3D Biomimetic Tongue-Emulating Surfaces for Tribological Applications

Effect of in vitro food oral coating and lubricity on satiety: A randomized controlled trial using milk protein beverages

We investigated the effects of complex textural attributes of food i.e. lubricity and oral coating, on appetite ratings, food intake, salivary and gut peptides for the first time. Milk protein-rich beverages (whey and casein) were instrumentally analyzed (tribology, viscosity and adsorption, latter representing oral coating) using in vitro measurements. Then these protein beverage preloads differing in their coating properties (low coating, medium coating and high coating) were assessed in two cross-over satiety trials (Study 1, n=37; Study 2, n=15; Total n= 52). Fullness ratings increased in the high coating beverage condition (p < .05) only after 20 min with limited effects on other time points, suggesting a sporadic effect of oral coating on appetite ratings (n=37). There was a correlation between concentration of protein in saliva and appetite ratings; the higher the concentration of protein in saliva the lower the desire to eat (r = - 0.963; p < 0.05) and prospective food consumption ratings (r =- 0.980; p < 0.05). Human saliva was more lubricating after ingesting preload with high coating properties, thus explaining the results on appetite ratings. There was no effect of oral coating on energy intake and gut peptides (n=15), suggesting that complex textural attributes having influence on oral processing might not have any effect on the later parts of the satiety cascade. Oral coating/ lubricity appears to have a subtle and sporadic effect on appetite suppression, which needs further investigation with changing macronutrients/energy load and degree of coating/ lubricity.

Effects of dispersing media on the rheological and tribological properties of basil seed mucilage-based thickened liquids

The development of thickening powders for the management of dysphagia is imperative due to the rapid growth of aging population and prevalence of the dysphagia. One promising thickening agent that can be used to formulate dysphagia diets is basil seed mucilage (BSM). This work investigates the effects of dispersing media, including water, milk, skim milk, and apple juice, on the rheological and tribological properties of the BSM-thickened liquids. Shear rheology results revealed that the thickening ability of BSM in these media in ascending order is milk < skim milk ≈ apple juice < water. On the other hand, extensional rheology demonstrated that the longest filament breakup time was observed when BSM was dissolved in milk, followed by skim milk, water, and apple juice. Furthermore, tribological measurements showed varying lubrication behavior, depending on the BSM concentration and dispersing media. Dissolution of BSM in apple juice resulted in the most superior lubrication property compared with that in other dispersing media. Overall, this study provides insights on BSM's application as a novel gum-based thickening powder in a range of beverages and emphasizes how important it is for consumers to have clear guidance for the use of BSM in dysphagia management.

Oral Astringency in Plant Proteins: An Underestimated Issue in Formulating Next-Generation Plant-Based Foods

Ensuring the supply of affordable, palatable, healthy, and sustainable nutrients to feed the growing population without transgressing the planetary boundaries remains a key challenge in the food science community. A dietary transition toward low-emission, plant-based foods, with less reliance on animal agriculture, is advocated for sustainability, health, and ethical reasons. A major hurdle for mainstream adoption of plant-based foods is their poor sensorial performance, such as nonjuicy and astringent textures as well as various off-flavors. This review presents the current understanding of astringency and oral friction of plant-based foods. It focuses on plant proteins and their application in plant-based meat and dairy analogs. In addition, the latest advances in the quantitative characterization of astringency using tribology, electrochemistry, and cellular tools are covered. Finally, we examine factors influencing astringency and propose easy-to-implement colloidal strategies that may mitigate astringency issues, thereby underpinning the design of the next generation of sustainable and pleasurable plant-based foods.

Exploring the effects of structure and melting on sweetness in additively manufactured chocolate

In view of the health concerns associated with high sugar intake, this study investigates methods to enhance sweetness perception in chocolate without increasing its sugar content. Using additive manufacturing, chocolate structures were created from masses with varying sugar and fat compositions, where hazelnut oil served as a partial cocoa butter replacement. The study found that while variations in sugar content minimally affected the physical properties of the chocolate masses, hazelnut oil significantly modified melting behavior and consumption time. Chocolate masses with higher hazelnut oil content but similar sugar content exhibited a 24% increase in sweetness perception, likely due to accelerated tastant (i.e., sucrose) release into saliva. Multiphase structures, designated as layered, cube-in-cube, and sandwich structures, exhibited less sensory differences compared to the homogeneous control. Nonetheless, structures with hazelnut oil-rich outer layers resulted in an 11% increase in sweetness perception, even without sugar gradients. This suggests that tastant release plays a more critical role than structural complexity in modifying sweetness perception. This research highlights the efficacy of simpler multiphase structures, such as sandwich designs, which offer sensory enhancements comparable to those of more complex designs but with reduced manufacturing effort, thus providing viable options for industrial-scale production.

