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.     

Shear and extensional viscosities of hard wheat flour dough using a capillary rheometer

The rheological behaviour of hard wheat flour dough was investigated for a high shear rate range (10-10⁴ s⁻¹) using a capillary rheometer. The shear viscosity obtained from capillary measurements demonstrated a shear thinning behaviour of dough and described by a power law model with a power law index n = 0.38, a consistency coefficient K = 1387 Pa sⁿ, and a coefficient of determination R² = 0.997. The extensional viscosity obtained from capillary measurements for a high extensional rate range (0.16-154 s⁻¹) showed a tension thinning behaviour and described by a power law model with a power law index m = 0.38, a consistency coefficient K_E = 353,000 Pa s^m, and a coefficient of determination R² = 0.977. Torsional measurements using a parallel plates rheometer for a shear rate range (10⁻³-20 s⁻¹) demonstrated the time or strain dependence of wheat flour dough, no steady state shear viscosity of dough, and the shear viscosity increased with time or strain to a maximum value and then decreased, suggesting a breakdown or rupture of the dough structure.     

The effect of different mixing processes on dough extensional rheology and baked attributes

BACKGROUND: Mixing is a significant part of the breadmaking process and is responsible for the development of the essential structure that will facilitate gas retention during proofing and the early stages of baking. The main objective of this study was to examine whether the dough extensional rheological and baking properties were affected from different mixers and energy inputs during mixing. RESULTS: It was found that extensional properties in uniaxial and biaxial extension were affected by the mixing equipment used and by the energy input used. Doughs mixed using a Farinograph had higher maximum resistance to uniaxial extension, higher P value and lower biaxial extensibility (Alveograph) and higher biaxial extensional viscosity than doughs mixed in a Stephan mixer (P < 0.01). The energy input was specific to each type mixing equipment and affected the biaxial extensional viscosity. Also, higher loaf volumes were achieved when higher energy inputs were used, whereas other baking properties were not affected. CONCLUSION: Altering the mixing equipment and the mixing speed affected the rheological properties of dough. Dough development during proofing as well as loaf volume was affected by the energy input levels and was increased by increasing the energy input and therefore the mixing time. Copyright © 2010 Society of Chemical Industry     

Rheological characterisation of polysaccharides extracted from brown seaweeds

Hydrocolloids from seaweeds have interesting functional properties, such as thickening or gelling ability. Structural characteristics of polysaccharides extracted from Québec seaweeds have not yet been established. Thus, the determination of the relationship between their structure and rheological behaviour is limited. Alginate and fucoidan were extracted using selective solvents from three species: Saccharina longicruris, Ascophyllum nodosum and Fucus vesiculosus. Structural analysis (total sugars, uronic acids, sulfates and molecular weight) and rheological characterisation were performed at different polysaccharide concentrations with and without the addition of NaCl. The results showed important variation between species. Fucoidan and alginate exhibited Newtonian behaviour. Fucoidan extracted from F. vesiculosus had the highest viscosity level, which might be explained by the degree of branching of the molecules. For alginate, the one extracted from S. longicruris showed a higher apparent viscosity. This result can partially be explained by the block proportion of alginate. The gelation profile of alginate was also determined for each species. The final storage modulus, G′, was variable for each species. Differences between species were observed for both polysaccharides as a result of structural variation. Copyright © 2007 Society of Chemical Industry     

Effect of Shear on the Rheology and Crystallization of Palm Oil

ABSTRACT:  This article reports on the impact of shear on crystallization upon cooling of palm oil. Samples were cooled down under shear from 70 to 10 °C, then kept at this temperature, while performing rheological measurements using a controlled shear rate rheometer and rheo-optical observations using optical microscopy and small-angle light scattering. Shear rates between 1 and 300 s⁻¹ were investigated. Two crystallization steps were observed, characterized by associated viscosity increases. The effect of shear on these 2 crystallization processes was investigated. Shear was shown to influence almost all of the steps of the structuring process of the crystallizing palm oil. The spherulite size and growth rate during the 1st crystallization are affected by shear. The onset time of the 2nd crystallization process strongly depends on the extent of shear. The steady state structures after the 1st and 2nd crystallization processes constituted of a suspension of aggregates of spherulites are controlled by the applied shear rate.
Practical Application: The texture of crystallized vegetal fats and subsequent end product properties depend on the structure developed during the crystallization process. This structuring process is strongly influenced by the thermo-mechanical history applied to the product (cooling rate, degree of undercooling, annealing time, application of flow). This article shows how the shear rate as well as extent of shear affects the different steps of the crystallization and aggregation processes in the case of palm oil after the 1st crystallization.     

Electrospinning of food-grade polysaccharides

A range of polysaccharides of different sources was investigated with respect to their ability to form fibers using electrospinning from aqueous solutions. Polysaccharides were chosen from different sources i.e. from plants, seaweeds and micro-organisms. The polysaccharides derived from plant sources were exudates (galactomannans, glucomannans) and other vegetable sources (e.g. starch, methylcellulose). The polysaccharides from the seaweeds were carrageenans and alginate and the polysaccharides from microbial origin ranged from non-branched (pullulan) to brush-like (e.g. dextran). The polysaccharides could be divided into three categories according to their electrospinning behaviour. The first category was able to form fibers, the second category was able to form a jet but no fibers and the third category (largest, containing all charged polysaccharides tested) was not able to form a jet at all. Possible reasons for a particular type of spinning behaviour are discussed, starting from the characterization of the polysaccharides and their solutions. The intrinsic viscosity, shear viscosity and conductivity were determined for the different polysaccharide solutions. Based on these results, possible relations with electrospinning behaviour are discussed. It was concluded that the overlap concentration and shear thinning properties of the polysaccharides are crucial for successful spinning. Concentrations in the range between 10 and 20 in units of the overlap concentration, probably giving rise to a sufficiently high Trouton ratio, were found to be a necessary condition for spinnability. Equipment settings and conductivity are of secondary importance and merely play a role in optimization of the process.     

