Role of fluid cohesiveness in safe swallowing

Carboxymethylcellulose-induced depletion attraction to stabilize high internal phase Pickering emulsions for the elderly: 3D printing and β-carotene delivery

In this study, a carboxymethylcellulose (CMC) induced depletion attraction was developed to stabilize high internal phase Pickering emulsions (HIPPEs) as age-friendly 3D printing inks. The results demonstrated that depletion force induced the adsorption of yolk particles at the droplet interface and the formation of osmotic droplet clusters, thereby increasing the stability of HIPPEs. In addition, the rheological properties and nutrient delivery properties of HIPPEs could be adjusted by the mass ratio of yolk/CMC. The HIPPEs stabilized at yolk/CMC mass ratio 20:7.5 showed optimal printability, viscoelastic, structural recovery, and swallowability. HIPPEs have been applied to 3D printing, International Dysphagia Dietary Standardization Initiative (IDDSI) test, and in vitro digestive simulation in the elderly, indicating their attractive appearance, safe swallowability, and enhanced bioaccessibility of β-carotene. Our work provides new ideas for developing age-friendly foods with plasticity and nutrient delivery capacity by depletion attraction stabilizing HIPPEs.

Sucrose and Ca2+ synergistically regulate the rheological properties of apple high-methoxyl pectin

The thickening and gelling mechanism of high-methoxyl pectins (HMPs) with different degree of esterification (DE) values (60.6 %, 66.1 %, and 72.4 %) synergistically affected by calcium ion (Ca2+) and sucrose was investigated using several technical methods. Rheological measurements, including steady-shear flow, thixotropy and dynamic viscoelasticity tests, texture analysis, water-holding capacity (WHC), thermal analyses (TG), and microstructure observation (TEM), were all systemically conducted. The results showed that the main thickening and gelling mechanism of Ca2+ on different HMPs was complex and the presence of sucrose had a synergistic effect on structure formation in HMP systems. Ca2+ was not always conducive to structure formation, and excessive Ca2+ addition may hinder structure formation. HMP systems with lower DE values had higher gel strengths due to the presence of more binding domains. The results of the texture properties, WHC, and thermal characteristics coincided with those obtained from the rheological measurements, which reflect the variations in HMPs affected by Ca2+ and DE. All of these results showed that Ca2+ addition at an appropriate concentration in the presence of sucrose favors HMP gelation even in the absence of acid. The results obtained here are expected to broaden the application of HMPs in acid-free gel food products.

Polysaccharide-dextrin thickened fluids for individuals with dysphagia: recent advances in flow behaviors and swallowing assessment methods

The global aging population has brought about a pressing health concern: dysphagia. To effectively address this issue, we must develop specialized diets, such as thickened fluids made with polysaccharide-dextrin (e.g., water, milk, juices, and soups), which are crucial for managing swallowing-related problems like aspiration and choking for people with dysphagia. Understanding the flow behaviors of these thickened fluids is paramount, and it enables us to establish methods for evaluating their suitability for individuals with dysphagia. This review focuses on the shear and extensional flow properties (e.g., viscosity, yield stress, and viscoelasticity) and tribology (e.g., coefficient of friction) of polysaccharide-dextrin-based thickened fluids and highlights how dextrin inclusion influences fluid flow behaviors considering molecular interactions and chain dynamics. The flow behaviors can be integrated into the development of diverse evaluation methods that assess aspects such as flow velocity, risk of aspiration, and remaining fluid volume. In this context, the key in-vivo (e.g., clinical examination and animal model), in-vitro (e.g., the Cambridge Throat), and in-silico (e.g., Hamiltonian moving particles semi-implicit) evaluation methods are summarized. In addition, we explore the potential for establishing realistic assessment methods to evaluate the swallowing performance of thickened fluids, offering promising prospects for the future.

Optimization of Ink Composition and 3D Printing Process to Develop Soy Protein-Based Scaffolds

Inks based on soybean protein isolate (SPI) were developed and their formulations were optimized as a function of the ink heat treatment and the content of other biopolymers to assess the effects of protein-polysaccharides and protein-protein interactions. First, the rheological behavior of the inks was analyzed in relation to the polyvinyl alcohol (PVA) concentration employed (20, 25, and 30 wt%) and, as a result of the analysis, the ink with 25 wt% PVA was selected. Additionally, sodium alginate (SA) and gelatin (GEL) were added to the formulations to improve the viscoelastic properties of the inks and the effect of the SA or GEL concentrations (1, 2, and 3 wt%) was studied. All inks showed shear thinning behavior and self-supporting abilities. Among all the 3D printed scaffolds, those with higher SA (3 wt%) or GEL (2 and 3 wt%) content showed higher shape fidelity and were selected for further characterization. Texture profile analysis demonstrated that the scaffolds prepared with previously heat-treated inks containing 3 wt% GEL showed the highest strength. Additionally, these scaffolds showed a higher water-uptake capacity profile.

