Comparison of the rheological properties of ready-to-serve and powdered instant food-thickened beverages at different temperatures for dysphagic patients

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.

Designing of texture modified fruit juices using food hydrocolloids: Storage influence on viscosity

Elderly individuals require special dietary considerations due to various physiological dysfunctions (such as dysphagia, constipation, etc.) and specific nutritional needs. Dysphagia, the difficulty associated with swallowing can lead to some challenges in containing and transitioning of food or liquids within the mouth, increasing the risk of aspiration pneumonia. Thickening fluid is an effective method for alleviating swallowing difficulties. It works by slowing down the flow of liquids during swallowing, thus reducing the risk of aspiration into the airway. The purpose of this research is to develop texture-modified (TM) fruit juices to cater to the needs of elderly individuals with impaired swallowing abilities. To achieve this goal, we created TM fruit juices thickened with hydrocolloids, specifically guar gum (GG), xanthan gum (XG), and starch (S), at different concentrations. The thickened liquids, classified at three National Dysphagia Diet levels, were stored at 4 °C for three months. Physicochemical analyzes of the fruit juices were performed before and after storage. The sensory differences and flow behaviors of orange juice samples containing ascending concentrations of all studied thickeners were investigated at the end of the three-month storage. The results indicated significant changes in the physicochemical properties of the samples, depending in the type of fruit, the hydrocolloid used, and the storage period. Sensory evaluation revealed that orange juices containing starch were more preferred compared to other samples. Therefore, using orange juice thickened with easily swallowed, and less viscous starch will be a safer option for the elderly and individuals with swallowing difficulties.

Proposal for a Standard Protocol to Assess the Rheological Behavior of Thickening Products for Oropharyngeal Dysphagia

Increasing shear viscosity (ShV) in thickening products (TP) is a valid therapeutic strategy for oropharyngeal dysphagia (OD). However, salivary amylase in the oral phase and shear rate in the pharyngeal phase of swallowing can change the viscosity of TPs when swallowed. This study aims to design and validate a rheological protocol to reproduce the oral and pharyngeal factors that affect the therapeutic effect of TPs and report the viscosity measurements in a standardized scientific and precise manner. We measured (a) the variability of the ShV measurements across several laboratories; (b) the in vitro and ex vivo properties of TPs and (c) the impact of the X-ray contrast Omnipaque, temperature and resting time on the rheological properties of TPs. A common protocol was applied in four international laboratories to assess five ShV values (100, 200, 400, 800 and 1600 mPa·s) for the xanthan-gum TP Tsururinko Quickly (TQ). The protocol included the dose (g/100 mL water), stirring procedure and standing time before measurement. Each value was characterized at the shear rate of 50 and 300 s^-1 pre- and post-oral incubation in eight volunteers. The effect of temperature, standing time and Omnipaque was assessed. The main results of the study were: (a) The mean intra-laboratory variability on the ShV at all levels was very low: 0.85%. The mean inter-laboratory variability was higher: 9.3%; (b) The shear thinning of TQ at 300 s^-1 was 75-80%. Increasing the temperature or standing time did not affect the ShV, and oral amylase caused a small decrease; (c) Omnipaque slightly decreased the dose of TP and hardly affected the amylase resistance or shear thinning. This study showed that different laboratories can obtain very accurate and similar ShV measurements using this protocol which uses scientific, universal SI units (mPa·s). Our protocol accurately reproduces oral and pharyngeal factors affecting the therapeutic effect of TPs. The addition of X-ray contrast did not produce significant changes.

The Protein-Rich Powdered Beverages Stabilized with Flax Seeds Gum—Antioxidant and Antiproliferative Properties of the Potentially Bioaccessible Fraction

The functional beverages market is one of the fastest-growing sectors of functional food production. An innovative recipe for powdered fruit and vegetable drinks fortified with lentil proteins (AGF) and stabilized with flax seed gums (FSG) was developed. The study focused on the analysis of potentially bioaccessible fractions from the produced beverages in terms of their antioxidant, antiproliferative activities and physicochemical properties. The contents of bioactive components were tailored by the incorporation of lyophilized fruits and vegetables, the FSG and the AGF. Digestion in vitro effectively released phenolics from all matrices. The highest contents of potentially bioavailable polyphenols were recorded for the AGF based beverages enriched with 5% of FSG and green-leafy vegetables (58 mg/100 mL) and those with lyophilized fruit (54 mg/100 mL). The reducing power of the beverages was mainly affected by the presence of the AGF, while the FSG and lyophilized fruit improved the chelating power. The digests applied in the concentrations mimicking physiological concentrations showed antiproliferative properties against gastric and colon adenocarcinoma—they seemed to be tailored by bioactive peptides and phenolics, respectively. The addition of the FSG improved the stability of the beverages increasing the time required for a reduction of 20% of the initial optical density by 16- and 28-times in the beverages without additives or enriched with vegetables. Both, the AGF and FSG stabilize the beverages after rehydration and are sources of bioaccessible antioxidant and anticancer components, which create their functionality.