Machine learning and topological data analysis identify unique features of human papillae in 3D scans

The tongue surface houses a range of papillae that are integral to the mechanics and chemistry of taste and textural sensation. Although gustatory function of papillae is well investigated, the uniqueness of papillae within and across individuals remains elusive. Here, we present the first machine learning framework on 3D microscopic scans of human papillae ([Formula: see text]), uncovering the uniqueness of geometric and topological features of papillae. The finer differences in shapes of papillae are investigated computationally based on a number of features derived from discrete differential geometry and computational topology. Interpretable machine learning techniques show that persistent homology features of the papillae shape are the most effective in predicting the biological variables. Models trained on these features with small volumes of data samples predict the type of papillae with an accuracy of 85%. The papillae type classification models can map the spatial arrangement of filiform and fungiform papillae on a surface. Remarkably, the papillae are found to be distinctive across individuals and an individual can be identified with an accuracy of 48% among the 15 participants from a single papillae. Collectively, this is the first evidence demonstrating that tongue papillae can serve as a unique identifier, and inspires a new research direction for food preferences and oral diagnostics.

Benchmarking of a microgel-reinforced hydrogel-based aqueous lubricant against commercial saliva substitutes

Xerostomia, the subjective sensation of 'dry mouth' affecting at least 1 in 10 adults, predominantly elders, increases life-threatening infections, adversely impacting nutritional status and quality of life. A patented, microgel-reinforced hydrogel-based aqueous lubricant, prepared using either dairy or plant-based proteins, has been demonstrated to offer substantially enhanced lubricity comparable to real human saliva in in vitro experiments. Herein, we present the benchmarking of in vitro lubrication performance of this aqueous lubricant, both in its dairy and vegan formulation against a range of widely available and employed commercial saliva substitutes, latter classified based on their shear rheology into "liquids", "viscous liquids" and "gels", and also had varying extensional properties. Strikingly, the fabricated dairy-based aqueous lubricant offers up to 41-99% more effective boundary lubrication against liquids and viscous liquids, irrespective of topography of the tested dry mouth-mimicking tribological surfaces. Such high lubricity of the fabricated lubricants might be attributed to their limited real-time desorption (7%) from a dry-mouth mimicking hydrophobic surface unlike the tested commercial products including gels (23-58% desorption). This comprehensive benchmarking study therefore paves the way for employing these microgel-based aqueous lubricant formulations as a novel topical platform for dry mouth therapy.

Out-of-contact peeling caused by elastohydrodynamic deformation during viscous adhesion

We report on viscous adhesion measurements conducted in sphere-plane geometry between a rigid sphere and soft surfaces submerged in silicone oils. Increasing the surface compliance leads to a decrease in the adhesive strength due to elastohydrodynamic deformation of the soft surface during debonding. The force-displacement and fluid film thickness-time data are compared to an elastohydrodynamic model that incorporates the force measuring spring and finds good agreement between the model and data. We calculate the pressure distribution in the fluid and find that, in contrast to debonding from rigid surfaces, the pressure drop is non-monotonic and includes the presence of stagnation points within the fluid film when a soft surface is present. In addition, viscous adhesion in the presence of a soft surface leads to a debonding process that occurs via a peeling front (located at a stagnation point), even in the absence of solid-solid contact. As a result of mass conservation, the elastohydrodynamic deformation of the soft surface during detachment leads to surfaces that come closer as the surfaces are separated. During detachment, there is a region with fluid drainage between the centerpoint and the stagnation point, while there is fluid infusion further out. Understanding and harnessing the coupling between lubrication pressure, elasticity, and surface interactions provides material design strategies for applications such as adhesives, coatings, microsensors, and biomaterials.