Pinching dynamics, extensional rheology, and stringiness of saliva substitutes

Saliva substitutes are human-made formulations extensively used in medicine, food, and pharmaceutical research to emulate human saliva's biochemical, tribological, and rheological properties. Even though extensional flows involving saliva are commonly encountered in situations such as swallowing, coughing, sneezing, licking, drooling, gleeking, and blowing spit bubbles, rheological evaluations of saliva and its substitutes in most studies rely on measured values of shear viscosity. Natural saliva possesses stringiness or spinnbarkeit, governed by extensional rheology response, which cannot be evaluated or anticipated from the knowledge of shear rheology response. In this contribution, we comprehensively examine the rheology of twelve commercially available saliva substitutes using torsional rheometry for rate-dependent shear viscosity and dripping-onto-substrate (DoS) protocols for extensional rheology characterization. Even though most formulations are marketed as having suitable rheology, only three displayed measurable viscoelasticity and strain-hardening. Still, these too, failed to emulate the viscosity reduction with the shear rate observed for saliva or match perceived stringiness. Finally, we explore the challenges in creating saliva-like formulations for dysphagia patients and opportunities for using DoS rheometry for diagnostics and designing biomimetic fluids.

Development of high internal phase Pickering emulsions stabilized by egg yolk and carboxymethylcellulose complexes to improve β-carotene bioaccessibility for the elderly

The work aimed to develop the multi-protein mixture of egg yolk as natural particles to stabilize high internal phase Pickering emulsions (HIPPEs) to improve the bioaccessibility of β-carotene in the elderly. The results showed that the depletion attraction drove the adsorption of egg yolk protein particles at the oil-water interface and the formation of osmotic droplet clusters due to the attachment of particle-coated droplets in the dispersed phase, leading to kinetic blocking and stable gelation of HIPPEs. Rheological measurements showed that HIPPEs had shear thinning, low shear stress, viscoelastic properties, and structural recovery properties, which facilitated easy consumption for the elderly. The stability of HIPPEs was verified by ionic and centrifugal stability tests, demonstrating their potential for application to complex gastric environments. HIPPEs have been applied to the International Dysphagia Dietary Standardization Initiative (IDDSI) test and simulated in vitro digestion in older adults, demonstrating their safe swallowability and high β-carotene bioaccessibility. Our findings suggest solutions for food practitioners facing the aging problem and provide new insights for preparing age-friendly foods.

Salmon protein gel enhancement for dysphagia diets: Konjac glucomannan and composite emulsions as texture modifiers

The growing prevalence of dysphagia among the aging population presents a significant challenge. Many highly nutritious foods, like salmon, are often unsuitable for the elderly due to their firm texture when heated. To address this concern, a combination of salmon myofibrillar protein (SMP), Konjac glucomannan (KGM), and different emulsion fillers-such as oil droplets, octenyl succinic anhydride (OSA)-modified potato starch emulsion, and high methoxylated pectin (HMP) emulsions-was selected to enhance the network of salmon protein gels with the aims to create potential applications as dysphagia-friendly foods. The International Dysphagia Dietary Standardization Initiative (IDDSI) test indicated that all gel samples were classified as level 5. The OSA-SMP-KGM gel exhibited notably higher cohesiveness (P < 0.05), reduced adhesion, and enhanced mouthfeel. The OSA-SMP-KGM gel exhibited a smooth surface and excellent water retention (92.4 %), rendering it suitable for individuals with swallowing difficulties, particularly those prone to experiencing dry mouth. The yield stress of OSA-SMP-KGM gel was 594.14 Pa and stable structure was maintained during chewing and swallowing (γe/γv = 62.5). This study serves as a valuable reference for developing salmon-based products that are not only highly nutritious but also fulfill the criteria for a desirable swallowing texture.

Impact of using whole chestnut flour as a substitute for cake flour on digestion, functional and storage properties of chiffon cake: A potential application study

Developing fresh cake product with rich nutrition and high quality has become a hot spot in food industry. In this study, whole chestnut flour as a high-quality dietary source was successfully substituted for cake flour in the production of chestnut chiffon cake with 40-55% substitution rate, and its application prospects were further evaluated through studying nutritional and storage properties. The results showed that chestnut chiffon cake with 45% and 50% substitution rate could significantly increase the resistant component, scavenging activity and ferric reducing antioxidant power, surprisingly decrease predicted glycemic index to 54.05-57.28, and reduce the acetate/propionate ratio and Firmicutes/Bacteroidetes value for human gut microbiota as well. Comparatively, chestnut chiffon cake with 45% substitution rate had more application potential due to its higher free water retention at day 7 and higher resilience throughout the storage time. Overall, this study could provide valuable information for the development of modern nutritional cake industry.

