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.     

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.     

Rheological properties of selected hydrocolloids as a function of concentration and temperature

In this study, rheological properties of several food hydrocolloids (carrageenan, pectin, gelatin, starch and xanthan) were evaluated using a rotational viscometer at three concentrations (1–6%, depending on the type of hydrocolloid) and four temperatures (20, 40, 60 and 80°C). Samples were subjected to a programmed shear rate increasing linearly from 0 to 300 s⁻¹ in 3 min, followed by a steady shear at 300 s⁻¹ for 10 min and finally a linearly decreasing shear rate from 300 s⁻¹ to 0 in 3 min. Experiments were performed in duplicate. In general, the power law model fitted most of the experimental results. Xanthan gum and carrageenan (at 20^oC) were exceptions, characterized by a yield stress and hence the rheograms were fitted with the Herschel-Bulkley model. Furthermore, gelatin showed a Newtonian behavior. Three models (power, exponential and polynomial) were used to evaluate the concentration effect on apparent viscosity. Arrhenius model was used to describe the temperature effect. Among the samples, carrageenan showed the most temperature dependency and xanthan gum, the least.     

Effect of temperature and concentration on Rheological properties of “Kesar” mango juice

Flow characteristics of juice of “Kesar” mango have been investigated and rheological parameters were evaluated using rotational viscometer at temperature 20, 30, 40, 50, 60 and 70°C at concentration of 7.6%, 11.69%, 16.37% and 26% total solid. The experimental results followed the power law model for the best fit and the values of flow behaviour index (n) was less than unity (0.20–0.33) at all temperature and concentration revealing the shear-thinning (pseudoplasticity) nature of juice. An obvious correlation between consistency coefficient, in the range of 0.32–80.09 Pa sⁿ and inverse absolute temperature has been exhibited by Arrhenius model. Power equation indicated that consistency coefficient increased non-linearly with increase in concentration. The magnitude of activation energy were found in the range of 3.8–13.7 kJ/mol K.     

Rheological study of xanthan and locust bean gum interaction in dilute solution: Effect of salt

An oscillatory capillary rheometer was used to investigate the effects of NaCl, KCl, and CaCl₂ on visco-elastic properties of xanthan and locust bean gum (LBG) blends in dilute solution. Gums were evaluated for intrinsic viscosity and elastic component. Molecular conformation of the xanthan–LBG complex was assessed by the power-law and Huggins equations. Addition of any of the three salts reduced significantly the intrinsic viscosity and elastic component of the gum blends, with a pronounced effect from divalent ions, compared with monovalent ions. The 60% xanthan–40% LBG blend exhibited the strongest attraction between xanthan and LBG. For the three salts, the attraction weakened when 5-mM salt was added and vanished with the addition of 50-mM salt. The strongest attraction between xanthan and LBG molecules was also evidenced by a positive Huggins miscibility coefficient K_m, and a positive attraction–repulsion coefficient α. With addition of 50 mM of any of the three salts, the coefficient α became negative, suggesting a strong repulsion between the two gums. The power-law coefficient b increased as salt concentration and LBG fraction increased in the blends for the three salts, suggesting a more flexible xanthan–LBG complex dependent on salt concentrations and LBG.     

Effect of gum arabic concentration and inlet temperature during spray drying on physical and antioxidant properties of honey powder

The research studied the effect of gum arabic concentration at 35, 40 and 45 % with inlet temperatures of 160, 170 and 180 °C on the physico-chemical, functional and thermal properties of honey powder enriched with aonla (Emblica officinalis. Gaertn) and basil (Ocimum sanctum) extract, wherein other parameters like concentration of aonla extract (8 %), basil extract (6 %) and feed rate (0.11 mL/s) were kept as constant. Powder recovery and glass transition temperature (T_g) showed significant increase with the increase in inlet temperatures. On the other hand hygroscopicity, tapped density, total phenolic content, antioxidant activity and vitamin C content showed inverse response to the increase in inlet temperatures. However powder recovery, T_g, total phenolic content, antioxidant activity and vitamin C content increased with the increase in concentration of gum arabic. On the basis of obtained results it can be concluded that honey powder with the concentration of 45 % gum arabic at 170 °C inlet temperature was found to be less hygroscopic with better powder recovery and overwhelming antioxidant properties.     