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.

Evaluation of thickened liquid viscoelasticity for a swallowing process using an inclined flow channel instrument

An inclined flow channel instrument that can be developed to be a structurally simple and easy-to-use rheometer was applied to control the thickness, specifically the viscosity and elasticity, of liquids thickened to support swallowing in nursing-care practice. Aqueous solutions containing salt or acid, which might be used as ingredients in drinks, were thickened with a commercial thickener. The thickener efficacy decreased because of the salt or acid in liquid phase. Analysis of the flows in the instrument by experimentation yielded a dimensionless relation representing changes of the Deborah number in the flow process, as indicated by the relative flow length, considering the shear rate in oral processing. One unique methodology to evaluate the viscoelasticities of thickened liquids during the swallowing process was presented utilizing the measurements such as elapsed time and velocity in the instrument.

Relationship between Syringe Flow Measurements and Viscosity of Nectar-Thick Beverages for Dysphagia Management

Commercial cold beverages thickened with a xanthan gum (XG)-based food thickener were examined at different thickness levels by using the simple, cost-effective syringe flow test (SFT) developed by the International Dysphagia Diet Standardization Initiative (IDDSI). We prepared cold thickened beverage (CTB) samples with different thickener concentrations and measured them by extrapolating the viscosity range (51–350 mPa·s) for nectar-like consistency. CTBs were also measured via the line-spread test (LST), and the flow distance value (cm) by LST and the volume remaining (mL) in the syringe by SFT was correlated with the apparent viscosity (η_a,50). Plots comparing η_a,50 with SFT or LST values showed good exponential relationships between the measurements. The SFT showed a better relationship (R² = 0.928) than LST (R² = 0.825), indicating that the former can predict the viscosity better in the range for nectar-like consistency. In particular, the SFT showed a significant difference (R² = 0.964) compared to the LST (R² = 0.709) for thickened protein-based beverages. These results suggest that the SFT using the IDDSI methodology is a more suitable instrument than the LST for accurately evaluating the viscosity of XG-based CTBs with nectar-like consistency.

How Accurate Are the Consistency Labels Used in Hong Kong? An Objective Study of the Consistency of Thickened Liquids Using International Dysphagia Diet Standardisation Initiative and Consistometric Measurements

OBJECTIVES

The present study objectively examined the consistency (thickness) of labels that are used in Hong Kong for the population with dysphagia using an International Dysphagia Diet Standardisation Initiative (IDDSI) flow test and Bostwick consistometric measurements.

METHODS

Liquids were prepared by thickening water to achieve 4 consistency labels (slightly thick, mildly thick, medium thick, and extra thick) according to manufacturer's instructions, employing 2 types of thickening products that are used in Hong Kong, i.e., starch based and gum based. For each consistency label prepared using each thickening product, the IDDSI flow test and consistometric measurements were obtained and compared.

RESULTS

The results showed that the actual thickness of liquids was highly dependent on the type of thickener (starch based vs. gum based) used. Thickened liquids prepared using the starch-based thickener were generally thinner than the actual value at a lower concentration.

CONCLUSION

Though prepared strictly following the manufacturer's instructions, the thickened liquids fail to faithfully correlate with the standardized norms established according to the IDDSI framework and the objective consistometric measurement using a Bostwick consistometer. Therefore, caution must be exercised when administering a thickened diet following the manufacturer's instructions for patients with dysphagia.

Texture-Modified Food for Dysphagic Patients: A Comprehensive Review

Food texture is a major food quality parameter. The physicochemical properties of food changes when processed in households or industries, resulting in modified textures. A better understanding of these properties is important for the sensory and textural characteristics of foods that target consumers of all ages, from children to the elderly, especially when food product development is considered for dysphagia. Texture modifications in foods suitable for dysphagic patients will grow as the numbers of elderly citizens increase. Dysphagia management should ensure that texture-modified (TM) food is nutritious and easy to swallow. This review addresses how texture and rheology can be assessed in the food industry by placing particular emphasis on dysphagia. It also discusses how the structure of TM food depends not only on food ingredients, such as hydrocolloids, emulsifiers, and thickening and gelling agents, but also on the applied processing methods, including microencapsulation, microgels as delivery systems, and 3D printing. In addition, we address how to modify texture for individuals with dysphagia in all age groups, and highlight different strategies to develop appropriate food products for dysphagic patients.

