The research, led by Yongquan Wang of Anhui Agricultural University together with colleagues including Haichuan Shi and Wenjia Yan, set out to answer a deceptively simple question: does the industrial method used to pull protein out of broken rice change the protein’s structure enough to alter its behavior as an emulsion stabilizer? The answer turned out to be a resounding yes, and the consequences ripple through every downstream property of the final food product, from droplet size and elasticity to vitamin retention and suitability for people with dysphagia, the swallowing disorder that affects millions of elderly and hospitalized patients worldwide.

The team compared two extraction routes. The first was enzymatic extraction, in which thermostable alpha-amylase digests the starch surrounding the protein, releasing it in stages. By repeating the enzymatic treatment, the researchers produced three protein samples with escalating purity: 29.47 percent protein after one round, 55.04 percent after two, and 67.95 percent after three. The second route was the classic alkali solubilization and acid precipitation method, the workhorse of industrial protein production because of its high yield and low cost. Here, rice flour was stirred in dilute sodium hydroxide to loosen the tight starch matrix, and the dissolved protein was then precipitated at pH 4.8, yielding a fourth sample that was 91.75 percent protein.

Structural analysis revealed that the two methods sculpted the protein in fundamentally different ways. Fourier transform infrared spectroscopy, focused on the amide I region of the spectra, showed that repeated enzymatic hydrolysis reduced beta-sheet content by roughly 8 percent and increased alpha-helix content by about 13 percent, consistent with proteins being progressively liberated from the starch matrix. Alkaline extraction, by contrast, disrupted the hydrogen bonds that hold alpha-helices together, producing a protein with less helical structure and more beta-turns, a signature of a more folded conformation. The alkaline sample also showed a weakened hydrogen-bonding network overall, with its NH and OH stretching bands shifted in a way that suggested freer, less constrained molecular groups.

Those molecular differences translated directly into particle-level behavior. The once-enzymatically extracted protein formed particles roughly 450 nanometers larger than its twice- and thrice-extracted counterparts, while the alkaline-extracted protein produced the smallest particles of all, at just 201 nanometers. More striking was the wettability. Measured through the three-phase contact angle at an oil-water interface, the enzymatic samples ranged from 66.8 to 77.8 degrees, indicating hydrophilic particles that favor oil-in-water emulsions. The alkaline sample registered 127.0 degrees, a dramatic swing toward hydrophobicity, apparently because alkali disruption of hydrogen bonds exposed hydrophobic groups on the molecular surface. Since contact angles near 90 degrees maximize the energy barrier against particle desorption, this shift matters enormously for interfacial anchoring.

All four proteins then faced the same test: stabilizing a high-internal-phase emulsion, or HIPE, in which the oil phase occupies 83 percent of the volume, far above the 74 percent threshold at which droplets are forced into densely packed, gel-like arrangements. Every sample succeeded in producing a self-supporting emulsion that did not flow when its container was inverted, with no visible creaming. But the details differed. Emulsions stabilized by the once-extracted enzymatic protein had droplets averaging 55 micrometers, while those made with the more refined enzymatic proteins produced droplets of 31 to 32 micrometers. Confocal laser scanning microscopy, with the oil stained red and the protein stained green, confirmed a classic oil-in-water architecture of tightly packed droplets in every case.

Stress testing separated the winners from the also-rans. After 30 days of storage, the emulsion made with the crudest protein showed slight oil separation and droplet growth to 132 micrometers, evidence of flocculation and coalescence. The emulsions stabilized by the thrice-enzymatically extracted and alkaline-extracted proteins, however, remained homogeneous through centrifugation at 9000 times gravity, a month of storage, heating at 90 degrees Celsius for 30 minutes, and salt concentrations up to 300 millimolar sodium chloride. Rheological measurements reinforced the picture: the alkaline and thrice-extracted samples showed the highest consistency coefficients and the strongest storage moduli, confirming that their emulsions were predominantly elastic, gel-like materials rather than simple viscous liquids.

