Texture and texture assessment of thickened fluids and texture‐modified food for dysphagia management

Thickened fluids and texture‐modified foods are commonly used in the medical management of individuals who suffer from swallowing difficulty (known as dysphagia). However, how to reliably assess texture properties of such food systems is still a big challenge both to industry and to academic researchers. This article aims to identify key physical parameters that are important for objective assessment of such properties by reviewing the significance of rheological or textural properties of thickened fluids and texture‐modified foods for swallowing. Literature reviews have identified that dominating textural properties in relation to swallowing could be very different for thickened fluids and for texture‐modified foods. Important parameters of thickened fluids are generally related with the flow of the bolus in the pharyngeal stage, while important parameters of texture‐modified foods are generally related with the bolus preparation in the oral stage as well as the bolus flow in the pharyngeal stage. This review helps to identify key textural parameters of thickened fluids and texture‐modified foods in relation to eating and swallowing and to develop objective measuring techniques for quality control of thickened fluids and texture‐modified foods for dysphagia management.     

Rheological,tribological and sensory attributes of texture-modified foods for dysphagia patients and the elderly: A review

Texture-modified foods (TMFs) and thickened fluids have been used as a therapeutic strategy in the management of food intake in the elderly and people with dysphagia. Despite recent advances in describing rheological features of TMFs for dysphagia management, there is still paucity of research regarding the sensory attributes, therapeutic thickness levels and swallowing safety of these foods. Additionally, the relationship between mechanical and structural properties of TMFs throughout the oral processing is not yet fully understood. The present review discusses several properties of food boluses that are important during oral processing to allow for safe swallowing. Dynamic changes that occur during oral processing of TMFs will be reviewed. The use of hydrocolloids to improve the cohesiveness of TMFs and how this impacts the sensory properties of TMFs will be also discussed. Additionally, this review will suggest potential new research directions to improve textural and sensory properties of TMFs.     

Clinical applications of IDDSI framework for texture recommendation for dysphagia patients

Dysphagia is a highly prevalent eating and swallowing disorder among elderly people, impacting negatively on the health and well‐being of those afflicted. With increasing populations of elderly people, food industries are under growing pressure to produce appropriately texture‐modified food for safe consumption by these vulnerable populations. Recently published International Dysphagia Diet Standardisation Initiative (IDDSI) framework provides a new global guideline on texture modification and standardization for dysphagia patients. This work was designed to test the feasibility of IDDSI framework for clinical applications by assessing the correlation between swallowing capability of dysphagia patients and the IDDSI texture levels. Altogether 26 elderly subjects were recruited and assessed for their dysphagia grades using the Water Drinking Test. Subjects were provided with fluid samples constituted at different consistencies from a commercial product and swallowing performance (time of swallowing, number of swallows, and number of coughs) was monitored and recorded. Correlations among swallowing capability parameters were observed. Most importantly, results from this work clearly demonstrated that the severity of dysphagia by water‐based swallow tests correlates positively with the IDDSI fluid thickness aimed at reducing dysphagia symptoms in those patients, confirming the reliability and feasibility of IDDSI framework for clinical applications.

Practical applications

Swallowing disorder or dysphagia occurs commonly among many elderly people and imposes negative impacts on their health and well‐being. Medical professionals can diagnose eating and swallowing capability in a qualitative manner, but have difficulty in making diet recommendation because of the lack of texture guidance. This work confirmed the feasibility of IDDSI framework for clinical and bedside applications. The correlation between the capability grades of swallowing and IDDSI texture levels established in this work provides a useful measure for such applications.     

The impact of modification techniques on the rheological properties of dysphagia foods and liquids