Effect of commercially available thickening agents on ready-to-feed infant formulas

Because of the importance of providing the appropriate fluid consistency for effective management of swallowing problems (dysphagia) in infants, this project sought to determine the effect of three commercially available thickening agents on the resulting thickened consistencies of commonly prescribed, ready-to-feed infant formulas. Nine ready-to-feed infant formulas were thickened with three different thickening agents to nectar and honey consistencies following manufacturer's instructions and their resulting thickness was measured via line spread test (LST). The nine formulas with nothing added to them (thin liquids) and the 27 target-nectar and 27 target-honey samples together created 63 unique samples for comparison. A series of one-way analysis of variance analyses were conducted to determine if the resulting thickness (as measured by LST values) for target categories of nectar and honey consistencies was significantly influenced by the type of thickening agent used. The achieved thickness of the formula samples as measured by LST values was statistically significantly different for the three different types of thickening agents used to achieve a target nectar consistency, F (2, 24) = 15.55, p < .001, η p 2 = .709. Additionally, the achieved thickness of the formula samples was statistically significantly different for the three different types of thickening agents used to achieve a target honey consistency, F (2, 24) = 16.18, p < .001, η p 2 = .709. The results of this study reveal that the choice of thickening agent impacts the resulting thickness of ready-to-feed infant formula.

Effect of Thermal Processing on Flow Properties and Stability of Thickened Fluid Matrices Formulated by Tapioca Starch, Hydroxyl Distarch Phosphate (E-1442), and Xanthan Gum Associating Dysphagia-Friendly Potential

The flow behavior of the administrated fluid matrices demands careful assessments for stability when consumed by individuals with dysphagia. In the present study, we incorporated tapioca starch (TS), hydroxypropyl distarch phosphate (HDP), and xanthan gum (XG) as thickeners into different nectars (300 ± 20 mPa.s) undergoing thermal processing and evaluated their stability. The thickened nectars presented better water holding and oil binding capacities at 25 °C than 4 °C, and the nectars with TS provided the best results for both capacities as well as the highest solubility index and swelling power (p < 0.05). All prepared nectars appeared to be shear-thinning fluids with yield stress closely fitting the power law and Casson models. XG-containing nectars presented a higher yield stress and consistency index. Matrices thickened by HDP exhibited a higher viscoelastic property compared to those thickened by TS during thermal processing. TS nectars presented viscous behavior, whereas HDP and XG nectars presented elastic behavior at 80 °C processing. The 3 min thermal processing HDP nectars remained stable and met dysphagia-friendly requirements under 4 °C storage for 28 days, regardless of the type of fluid base (distilled water, sport drink, or orange juice). The employed thickeners present adequate physicochemical properties to be potentially utilized for producing dysphagia-friendly formulations.

Effect of mixing method on resulting thickness of infant formula

Previous research shows that factors such as time, temperature, nutritional make-up of a liquid, and type of thickening agent can significantly alter the resulting thickness of liquids. This study sought to determine the effect of three distinct mixing methods on the resulting thickness of ready to feed infant formulas mixed to Mildly and Moderately Thick (International Dysphagia Diet Standardization Initiative [IDDSI] Levels 2 and 3) with three different thickening agents. Eight commercially available infant formulas were mixed with three different thickening agents by three different mixing methods. The IDDSI Syringe Flow Test was used to categorize the thickened formulas. Chi square analyses were completed to determine the impact of mixing method on the thickened formulas. The majority (94%) of thickened formula combinations prepared to a target Mildly Thick consistency produced thickened formula that was thinner or thicker than the target. In contrast, the majority (76%) of thickened formula combinations prepared to a target Moderately Thick (IDDSI Level 3) consistency produced thickened formula that was equivalent to the target consistency. A statistically significant relationship was found between mixing methods and resulting IDDSI category for samples mixed to a target of Moderately Thick. The thickening agent and method of mixing must be considered carefully when preparing infant formulas to Mildly and Moderately Thick target IDDSI categories. Based on results of this study, it is recommended that providers utilize a clinical testing method, such as the IDDSI Syringe Flow Test, when attempting to create a Mildly Thick formula consistency.

Standard Recipes for the Preparation of Thickened Barium Liquids Used in the Diagnosis of Dysphagia

Barium sulfate is commonly used to prepare contrast media for videofluorograpy. The flow characteristics of thickened liquids formulated for oropharyngeal imaging are known to be greatly affected by the addition of barium. In this study, thickened barium liquids were prepared by mixing a commercial xanthan gum (XG)-based thickener (Visco-up^®) at different concentrations (0.1%-3.0%) with barium powder (Baritop HD^®), and differences in the viscosity between thickened non-barium and thickened barium liquids were investigated. In addition, the thickness levels of thickened barium liquids, which are based on the National Dysphagia Diet (NDD) and International Dysphagia Diet Standardization Initiative (IDDSI) guidelines, were classified by measuring the viscosity (NDD) and gravity flow through a syringe (IDDSI) with 0.1%-3.0% thickener concentrations. The apparent viscosity (η_a,50) values of thickened barium liquids were much higher than those of thickened non-barium liquids, indicating that the addition of barium to the XG-based thickener resulted in further thickening. Standard recipes for preparing thickened barium liquids with desirable thickness levels were also established, showing the different thickener concentrations corresponding to the different NDD and IDDSI levels.

