator. Adding 1% KG+6% GB (w/w, dry base) to the hybrid gelator has good shear thinning and self-supporting properties and showed the best geometric accuracy. In the extrusion stage, the yield stress, the consistency index (K), and the flow behavior index (n) of MP were 470.69 Pa, 313.48 Pa·sn, and 0.159, respectively. In the recovery stage, the shear recovery time is 30 s. In the self-supporting stage, the storage modulus and loss modulus are significantly higher than those of other groups and have the strongest mechanical properties. Moreover, water distribution, Fourier transform infrared spectroscopy, X-ray diffraction analysis, and microstructure of printed MP with different hybrid gelators were observed. The addition of hybrid gelators reduced the content of free water in MP. Hybrid gelators did not produce new functional groups in the printed materials and did not change the structure of starch. These results provide new insights for applying protein and polysaccharide hybrid gelators in 3D printing.

Effects of starch-fatty acid complexes with different fatty acid chain lengths and degrees of saturation on the rheological and 3D printing properties of corn starch

The effect of corn starch-fatty (CS-FA) complexes from varying carbon chain length and degree of unsaturation on the rheological and 3D printing properties of corn CS-FA complex gels. The CS-FA complexes with longer carbon chain lengths and lower saturation enhanced the ability of gels to bind water, promoting the formation of intermolecular hydrogen bonds. The CS-FA complexes inhibit retrogradation and increase the amount of bound water, thereby reducing the structural integrity and transforming the original skeleton structure into a flake-like structure. These changes in gel structure led to lower flow stress and storage modulus for CS-FA gels containing FAs with shorter carbon chain lengths and lower saturation, resulting in reduced "extrusion swelling" of the material and facilitating its extrusion. The decreased "extrusion swelling" of gel improved print line width and printing performance. The CS-FA complex gel-printed product with a 12-carbon chain FA has the greatest printing accuracy, thanks to its moderate G', flow stress, and viscosity. This study provides important information for the CS-FA complexes for the preparation of starch-based 3D printing materials.

The synergistic effect of κ-carrageenan and l-lysine on the 3D printability of yellow flesh peach gels: The importance of material elasticity in the printing process

This study investigated the effect of κ-carrageenan and l-lysine on the physical, chemical and textural properties of yellow flesh peaches and their suitability for 3D printing. The addition of κ-carrageenan and l-lysine was found to improve the apparent viscosity, elasticity, gel strength, and Young's modulus of the yellow flesh peach with κ-carrageenan and l-lysine gels (PCLG) and increase the minimum piston pressure required for 3D printing, thereby improving the printing performance. Optimum levels of κ-carrageenan and l-lysine (0.1 mmol/mL and 3.42 × 10-2 mmol/mL, respectively) were found to enhance mechanical strength, viscoelasticity and print fidelity. On the other hand, when the addition of κ-carrageenan is 0.1 mmol/mL, the addition of l-lysine causes an increase in the G0 value and a decrease in the η0 value of the PCLG according to Burger's model, indicating a transition from viscosity to elasticity and an increase in maximum extrusion force, while the apparent viscosity does not change significantly. The results of 3D printing showed that when the addition of κ-carrageenan and l-lysine reached 0.1 mmol/mL and 6.84 × 10-2 mmol/mL, respectively, the PCLG could not be smoothly extruded, indicating that elasticity also plays an important role during the extrusion process of the mixed gel.

Effect of peach gum polysaccharide on the rheological and 3D printing properties of gelatin-based functional gummy candy

Excellent 3D printing materials must exhibit good extrudability and supportability, but these two characteristics are often contradictory. In this study, peach gum polysaccharide (PGP) was added to gelatin to prepare a 3D-printed functional gummy candy encapsulating curcumin. Rheology tests indicated that adding PGP could effectively improve the apparent viscosity and thermal stability and consequently improve the 3D printability and supportability of the products. When PGP addition was 6 %, the printing accuracy was higher than 90 %. Texture and microstructure analysis further revealed that PGP addition promoting a dense gel structure formed and the water holding capacity and supportability of gel materials were enhanced. Furthermore, the in vitro gastrointestinal digestion tests showed that after 6 h of simulated gastrointestinal fluid digestion, the retention rate of curcumin was nearly 80 %. The above results indicated that the composite gel of PGP and gelatin is a good 3D printing base material for nutrient delivery.

Structural, rheological, and gelling characteristics of starch-based materials in context to 3D food printing applications in precision nutrition

Starch-based materials have viscoelasticity, viscous film-forming, dough pseudoplasticity, and rheological properties, which possess the structural characteristics (crystal structure, double helix structure, and layered structure) suitable for three-dimensional (3D) food printing inks. 3D food printing technology has significant advantages in customizing personalized and precise nutrition, expanding the range of ingredients, designing unique food appearances, and simplifying the food supply chain. Precision nutrition aims to consider individual nutritional needs and individual differences, which include special food product design and personalized precise nutrition, thus expanding future food resources, then simplifying the food supply chain, and attracting extensive attention in food industry. Different types of starch-based materials with different structures and rheological properties meet different 3D food printing technology requirements. Starch-based materials suitable for 3D food printing technology can accurately deliver and release active substances or drugs. These active substances or drugs have certain regulatory effects on the gut microbiome and diabetes, so as to maintain personalized and accurate nutrition.

