Starch-based Thickeners Research Articles

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.

The Effect of Oral Processing on the Viscosity of Thickened Drinks for Patients With Dysphagia.

ObjectiveTo determine whether a gum-containing thickener maintains its viscosity better during oral processing than a completely starch-based thickener.MethodsThirty-five healthy volunteers participated in a double-blind, cross-over study. Artificial tap water was thickened to honey-like consistency (effective viscosity of 1,300±100 mPa·s at a shear rate of 50 per second at 20℃) with a starch-based thickener (SB) or a gum-containing thickener (GC). Bolus viscosity was determined after standardized oral processing of the thickened water by the subjects for 10 and 20 seconds. Significant effects were determined by ANOVA analysis and pairwise comparisons.ResultsBoth thickeners were susceptible to breakdown during oral processing. However, GC-thickened water retained its viscosity significantly better than SB-thickened water.ConclusionThe presence of gums has a protective effect on the starch hydrolysis by salivary amylase in thickened drinks, which may facilitate safer swallowing.

Variations in tongue-palate swallowing pressures when swallowing xanthan gum-thickened liquids.

Thickened liquids are frequently recommended to reduce the risk of aspiration in patients with oropharyngeal dysphagia. Although it has previously been reported that tongue-palate pressures increase when swallowing spoon-thick and semi-solid consistencies compared to thin liquids, relatively little is known about how swallowing behaviors differ when swallowing liquids of nectar- or honey-thick consistency. Furthermore, previous studies have primarily used starch-based thickeners, and little is known about swallowing behaviors with xanthan gum-thickened liquids, which have recently been introduced for dysphagia management. In this study, we measured variations in tongue-palate pressures during the swallowing of liquids thickened to apparent viscosities of 190, 250, and 380 mPa s at 50/s using increasing concentrations of xanthan gum (0.5, 0.63 and 0.87 w/w%). The viscosity differences between these nectar- and honey-thick stimuli were confirmed to exceed sensory perceptual discrimination thresholds. Data were collected from 78 healthy adults in two sex-balanced age-groups (young; mature) and compared to reference values obtained during water swallowing. The results confirm that increased amplitudes of tongue-palate pressure were used when swallowing the thickened liquid stimuli, compared to swallows of water, and for the honey-thick liquid compared to the two nectar-thick liquids. Age-related reductions were seen in tongue strength but not in swallowing pressures, which fell below 40 % of maximum isometric pressure values. Thus, the use of xanthan gum-thickened liquids is unlikely to tax the swallowing system in terms of tongue pressure generation requirements, even in seniors with reduced maximum isometric tongue pressure measures.

Viscosity differences between thickened beverages suitable for elderly patients with dysphagia.

Dysphagia has been associated with a high risk of undernutrition and aspiration pneumonia in the elderly. It is commonly managed by adding commercial thickening agents to thicken liquids. The rheological behavior of these thickeners in water is known but there is lack of information with regard to other liquids. The aim of this study was to determine the viscosity of 11 beverages after adding commercial thickeners and to compare their viscosity with that of thickened water and also with the reference limits of the National Dysphagia Diet (NDD). We added starch-based and gum-based thickeners to 11 beverages to achieve a honey-like consistency. The 11 beverages were five juices (apple, orange, grape, peach-grape, and pineapple), two teas (black tea and chamomile), milk (whole and skimmed), instant coffee, and a vegetable milk (tigernut milk). Viscosity measurements were made in a controlled environment for the resulting 22 samples. Compared to thickened water, significant changes were found for all beverages except apple juice, with both starch- and gum-based thickeners, and orange juice, pineapple juice, and chamomile with the gum-based thickener. Results with respect to the NDD reference limits showed significant changes in viscosity only for peach-grape juice and pineapple juice with starch-based thickener. These findings show that changes arise in the viscosity of some thickened beverages compared to thickened water and also compared to the range recommended by the NDD. Further studies are needed to describe the rheological behavior of other beverages, thickeners, and consistencies. Recommendations to ensure feeding safety may be required for elderly patients with dysphagia.

LB016-SUN THERAPEUTIC EFFECT OF XANTHAN GUM-BASED THICKENER ON SWALLOWING FUNCTION IN PATIENTS WITH OROPHARYNGEAL DYSPHAGIA