Rheological properties and stability of low-in-fat dressings prepared with high-pressure homogenized yeast

The aim of present study was to investigate the feasibility of application high-pressure homogenized (HPH) yeast aqueous dispersions with low nucleic acid content for the formulation of low-in-fat dressings. The HPH treatment (1500 bar, 3 passes) in alkaline medium improved the protein dispersibility (>50%). Emulsions were prepared using sunflower oil (12.0% or 25% w/w oil), xhantan/guar gums (0.5% w/w), modified starch (0–4.0% w/w), salt, sucrose, acidulants, EDTA, and antimicrobial agents. All emulsions (pH 3.97 ± 0.27; a_w = 0.97 ± 0.01), whatever the starch content, behaved clearly as pseudoplastic fluids in steady flow measurements. Moreover, as the frequency sweep measurements were made they also exhibited a weak gel behavior. Although the presence of starch produced an increase of mean particle size (D_3,2 values), the rheological parameters (consistency index, proportionality coefficient and coordination number) also increased, so that the starch contributes to reinforce the three-dimensional network formed by oil droplets, protein aggregates and other polysaccharides. Yeast dressings were stable to coalescence after 28 days of quiescent storage (7.0 ± 0.5 °C) and only the highest starch concentration at 25% w/w oil was sufficient to maintain the stability of network.     

Rheological behaviour of acorn starch dispersions: effects of concentration and temperature

Rheological properties of acorn starch dispersions at different concentrations (4%, 5%, 6% and 7%) were evaluated under steady and dynamic shear conditions. The flow behaviours of the acorn starch dispersions at different temperatures (25, 40, 55 and 70 °C) were determined from the rheological parameters provided by the power law model. The acorn starch dispersions at 25 °C exhibited high shear-thinning fluid characteristics ( n  = 0.23–0.36). Consistency index (K) and apparent viscosity (η_a,100) increased with an increase in starch concentration, and were also reduced with increasing temperature. Within the temperature range of 25–70 °C, the η_a,100 obeyed the Arrhenius temperature relationship with a high determination coefficient ( R ² = 0.97–0.99), with activation energies (E_a) ranging between 16.5 and 19.0 kJ mol⁻¹. Both the power law and exponential type models were employed in order to establish the relationship between concentration and apparent viscosity (η_a,100) in the temperature range of 25–70 °C. Magnitudes of storage ( G' ) and loss ( G ") moduli increased with an increase in the starch concentration and frequency (ω). The magnitudes of G ' were higher than those of G " over most of the frequency range (0.63–62.8 rad s⁻¹). The dynamic (η*) and steady shear (η_a) viscosities of acorn starch dispersion at 7% concentration follow the Cox–Merz superposition rule.     

Intrinsic viscosity and viscoelastic properties of xanthan/guar mixtures in dilute solutions: Effect of salt concentration on the polymer interactions

An oscillating capillary rheometer was used to investigate the dynamic viscoelastic and intrinsic viscosity properties of deacetylated xanthan (0.025%), native xanthan (0.025%), guar gum (0.075%), and xanthan–guar mixtures in dilute solutions. Influence of ionic strength on xanthan conformation and interaction with guar gum was elaborated. As the salt concentration increased, a significant (P < 0.05) decrease in viscosity (η′) and elasticity (η″) values was observed for both native xanthan–guar mixtures and deacetylated xanthan–guar mixtures. In water and 2 mM NaCl solution, the relative viscosity and η″ of both native xanthan–guar mixtures and deacetylated xanthan–guar mixtures were much higher than of those calculated for mixtures assuming no interaction, whereas no pronounced increase was found for polysaccharide mixtures in 40 mM NaCl. The intrinsic viscosities of deacetylated xanthan–guar mixtures in water and 2 mM NaCl were higher, whereas the intrinsic viscosities of native xanthan–guar mixtures were lower than those calculated from the weight averages of the two individually, assuming no interaction. These results demonstrated that intermolecular interaction has occurred between xanthan and guar mixtures in water and 2 mM NaCl, but may not occur in 40 mM NaCl, and mutual incompatibility may occur. The results suggest that the degree of disordering of xanthan played a critical role in xanthan–guar interaction and may explain the differences in η′, η″, and intrinsic viscosity measurements between 2 and 40 mM NaCl.     

The effects of xanthan conformation and sucrose concentration on the rheological properties of acidified sodium caseinate–xanthan gels

Xanthan solution transitions caused by annealing at different temperatures were studied by oscillatory rheology. The rheological behaviour of solutions evaluated at 10 °C showed different irreversible xanthan transitions, depending on the annealing temperature. The effect of xanthan conformation and caseinate, xanthan and sucrose concentrations on the mechanical and stress relaxation properties of acidified dairy gels were also investigated. Xanthan transitions produced different structural characteristics in mixed gels, as observed by their relaxation time and residual stress. The amount of sucrose played an important role in the network formation of gels and on the final elasticity. Intermediate concentrations of sucrose yielded gels that were finer than those obtained with low sucrose content, whereas at high amounts of this co-solute, the gels became more fragile. This quadratic effect of sucrose occurred at lower sucrose contents than in protein–sucrose or polysaccharide–sucrose systems. The mechanical properties at equilibrium were affected only by the strength of the interactions between caseinate and xanthan.     

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.     