Incremental Adjustments to Amount of Thickening Agent in Beverages: Implications for Clinical Practitioners Who Oversee Nutrition Care Involving Thickened Liquids

This study examined the changes in viscosity in response to small alterations in the amount of a thickening agent mixed with three commonly thickened beverages. A total of 11 incremental adjustments in the amount of a starch-based thickening agent (5.0 g to 7.0 g) were made. The results showed that the incremental increases resulted in systematic changes to the liquid thickness, reflecting modifications that ranged from a nectar (mildly thick) to a honey-like (moderately thick) level of consistency. The findings emphasize the importance of the proper preparation of thickened beverages, highlighting the need for standards in training practices and the use of simple measurement tools for assuring the prescribed levels of consistency.

Comparison of two methods to categorize thickened liquids for dysphagia management in a clinical care setting context: The Bostwick consistometer and the IDDSI Flow Test. Are we talking about the same concept?

The Bostwick consistometer and the International Dysphagia Diet Standardization Initiative (IDDSI) Flow Test are both proposed methods to measure and categorize thickened liquids for dysphagia management. The objectives were to: (a) compare the Bostwick consistometer reference values used in clinical settings and the IDDSI reference values of thickened liquids suggested for nutrition care plans in the management of dysphagia when measuring commercially available preprepared thickened liquids; (b) explore the relationship between the two methods; (c) assess the interchangeability; (d) document the intra-rater reliability. Preprepared thickened liquids (n = 32) were measured twice with the Bostwick consistometer and 3 times with the IDDSI Flow Test, using a rigorous methodology. A registered dietitian nutritionist and a registered nutrition and dietetic technician performed the measurements. The Pearson's correlation coefficient was calculated to explore the relationship between the two methods. Using a linear regression equation, back-calculations of the IDDSI Flow Test values were done, based on the experimental Bostwick results. Interchangeability was assessed by documenting the level of agreement between the results with a Bland and Altman graphical analysis. Intraclass correlation coefficients calculation and a Bland and Altman graphical analysis were performed to assess reliability. The strong correlation (r = -.93, p < .001) between the IDDSI Flow Test and the Bostwick consistometer measurements suggests that they measure flow rate in a similar manner, but not exactly the same, as confirmed with the Bland and Altman graphical analysis. Thus, they produced results that are not interchangeable. However, both tests show excellent intra-rater reliability (ICC ≥ 0.99) when using a rigorous methodology. PRACTICAL APPLICATIONS: Thickened liquids are used to manage oropharyngeal dysphagia. Clinicians need to provide quality assurance/quality control (QA/QC) support in the selection or production of thickened liquids as well as staff training or patient education regarding these products. Methods and classification have been proposed to measure and categorize thickened liquids for dysphagia management, such as the line spread test, the Bostwick consistometer method, and the IDDSI Flow Test. Although empirical, these methods are more accessible to clinicians than viscometer or rheometer assessments. Clinicians need to understand the limitations of these techniques as neither appear to capture the full extent of consistency for potential beverages available on the market or produced in-house. In this article, we compare the Bostwick consistometer and the IDDSI Flow Test methods and classifications and propose a standard operating procedure in order to maximize the quality of results. We point out the large variations in consistency levels of commercial preprepared thickened liquids in light of the absence of evidence of clinical outcomes associated with either proposed methods or consistency classifications.

Comparative study of IDDSI flow test and line-spread test of thickened water prepared with different dysphagia thickeners