Modifying food and the textures of food has been done for decades within the food science and technology field. More recently, modifying the texture of foods has been used to manage swallowing disabilities (dysphagia). Swallowing disabilities are often associated with dehydration and malnutrition, thus nutritional intervention has formed part of serving texture-modified diets. The question remains whether these modification techniques are viable for individuals with swallowing disabilities living in majority world countries. This study used two modification methods on a widely used specialized nutritious food (SNF) to determine whether it may be modified and used in dysphagia management. The techniques had to be ergonomic and economically appropriate for individuals with swallowing disabilities living in majority world countries. The International Dysphagia Diet Standardization Initiative's (IDDSI) standards were used to determine whether the texturally modified SNF is safe for swallowing. Rheological measurements were performed to determine apparent viscosity and structure recovery of each sample. The effects of two modification techniques, aeration and particle separation, on the rheological properties of the SNF were also measured and analyzed. It was determined that both milk and water could be used with this SNF to create a dysphagia diet, but only under certain conditions. The overall results indicated that heating the samples increased the apparent viscosity and exacerbated lumping. Room temperature samples had less lumps and could be classified to the desired levels of the IDDSI (Level 2 and Level 4). Using a whisk to aerate the samples reduced lumps significantly and using a sieve to separate particles of liquid samples eliminated lumps. This study provides new data on how texture modification techniques and the IDDSI framework could be adapted to individuals living in majority world countries. By using modification techniques that are ergonomic and economically viable and an SNF with longevity, this study could be useful in guiding future training of nursing staff and caregivers of individuals living in poverty or resource-constrained communities. This study also adds to the data on the rheological properties of dysphagia foods, although this study did not make use of commercial thickeners generally used in the modification of diets.     

Steady and dynamic rheological properties of thickened beverages used for dysphagia diets

Thickened beverages prepared with commercial food thickeners are widely used to promote safer and more successful swallowing in patients with dysphagia. In this study, the rheological properties of cold thickened beverages (bottled water, orange juice, apple juice, and whole milk) prepared with a commercially available gum-based food thickener (xanthan-guar gum mixture) marketed in Korea were investigated at 3 different thickener concentrations (2, 3, and 4%, w/w). Thickened beverages showed high shearthinning (n=0.12–0.21) behavior with Casson yield stress at all concentrations. Their apparent viscosity (η_a,50), consistency index (K), Casson yield stress (σ_oc), storage modulus (G′), and loss modulus (G″) increased with an increase in thickener concentration. Steady and dynamic rheological parameters also demonstrated greater differences in rheological behaviors between thickened beverages with different thickener concentrations. These results suggest that rheological properties of thickened beverages are strongly affected by thickener concentration and the type of beverage prepared.     

Evaluating chewing function: Expanding the dysphagia field using food oral processing and the IDDSI framework

The dysphagia field is still in relative infancy with a sophisticated knowledge base amassed since the early 1980's. The desire to identify aspiration and prevent life threatening pneumonia has resulted in a focus on the complexities of swallowing liquids. However, humans also ingest saliva, food, and oral medications, with the potential for these substances to incompletely clear the pharynx, be aspirated or block the airway. Safe swallowing of solid food in particular requires adequate chewing function, good oral control, and sufficient higher cortical function. Although screening and assessment for liquid swallowing safety is well established, the same cannot be said for the evaluation of safety to chew and swallow different food textures. While research into liquid swallowing physiology and its clinical application has largely come from the medical and allied health fields, our knowledge of chewing function for food textures comes from food texture research and food sensory science arenas. There is an exciting opportunity to bring the medical and food texture science fields together to expand our knowledge base on human chewing function, with clinical application to people with dysphagia. The development of the IDDSI Framework as an international standardized way of describing and labelling food texture and drink thickness allows the field to move toward management of texture modified food and thick liquids in a coordinated fashion, speaking the same language. This commentary will describe what we know of chewing function and how it is assessed clinically, proposing methods of assessment that utilize the IDDSI Framework.     

Cluster classification of dysphagia-oriented products considering flow,thixotropy and oscillatory testing

The present paper proposes an objective classification of commercial thickened food widely used in patients with dysphagia. A total of 34 commercial enteral nutrition products were analyzed (beverages, main courses and desserts) corresponding to 6 different commercial brands. All these products contain different hydrocolloids (i.e., starch, xanthan gum, carrageenans, etc.) as thickeners, in order to get the desired texture.     

Using Sensory Properties of Food to Trigger Swallowing: A Review

The effect of food consistency on swallowing function has been widely studied, and it is well recognized that by delaying the flow of the food bolus, thickened liquids can help in the management of swallowing dysfunction. However, fewer studies have been carried out on the impact of food sensory properties and related liking on swallowing function. This paper reviews the role of taste, olfaction, and trigeminal perceptions on swallowing function and highlights the need for a deeper investigation of this aspect of patient diet modification.     