葫芦巴胶改善吞咽障碍者饮水安全性的流变学研究

参照美国吞咽障碍膳食标准,以样品的 η50黏度为分类依据,将葫芦巴胶制备成黏度分别为180 cP(花蜜型)、1000 cP(蜂蜜型)和2500 cP(布丁型)的增稠流体,对其流变学性质进行研究,并评价葫芦巴胶用于改善吞咽障碍者的饮水安全性.结果表明,溶解温度是葫芦巴胶流变性质能否满足改善饮水安全性要求的关键.80℃制备...     

Rheological properties of Lepidium sativum seed extract as a function of concentration, temperature and time

The seeds of Lepidium sativum (Garden Cress) were selected as a new source of hydrocolloid and its chemical composition and molecular parameters were determined. The macromolecular component of the extract had a molecular weight of 540 kDa, and was nearly as rigid as xanthan with regard to chain conformation. The main rheological features were investigated as a function of shear rate, concentration and temperature. The extract exhibited strong shear-thinning behaviour, which was even more pronounced than for xanthan. An increase in concentration or temperature led to an increase in pseudoplasticity. The Arrhenius model was applied to the temperature dependence of viscosity, and the activation energy (E_a) was found to decrease with increasing concentration. The extract solutions showed thixotropic behaviour at all the concentrations and temperatures studied, and the first-order stress decay model with a non-zero equilibrium stress fairly described the time-dependent behaviour. The rheological characteristics found indicated a potential application of the extract as a novel thickener.     

黄原胶对酸乳凝胶特性的影响及其作用机理探讨

为探索增稠剂对酸乳体系的影响作用机理,以在原料鲜牛乳中分别加入0.0%、0.1%、0.2%、0.3%的黄原胶制作的酸乳为材料,对其流变特性和微观结构进行了观测.结果表明:4种样品都是正触变性流体,其触变环面积之比为1:1.08:0.64:0.77.在加入量为0.1%、0.2%和0.3%的三个样品中,随着黄原胶加入量的增加,酸乳样品的表观黏度和剪切应力逐渐降低.电镜观察显示,不加入黄原胶时酪蛋白相互凝集成立体网状结构,加入黄原胶后酪蛋白凝集胶束变成了散乱的片状结构.初步分析认为,黄原胶对酸乳发生作用的机理是通过其大分子的空间位垒效应干扰酪蛋白发生凝集的方式,导致酪蛋白胶束结构散乱,从而降低酸乳凝胶的表现黏度和剪切应力.     

Effect of inlet temperature on the physicochemical properties of spray-dried seed-watermelon seed protein powder

Here, we studied the effects of inlet temperature on the physicochemical properties of the hydrolyzed protein (seed-watermelon seed hydrolyzed protein [SWSP]) powder in seed-watermelon seeds. The inlet temperature of the study was in the range of 150 to 180 °C, and the remaining experimental parameters remained constant, that is, the feed flow rate was 0.2 L/hr, the concentration of maltodextrin was 30%, and the outlet temperature was 80 °C. We studied the water activity and moisture content, bulk density, flowability (Carr index and Hausner ratio), angle of repose, solubility, color, hygroscopicity, powder morphology, particle size, crystallinity, and odor of the sample. Inlet temperature of 170 to 180 °C reduced the moisture content and increased the particle size. It was found that the value of measured water activity was less than 0.5, which helped in maintaining stability of the sample. Powders produced at the temperatures showed smoother particle surfaces, whereas higher inlet temperature showed spherical particles with some shrinkage as analyzed by scanning electron microscope. The inlet temperature affected the color of the sample, thus at high temperature, the sample had a brighter color. The sample was approximately 18% crystalline. At a preparation temperature of 160 °C, the sample showed significant antioxidant activity (P < 0.05).     

Rheological properties of polysaccharides from Pholiota nameko with different temperature extraction: Concentration,pH, temperature,and saltion

Cold and hot water extracted polysaccharides (CW-PNPs and HW-PNPs) were isolated from Pholiota nameko. The rheological properties of PNPs were investigated by steady shear and oscillatory rheological measurements. The PNPs exhibited typical non-Newtonian and shear-thinning behavior, which are affected by PNP concentration, temperature, pH value, salt ion, and concentration. Specifically, the apparent viscosity of the two PNPs solutions at concentration of 1% (w/w) was shown as HW-PNPs > CW-PNPs. The apparent viscosity of PNPs decreases under acidic and alkaline conditions and when the temperature rises; K⁺ and Na⁺ cause the apparent viscosity of CW-PNPs to decrease, while Ca²⁺ and Al³⁺ are opposite. The addition of four different salt ions all caused the apparent viscosity of the HW-PNPs to decrease. The results of dynamic rheological experiments show that G′ and G″ showed slightly frequency dependency with G′ exceeding G″ throughout the accessible range of frequency for CW-PNPs and HW-PNPs.