The flow behaviors of thickened water samples prepared with six commercial instant thickeners (A-F) were investigated at different thickness levels using the inexpensive, simple, and visual clinical tools, such as a line-spread test (LST) and a syringe flow test developed by the International Dysphagia Diet Standardization Initiative (IDDSI). Both the flow distance value measured by the LST and the volume remaining in syringe by IDDSI flow test were compared with the apparent viscosity (η_a,50 ) values measured with a sophisticated computer-controlled rheometer. The η_a,50 values of thickened water samples increased as thickener concentration increased, whereas the flow distance (cm; LST) or remaining volume (ml; IDDSI flow test) were decreased. Plots comparing η_a,50 values to LST flow distances and IDDSI volumes revealed exponential relationships (R²  = 0.926 for the LST and R²  = 0.898 for IDDSI test) between the two measurements. Such lower determination coefficient (R² ) values (0.898) by IDDSI flow test seems to be due to the stickiness characteristics of starch component in starch-based thickeners (E and F), indicating that the syringe flow test is not suitable for starch-based thickeners. However, the thickened water samples prepared only with xanthan gum (XG)-based thickeners (A-D) showed strong relationships (R²  = 0.972 for the LST and R²  = 0.939 for IDDSI test). These results suggest that the LST is a more reliable method than the IDDSI test for evaluating the correct and desirable viscosity for the dysphagia diet, and that the IDDSI test provides a means to predict the rheometer-measured viscosity of water thickened with only XG-based thickeners. PRACTICAL APPLICATIONS: The effective management of dysphagia requires the thickened fluids prepared with the correct and desirable viscosity. In terms of clinical practice, it is very important to observe the comparison of LST with IDDSI flow test to determine a suitable method for estimating the correct viscosity of thickened fluids. Our results showed good relationships between the rheometer-measured viscosity and flow values measured by the LST and IDDSI test methods for the thickened water samples prepared with different foods thickeners. The IDDSI flow test may be useful as a clinical training tool for preparing thickened fluids with only XG-based thickeners to a target level of viscosity. These results presented in this study will provide clinicians, caregivers, and patients with valuable information for IDDSI flow test as an inexpensive and simple method for measuring the correct viscosity.

Use of Textured Thin Liquids in Patients With Dysphagia

PURPOSE

The goals of this article are to explore the use of textured thin liquids for dysphagic patients who require thickened liquids and to illustrate their impact on hydration and patient satisfaction.

METHOD

A retrospective evaluation of textured thin liquids was completed using patient data looking at laboratory values relevant to the detection of dehydration (blood urea nitrogen, creatinine, sodium) and patient satisfaction (using a clinician-generated questionnaire) on different modified liquid textures. In addition, the viscosity for all liquids was tested using a rheometer.

RESULTS

Measurements show that the viscosity of the textured thin liquids examined in this pilot study are significantly lower than the viscosity of nectar-thick liquids and fall within the "thin" category as defined by the National Dysphagia Diet guidelines. Patients on honey- and nectar-thick liquids had laboratory values signifying dehydration, whereas those receiving the textured thin liquid consistency were within the normal range for all laboratory values. Importantly, when consuming textured thin liquids, patients reported significant improvement in their satisfaction related to their thirst.

CONCLUSION

The results of this pilot study highlight the consequences of common thickened liquid dietary recommendations and of the potentially beneficial clinical application of textured thin liquids for patients with dysphagia as well as the need for future prospective research.

Visualizing the Consistency of Thickened Liquids With Simple Tools: Implications for Clinical Practice

PURPOSE

Accurate texture modifications to thin liquids are a critical aspect of patients' nutritional health and well-being. This study explored the use of 3 tools (2 distance- and 1 time-measuring devices) to characterize texture-modified liquids. The objectives were to use the tools to measure modified liquids, to determine if measurements differentiated nectar and honey levels of modification, and to compare measurements with other published reports.

METHOD

We measured the flow distance of 33 prethickened water samples in centimeters (cm) using a line spread apparatus and a Bostwick Consistometer (Christison Particle Technologies). We selected a Zahn viscosity cup to measure the stream time of each prethickened liquid in seconds.

RESULTS

The 2 distance-measuring devices (line spread and Bostwick Consistometer) showed that thinner (nectar-thick) modifications spread or flowed a farther distance in comparison to thicker (honey-like) modifications. Testing with the line spread indicated that an average spread distance of 4.5 cm differentiated nectar-thick and honey-like consistencies. A flow distance of greater than 15 cm differentiated nectar from honey consistency measured with a Bostwick Consistometer. We were not successful in using the Zahn viscosity cup to determine the stream time of modified liquids.

CONCLUSIONS

Two of the tools provided objective information about levels of liquid modification, which has implications for day-to-day preparation. Measurement tools that are accurate and easy to use have the potential to provide quick and dependable feedback to verify a prescribed level of liquid modification. Further efforts are needed to standardize the application of simple measurement tools in the management of patients who consume thickened liquids.