Investigation of 3D printing product of powder-based white mushroom incorporated with soybean protein isolate as dysphagia diet

The elderly people are prone to dysphagia due to weakened muscle strength. 3D food printing could modify the nutritional ratio and shape design to produce personalized nutritious food suitable for patients with dysphagia. White mushroom (Agaricus bisporus) is rich in a variety of active ingredients such as polysaccharides and polyphenols which are beneficial to human body, but its unique texture is not suitable for patients with dysphagia to chew. This study investigated the impact of different concentrations of soybean protein isolate (SPI, 3%, 5%, 7%, w/w) on 3D food printing of white mushroom powder and carried out the hierarchical representation of dysphagia diet within the framework of International Dysphagia Diet Standardization Initiative (IDDSI). The results illustrated that SPI addition to white mushroom gel reduced water mobility and promoted hydrogen bond formation, which significantly improved the mechanical strength and cohesiveness of printing inks, including yield stress, viscosity and hardness. IDDSI tests showed that the SPI addition of 3% and 5% helped the printing ink pass the spoon tilt test and the fork drip test, which could be classified as level 5 minced and moist food under the consideration of the fork pressure test. The 3D printing results indicated that the 7% SPI addition made the yield stress too high and was not easy for extrusion, resulting in the appearance defects of the printed sample. The addition of 3% SPI could make the printed sample have smooth surface and excellent self-supporting capacity. This work provides insights of white mushroom 3D printing technology as a more visually appealing dysphagia diet.

Three-dimensional food printing: its readiness for a food and nutrition insecure world

Three-dimensional (3D) food printing is a rapidly emerging technology offering unprecedented potential for customised food design and personalised nutrition. Here, we evaluate the technological advances in extrusion-based 3D food printing and its possibilities to promote healthy and sustainable eating. We consider the challenges in implementing the technology in real-world applications. We propose viable applications for 3D food printing in health care, health promotion and food waste upcycling. Finally, we outline future work on 3D food printing in food safety, acceptability and economics, ethics and regulations.

Effects of barium sulfate on rheological properties and IDDSI flow consistency of liquid stimuli prepared using commercial thickening powders

During videofluoroscopic swallowing study (VFSS), barium sulfate (BaSO4 ) is commonly added into food samples as a radiopaque contrast media for bolus visualization and examination. Accordingly, the consistency and flow behavior of barium stimuli can differ significantly from their non-barium counterparts. Such differences may have a subsequent impact on the validity of VFSS. Therefore, in this study, effects of barium sulfate on the shear and extensional rheological properties and IDDSI (International Dysphagia Diet Standardization Initiative) flow consistency of liquids prepared using various commercial thickening powders were investigated. Results showed that all barium stimuli exhibited shear thinning behavior but with significantly higher shear viscosity compared to the non-barium counterparts. A shift factor of viscosity at shear rate 50 s-1 with values in range of 1.21-1.73 could be used to describe the increase in the viscosity for samples thickened with gum-based thickeners. However, the change in the viscosity was not invariant for the stimuli prepared starch-based thickener. The addition of BaSO4 had a negative impact on extensional properties of samples by demonstrating a faster filament rupture. The extent of impact on the decrease in filament breakup time was more pronounced in xanthan > guar gum ≈ tara gum-based thickeners. Based on the IDDSI flow test, no significant effect of BaSO4 was found on the gum-based thickeners, whereas there was a marked effect in the starch-based sample. These results can be used beneficially to assist clinicians in the dysphagia diagnosis for matching rheological properties of the barium stimuli to enhance effectiveness dysphagia interventions.

Characterization and Evaluation of Heat-Moisture-Modified Black and Red Rice Starch: Physicochemical, Microstructural, and Functional Properties

This study sought to evaluate starch from black and red rice modified by heat-moisture, investigating the extraction yield, starch and amylose content, color, and phenolic compounds. The water and oil absorption capacity, whole milk and zero lactose absorption index, syneresis index, and texture were also analyzed. Microstructural analysis included Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The heat-moisture treatment (HMT) reduced the extraction yield and the starch and amylose content, with native black rice starch having the highest values for these parameters. The modification also affected the color and phenolic compounds of the starch, making it darker and changing its appearance. The modification improved the absorption of water, oil, and milk, reducing syneresis and increasing stability during storage. The starch surface was altered, especially for modified black rice starch, with larger agglomerates. The type of starch also changed from A to Vh, with lower relative crystallinity. The textural properties of modified red rice starch were also significantly altered. The HMT proved to be a viable and economical option to modify the analyzed parameters, influencing the texture and physicochemical properties of pigmented rice starch, expanding its applications, and improving its stability during storage at temperatures above 100 °C.