That gel-like elasticity is precisely what 3D food printing demands. Loaded into a FOODBOT D1 printer and extruded through a 0.84-millimeter nozzle, the emulsions made from the two most refined proteins retained crisp pentagonal shapes, while those from the crudest proteins slumped and lost their structure. The researchers then ran the standardized tests of the International Dysphagia Diet Standardisation Initiative, the framework that classifies texture-modified foods on an eight-level scale. The fork drip, spoon tilt, and fork pressure tests showed that the printed products from the thrice-enzymatic and alkaline samples met the criteria for Level 4, the pureed and extremely thick consistency prescribed for people with swallowing difficulties, deforming easily under a fork without leaving residue or whitening a thumbnail pressed against them.

The delivery payload was alpha-tocopherol, the most biologically active form of vitamin E, a compound with antioxidant, immunoregulatory, anti-inflammatory, and neuroprotective functions that is nonetheless crippled by poor water solubility, instability, and low bioavailability. Dissolved in the corn oil phase at 1 percent, the vitamin was encapsulated with efficiency exceeding 97 percent and loading capacity above 23 percent. When the emulsions were bombarded with ultraviolet light for 48 hours, more than 78 percent of the encapsulated alpha-tocopherol survived, a 41 percent improvement over the free compound, an effect the authors attribute to the protein layer at the oil-water interface acting as a physical sunshade. During simulated digestion, gastric release was held to between 19.1 and 22.0 percent, protecting the vitamin through the stomach, while the intestinal phase delivered a bioaccessibility of 66.3 to 70.0 percent.

The study sketches a clear causal chain with implications well beyond rice. The extraction method dictates protein structure; structure governs particle size, wettability, and interfacial behavior; and those interfacial properties determine whether the final emulsion can survive storage, heat, and salt, hold a printed shape, and shield a delicate nutrient on its journey through the digestive tract. For a protein stream that has historically been waste, the work suggests a route into premium functional foods, particularly for aging populations. The authors caution that considerable work remains before industrial scale-up: future studies must test the system in varied food matrices, verify bioavailability in animal models, conduct sensory characterization and clinical swallowing trials, and complete life-cycle and techno-economic analyses. But the core demonstration stands: a byproduct once fit only for feed can be transformed, with the right chemistry, into a printable, swallow-safe carrier for essential nutrients.

Subject of Research: Rice protein extraction methods and their influence on high-internal-phase emulsions for 3D-printed dysphagia-friendly food delivery of alpha-tocopherol

Article Title: Rice protein stabilized high-internal-phase emulsions for delivery of α-tocopherol in 3D-printed dysphagia-friendly foods: Influence of extraction methods

Article References: Shi, H., Yan, W., Zhang, M., Qin, M., Wang, J., Liu, X., & Wang, Y. (2026). Rice protein stabilized high-internal-phase emulsions for delivery of α-tocopherol in 3D-printed dysphagia-friendly foods: Influence of extraction methods. Food Chemistry: X, 39, Article 104509. https://doi.org/10.1016/j.fochx.2026.104509

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104509

Keywords: rice protein, high-internal-phase emulsion, Pickering emulsion, 3D food printing, dysphagia, alpha-tocopherol, protein extraction, encapsulation, IDDSI, rheology, bioaccessibility, food chemistry

The research team, led by Yuqian Zheng and Sheng Li, set out to resolve a question that has lingered in food science: while HHP is known to alter the short-term behavior of starch, and polyphenols are known to bind starch through non-covalent interactions, the combined effect of these two interventions on long-term retrogradation remained poorly understood. The researchers treated corn starch with 600 megapascals of pressure for 15 minutes, blended it with three grape polyphenol preparations at concentrations ranging from 0.1 to 2.0 percent, gelatinized the mixtures, and then stored the resulting gels at 4 degrees Celsius for 14 days to track how their structure, texture, and water distribution evolved.

The three polyphenols were deliberately chosen to represent different corners of grape chemistry. Grape seed oligomeric proanthocyanidins, or GSOP, are oligomeric mixtures built from catechin, epicatechin, and their gallate derivatives. Grape seed polyphenols, or GSP, are a broader commercial extract whose components were characterized by liquid chromatography-mass spectrometry. Grape skin anthocyanins, or GSA, were extracted from the variety Vitis amurensis cv. Beibinghong, with malvidin-3-glucoside as the dominant pigment. Because anthocyanins carry hydrophobic methoxy groups that the other two preparations lack, the comparison offered a natural test of how molecular structure shapes function.