Study on viscosity modification of human and formula milk for infants with dysphagia

ABSTRACT Purpose: to analyze the modification of the viscosity of human milk and infant formula. Methods: three studies were performed to assess the viscosity and effect of time on infant formula with a thickener, at concentrations of 2, 3, and 5%, as well as raw and pasteurized human milk at concentrations of 2, 3, 5, and 7% at 37ºC, for 60 minutes. Rice cereal was used as a thickening agent. The viscosity was evaluated using a Ford Cup-type viscometer, and the samples were analyzed at 20-minute intervals. Significant differences were assessed using the ANOVA test. Results: no significant differences in viscosity were observed over time in concentrations of 2, 3, and 5%. There was a difference in the viscosity between human milk and infant formula, in concentrations of 2% and 5%, 2% and 7%, 3% and 5%, and 3% and 7%, independently of the time intervals evaluated. Conclusion: the findings of this study demonstrate the need for different concentrations of the thickening agent for human milk and infant formula. Rice cereal is a suitable therapeutic option for newborns presented with dysphagia in concentrations of 2, 3, 5, and 7%, due to its effect on the viscosity and flow reduction, provided that the feeding time is considered.

Development of a simple and objective evaluation method for thickened liquids using funnels

Some patients with dysphagia are prone to aspiration of low-viscosity liquids. Thickened liquids are often used in attempts to prevent aspiration. The patients should be given thickened liquids with suitable thickness, and the thickness should be constant at all time. While rotational and cone-and-plate viscometers are used for the evaluation of thickened liquids, they are high-precision and expensive equipment. To control the thickness of liquids, a simple and objective evaluation method is thus necessary. We developed a method to evaluate thickened liquids using funnels, and verified the appropriateness of this method. We measured the outflow times of five thickened liquids through funnels. One of the thickened liquids was a commercially available nutritional supplement, another was made with a thickening agent that contained guar gum, and all others were made with a thickening agent that contained xanthan gum. Four funnels with different stem sizes were tested. We found that the outflow time of thickened liquids through a funnel depended on their viscosities at a shear rate between 10 and 50 s^-1 , when the average inner diameter of the stem was in the range of 5.3-9.0 mm, and the volume of the liquid poured into the funnel was 30 mL. The correlation coefficient between the value of the sensory evaluation and the outflow time of the funnel with an average stem ID of 5.3 mm was 0.946. Therefore, this method may be useful in hospital and nursing home kitchens for evaluating thickened liquids.

PRACTICAL APPLICATIONS

The findings of this study will help develop a new method for the evaluation of thickened liquids. Funnels made from polypropylene, which are inexpensive and light, were used in this method. The process for measuring the outflow time of thickened liquids through a funnel is simple, and we can obtain quantitative data that are objective. Even though line spread test (LST) is well known as a simple measurement method, nutritional supplements and liquids thickened using a thickening agent containing guar gum have not been evaluated accurately. The funnel method was found to have a stronger correlation with sensory evaluation compared to LST. This method is useful in hospital and nursing home kitchens for evaluating thickened liquids.

Effect of Time and Temperature on Thickened Infant Formula

BACKGROUND

Unlike adult populations, who primarily depend on liquids for hydration alone, infants rely on liquids to provide them with hydration and nutrition. Speech-language pathologists working within pediatric medical settings often identify dysphagia in patients and subsequently recommend thickened liquids to reduce aspiration risk. Caregivers frequently report difficulty attempting to prepare infant formula to the prescribed thickness.

MATERIALS AND METHODS

This study was designed to determine (1) the relationship between consistencies in modified barium swallow studies and thickened infant formulas and (2) the effects of time and temperature on the resulting thickness of infant formula. Prepackaged barium consistencies and 1 standard infant formula that was thickened with rice cereal and with 2 commercially available thickening agents were studied. Thickness was determined via a line spread test after various time and temperature conditions were met.

RESULTS

There were significant differences between the thickened formula and barium test consistencies. Formula thickened with rice cereal separated over time into thin liquid and solid residue. Formula thickened with a starch-based thickening agent was thicker than the desired consistency immediately after mixing, and it continued to thicken over time. The data from this project suggest that nectar-thick and honey-thick infant formulas undergo significant changes in flow rates within 30 minutes of preparation or if refrigerated and then reheated after 3 hours.

CONCLUSIONS

Additional empirical evidence is warranted to determine the most reliable methods and safest products for thickening infant formula when necessary for effective dysphagia management.

Effect of pH on Rheological Properties of Dysphagia-Oriented Thickened Water

Flow and dynamic rheological properties of thickened waters prepared with commercial food thickeners were investigated at different pH levels (3, 4, 5, 6, and 7). The commercial xanthan gum (XG)-based thickener (thickener A) and starch-based thickener (thickener B), which have been commonly used in a domestic hospital and nursing home for patients with swallowing difficulty (dysphagia) in Korea, were selected in this study. Thickened samples with both thickeners at different pH levels showed high shear-thinning flow behaviors (n=0.08~0.22). Thickened samples at pH 3 showed higher n values and lower consistency index (K) values when compared to those at other pH levels. The K values of thickener A increased with an increase in pH level, while the n values decreased, showing that the flow properties greatly depended on pH. There were no noticeable changes in the K values of thickener B between pH 4 and 7. At pH 3, the thickened water with thickener A showed a higher storage modulus (G′) value, while that with thickener B showed a lower G′. These rheological parameters exhibited differences in rheological behaviors between XG-based and starch-based thickeners, indicating that the rheological properties of thickened waters appear to be greatly influenced by the acidic condition and the type of food thickener. Appropriately selecting a commercial food thickener seems to be greatly important for the preparation of thickened acidic fluids with desirable rheological properties for safe swallowing.