Enhancing Spiritual Well-Being, Physical Activity, and Happiness in Hospitalized Older Adult Patients with Swallowing Difficulties: A Comparative Study of Thickeners and Swallowing Exercises

Swallowing difficulties often occur in older adult patients during acute hospitalization, leading to reduced nutritional intake, increased frailty, and various psychosocial challenges. This randomized controlled study aimed to assess the effects of two interventions, thickeners and swallowing exercises, on the spiritual well-being, physical activity, and happiness of older adult patients with swallowing difficulties during acute hospitalization from October 2019 to August 2020. Sample size calculation was performed using a conservative estimate approach, resulting in an estimate-required sample size of 42 participants. The sampling method was a random cluster sampling approach, with three ward rooms assigned to the thickeners group, swallowing exercises group and control group, respectively. Seventy-two participants were assigned to the intervention groups (thickeners or swallowing exercises) or the control group using a 1:1:1 stratified random assignment. Data were collected before and after the intervention, and matched samples were analyzed using t-tests, ANOVA, and generalized estimating equations for statistical analysis. Both intervention groups showed significant improvements in spiritual well-being (p < 0.001), physical activity (p < 0.001), and happiness (p < 0.001) compared to the control group. However, there were no significant differences between the intervention groups. Our findings suggest that interventions involving thickeners and swallowing exercises have positive effects on the spiritual well-being, physical activity, and happiness of older adult patients with swallowing difficulties during acute hospitalization and emphasize the importance of implementing these interventions to enhance the overall well-being and quality of life of this vulnerable patient population.

The influence of MPL addition on structure, interfacial compositions and physicochemical properties on infant formula fat globules

The lack of milk fat globule membrane phospholipids (MPL) at the interface of infant formula fat globules has an impact on the stability of fat globules, compared to human milk. Therefore, infant formula powders with different MPL contents (0%, 10%, 20%, 40%, 80%, w/w of MPL/whey protein mixture) were prepared, and the effect of interfacial compositions on the stability of globules was investigated. With increasing MPL amount, the particle size distribution had two peaks and returned to a uniform state when 80% MPL was added. At this composition, the MPL at the oil-water interface formed a continuous thin layer. Moreover, the addition of MPL improved the electronegativity and the emulsion stability. In terms of the rheological properties, increasing the concentration of MPL improved the elastic properties of the emulsion and the physical stability of the fat globules, while reducing the aggregation and agglomeration between fat globules. However, the potential for oxidation increased. Based on these results, the interfacial properties and stability on infant formula fat globules was significantly influenced by the level of MPL, which should be considered in the design of infant milk powders.

Application of HPP for the Development of a Dessert Elaborated with Casein and Cocoa for a Dysphagia Diet

In this study, the application of high-pressure processing (HPP) for optimizing the texture of a cocoa dessert rich in casein and developed for people with dysphagia was investigated. Different treatments (250 MPa/15 min; 600 MPa/5 min) and protein concentrations (10-15%) were combined and evaluated for choosing the optimum combination leading to an adequate texture. The selected formulation was a dessert containing 4% cocoa and 10% casein and subjected to 600 MPa for 5 min. It showed a high nutritional value (11.5% protein) and high antioxidant capacity, which was slightly affected by the HPP processing. The rheological and textural properties showed that HPP had a clear effect on the dessert structure. The loss tangent decreased from 2.692 to 0.165, indicating the transition from a liquid to a gel-like structure, which is in a suitable range for dysphagia foods. During storage (14 and 28 days at 4 °C), progressive significant changes in the structure of the dessert were observed. A decrease in all rheological and textural parameters occurred, except for the loss of tangent, which increased its value. In any case, at 28 days of storage, samples maintained the weak gel-like structure (0.686 loss tangent) that is acceptable for dysphagia management.

Development and Characteristics of Plant-Based Product Prototypes for Oro-Pharyngeal Dysphagia Diet

Patients with dysphagia diseases require food with acceptable textural characteristics. Additionally, due to the consumption of smaller portions, these patients receive insufficient amounts of nutrients. Therefore, this study aimed to develop plant-based purée as a meal for an oro-pharyngeal dysphagia (OD) diet, enriched with proteins, fiber and antioxidant vitamins. The suitability of three protein sources-soy protein isolate, whey protein isolate and brown pea protein concentrate-was tested through evaluation of their effect on the rheological properties of protein-enriched plant-based purées for OD diets. Based on the rheological analysis, whey protein was selected for incorporation into the new product formulations. Two prototypes of soups and two prototypes of desserts produced in this study demonstrated acceptable textural properties and high nutritional value.

Instrumental texture assessment of IDDSI texture levels for dysphagia management. Part 2: Texture modified foods

Texture-modified foods and thickened fluids play a major role in clinical treatment for individuals who suffer from swallowing difficulties (known as dysphagia). International Dysphagia Diet Standardization Initiative (IDDSI) developed a standardized terminology and description for texture-modified foods and thickened fluids to allow dysphagia patients to receive the correct consistency of food/drink. While the IDDSI framework provides a consistent texture description (Levels 0-7) and is widely accepted as an international standard, testing and assessment of IDDSI texture level are qualitative in nature and subjective in manner. These methods were proposed primarily for use by frontline carers, but are not most ideal for industrial purposes of quality control of such products. Therefore, the main aim of this work was to develop a quantitative instrumental method that best describes IDDSI levels as an objective framework. A set of test samples, including commercially available instant mashed potato, baby rice cereal, and cooked potato cubes of varying texture, were prepared. Two IDDSI measuring techniques, fork pressure test and spoon tilt test, were used to evaluate texture grades of these samples. Puncture and compression tests based on texture analyzer were used to assess cohesiveness, adhesiveness, firmness, and hardness for each food category (Levels 4-7). Thresholds of cohesiveness and adhesiveness, as well as bands of acceptable firmness and hardness for each food category were clearly identified and are proposed as objective complements to the IDDSI framework.

