This study aimed to analyze the printability of corn-based dough during screw-based three-dimensional (3D) food printing (3DFP) by relating its rheological and mechanical properties to its screw-based 3DFP performance, with the objective of providing insights into the utilization of corn-based dough to produce 3D-printed foods. Screw-based 3DFP was performed using seven corn-based doughs with different nixtamalized corn flour (NCF) and water contents. Afterward, their rheological and mechanical properties were analyzed and associated with their screw-based 3DFP performance. The results showed that stable printability was obtained within a specific range of NCF content in the dough (30–32.5 wt%). Below this range, the 3D-printed foods flattened, while above it, the extrudability of the dough was affected. The printability of the dough was influenced by different rheological and mechanical properties, depending on the stage of the screw-based 3DFP process. During the extrusion stage, the loss tangent at nozzle strain, yield stress, apparent viscosity, and adhesiveness mainly affected the extrudability of the dough. In contrast, the loss tangent at minimum strain, elastic modulus, Young’s modulus, and hardness influenced the self-supporting stage. Therefore, it is important to find a balance between all of these properties, where stable extrudability and self-supporting of the 3D structure are achieved.

This study investigates the effect of the texture of agar gel as a model solid food on gastric digestion using a human Gastric Digestion Simulator (GDS). The GDS, which simulates gastric peristalsis, can investigate physical digestion phenomena such as disintegration of solid foods. Agar gels with different fracture stresses (56 to 219 kPa) and constant fracture stain (29%) were prepared by varying the agar concentration (1.5 to 4.5 wt%). Direct observation demonstrated that agar gel particles initially cut to a 5.0 mm cube gradually reduced in size and broke down into random shapes during simulated gastric peristalsis. The size distribution of the agar gel particles after the digestion experiment was analyzed using the sieving method. The fraction larger than 2.36 mm, which corresponds to the pylorus size, decreased with time: the wet weight ratio of that fraction to the total amount of agar gel particles was 18.0% at 180 min in the case of 1.5 wt% agar gel. The agar gel concentration did not affect the size distribution after 180 min, which shows that fracture strain plays a more important role in agar gel digestion. Our results provide useful information about the relationship between solid food texture and gastric digestion.

Food digestion in the gastrointestinal is a series of processes consisting of chemical and physical digestion. Recently, developing foods with controlled digestion in the stomach may attract more attention. Hydrogel foods are useful tools for designing foods with controlled digestion because it is relatively easy to design their food characteristics by adjusting the type and content of the additives. This review introduces the latest status of in vitro gastric digestion as a food characterization system. The in vitro evaluation of chemical gastric digestion by gastric acid and digestive enzymes focuses on INFOGEST-standardized gastrointestinal digestion protocols for healthy adults, infants, and older adults. For the in vitro evaluation of physical gastric digestion by peristalsis, the current development of gastrointestinal tract devices that precisely or efficiently simulate the shape of the stomach and gastric peristalsis is described. In addition, we introduce studies that have utilized these devices to investigate the gastric digestion behavior of hydrocolloid foods with different mechanical characteristics.

Extrusion-based three-dimensional (3D) food printing (3DFP) enhances the customization of 3D-printed foods by using multiple food pastes. Post-printing processes like baking are usually necessary and significantly impact the stability of the 3D-printed foods. This study aimed to produce multi-material 3D-printed foods using nixtamalized corn dough and chickpea paste (CP) in extrusion-based 3DFP and to study the effect of post-printing processes (water oven cooking and steam cooking) and the type of material used (single- or multi-material) on the final appearance, weight, size, and texture of the 3D-printed foods. Multi-material 3D-printed foods were successfully produced using extrusion-based 3DFP. Steam-cooked 3D-printed foods cooked uniformly and had a better appearance, as they did not develop surface cracks compared to water oven-cooked foods. Water-oven cooked foods experienced a greater weight loss of 35.6%, and higher height and length reduction of 1.5% and 8.4%, respectively. Steam-cooked multi-material 3D-printed foods were harder at 40% of strain, with force values of 66.9 and 46.3 N for water-oven cooked foods. Post-printing processes, as well as the presence of CP in the middle of the 3D-printed foods, influenced their final appearance, weight, size, and texture. This study offers interesting findings for the innovative design of chickpea- and corn-based multi-material 3D-printed foods.

Lipids are often ingested via oil-in-water (O/W) emulsions, where interfacial properties and droplet size influence their digestibility. In this study, a bimodal O/W emulsion, termed Food Emulsion Blend (FEB), was prepared by mixing two monodisperse emulsions of different droplet sizes and compositions. The influence of droplet size and emulsifier type on in vitro digestion was evaluated. Soybean oil was used as the dispersed phase, and monodisperse emulsions were prepared via premix membrane emulsification using membranes with pore sizes of 1, 10, and 50 µm. Two selected emulsions were mixed in equal proportions to form FEB. The emulsifiers included 1.0% (w/w) Tween 20 (TW) or 0.5% (w/w) Tween 20 and 0.5% (w/w) citrus pectin (TWCP). The $d_{\mathrm{4,3}}$ values of the emulsions stabilized by TW and TWCP ranged from 1.05 to 51.99 µm and from 1.19 to 46.94 µm, respectively. In vitro digestion revealed that all FEB samples retained bimodal size distributions post-gastric digestion. Free fatty acid release correlated strongly with the initial total droplet surface area for the TW- and TWCP-stabilized FEBs (R² > 0.8). These results suggest that FEB allows for the precise control of lipid release, offering potential applications in food formulation.

The digestion behavior of a food bolus comprising bread particles in the presence of gastric peristalsis remains poorly understood. This study systematically investigated the effect of bread type on in vitro gastric digestion behavior using a human gastric digestion simulator (GDS) that is capable of quantitatively simulating gastric peristalsis. A food bolus consisting of 60 g of bread (white bread, bagel, German bread, French bread, or croissant), 15 mL of a simulated salivary fluid, and 240 mL of a simulated gastric fluid was used for gastric digestion in vitro using the GDS for 3 h at 37 °C. Direct observation of the gastric digestion behavior in the GDS vessel demonstrated that the structure and composition of breads considerably influenced the physical digestion processes of bread particles. These processes include their fracture, rubbing, disintegration, swelling owing to the penetration of gastric fluid, and release of fat from their surface. Fluorescence microscopy enabled an improved understanding of the variations in the microstructure and major component distribution of the breads during the gastric digestion in vitro. The results showed how the different breads influenced gastric digestibility in vitro through quantitative gastric peristalsis. The GDS can also be applicable to studying gastric digestibility in vitro of other types of bread.