Viability Study on the Use of Three Different Gels for 3D Food Printing

Three-dimensional food printing is one of the modern techniques for food customization. The difficulty of this technique lies in the formulation of new matrices. These new formulations must have good extrusion characteristics and, at the same time, maintain the structure once printed. These qualities are related to textural and rheological properties. Printability studies are those whose objective is to know the above properties. Some authors have correlated printability with rheological and physicochemical parameters. The aim of this study was to characterize three gels to test prediction models and to determine the most important rheological and textural parameters (G', G″, Tanδ, maxF, average) in printability. The formulations studied were bovine gelatin (4%) with kappa-carrageenan (0.5%) (Gb + K), porcine gelatin (5%) plus iota-carrageenan (2%) (Gp + I), and methylcellulose (4%) (MC). The samples were characterized by an oscillatory test for the rheological properties and an extrusion test for the textural properties. In addition, the density was obtained to apply the predictive models and correlate the rheological and textural parameters to determine their influence. Gp + I and Gb + K showed higher values of maximum force in the extrusion test than MC, but MC had less deviation in the mean force during the test. All the samples showed a predominantly elastic behavior and damping factor (Tanδ) between 0.14 (Gb + K) and 0.37 (MC). It was observed that the tangent of the phase angle (Tanδ) had a large positive influence on the maximum and average force studied in the extrusion tests. The sample results did not match 100% with the predictions made from the models. It was possible to print samples that were higher in height without obtaining deformations over time of more than 5%. Further work is needed to optimize models and parameters for more accurate prediction.

Influence of pH on the release of an active principle from 3D printed carrageenan-k combined with alginate or xanthan gum

The use of 3D printing began to diffuse in the pharmaceutical field in recent times, since 2015, with the approval of the first 3D printed drug from the FDA. The most used materials in association with this technique in this specific scope are hydrogels, already used widely in tissue engineering to produce scaffolds used in the realization of synthetic tissues. The aim of this project was to study the influence of different pH conditions on the release of a therapeutic molecule from a Carrageenan-k combined with alginate or xanthan gum hydrogel with a high level of biocompatibility and enough mechanical resistance to be used as printing material for a 3D bioprinter. The addition of biologically active supplements without affecting the model of the 3D printing structure of the biocompatible polymers was achieved by adopting the extrusion at moderately low temperatures. This study aimed to produce the necessary percentage of hydrogels which is responsible for the release of active drugs which respect to the pH of the system. In this case, the chosen curcumin drug which exhibits active release in the pH of the small intestine is a pH value of 6.

Progress in Extrusion-Based Food Printing Technology for Enhanced Printability and Printing Efficiency of Typical Personalized Foods: A Review

Three-dimensional printing technology enables the personalization and on-demand production of edible products of individual specifications. Four-dimensional printing technology expands the application scope of 3D printing technology, which controllably changes the quality attributes of 3D printing products over time. The concept of 5D/6D printing technology is also gradually developing in the food field. However, the functional value of food printing technology remains largely unrealized on a commercial scale due to limitations of printability and printing efficiency. This review focuses on recent developments in breaking through these barriers. The key factors and improvement methods ranging from ink properties and printer design required for successful printing of personalized foods (including easy-to-swallow foods, specially shaped foods, and foods with controlled release of functional ingredients) are identified and discussed. Novel evaluation methods for printability and printing precision are outlined. Furthermore, the design of printing equipment to increase printing efficiency is discussed along with some suggestions for cost-effective commercial printing.

Polymer-Solvent Interactions in Modified Starches Pastes-Electrokinetic, Dynamic Light Scattering, Rheological and Low Field Nuclear Magnetic Resonance Approach

Starch paste is a very complex dispersion that cannot be clearly classified as a solution, colloid or suspension and many factors affects its properties. As these ambiguities constitute a barrier to technological development, the aim of this study was to investigate the interaction of starch macromolecules with water by analysing the results of rheological properties, low field nuclear magnetic resonance (LF NMR), dynamic light scattering (DLS) and ζ potential analyses. Starch pastes with a concentration of 1%, prepared with distilled water and buffered to pH values of 2.5, 7.0 and 9.5 were analysed. It was proved that the pH buffering substantially decreased the values of consistency index but the pH value itself was not significant. LF NMR studies indicated that the dissolution of starch in water resulted in a reduction in spin-lattice as well as spin-spin relaxation times. Moreover, changes in relaxation times followed the patterns observed in rheological studies. Electrokinetic and DLS analyses showed that potential values are primarily influenced by the properties of the starches themselves and, to a lesser extent, by the environmental conditions. The conducted research also showed complementarity and, to some extent, substitutability of the applied research methods as well as exclusion chromatography (a method not used in this work).