Fourier transform infrared spectroscopy provided the first molecular clues. After two weeks of storage, all samples showed increased short-range molecular ordering, but the polyphenol-containing samples displayed a notably narrower hydroxyl stretching band between 3100 and 3700 inverse centimeters, signaling a more homogeneous hydrogen-bonding environment. The ratio associated with ordered double-helical structures dropped by 14.46 percent in the 1.5 percent GSOP sample, 16.03 percent in the 2 percent GSP sample, and 16.48 percent in the 0.5 percent GSA sample relative to pressurized starch alone. The authors interpret this as evidence that polyphenol aromatic rings can slip into the hydrophobic cavity of amylose single helices while their hydroxyl groups form intermolecular hydrogen bonds, together restricting the alignment and reassociation of starch chains.

X-ray diffraction told a complementary story. The original A-type crystalline pattern of corn starch vanished entirely during storage, replaced by peaks near 17 and 20 degrees two-theta that mark the formation of V-type crystals, the signature of inclusion complexes between leached amylose and small guest molecules. Crucially, the increase in relative crystallinity over the storage period was significantly smaller in every polyphenol-treated sample than in pressurized starch alone, confirming that the additives retarded the growth of long-range ordered domains even as they permitted local molecular rearrangement. Scanning electron microscopy revealed the structural consequences: polyphenol gels developed heterogeneous, layered networks with visible cavities, in contrast to the compact, contracted architecture of the control.

Texture measurements translated these molecular events into something tangible. Gel hardness rose in all samples over 14 days, as expected from the slow recrystallization of amylopectin, but the polyphenol-containing gels hardened far less, indicating a slower transition from disorder to order and reduced water exudation. Low-field nuclear magnetic resonance added a fourth dimension by tracking water itself. Four water populations were identified, from tightly bound water to highly mobile freezable water, and the polyphenol samples retained significantly higher transverse relaxation times for weakly bound water, meaning water molecules kept more of their mobility. Magnetic resonance imaging visualized this directly, showing more uniform proton density across the polyphenol gels after storage. Notably, GSA was less effective at restraining water migration than GSOP and GSP, a difference the authors attribute to its methoxy-substituted structure, which interacts more weakly with starch and water.

With the anti-retrogradation mechanism established, the team turned to application. The best-performing starch-polyphenol systems were substituted for 30 percent of the wheat flour in a standard cookie dough formulation, and the results were striking. Infrared analysis of the amide I band showed that the dough containing grape seed polyphenols increased its beta-sheet content by 38.73 percent and its alpha-helix content by 47.55 percent relative to the control, indicating a more stable gluten network. At the same time, dough hardness fell sharply, springiness dropped by roughly 45.65 percent, and chewiness in the GSP group declined by approximately 56.57 percent, producing a softer, more cohesive matrix that requires less oral processing.

Rheology reinforced the picture. In frequency sweeps from 0.1 to 10 hertz, the storage modulus of the formulated doughs fell below that of the control while the loss modulus rose, shifting the material toward a less elastic, more viscous character. Creep-recovery tests showed that the polyphenol doughs resisted deformation under constant stress yet recovered their shape more completely once the stress was removed, a balance the authors consider favorable for bolus cohesion during swallowing. Low-field NMR of the doughs mirrored the gel findings, with a higher proportion of bound water and less mobile free water, conditions that maintain lubrication without sacrificing structural integrity.

The dysphagia connection was formalized through the International Dysphagia Diet Standardization Initiative framework, the global standard that classifies texture-modified foods from Level 0 to Level 7. In fork pressure tests, all the composite gels crushed under a force of roughly 17 kilopascals, comparable to the pressure the tongue exerts during swallowing, and failed to spring back. In fork drip tests they held their position on the tines without flowing through the gaps, and in spoon tilt tests every polyphenol formulation slid off intact, unlike the sticky control. Taken together, the composite gels met the qualitative criteria for IDDSI Level 4, the category of smooth, pureed foods that hold their shape under gravity but require no chewing.

The authors are careful to mark the limits of the work. The precise molecular arrangement of the amylose-polyphenol complexes has not been directly verified, and future studies using molecular dynamics simulations, solid-state carbon-13 NMR, or synchrotron X-ray scattering are needed. The observed effects may also reflect the combined influence of pressure pretreatment and subsequent thermal gelatinization rather than HHP alone, and neither swallowing safety nor consumer acceptability was tested. Even so, the study offers a compelling proof of concept: two gentle interventions, one physical and one derived from an agricultural byproduct, can simultaneously extend the storage stability of starch foods and tune their texture toward the needs of people who struggle to swallow. If the molecular mechanisms hold up under closer scrutiny, grape polyphenols may find a second life far from the winery, inside the texture-modified foods of an aging world.