Instrumental and sensory techniques to characterize the texture of foods suitable for dysphagic people: A systematic review

The interest to characterize texture-modified foods (TMFs) intended for people with oropharyngeal dysphagia (OD) has grown significantly since 2011. Several instrumental and sensory techniques have been applied in the analysis of these foods. The objective of the present systematic review was to identify the most appropriate techniques, especially for the food industry and clinical setting. The search was carried out in three online databases according to the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA). Across the multiple trials reviewed, Texture Profile Analysis and the Uniaxial Compression Test were most used as the instrumental technique for solid foods, and the Back Extrusion Test for fluid and semisolid foods. All trials used descriptive analysis as the sensory technique. However, the experimental conditions of the trials lacked standardization. Consequently, the results of the trials were not comparable. To properly characterize the texture of TMFs intended for OD by each technique, an international consensus is needed to establish standardized experimental conditions. Methods based on these techniques should also be validated by collaborative studies to verify repeatability, replicability, and reproducibility.

A method for evaluating time-resolved rheological functionalities of fluid foods

We have developed an effective method for evaluating time-resolved rheological functionalities of swallowed foods using ultrasonic spinning rheometry (USR). USR can obtain variations over time in the rheological properties of fluids despite the fluids being in heterogeneous and non-equilibrium conditions. In addition, USR can evaluate time variations of shear-thinning property changing in a few seconds. Demonstrations were conducted with typical thickener solutions: starch, guar gum, and xanthan gum-based solutions, with alpha-amylase as a digestive enzyme. The flow curve of the starch-based solutions lowered with time, and a few minutes after addition of the amylase, the viscosity dropped to one-hundredth of the original value. In contrast, the guar gum and xanthan gum-based solutions maintained the original viscosities as generally known. Applying the power law fitting to series of these flow curves, the time variation of the shear thinning property is quantitatively characterized by the plots on typical K-n space, where K and n are parameters in the model, consistency index and power law exponent. The qualitative characteristics of the thickeners are successfully quantified in the K-n space, and this will be a practical tool for evaluating the time-resolved rheological properties of swallowed 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.

Role of Food Hydrocolloids as Antioxidants along with Modern Processing Techniques on the Surimi Protein Gel Textural Properties, Developments, Limitation and Future Perspectives

Texture is an important parameter in determining the quality characteristics and consumer acceptability of seafood and fish protein-based products. The addition of food-based additives as antioxidants (monosaccharides, oilgosaccharides, polysaccharides and protein hydrolysates) in surimi and other seafood products has become a promising trend at an industrial scale. Improvement in gelling, textural and structural attributes of surimi gel could be attained by inhibiting the oxidative changes, protein denaturation and aggregation with these additives along with new emerging processing techniques. Moreover, the intermolecular crosslinking of surimi gel can be improved with the addition of different food hydrocolloid-based antioxidants in combination with modern processing techniques. The high-pressure processing (HPP) technique with polysaccharides can develop surimi gel with better physicochemical, antioxidative, textural attributes and increase the gel matrix than conventional processing methods. The increase in protein oxidation, denaturation, decline in water holding capacity, gel strength and viscoelastic properties of surimi gel can be substantially improved by microwave (MW) processing. The MW, ultrasonication and ultraviolet (UV) treatments can significantly increase the textural properties (hardness, gumminess and cohesiveness) and improve the antioxidative properties of surimi gel produced by different additives. This study will review potential opportunities and primary areas of future exploration for high-quality surimi gel products. Moreover, it also focuses on the influence of different antioxidants as additives and some new production strategies, such as HPP, ultrasonication, UV and MW and ohmic processing. The effects of additives in combination with different modern processing technologies on surimi gel texture are also compared.

Kinetics of denaturation and renaturation processes of double-stranded helical polysaccharide, xanthan in aqueous sodium chloride

Circular dichroism (CD) and small-angle X-ray scattering (SAXS) measurements were made for three xanthan samples, a double helical polysaccharide, in 5 or 10 mM aqueous NaCl after rapid temperature change to investigate the kinetics of the conformational change between the ordered and disordered states. After the rapid heating, the CD signal mainly reflecting the carbonyl groups on the side chains quickly changed (<150 s) while the scattering intensity from SAXS around q (magnitude of the scattering vector) = 1 nm^-1 changed more gradually, reflecting the main-chain conformation. The difference between CD and SAXS implies us the intermediate conformation which can be regarded as a loose double helix. The SAXS profile in the rapid cooling process showed that the loose double helical structure was constructed within 150 s, but the CD signal slowly changed with around 2 days to recover the native tight double helix.