吞咽障碍者增稠流体食品流变学研究进展

吞咽障碍已经成为当今社会面临的一项严重的健康问题。增稠流体能够有效降低吞咽障碍病人吸入性肺炎 的风险,在吞咽障碍病人的治疗和护理过程中应用广泛。增稠流体的生产和使用与其流变特性密切相关,因而流变 学成为了吞咽障碍食品领域一个十分重要的研究方向。本文根据近期国际上在该方向的最新研究成果,详细介绍了 利用流变特性评判增稠流体黏稠程度的原则以及测量方法,深入分析了各种因素对于增稠流体流变特性的影响,并 对影像学造影剂、增稠流体食品流变特性的差异和匹配、口腔对于流变特性变化的分辨能力等问题进行了探讨。目 的是为我国增稠流体食品研究提供理论指导和技术参考。     

增稠组件在老年吞咽功能障碍患者中的使用

随着我国特殊消费者人群数量的不断增加,市场对增稠组件类产品的需求也在迅速增长。如何对这类产品进行科学有效的规范和管理,引导企业研究开发出满足特殊人群特定营养需求的个性化产品,不仅是生产企业和消费者十分关注的问题,也是监管部门十分紧迫的任务。本文阐述了老年吞咽功能障碍的流行病学、吞咽困难评估方法、增稠组件类产品在老年吞咽功能障碍患者中的使用、增稠流体黏稠程度影响因素、食物质构等级的分类标准和评价方法,提出生产企业依据食物的质构特性,以及不同质构特性产品与不同吞咽困难严重程度患者之间的对应关系,研究设计符合或匹配于目标人群饮食能力的产品,有望成为增稠组件类产品未来的研究方向。     

老年饮食障碍与老年食品:食品工业的挑战与机遇

老龄化是当今社会发展的一大趋势,也是人类发展史上前所未有的挑战。老年人随着生理功能的减弱,出现了饮食功能障碍,尤其是咀嚼和吞咽能力受到了很大的影响。不当的饮食会引起呛食,甚至引发吸入性肺炎,严重的还会导致生命危险。因此,如何给老年人提供既营养可口又安全可靠的食品是当今各主要经济发达国家和包括中国在内的一些新兴经济体所要面临的一个重大挑战和民生问题,也是食品工业需要急迫解决的重大课题。本文通过对老年人饮食机理的分析,揭示老年人安全饮食的主要控制机理以及开发老年食品的一些关键因素。同时详细介绍了不同国家饮食障碍者的膳食标准,以给我国养老行业护理人员提供相关的指导,也为我国食品工业开发老年产品提供技术支持。     

Gravity flow test comparisons for mildly thick consistency

Simple measurement tools that provide objective information about the consistency of thickened liquids have received increasing attention given possible application to clinical practice for dysphagia. The International Dysphagia Diet Standardization Initiative (IDDSI) advocates the use of the IDDSI Flow Test for measuring thickness and verifying a prescribed level of consistency. This study compares gravity flow test measurements taken with two 10-ml syringes of starch and gum-thickened samples prepared to a mildly thick consistency using product label information. One of the 10-ml syringes met IDDSI specification and the other 10-ml syringe did not. Thickened samples also were measured using the line spread apparatus. The results showed that two syringes yielded significantly different gravity flow test measurements, often resulting in changes to the classification level of thickness. There was no effect of thickening agent. Line spread measurements did not vary from one another. Study findings indicate the importance of continued testing with the IDDSI Flow Test and education/awareness about the use of the IDDSI reference syringe. An essential aspect about the use of thickened liquids in dysphagia management is that beverage preparations represent their prescribed level of modification. The findings of this study indicate the importance of following syringe specifications when conducting gravity flow testing using the IDDSI methodology. The implication is that the wrong 10-ml syringe could result in errant clinical decisions in determining the accuracy of texture modifications, resulting in care providers who are more likely to over or under thicken modifications to achieve a targeted level of thickness.     