Inkjet-based surface structuring: amplifying sweetness perception through additive manufacturing in foods

Additive manufacturing (AM) is creating new possibilities for innovative tailoring of food properties through multiscale structuring. This research investigated a high-speed inkjet-based technique aimed to modify sweetness perception by creating dot patterns on chocolate surfaces. The dots were formulated from cocoa butter with emulsified water droplets containing the sweetener thaumatin. The number and surface arrangement of dots, which ranged from uniformly distributed patterns to concentrated configurations at the sample's center and periphery, were varied while maintaining a constant total amount of thaumatin per sample. A sensory panel evaluated sweetness perception at three consumption time points, reporting a significant increase when thaumatin was concentrated on the surface. Specifically, an amplification of sweetness perception by up to 300% was observed, irrespective of dot pattern or consumption time, when compared to samples where thaumatin was uniformly distributed throughout the bulk. However, when thaumatin was concentrated solely at the sample center, maximum sweetness perception decreased by 24%. Conclusively, both the proximity of thaumatin to taste receptors and its spatial distribution, governed by different dot arrangements, significantly influenced taste responsiveness. These findings present a more effective technique to substantially enhance sweetness perception compared to traditional manufacturing techniques. This method concurrently allows for sensorial and visual customization of products. The implications of this study are far-reaching, opening avenues for industrially relevant AM applications, and innovative approaches to study taste formation and perception during oral processing of foods.

Transforming sustainable plant proteins into high performance lubricating microgels

With the resource-intensive meat industry accounting for over 50% of food-linked emissions, plant protein consumption is an inevitable need of the hour. Despite its significance, the key barrier to adoption of plant proteins is their astringent off-sensation, typically associated with high friction and consequently poor lubrication performance. Herein, we demonstrate that by transforming plant proteins into physically cross-linked microgels, it is possible to improve their lubricity remarkably, dependent on their volume fractions, as evidenced by combining tribology using biomimetic tongue-like surface with atomic force microscopy, dynamic light scattering, rheology and adsorption measurements. Experimental findings which are fully supported by numerical modelling reveal that these non-lipidic microgels not only decrease boundary friction by an order of magnitude as compared to native protein but also replicate the lubrication performance of a 20:80 oil/water emulsion. These plant protein microgels offer a much-needed platform to design the next-generation of healthy, palatable and sustainable foods.

Frictional behaviour of plant proteins in soft contacts: unveiling nanoscale mechanisms

Despite the significance of nanotribology in the design of functional biomaterials, little is known about nanoscale friction in the presence of protein-coated soft contact surfaces. Here, we report a detailed investigation of frictional behaviour of sustainable plant proteins at the nanoscale for the first time, using deformable bio-relevant surfaces that achieve biologically relevant contact pressures. A combination of atomic force microscopy, quartz crystal microbalance with dissipation monitoring, and friction force microscopy with soft polydimethylsiloxane (PDMS, 150 kPa) surfaces was employed to elucidate the frictional properties of model plant proteins, i.e. lupine, pea, and potato proteins at the nanoscale while systematically varying the pH and ionic strength. Interactions of these plant proteins with purified mucins were also probed. We provide the much-needed direct experimental evidence that the main factor dictating the frictional properties of plant proteins is their affinity towards the surface, followed by the degree of protein film hydration. Proteins with high surface affinity, such as pea and potato protein, have better lubricating performance than lupine at the nanoscale. Other minor factors that drive lubrication are surface interactions between sliding bodies, especially at low load, whilst jamming of the contact area caused by larger protein aggregates increases friction. Novel findings reveal that interactions between plant proteins and mucins lead to superior lubricating properties, by combining high surface affinity from the plant proteins and high hydration by mucins. We anticipate that fundamental understanding gained from this work will set the stage for the design of a plethora of sustainable biomaterials and food with optimum nanolubrication performance.

In vitro oral simulation based on soft contact: The importance of viscoelastic response of the upper jaw substitutes

Real oral processing is the squeezing and shearing between two soft surfaces. The importance of soft palate surface cannot be ignored while focusing on tongue substitutes. Thus the effects of viscoelasticity, roughness of upper jaw substitutes, and fluid rheological properties on lubrication properties were explored by in vitro oral tribology experiments. Different palate substitutes significantly changed the friction curves of pure water, milk, and yogurt. The boundary friction coefficients of pure water and milk are higher under softer or smooth palate substitutes due to stronger viscoelastic responses of friction pairs. Their boundary friction coefficients are lowest at rigid upper jaw substitutes owing to smaller contact angles and deformation. However, the boundary friction coefficient of yogurt is lower owing to its high viscosity, low loss factor, and large particle size under soft friction pairs. In addition, it is highest at rigid palate friction pair because a smaller contact area reduces the entrainment of yogurt, resulting in poor lubricating performance.