Relationships Among Rheological, Sensory Texture, and Swallowing Pressure Measurements of Hydrocolloid-Thickened Fluids

The objective of this study was to examine the relationships among three categories of measurements (rheological, sensory texture, and swallowing pressure) from fluids thickened to two different viscosities with 15 different hydrocolloids. Fluids at viscosities of 300 and 1500 cP (at 30 s(-1)) were targeted because these are the viscosities corresponding to the barium standards used in radiographic dysphagia diagnosis. Within the low viscosity (nectar) fluids (300 cP), the sensory properties thickness, stickiness, adhesiveness, mouth coating, and number of swallows were highly positively correlated with each other and highly positively correlated with the flow behavior index, n value (an indicator of shear-thinning behavior). Within the higher viscosity (thin honey) fluids (1500 cP), the sensory textures of adhesiveness, stickiness, mouth coating, and number of swallows correlated positively with rheological measures of n value. Swallowing pressures measured in the anterior oral cavity correlated negatively with the consistency coefficient k [shear stress/(shear rate) (n) ]. Samples that were more shear thinning (lower n values, higher k values) were generally perceived as less thick, with less adhesive properties (stickiness, adhesiveness, mouthcoating, and number of swallows). This information can be useful for selecting thickeners for people with dysphagia. A desirable thickener for many dysphagic patients would be one that allowed for a safe swallow by being viscous enough to reduce airway penetration, yet pleasant to drink, having the minimal perceived thickness and mouthcoating associated with greater shear thinning.

Effect of NaCl Addition on Rheological Behaviors of Commercial Gum-Based Food Thickener Used for Dysphagia Diets

Rheological properties of thickened fluids used for consumption by people with dysphagia (swallowing difficulty) are very sensitive to several factors, such as thickener type, temperature, pH, sugar, protein, and NaCl. In this study, steady and dynamic rheological properties of thickened water samples mixed with five commercial xanthan gum-based food thickeners (A~E) were studied in the presence of NaCl at different concentrations (0.3%, 0.6%, 0.9%, and 1.2%). The magnitudes of apparent viscosity (η_a,50), consistency index (K), yield stress (σ_oc), and dynamic moduli (G′ and G″) showed significant differences in rheological behaviors between thickened samples with various NaCl concentrations. Dynamic moduli values of all thickened samples, except for samples with thickener C, were much higher than those of the control (0% NaCl). All rheological parameter values (K, G′, and G″) in a thickener A were much higher than those in other thickeners. These results suggest that rheological properties of thickened samples containing NaCl are strongly affected by xanthan gum-NaCl interaction and depended on the type of thickener.

Relationship between Apparent Viscosity and Line-Spread Test Measurement of Thickened Fruit Juices Prepared with a Xanthan Gum-based Thickener

The flow behaviors of three thickened fruit juices (orange, apple, and grape juice) prepared with a commercial instant xanthan gum (XG)-based thickener that is marketed in Korea were investigated at different thickener concentrations (1.0%, 1.5%, 2.0%, 2.5%, 3.0%, and 3.5%) and setting times (5 and 30 min) using a rheometer and a line-spread measurement method. The flow distance values measured by the line-spread test (LST) were compared with the apparent viscosity (η_a,50) values measured with a sophisticated computer-controlled rheometer. The η_a,50 values of the juices increased as thickener concentration increased, whereas their flow distances decreased. The η_a,50 values at the 30-min setting time were much higher than those at the 5-min setting time, indicating that the setting time before serving or consuming thickened juices can affect viscosity values. Plots comparing η_a,50 values to LST flow distances revealed strong exponential relationships between the two measures (R²=0.989 and R²=0.987 for the 5- and 30-min setting times, respectively). These results indicate that the LST can be a suitable instrument for evaluating the viscosity of thickened fruit juices prepared with different XG-based thickener concentrations and setting times for the dysphagia diet.

Comparison of different gum-based thickeners using a viscometer and line spread test: a preliminary study

Objective

To compare fluid thickeners composed of starch polysaccharide (STA), guar gum-based polysaccharide (GUA), and xanthan gum-based polysaccharide (XAN) with the use of a viscometer and a line spread test (LST) under various measurement conditions.