Subject of Research: Regulation of corn starch retrogradation and dough functionality by grape polyphenols and high hydrostatic pressure treatment for dysphagia food development

Article Title: Regulation of corn starch long-term retrogradation and dough functionality by grape polyphenols and HHP treatment with potential implications for dysphagia food development

Article References: Zheng, Y., Qin, X., Wang, W., Wen, X., Ren, P., Ren, F., Liu, T., & Li, S. (2026). Regulation of corn starch long-term retrogradation and dough functionality by grape polyphenols and HHP treatment with potential implications for dysphagia food development. Food Chemistry: X, 39, Article 104515. https://doi.org/10.1016/j.fochx.2026.104515

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104515

Keywords: corn starch, starch retrogradation, grape polyphenols, high hydrostatic pressure, dysphagia, IDDSI, cookie dough, food texture, V-type complexes, water migration, food chemistry, shelf life

The motivation is pressing. A rapidly aging global population, together with growing numbers of people living with dysphagia — difficulty swallowing — has created urgent demand for foods that are simultaneously safe, nutritious, and appealing. Such foods must meet strict texture standards to reduce the risk of aspiration, yet they also need to carry meaningful nutrition, particularly lipophilic bioactive compounds, to counter the malnutrition that often accompanies chewing and swallowing disorders. Traditional thickening systems built on starches or hydrocolloids fall short: they struggle to deliver high nutrient density, they cannot structure healthy lipids efficiently, and they tend to break down or separate during long storage.

The team’s starting point was a protein-based Pickering emulsion, a class of systems in which solid particles — rather than synthetic surfactants — adsorb at the oil–water interface and form a protective shell around droplets. The researchers built their interface from ovalbumin, the main protein of egg white, working together with tea polyphenols and hyaluronic acid. Ovalbumin’s amphiphilic character lets it anchor at the interface and form a film, tea polyphenols reinforce the particles through hydrogen bonding and hydrophobic interactions while adding antioxidant capacity, and hyaluronic acid thickens the interfacial layer. When the oil fraction is pushed above 74 percent, the result is a high internal phase emulsion, or HIPE: a material so packed with droplets that it behaves like a soft solid, self-supporting and stable, ideal for loading fat-soluble nutrients.

But stability alone was not enough. A HIPE’s solid-like rheology, the very property that makes it stable, also makes it difficult to process by conventional filling and molding, and even harder to shape with the precision that modern personalized nutrition demands. Enter 3D printing. Extrusion-based food printing promises digital control over both geometry and internal microstructure, which in turn governs how a food breaks apart in the mouth and how nutrients are released. The catch is that a good printing ink must be a rheological paradox: thin and flowing under the high shear of the nozzle, yet instantly stiff and self-supporting the moment extrusion stops.

To resolve that paradox, the researchers turned to the mud–sand analogy. Undissolved gellan gum particles, added at 0.3 percent, played the role of sand: rigid fillers that embed in the droplet network, anchor it physically, and boost mechanical strength. Xanthan gum, tested at 0.2, 0.6, and 1 percent, played the role of mud: its long molecular chains weave a continuous viscoelastic network through the aqueous phase, thickening the system, imparting the shear-thinning behavior needed for smooth extrusion, and reconnecting the gellan particles into a coherent whole. The base formulation — 25 percent composite aqueous phase and 75 percent soybean oil — was homogenized at 12,000 rpm to produce emulsions containing 75 percent oil, well into high internal phase territory.

Spectroscopic and scattering analyses confirmed that the additions were gentle on the protein. Fourier-transform infrared spectra showed that the amide bands of ovalbumin, near 1635 and 1534 per centimeter, remained essentially unchanged across all formulations, meaning the protein’s conformation was barely disturbed. X-ray diffraction revealed a broadly amorphous structure, with xanthan gum actually suppressing the local crystallization of tea polyphenols at higher concentrations, yielding a more uniform composite. Zeta potential measurements told a subtler story: adding gellan gum diluted the system’s net negative charge from about −32 to −26 millivolts, yet the steric hindrance and physical network of the undissolved particles more than compensated, and xanthan gum restored the potential to roughly −35 millivolts at the optimal dose.