Rationale: Oropharyngeal dysphagia (OD) is a major contributor to malnutrition. Starch-based thickeners improve safety of deglutition but increase residue. We aimed to evaluate the therapeutic effect of a xanthan gum-based thickener, Resource®ThickenUp Clear (RTUC, Nestle Health Science). Methods: We studied 120 patients with OD with videofluoroscopy while swallowing a series of 5 20mL liquid boluses at nectar, thin and extreme spoon-thick (EST) viscosities measured at 50/s 20oC and obtained with a hydrosoluble X-Ray contrast (50/50 vol with water) and RTUC. We assessed prevalence of penetrations and aspirations for impaired safety, oropharyngeal residue for impaired efficacy, bolus velocity, timing of the swallow response, and the nutritional risk (MNASF, NRS 2002). Results: Prevalence of malnutrition or risk of malnutrition was 71% according to MNA-SF and 76% according to NRS 2002. Increasing bolus viscosity: a) improved safety of swallow as 24% of patients with OD presented safe swallow at thin, 55% at nectar (P< 0.001) and 85% at EST (P< 0.001). Prevalence of aspiration was 16% at thin, 9% at nectar (P< 0.01) and 5% at EST (P< 0.01). The score of the penetration-aspiration scale was 3.3±0.2 (thin), 2.2±0.2 (P< 0.001, nectar) and 1.5±0.1 (P< 0.001, EST); b) did not enhance oropharyngeal residue; c) did not affect timing of swallow response; d) reduced bolus velocity from 0.25±0.01m/s at thin to 0.21±0.01m/s at EST (P< 0.05). Conclusion: Prevalence of malnutrition among neurological and older patients with OD is very high. Increasing bolus viscosity with RTUC exerts a strong therapeutic effect by improving the safety of swallow without increasing oropharyngeal residue, an advantage of new generation versus conventional thickening agents. This effect might help to improve the nutritional treatments for these patients. Disclosure of Interest: L. Rofes: None Declared, V. Arreola: None Declared, R. Mukherjee: None Declared, P. Clave Grant/Research Support from: Nestec Ltd

Effects of Saliva on Starch-thickened Drinks with Acidic and Neutral pH

Powdered maize starch thickeners are used to modify drink consistency in the clinical management of dysphagia. Amylase is a digestive enzyme found in saliva which breaks down starch. This action is dependent on pH, which varies in practice depending on the particular drink. This study measured the effects of human saliva on the viscosity of drinks thickened with a widely used starch-based thickener. Experiments simulated a possible clinical scenario whereby saliva enters a cup and contaminates a drink. Citric acid (E330) was added to water to produce a controlled range of pH from 3.0 to 7.0, and several commercially available drinks with naturally low pH were investigated. When saliva was added to thickened water, viscosity was reduced to less than 1% of its original value after 10-15min. However, lowering pH systematically slowed the reduction in viscosity attributable to saliva. At pH 3.5 and below, saliva was found to have no significant effect on viscosity. The pH of drinks in this study ranged from 2.6 for Coca Cola to 6.2 for black coffee. Again, low pH slowed the effect of saliva. For many popular drinks, having pH of 3.6 or less, viscosity was not significantly affected by the addition of saliva.

Inconsistent rheological behaviour of starch-based dysphagia products

Starch-based thickeners may be given to individuals with dysphagia to favourably alter variables of the swallow reflex (1) . These are prepared to different consistencies (syrup, custard and pudding), which correspond to different viscosity levels at a shear rate of 50 1/s, which is thought to represent “the average” shear rate operating in the mouth (2‐5) . The viscosity ranges were established by the American Dietetic Association for the National Dysphagia Diet task force (NDD) (6) . Starch-based pre-made beverages and instant thickeners were found to be shear thinning and to exhibit great variation in consistency, especially at lower shear rates as shown by simple viscosity and the rheological profile parameters complex (G*), viscous (G 00 ) and elastic modulus (G 0 ) over a range of physiological shear rates denoting the variation in structure and behaviour. At low shear rates, the large range of viscosity values for “Custard consistency” samples was found to be significant at P < 0.0001 (F = 77.56). At a shear rate of 50 1/s, the viscosity was reduced considerably and the range narrowed to allow all samples to fall within the NDD guidelines. However, the variation was still found to be significant at P < 0.0001 (F = 98.21) and was largely attributed to the considerable differences between the pre-thickened instantly thickened beverages.

Time-Dependent Rheology of Starch Thickeners and the Clinical Implications for Dysphagia Therapy

The viscosity of nonsolid foods and the stability of their viscosity over time is critical in managing dysphagia. The time-dependent viscosity of liquids thickened with starch-based thickeners was measured at constant temperature and shear rate. Viscosity was measured between 30-min intervals of rest (zero shear) over a period of 17 h at 20.0 degrees C. Two common types of thickeners were evaluated: maize-based and maltodextrin-based (the latter commonly used in pediatrics). The maize-based thickeners undergo a significant decrease in viscosity over the initial 1-4 h following preparation. The maltodextrin-based thickener's viscosity increases significantly 30 min following preparation and is then more stable over time than its maize-based equivalent. These findings suggest that the success of current dysphagia therapies that use thickeners could be influenced by the time-dependent nature of thickened fluid viscosity. Acknowledgment and appropriate selection of the thickener type is shown to be of great importance.