Food for the elderly based on sensory perception: A review

Background

The impairments of physiological functions caused by aging are common problems in the elderly, especially the impairments of sensory perception. Besides, close relationship between food sensory perception and nutritional status also suggests the importance of dietary management for the elderly population. The foods taking sensory perception into account are urgently needed by the elderly.

Scope and approach

This review analyzed sensory perception changes and their effects on food behaviors and nutritional status. Besides, sensory properties essential for aged-foods and acquisition methods, as well as current status of such foods were summarized.

Key findings and conclusions

Soft, smooth and moisty foods were more suitable for the elderly with chewing and swallowing dysfunction, which can be prepared by gelation, enzyme treatment, blade tenderization and other non-thermal technologies. Flavor enhancement/enrichment, irritant addition and packet sauces were recommended to compensate the impairment of chemical sensory. Molds, piping bag and 3D printing were suggested for refining appearance of pureed foods, and improving appetite of the elderly.

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Sensory perception changes of the elderly affect food behaviors and health.

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Soft, smooth, and moisty foods are more suitable for the elderly.

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Gelation and enzyme treatment are applied to modify the texture of aged food.

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Packet sauces may meet the heterogenetic flavor requirements of the elderly.

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Visually attractive food made by 3D printing can increase the appetite of elderly.

Muscle activity during oral processing of sticky-cohesive foods

We investigated muscle activity during oral processing of sticky model foods. Chewing Time extracted from the EMG data distinguished the most sticky and least sticky model foods from the others, but was not a good discriminator between the other models. Mean chew work declined by 25.4%, while the median frequency shift (which is related to muscle fatigue) increased by 54.9% during oral processing for all the model foods, with the effect being greatest for the stickiest foods. We conclude that the degree of stickiness is not a trigger for swallowing and changes in the other bolus properties, such as softness, may influence muscle activity to a level at which we can swallow.

Correlation of human perception in swallowing with extension rheological and tribological characteristics in comparison with shear rheology

Correlation was investigated between instrumental characteristics obtained by extension rheological or tribological measurements and human perception while swallowing using aqueous solutions of xanthan gum and locust bean gum. Extension viscosity and the friction coefficient were measured using a capillary breakup rheometer and a rotation tribometer, respectively, as in our previous study. Results were compared with shear viscosity to clarify novelty and advantage of these mechanical parameters. It was indicated that perceived cohesiveness correlated the highest with the maximum extension viscosity immediately after the onset of extensional flow, perceived spinnability correlated with extension viscosity in high Hencky strain region, and perceived sliminess correlated with the friction coefficient at the critical point between the boundary lubrication and the mixed lubrication. These correlations were discussed and tried to validate considering biomechanics of human swallowing and food-human interactions.

Predicting thickness perception of liquid food products from their non-Newtonian rheology

The "mouthfeel" of food products is a key factor in our perception of food quality and in our appreciation of food products. Extensive research has been performed on what determines mouthfeel, and how it can be linked to laboratory measurements and eventually predicted. This was mainly done on the basis of simple models that do not accurately take the rheology of the food products into account. Here, we show that the subjectively perceived "thickness" of liquid foods, or the force needed to make the sample flow or deform in the mouth, can be directly related to their non-Newtonian rheology. Measuring the shear-thinning rheology and modeling the squeeze flow between the tongue and the palate in the oral cavity allows to predict how a panel perceives soup "thickness". This is done for various liquid bouillons with viscosities ranging from that of water to low-viscous soups and for high-viscous xanthan gum solutions. Our findings show that our tongues, just like our eyes and ears, are logarithmic measuring instruments in agreement with the Weber-Fechner law that predicts a logarithmic relation between stimulus amplitude and perceived strength. Our results pave the way for more accurate prediction of mouthfeel characteristics of liquid food products.

Instrumental characteristics from extensional rheology and tribology of polysaccharide solutions

Instrumental characteristics from extensional rheology and tribology for aqueous xanthan gum (XG) and locust bean gum (LBG) solutions were studied in the presence or absence of simulated saliva. Extensional viscosity was calculated from the filament shrinkage behavior using a capillary breakup extensional rheometer, whereas the friction coefficient was measured using a set-up consisting of polydimethylsiloxane substrate and a glass ball bearing on a rotational rheometer. Increase in extensional viscosity was detected immediately after initiation of extensional flow, particularly XG, and also immediately before the filament rupture, particularly LBG. Extensional viscosity tended to decrease with increased addition of simulated saliva for XG, while to increase for LBG. In both cases, effect of cations in the saliva was greater than that of mucin. From the shape of the Stribeck curve (i.e., dependence of the friction coefficient on the entrainment speed) and comparison of the friction coefficient itself, lubricity of XG was greater than that of LBG. Simulated saliva added decreased the friction coefficient for each polysaccharide through functions of cations rather than mucin. Extensional viscosity and tribological measurements revealed mechanical properties of polysaccharide solutions which cannot be determined or quantified by shear viscosity alone.