Insights into the Multiscale Lubrication Mechanism of Edible Phase Change Materials

Investigation of a lubrication behavior of phase change materials (PCM) can be challenging in applications involving relative motion, e.g., sport (ice skating), food (chocolates), energy (thermal storage), apparel (textiles with PCM), etc. In oral tribology, a phase change often occurs in a sequence of dynamic interactions between the ingested PCM and oral surfaces from a licking stage to a saliva-mixed stage at contact scales spanning micro- (cellular), meso- (papillae), and macroscales. Often the lubrication performance and correlations across length scales and different stages remain poorly understood due to the lack of testing setups mimicking real human tissues. Herein, we bring new insights into lubrication mechanisms of PCM using dark chocolate as an exemplar at a single-papilla (meso)-scale and a full-tongue (macro) scale covering the solid, molten, and saliva-mixed states, uniting highly sophisticated biomimetic oral surfaces with in situ tribomicroscopy for the first time. Unprecedented results from this study supported by transcending lubrication theories reveal how the tribological mechanism in licking shifted from solid fat-dominated lubrication (saliva-poor regime) to aqueous lubrication (saliva-dominant regime), the latter resulted in increasing the coefficient of friction by at least threefold. At the mesoscale, the governing mechanisms were bridging of cocoa butter in between confined cocoa particles and fat coalescence of emulsion droplets for the molten and saliva-mixed states, respectively. At the macroscale, a distinctive hydrodynamic viscous film formed at the interface governing the speed-dependent lubrication behavior indicates the striking importance of multiscale analyses. New tribological insights across different stages and scales of phase transition from this study will inspire rational design of the next generation of PCM and solid particle-containing materials.

High-Resolution Surface Replication of Living Organisms using Air-Through-Precursor Suction-Augmented Replica Molding

Replica molding is widely used to reproduce the surface microstructures that provide living organisms with distinct and useful functions. However, the existing methods are limited by the low resolution resulting from the air trapped in the structures during precursor solution loading. This study investigated replica molding with an air-through-precursor suction (APS) process, which used a degassed polydimethylsiloxane substrate to remove the trapped air through the precursor solution. The liquid loading times are characterized using a model template, and air suction that is up to 36 times faster can be achieved using the APS process relative to a conventional method. Using APS replica molding, biocompatible replicates from human fingerprints and gecko skin are fabricated using only a 3 min precursor solution loading step. Owing to the enhanced and reproducible resolution from APS replica molding, for the first time, the structural changes in the foot of a living gecko at the microscale can be observed when standing on a horizontal or vertical surface.

Advances in 3D bioprinting of tissues/organs for regenerative medicine and in-vitro models

Tissue/organ shortage is a major medical challenge due to donor scarcity and patient immune rejections. Furthermore, it is difficult to predict or mimic the human disease condition in animal models during preclinical studies because disease phenotype differs between humans and animals. Three-dimensional bioprinting (3DBP) is evolving into an unparalleled multidisciplinary technology for engineering three-dimensional (3D) biological tissue with complex architecture and composition. The technology has emerged as a key driver by precise deposition and assembly of biomaterials with patient's/donor cells. This advancement has aided in the successful fabrication of in vitro models, preclinical implants, and tissue/organs-like structures. Here, we critically reviewed the current state of 3D-bioprinting strategies for regenerative therapy in eight organ systems, including nervous, cardiovascular, skeletal, integumentary, endocrine and exocrine, gastrointestinal, respiratory, and urinary systems. We also focus on the application of 3D bioprinting to fabricated in vitro models to study cancer, infection, drug testing, and safety assessment. The concept of in situ 3D bioprinting is discussed, which is the direct printing of tissues at the injury or defect site for reparative and regenerative therapy. Finally, issues such as scalability, immune response, and regulatory approval are discussed, as well as recently developed tools and technologies such as four-dimensional and convergence bioprinting. In addition, information about clinical trials using 3D printing has been included.

Local lateral contact governs shear traction of micropatterned surfaces on hydrogel substrates

Micropatterned surfaces exhibit enhanced shear traction on soft, aqueous tissue-like materials and, thus, have the potential to advance medical technology by improving the anchoring performance of medical devices on tissue. However, the fundamental mechanism underlying the enhanced shear traction is still elusive, as previous studies focused on interactions between micropatterned surfaces and rigid substrates rather than soft substrates. Here, we present a particle tracking method to experimentally measure microscale three-dimensional (3D) deformation of a soft hydrogel in normal and shear contact with arrays of microscale pillars. The measured 3D strain and stress fields reveal that the lateral contact between each individual pillar and the deformed hydrogel substrate governs the shear response. Moreover, by comparing pillars with different cross-sectional geometries, we observe experimental evidence that the shear traction of a pillar on the hydrogel substrate is sensitive to the convex features of its leading edge in the shear direction.