Older US adults like sweetened colas,but not other chemesthetic beverages

Many older adults suffer from difficulty swallowing thin beverages like water or coffee. To improve swallowing safety, beverages are typically thickened. This creates a new problem: the thickened beverages can be disgusting. New research suggests chemesthesis, particularly spiciness, carbonation, or intense sourness, could improve swallowing without the need for thickeners. Yet, whether such beverages would be liked by older adults is unknown. We thus conducted this experiment to establish older adults' sensory perception and liking/disliking of commercially available chemesthetic beverages. We recruited participants to rate sweetness, sourness, fizziness, stinging, and liking/disliking of unsweetened carbonated waters (1 plain, 5 flavored), sour orange juice, spicy ginger beer, and colas (sugar or aspartame-sweetened). Initial tests (N = 30 older adults) indicated sour orange juice, spicy ginger beer, and two of the flavored waters were not well-liked, so other beverages were selected for a second test (N = 94, 30 younger adults, 64 older adults). Sweetened, carbonated colas were the best-liked of the beverages. The unsweetened, flavored carbonated waters were in general not liked. Regarding comparisons of sensory ratings between older and younger adults, only sweetness differed between age groups. In particular, intensity ratings for the chemesthetic aspects of the beverages (stinging/burning/spiciness, fizziness) and the sour taste did not differ by age. As the chemesthetic properties are the most likely reason the beverages could aid in swallowing safety, observing no suppression of these sensations in older adults is encouraging for the potential of these products as a treatment option.     

Next target for food hydrocolloid studies: Texture design of foods using hydrocolloid technology

Texture is important in terms of both food palatability and the safety of eating. Recently, the importance of texture has been emphasized for the development of nursing-care foods, including dysphagia foods, in recent aged society, where the number of patients with mastication and swallowing difficulties is increasing. Texture design of these food products is now one of the most important tasks in the food industry in Japan. Texture of these food products should be optimized by modulating viscoelasticity using hydrocolloids so that they can easily transform to ‘ready-to-swallow’ bolus during oral processing. This article reviews the importance of texture as an essential attribute of foods and also the usefulness of hydrocolloids as an ingredient to modify and control food texture. The article also covers recent trials by the author’s research team on bolus rheology and in vivo acoustic analysis. The trials are to find some objective parameters describing the mastication and swallowing eases as an alternative to conventional bulk rheology and subjective sensory analysis.     

Improving the swallowability of representative foods for the elderly and people with dysphagia

It is necessary to find food additives that can reduce the food friction coefficient, in order to make it easier for the elderly and people with dysphagia to swallow. The sesame paste and rice paste are two typical foods eaten by the elderly. In this research, the tribological and rheological properties of 2 paste with 12 hydrocolloids were investigated. The results showed that three hydrocolloids (xanthan gum, gellan gum, and pectin) could reduce the friction coefficients of sesame paste and rice paste within a certain range of oral friction velocity. The friction coefficients of two kinds of original paste are in the order of 10⁻¹. The addition of three hydrocolloids can reduce them to about 10⁻², effectively improving lubrication. After adding hydrocolloids, the particles cross-link to form a network structure, which improves the viscosity and lubrication of food to a certain extent. This has potential application value for designing food that is more conducive to swallowing.     

透明质酸多糖增稠适用于吞咽困难的肠内营养制剂及其流变学性质

胶体增稠的食物流体黏度是吞咽困难饮食护理中的关键参数。这类流体需有较高的黏度和较强的非牛顿流体行为。本研究采用流变学方法表征了透明质酸多糖对含豌豆蛋白和大豆油的营养制剂的增稠效果,研究了增稠营养制剂的流动性质、黏弹性和黏度的剪切时间依赖性。结果表明：未经增稠的营养制剂是表观黏度很低（仅约为0.010 Pa·s）的牛顿流体,不能满足安全吞咽的要求;而透明质酸具有良好的增稠效果,当透明质酸质量分数为0.5%时,营养制剂的初始黏度可达8 Pa·s,增稠后营养制剂具有方便可调节的表观黏度、剪切变稀性质以及良好的黏弹性,流变学性质能满足安全吞咽的要求。     

Texture Modification Technologies and Their Opportunities for the Production of Dysphagia Foods: A Review

Dysphagia or swallowing difficulty is a common morbidity experienced by those who have suffered a stroke or those undergone such treatments as head and neck surgeries. Dysphagic patients require special foods that are easier to swallow. Various technologies, including high‐pressure processing, high‐hydrodynamic pressure processing, pulsed electric field treatment, plasma processing, ultrasound‐assisted processing, and irradiation have been applied to modify food texture to make it more suitable for such patients. This review surveys the applications of these technologies for food texture modification of products made of meat, rice, starch, and carbohydrates, as well as fruits and vegetables. The review also attempts to categorize, via the use of such key characteristics as hardness and viscosity, texture‐modified foods into various dysphagia diet levels. Current and future trends of dysphagia food production, including the use of three‐dimensional food printing to reduce the design and fabrication time, to enhance the sensory characteristics, as well as to create visually attractive foods, are also mentioned.