Methods

The viscosity of thickened fluid with various concentrations (range, GUA 1%-4%, XAN 1%-6%, STA 1%-7%, at intervals of 1%) was measured with a rotational viscometer with various shear rates (1.29 s^-1, 5.16 s^-1, 51.6 s^-1, and 103 s^-1) at a temperature of 35℃, representing body temperature. The viscosity of STA showed time dependent alteration. So STA was excluded. Viscosities of GUA and XAN (range of concentration, GUA 1%-3%, XAN 1%-6%, at intervals of 1%) were measured at a room temperature of 20℃. LST was conducted to compare GUA and XAN (concentration, 1.5%, 2.0%, and 3.0%) at temperatures of 20℃ and 35℃.

Results

The viscosities of 1% GUA and XAN were similar. However, viscosity differences between GUA and XAN were gradually larger as concentration increased. The shear thinning effect, the inverse relationship between the viscosity and the shear rate, was more predominant in XAN than in GUA. The results of LST were not substantially different from GUA and XAN, in spite of the difference in viscosity. However manufacturers' instructions do not demonstrate the rheological properties of thickeners.

Conclusion

The viscosities of thickened fluid were different when the measurement conditions changed. Any single measurement might not be sufficient to determine comparable viscosity with different thickeners. Clinical decision for the use of a specific thickener seems to necessitate cautious consideration of results from a viscometer, LST, and an expert's opinion.

Line spread as a visual clinical tool for thickened liquids

PURPOSE

Preparing modified liquids to a target level of consistency is critical to patients' nutritional care. This study examined the relationship of line spread (i.e., the distance a liquid flows) to viscometer measurements for a variety of product/liquid combinations and determined if flow distance visually differentiated nectar-thick versus honey-like consistency.

METHOD

Combinations of 4 thickening products (3 starch-based and 1 gum-based thickener) prepared with 6 serving-temperature liquids that had various levels of fat, fiber, and added nutrients were tested. A total of 32 product/liquid combinations tested within the target range of 80-800 centipoise (cP). Measurements were recorded using line spread and a Brookfield RVDV-II+ viscometer.

RESULTS

Nectar-thick and honey-like consistencies significantly differed in their degree of line spread. Using our line spread apparatus, a value of 4.5 cm differentiated between nectar-thick and honey-like consistencies. There was an inverse correlation (-.75) between viscometer data and line spread results. That is, high viscosity values represented samples with less flow distance (line spread), and low viscosity values represented samples with more flow distance.

CONCLUSION

Line spread appears to be a quick, objective, and visual method that might be used to help patients and their caregivers achieve more accurate and consistent thickened liquid preparation.

Adequate oral fluid intake in hospitalized stroke patients: does viscosity matter?

PURPOSE

Sufficient intake of oral fluids to meet hydration needs is a critical recovery issue for patients hospitalized post stroke. Concerns for adequate oral fluid intake are generally focused on dysphagic patients restricted to thickened liquids; however, fluid intake patterns in stroke patients receiving thin liquids are unknown.

METHOD

This study examines the oral fluid intake patterns of three groups over 72 hours: community dwelling individuals, patients hospitalized post stroke receiving thin liquids and patients hospitalized post stroke receiving thickened liquids.

RESULTS

Mean oral fluid intake differed significantly between the two hospitalized groups (p = .04), with individuals receiving thickened liquids consuming less. Less than 1% of patients hospitalized post stroke met a minimum standard of 1500 mL/day, regardless of liquid viscosity. Conversely, community dwelling participants consumed significantly more fluids on average than their hospitalized counterparts.

CONCLUSION

Compliance with beverage preference, frequency of beverage offering, and inaccurate preparation of thickened beverages were identified as factors potentially influencing fluid intake.

Gender effect on oral volume capacity

Studies have shown anatomical and functional differences between men and women with respect to the mouth, pharynx, upper esophageal sphincter, and esophagus. The aim of this investigation was to analyze the influence of gender, body mass index (BMI), age, and orofacial anthropometric measurements on the intraoral maximum volume capacity for liquid. The investigation included asymptomatic subjects, 56 females and 44 males, aged 19-53 years. The volunteers sucked water through a straw up to the maximum tolerated oral volume, which was greater in men (71.2 ± 15.0 ml) than in women (55.4 ± 13.4 ml). Age, BMI, height, and number of teeth had no influence on the intraoral tolerated volume. Anthropometric orofacial measurements were greater in men than in women. In individuals with height between 1.66 and 1.89 m, anthropometric orofacial measurements were greater in men than in women, and the tolerated intraoral volume was greater in men than in women. There was a positive correlation between orofacial measurements and intraoral maximum volume. In conclusion, men have the capacity to place a larger volume of water inside their mouth than women. This observation is associated with higher anthropometric orofacial measures, but not with age, number of teeth, height, or BMI.