Colloidal dynamics of emulsion droplets in mouth

The interaction of emulsions with the tongue is key to the sensory appeal of food and can potentially be exploited for oral/buccal pharmaceutical delivery. Whilst there is good understanding of the different mucoadhesive forces governing emulsion interaction with the tongue, their relative importance is not well understood. In addition, the physical location of emulsions within the saliva papillae on the tongue is not understood at all. A combination of ex vivo salivary film, and in vivo oral coating experiments were used to determine the importance of different mucoadhesive forces. Mucoadhesion of cationic emulsions was largely driven by electrostatic complexation. SDS-PAGE of the in vivo saliva coating highlighted that mucins were largely responsible for cationic emulsion mucoadhesion. Anionic emulsions were bound via hydrophobic/steric interactions to small salivary proteins typically located away from the mucin anchor points. The physical location and clustering of emulsions relative to the salivary film/papillae was probed via the invention of a fluorescent oral microscope. Cationic emulsions were densely clustered close to the papillae whilst anionic emulsions were suspended in the salivary film above the papillae. Interestingly, non-ionic emulsions were also trapped within the salivary film above the papillae as individual droplets. These findings highlight that whilst electrostatic complexation with saliva is a powerful mucoadhesive force, hydrophobic and steric interactions also act to induce oral retention of emulsions. The differences in physical location and clustering of emulsions within the salivary film hint at the 3D locations of the different salivary proteins driving each mucoadhesive interaction. This novel understanding of emulsion saliva/papillae interactions has potential to aid efficacy of buccal pharmaceutical delivery and the reduction of astringency in plant-based foods.

Current Perspectives on Food Oral Processing

Food oral processing (FOP) is a fast-emerging research area in the food science discipline. Since its first introduction about a decade ago, a large amount of literature has been published in this area, forming new frontiers and leading to new research opportunities. This review aims to summarize FOP research progress from current perspectives. Food texture, food flavor (aroma and taste), bolus swallowing, and eating behavior are covered in this review. The discussion of each topic is organized into three parts: a short background introduction, reflections on current research findings and achievements, and future directions and implications on food design. Physical, physiological, and psychological principles are the main concerns of discussion for each topic. The last part of the review shares views on the research challenges and outlooks of future FOP research. It is hoped that the review not only helps readers comprehend what has been achieved in the past decade but also, more importantly, identify where the knowledge gaps are and in which direction the FOP research will go.

Application of a balloon-type pressure sensor in texture evaluation of tongue-crushable foods

A relationship has recent been suggested to exist between tongue pressure measured using balloon-type sensors and the tongue-crushable food range of individuals. This study was conducted to investigate the applicability of a balloon-type pressure sensor for texture evaluation of tongue-crushable soft foods. Six gellan gum gels were used as a soft food model. The fracture force and strain of gels were controlled at two and three levels by changing the gum concentration and acyl-group content, respectively. The pressure sensor was inserted between a food sample and texture analyzer probe, and pressure values during compression of gels was measured. During the compression test, both the food and tongue-pressure sensor were deformed, eventually leading to fracture of food gels. Using the tongue-pressure sensor, the food gels fractured at lower force because of the shape of the sensor but showed longer displacement as the sensor deformed compared to without the sensor. Gels with low fracture force in the conventional test without the sensor exhibited lower fracture force, work, gradient, and true stress than those with high fracture force in the sensor test. Displacement, clearance or distance from the bottom plate, and true stress at fracture were appropriate parameters for expressing the fracture characteristics. Both the true fracture stress and fracture pressure in the sensor test decreased with the fracture strain of gels in a conventional test. These results suggest that by using a larger balloon and faster sampling, the sensor can be used to determine the fracture behavior of tongue-crushable foods.