Microscopy and stability testing made the synergy vivid. Confocal laser scanning images of the control emulsion showed heterogeneous, flocculated droplets with clear signs of coalescence — the thin interfacial film simply could not withstand the capillary pressures inside a HIPE. Gellan gum alone produced a bipolar droplet distribution, but the combination of gellan and xanthan gum produced small, evenly dispersed droplets locked inside a dense gel matrix. Under centrifugation, the control lost nearly 13 percent of its oil; the best dual-polysaccharide formulation lost none. After 30 days of refrigerated storage, every emulsion remained free of visible phase separation, and heat treatment at 85 degrees Celsius actually strengthened most of the modified systems, as denatured protein formed tougher interfacial films and hydrated gellan molecules tightened the gel network.

The rheological measurements revealed exactly why the material prints so well. All samples showed pronounced shear-thinning, and the storage modulus exceeded the loss modulus throughout, confirming solid-like behavior. As xanthan gum concentration rose, the storage modulus climbed from about 1049 pascals in the control to more than 2500 pascals, while the loss tangent fell — hallmarks of a stronger, more elastic gel. Critically, three-interval thixotropy tests showed that the xanthan-rich formulations recovered roughly 85 percent of their structure after 300 seconds of high shear, thanks to flexible xanthan chains that rapidly re-entangle and bridge the disrupted gellan particles. Yield points shifted to strains above 50 percent, meaning the ink resists deformation during handling yet flows cleanly through the nozzle.

Printing trials put those numbers to the test. The control emulsion exceeded its target dimensions by up to 110 percent, with broken filaments, blurred contours, and collapsed cylinders. Adding gellan gum helped, but deviations still reached 45 percent. The dual-polysaccharide inks, by contrast, achieved near-zero deviation — within a ±3 percent tolerance — producing cylinders and cuboids with crisp edges, uniform layers, and robust interlayer adhesion. The optimal formulation, 0.3 percent gellan gum with 0.6 percent xanthan gum, also proved the most resilient: it survived freeze–thaw cycling better than the 1 percent xanthan version, whose overly rigid network was punctured by growing ice crystals, and it showed the mildest oxidation during a week of storage at −4 degrees Celsius.

Perhaps most importantly for its intended users, the printed foods passed the international standard for dysphagia diets. In fork pressure and spoon tilt tests aligned with the IDDSI framework, the samples deformed under roughly 17 kilopascals — comparable to the force of the tongue during swallowing — broke into small, safe pieces with no large lumps, and held their shape on a tilted spoon, placing them at Levels 6 to 7, soft and bite-sized to easy-to-chew. After steam treatment, the printed constructs retained their form, held water well, and showed a tender texture with reduced adhesiveness, lowering choking risk. The mud–sand design, the authors conclude, offers a generalizable strategy for turning protein-based HIPEs into precision food inks — a step toward printed meals that are simultaneously beautiful, stable, nutrient-dense, and safe for those who need them most.

Subject of Research: Polysaccharide-reinforced protein-based high internal phase emulsions for 3D-printed dysphagia foods

Article Title: “Mud-Sand Structure”-Inspired Synergistic Reinforcement of Gellan Gum and Xanthan Gum on the 3D Printing Properties of Protein-Based High Internal Phase Emulsions

Article References: Xie, Y., He, C., Yu, X., Ma, J., Zhao, E., Liu, M., Zhang, H., Yuan, J., Zhou, Y., Zhu, Q., Cheng, Y., & Liu, Y. (2026). “Mud-Sand Structure”-Inspired Synergistic Reinforcement of Gellan Gum and Xanthan Gum on the 3D Printing Properties of Protein-Based High Internal Phase Emulsions. Current Research in Food Science, Article 101579. https://doi.org/10.1016/j.crfs.2026.101579

Image Credits: AI Generated

DOI: 10.1016/j.crfs.2026.101579

Keywords: 3D food printing, high internal phase emulsion, Pickering emulsion, gellan gum, xanthan gum, ovalbumin, dysphagia, rheology, food ink, IDDSI, tea polyphenols, hyaluronic acid