Moisture absorption characteristics of food thickeners used for the management of swallowing dysfunctions

Six commercial food thickeners, based on starch, and guar and xanthan gums, were investigated for their moisture absorption properties. The thickeners were exposed to 100% relative humidity as well as soaked in water for selected time periods. The gum-based thickeners dissolved in water to yield 100% water solubility index. The water absorption index of the starch-based thickeners ranged from 14.7 to 18.0 g/g dry solids of thickener. The starch-based thickeners sorbed less moisture than the gum-based ones, with the xanthan gum-based thickeners having the highest sorptive ability on mass basis. The Peleg model was the most suitable (r2=0.966–0.997) of the sorption models investigated to describe the sorption data. The diffusion rate constant of the thickeners ranged from 8.7 to 13.5 day%−1, while the equilibrium moisture content was between 35.7 and 46.8%. The sorptive ability explained viscosity development in some of the thickeners, but was unsuitable in fully describing comparisons of the solutions viscosities of starch-based and xanthan gum-based thickeners.

Sensory Characteristics of Beverages Prepared with Commercial Thickeners Used for Dysphagia Diets

Objective To describe and compare sensory characteristics of six beverages prepared with four commercial thickeners used in dysphagia diets. Design The study used a completely randomized design within a test of each beverage. Subjects/setting Five highly trained descriptive sensory analysis panelists conducted the testing in a laboratory environment. Intervention Coffee, milk, apple juice, orange juice, Ensure (Abbott Laboratories, Abbott Park, IL), and water were thickened using two starch-based and two gum-based commercial thickeners according to manufacturers’ instructions to achieve nectar-like and honey-like consistencies. Main Outcome Measures Sensory attributes of the original beverages and the thickened samples were defined and scored. Statistical Analyses Performed Sensory scores were analyzed by analysis of variance using general linear models and Fisher’s least significant difference test to determine specific differences. Results All thickeners suppressed the main flavors of the base beverages and imparted slight off-flavors (bitter, sour, metallic, or astringent) in some beverages. Starch-based thickeners imparted a starchy flavor and grainy texture, whereas gum-based thickeners gave added slickness to the beverages. Although thickeners mixed well with some beverages, they were difficult to disperse in others, making some thickened beverages lumpy. Conclusions All thickeners added either a starchy, grainy, or slick flavor or texture and tended to suppress the base flavor of beverages, especially at honey-like consistencies. Thus, individual decisions about which characteristics are more negative (eg, slick vs grainy texture) for specific patients must be made. Additional development of thickening agents seems necessary for improved sensory properties. Information from this article should help professionals and their patients with dysphagia better understand the sensory issues associated with the use of commercial thickening agents in various beverages.

The thixotropic and rheopectic behaviour of maize starch and maltodextrin thickeners used in dysphagia therapy

The viscosity of starch-thickened foods is critical in managing dysphagia (impaired swallowing). These fluids are highly non-Newtonian and exhibit thixotropic behaviour. The thixotropy of the starch-based thickeners that are used to achieve this critical viscosity is presented. Two types of thickeners were evaluated; maize-based and maltodextrin-based. The thixotropy of these thickeners proved to be complex and the behaviour could be toggled between thixotropy and rheopexy by changing certain variables. The sol to gel transition favours low or zero shear rates when the initial viscosity is low (low starch concentration), but shearing is preferred for structure formation of high viscosity (concentrated) samples. This is likely to be due to Brownian motion being restricted in thicker samples due to less solvent between starch molecules. This may also cause starch granules to be sheared open causing more amylose to enter the viscous matrix.

Texture and Flavor Characteristics of Beverages Containing Commercial Thickening Agents for Dysphagia Diets

ABSTRACTStarch‐based thickeners often are recommended to facilitate fluid intake for dysphagia patients. Four beverages (water, milk, orange juice, apple juice) were prepared to a “honey‐like” consistency using 4 commercially available starch‐based thickeners. Sensory characteristics of the beverages were described using descriptive sensory analysis. The brands of thickeners differed in the perceived viscosity of the products they produced. With thickeners, the main flavors of the base beverages were suppressed, all imparted a starchy flavor, and some products imparted slight off‐flavors, such as metallic, astringent, or bitter, and a grainy texture that might be perceived as reducing quality. This sensory information could be related to physicochemical information to improve product quality.

Effect of salts on interactions of starch with guar gum

The cold paste viscosity and the gelatinization temperature of starch, when used alone and in combination with guar was found to be sensitive to the presence of salts at concentrations normally encountered in food systems. It is thought that gums facilitate the formation of an electrical double layer of cations around the starch and hence delay the gelatinization temperature. Since the starch exchanges cations from the solution for hydrogen ions in the presence of salts, an increase in volume results, causing an increased cold paste viscosity of starch—salt systems. However, in the starch—guar gum system, different salts show different behaviours. While calcium chloride and potassium chloride showed an increase in cold paste viscosity, sodium sulphate and sodium phosphate showed a decrease. Sodium chloride on the other hand showed a behaviour dependent on the concentration of guar gum. While no significant effect of sodium chloride on the cold paste viscosity was observed at 0.05 and 0.1% guar, the viscosity was found to decrease with increasing sodium chloride concentration in the presence of 0.2% guar. These results generally were in line with the rheological profile, as seen from the values of the consistency index. The addition of salts to starch alone as well as starch—guar combinations caused a decrease in flow behaviour index, suggesting that both guar and salts make the starch pastes more pseudoplastic. These results would be valuable in developing starch-based thickeners for food products containing salts.