3D Printing of Shiitake Mushroom Incorporated with Gums as Dysphagia Diet

With the speeding tendency of aging society, the population experienced dysphagia is increasing quickly. Desirable dysphagic diets should be safe, visually appealing and nutritious. 3D printing allows for creation of personalized nutritious foods with regular-like appearance. Shiitake mushroom, rich in protein and bioactive compounds, is suitable for elderly, but its hard texture was not friendly to the elderly with dysphagia. This study investigated the feasibility of production of dysphagic product using shiitake mushroom by 3D printing with various gums addition, including arabic gum (AG), xanthan gum (XG) and k-carrageenan gum (KG) at concentrations of 0.3%, 0.6% and 0.9% (w/w). Data suggested that XG and KG incorporation significantly increased inks’ mechanical strength by decreasing water mobility and promoting the formation of hydrogen bond, enabling 3D printed objects with great self-supporting capacity. The XG containing and KG-0.3% samples were categorized into level 5—minced and moist dysphagia diet within international dysphagia diet standardization initiative (IDDSI) framework. AG addition decreased mechanical strength and viscosity, hardness and self-supporting capacity of 3D printed constructions. AG-0.3% and AG-0.6% samples could not be classified as dysphagia diets based on IDDSI tests. This study provides useful information for dysphagia diet development with appealing appearance by 3D printing.

Food polysaccharides and roles of rheology and tribology in rational design of thickened liquids for oropharyngeal dysphagia: A review

In today's market environment, an aging society is recognized as one of the megatrends in the world. The demographic change in the world population age structure has driven a huge demand in healthcare products as well as services that include the technological innovation for the health and wellness of the elderly. Dysphagia or swallowing difficulty is a common problem in the elderly as many changes in swallowing function come with aging. The presence of a strong relationship between swallowing ability, nutritional status, and health outcomes in the elderly leads to the importance of dysphagia management in the population group. Modification of solid food and/or liquid is a mainstay of compensatory intervention for dysphagia patients. In this regard, texture-modified foods are generally provided to reduce risks associated with choking, while thickened liquids are recommended for mitigating risks associated with aspiration. In this review, we discuss thickened liquids and other issues including the importance of their rheological and tribological properties for oropharyngeal dysphagia management in the elderly. The review focuses on both commercial thickeners that are either based on modified starch or xanthan gum and other potential polysaccharide alternatives, which have been documented in the literature in order to help researchers develop or improve the characteristic properties of thickened liquids required for safe swallowing. Furthermore, some research gaps and future perspectives, particularly from the nutrition aspect related to the interaction between thickeners and other food ingredients, are suggested as such interaction may considerably control the rate of nutrient absorption and release within our body.

Effect of the rheological properties of the liquid carrier on the in vitro swallowing of solid oral dosage forms

Solid oral dosage forms (SODF) are the most popular oral drug delivery forms, but they can be difficult to swallow, especially for patients suffering from swallowing disorders. This study investigated the dynamics of different combinations of liquid carriers and SODF during the oral phase of swallowing using an in vitro model. The rheological properties of the carriers were characterized using shear and extensional rheometry, and their effect on bolus velocity, bolus shape, post-swallow residues, and SODF position within the bolus was evaluated. The latter has been identified as a novel and promising variable to discriminate between alternative formulations. When swallowed with water, capsules and tablets did not impact significantly the velocity of the bolus, but they lagged behind the liquid bolus, suggesting that low viscosity Newtonian fluids are not efficient carriers for SODF. Increasing the viscosity of the carrier at high shear rates improved the ability of the liquid to transport the SODF but also increased the amount of post-swallow residues. At equivalent shear viscosity, elastic and extensional properties of carriers influenced positively the position of the SODF in the bolus. Capsules and tablets were transported toward the front of these boluses, during the oral phase of swallowing, which is considered beneficial to avoid SODF sticking to the mucosa in the following stages of swallowing. Thin elastic liquids appear as an interesting option to promote safe swallowing of capsules and tablets. Clinical studies are, however, necessary to confirm this positive effect in healthy and dysphagic patients.

Exploring Tools for Designing Dysphagia-Friendly Foods: A Review

Dysphagia is a medical condition that affects normal swallowing. To prevent the risk of aspiration or choking, thickened fluids and texture-modified foods have been used for dysphagia management with the goal of slowing down the flow of liquids and protecting the airway. This article summarizes the available information about the rheological and textural parameters, the characterization of the most-used thickeners and the application of alternative texture modification technologies that are crucial to developing safe dishes for people who suffer from swallowing difficulties. Regarding rheological and textural measurements, fundamental and empirical methods are described.