Understanding relations between rheology, tribology, and sensory perception of modified texture foods

The aim of this work was to examine relations between instrumental and sensory parameters in a texture modified food matrix, with and without saliva. Nine pureed carrot samples (eight thickened and a control) were developed with starch (0.4 and 0.8% wt/wt), xanthan (0.2 and 0.4% wt/wt) or starch-xanthan blends that met International Dysphagia Diet Standardisation Initiative (IDDSI) Level 4 guidelines using fork and spoon tests. Rheological and tribological tests were conducted on the food and simulated bolus prepared by adding fresh stimulated saliva to the food (1:5, saliva:food) to mimic oral processing. Perceived sensory properties were identified using a temporal dominance of sensations (TDS) test (n = 16) where panelists were given a list of nine attributes. The area under the curve was extracted from TDS curves for each attribute/sample and this was correlated with rheological (viscosity at 10 s^-1 , G', G″, and tan δ at 1 Hz) and tribological (friction coefficient in three regimes) data. The viscosity of the control sample decreased after adding hydrocolloids (except Starch_0.8%) and with saliva incorporation. G' and G″ either increased or were similar for xanthan and blends and decreased for starch-thickened samples. Hydrocolloid addition increased friction for all samples and was higher with saliva addition. Sensory results showed that samples with starch were perceived as thick and grainy while xanthan was perceived as smooth and slippery. A greater number of sensory attributes correlated with viscoelastic parameters compared to friction coefficients. Correlations were highest with the saliva added samples, further highlighting the importance of including saliva during instrumental testing.

Texture contrast: Ultrasonic characterization of stacked gels' deformation during compression on a biomimicking tongue

When undergoing compression during oral processing, stacked gels display different mechanical properties that shape perceptions of texture contrasts (Santagiuliana et al., 2018). However, to date, characterizing the mechanical responses of individual gel layers has been impossible. In this study, an ultrasound (US) technique was developed, that allowed such deformation dynamics to be visualized in real time. Stacked gels were created using layers (height: 5 mm) of brittle agar and elastic gelatin in different combinations. In a series of experimental tests, different stacked gel combinations were placed on a rough, deformable artificial tongue model (ATM) made of polyvinyl alcohol; a texture analyzer was used to apply uniaxial force, and deformation was monitored by an US transducer (5 MHz) located under the ATM.

From the obtained results, it was observed that the deformation of ATM surface during compression was in accordance with the force recorded by the texture analyzer, suggesting a collaborative response of different layers under compression. Moreover, US imaging revealed that differences in Young's modulus values between layers led to heterogeneous strain distributions, which were more pronounced for the agar layers. Biopolymer elasticity was also a key factor. Regardless of combination type, the gelatin layers never fractured; such was not the case for the agar layers, especially those with lower Young's modulus values. The results of this US study have thus paved the way for a better understanding of the mechanical deformation that occurs in heterogeneous foods, a phenomenon that has been difficult to examine because of the limitations of conventional techniques.

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Agar and gelatin bilayer gels were compressed on deformable artificial tongue models.

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Compressions and relaxations were monitored with a non-invasive ultrasound method.

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Deformations in artificial tongue and food layers were assessed with signal processing.

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The method shows potential for understanding texture contrast perception.

Food Oral Processing-An Industry Perspective

We illustrate how scientific understanding of Food Oral Processing enables food product development with specific benefits for several target populations. in vivo, in vitro, and in silico approaches are discussed in the context of their ability to quantify oral processing from the molecular to the macroscopic scale. Based on this understanding, food structures with enhanced performance in terms of hedonic and nutritional properties as well as appropriateness for age and certain medical conditions can be developed. We also discuss current gaps and highlight development opportunities from an industry perspective.

Synergistic Microgel-Reinforced Hydrogels as High-Performance Lubricants

The ability to create a superlubricious aqueous lubricant is important for various biological and technological applications. Here, a nonlipid biolubricant with strikingly low friction coefficients is fabricated (patented) by reinforcing a fluid-like hydrogel composed of biopolymeric nanofibrils with proteinaceous microgels, which synergistically provide superlubricity on elastomeric surfaces in comparison to any of the sole components. This two-component lubricant composed of positively charged lactoferrin microgels and negatively charged κ-carrageenan hydrogels is capable of exceeding the high lubricating performance of real human saliva in tribo tests using both smooth and textured surfaces, latter mimicking the human tongue's wettability, topography, and compliance. The favorable electrostatic attraction between mutually oppositely charged microgels and the hydrogel reinforces the mechanical properties of the hydrogel, allowing friction reduction by combining the benefits of both viscous and hydration lubrication. The superlubricity of these microgel-reinforced hydrogels offers a unique prospect for the fabrication of biocompatible aqueous lubricants for dry-mouth therapy and/or designing of nonobesogenic nutritional technologies.