Assessment of tomato-based thick fluid diet for patients with dysphagia using a simple and cheap test

Swallowing difficulty, also known as dysphagia, is a health condition that can be managed by different approaches, such as changing the viscosity of fluid foods with thickener agents. Tomato-based beverages such as "gazpacho" and "salmorejo" are common foods much appreciated by the populations that adopt a Mediterranean diet, mainly in Spain. These beverages usually present a low viscosity, challenging to include in diets for dysphagia patients. Thus, this work aimed at evaluating the flow properties of tomato-based beverages with or without the addition of thickener agents (based on maltodextrin or gum) using a simple and cheap method proposed by the International Dysphagia Diet Standardization Initiative (IDDSI) to verify the suitability of using those products in a diet of patients with dysphagia. The study also evaluated the differences in using BD-type syringes on the test. Results indicated that the type of thickener significantly (p < .05) affects the samples' flow properties, enhancing their rheological behavior. The type of syringe can also affect the results, as they present different Luer slip tips. The results revealed that tomato-based beverages may have their properties improved simply by using low amounts of thickener agents (1.2-3.0 g 200 ml^-1 ) and that the IDDSI test can be an alternative, cheap and straightforward method for evaluating these types of foods in hospital environments. Including tomato-based beverages in the diet of patients with dysphagia may present many benefits as these products have a rich nutritional composition (fiber) in addition to biocompounds such as lycopene and phenolic compounds.

[Laboratory study on bacteriological aspects of beverages and thickeners for dysphagia patients : Growth survey of Escherichia coli on thickeners and beverages]

BACKGROUND

Currently, there is little evidence-based guidance on bacteriological aspects of thickeners or beverages for dysphagia patients in Germany that can be recommended to prevent aspiration pneumonia. Therefore, the aim of this study was to evaluate the lowest cell amount of E. coli on M9 agar media with beverages and thickeners.

METHODOLOGY

In the laboratory experiment 1 · 10⁷ cells of E. coli were plated on a defined minimal medium (M9 agar plates) with different carbon sources and incubated at 37 °C for 2 days. The increase in cell number was determined using a photometer. Carbon sources were water, beer, orange juice, thickened beer, maltodextrin-xanthan gum-based thickeners, corn starch-based thickeners and potato starch-based thickeners.

RESULTS

The lowest E. coli cell amount was measured on water compared to beer, orange juice and all thickeners. A higher E. coli cell count was measured on maltodextrin-based thickeners than on potato starch-based and corn starch-based thickeners.

DISCUSSION

In the present laboratory experiment, no individual risk factors for the development of aspiration pneumonia in humans were considered; however, initial bacteriological evidence for dysphagia patients could be collected. Due to the high growth of E. coli on maltodextrin, yeast, fructose and glucose, these ingredients should be used with caution by dysphagia patients. Further research on thickeners and beverages is needed to make a comprehensive recommendation for action in this aspect.

Understanding the oral processing of solid foods: Insights from food structure

Understanding the relationship between the structure of solid foods and their oral processing is paramount for enhancing features such as texture and taste and for improving health-related factors such as management of body weight or dysphagia. This paper discusses the main aspects of the oral processing of solid foods across different categories: (1) oral physiology related to chewing, (2) in-mouth food transformation, (3) texture perception, and (4) taste perception, and emphasis is placed on unveiling the underlying mechanisms of how food structure influences the oral processing of solid foods; this is exemplified by comparing the chewing behaviors for a number of representative solid foods. It highlights that modification of the texture/taste of food based on food structure design opens up the possibility for the development of food products that can be applied in the management of health.

Influence of thickening agents on rheological properties and sensory attributes of dysphagic diet

Dysphagia is the difficulty during the progression of the bolus from the mouth to the stomach. Modifying the texture of the food is a fundamental factor for safe swallowing in patients with dysphagia since inadequate consistency can result in complications. To personalize and develop diets for dysphagia, understanding, and controlling the rheological and sensory properties of thickeners is useful. This review examines the different types of thickeners used to modify the texture of foods, as well as their influence on rheological properties and sensory attributes to efficiently manage the diet in dysphagia. The study discusses characteristics such as: hardness, viscosity, viscoelasticity, as well as sensory attributes related to rheology. The thickeners xanthan gum, methylcellulose, carboxymethylcellulose, guar gum, linseed, and chia, carboxymethylated curdlan, and konjac glucomannan were reviewed in this work. Sensory evaluations of different foods have already been carried out on some products such as: meats, carrots, soups, pates, and timbales with their modified textures. The sensory attributes measured among hydrocolloids are strongly correlated with rheological parameters. Dysphagic diets should have less hardness and adherence, but with adequate cohesiveness to facilitate chewing, swallowing to protect from aspiration and reduction of residues in the oropharynx. The use of a single type of thickener may not be ideal, their mixtures and synergistic effect can improve the viscous and elastic characteristics of foods, to obtain safe food to swallow and to improve the sensory interest of dysphagic patients. Personalized recommendations with follow-up on swallowing approaches, respecting patient's individuality, explaining thickening agents' differences would be pertinent.