Effects of concentration and temperature on carboxymethylcellulose rheology

The rheological properties of 0.5 to 2.0% carboxymethycellulose (CMC) solutions were measured at 30–90°C with a computer controlled rotational viscometer in a linearly increasing and decreasing three-cycle shearing sequence. CMC solutions showed power-law flow behaviour and rheological properties were significantly ( P < 0.01) influenced by both temperature and concentration. an empirical model was developed to relate the power-law parameters to both concentration and temperature.     

凉粉草胶的稳剪切流变学性质

研究了凉粉草胶在不同质量浓度、温度、pH、盐的种类及盐浓度和不同蔗糖浓度下的流体行为以及固定剪切速率下的表观粘度随不同条件的变化情况。结果表明,凉粉草胶溶液在不同的条件下呈牛顿流体或假塑性流体行为,在剪切速率52.8s-1下,10 g/dL凉粉草胶溶液的表观粘度随胶质量分数(1~20 g/dL)的增加而递增,随温度(25~70℃)的升高而递减,随pH(5~12)的变化则不具有单调性,随NaCl(0~3.0 g/dL)的添加而递减,随CaCl2(0~3.0 g/dL)的添加则先减小后增大,随蔗糖(10~50 g/dL)的添加则递增。     

米糠多糖及硫酸酯化米糠多糖的体外免疫应答和抗肿瘤活性研究

以小鼠黑色素瘤细胞(B16)为抗肿瘤模型,通过MTT比色法评价米糠多糖及硫酸酯化米糠多糖对B16增殖抑制能力。以小鼠巨噬细胞Raw264.7细胞系为免疫模型,通过MTT比色法评价Raw264.7增殖能力,中性红吞噬试验评价巨噬细胞活性,Griess方法检测一氧化氮(NO)释放量,以及酶联免疫(ELISA)检测肿瘤坏死因子(TNF-α)分泌量,考察米糠多糖及硫酸酯化米糠多糖的免疫活性。研究发现:米糠粗多糖(RBP)和米糠多糖纯化组分(RBP2a)主要通过增强机体的免疫功能而间接抑制肿瘤细胞。质量浓度为250μg/m L时,RBP和RBP2a样品组的NO释放量分别为对照组的4.67、6.36倍,TNF-α分泌量为对照组的441.1、465.5倍;RBP直接组和间接组的B16抑制率分别为8.16%、45.55%,间接组的B16抑制率比直接组增长458%。硫酸酯化米糠多糖(SRBP-B,SRBP-D,SRBP2a-B)一方面可以直接抑制B16增殖,质量浓度为1 000μg/m L时,对B16抑制率达73.65%、65.53%、78.43%,另一方面也可通过免疫途径提高NO和TNF-α等细胞因子释放,进一步提高抗肿瘤活性。但高浓度SRBP-B,SRBP-D,SRBP2a-B能抑制Raw264.7增殖,在500μg/m L时,Raw264.7存活率仅为83.26%、81.8%、79.78%。     

The rheological properties of exudates from cured porcine muscle: effects of added polysaccharides and whey protein/polysaccharide blends

Meat exudates collected from massaged cured porcine M semimembranosus were used to observe changes in gelation properties of test exudates containing added polysaccharides, both on their own and in combination with selected whey protein concentrates (WPCs). Three polysaccharide powders, namely sodium alginate, low‐methoxy (LM) pectin and modified potato starch, were assessed at a residual powder level of 2% with Na alginate used at a 0.5% level. Polysaccharides were evaluated both individually and as dry blends with selected WPCs. WPCs assessed included high‐gelling A 35%, B 75% and C 55% protein β‐lactoglobulin powders, as well as a regular 76.5% protein, WPC D. All WPCs were incorporated at a 2% residual powder level in the final meat. Treatment and control meat samples and resulting exudates were prepared in duplicate with analysis performed in triplicate. Viscoelastic properties of control and test meat exudate samples (n = 6) were analysed using control stress rheology in oscillatory mode. Exudates were heated from 20 to 80 °C at 1 °C min⁻¹ with subsequent cooling after 30 min to 20 °C at 1 °C min⁻¹. Combinations of high‐gelling WPCs (especially β‐lactoglobulin) together with modified starch or pectin were found to increase storage modulus G′ (Pa) values compared with control values, with significant (P < 0.05) synergies being observed on dry blending these ingredients. Sodium alginate was found to have a negative effect on G′ (Pa) results, giving lower values compared with control treatments. © 1999 Society of Chemical Industry     

多糖的硫酸酯化及其对结构和功能活性的影响研究进展

硫酸酯化是近年来常见的多糖分子修饰方法,通过对多糖进行硫酸酯化修饰可以极大的改善多糖的功能特性。因此,本文首先综述了近年来常见的多糖硫酸酯化方法,然后从结构和功能两个方面,深入阐述了硫酸酯化对多糖分子结构和功能活性的影响,旨在为多糖硫酸酯的进一步研究提供参考。      

墨水的流变特性及流变调节剂

讨论了墨水的流变特性,介绍了墨水中常用的和新型的流变调节剂。     

青钱柳多糖抑菌活性及及作用机理

为研究青钱柳多糖的抑菌活性和作用机制，用不同质量浓度的青钱柳多糖处理细菌，通过最小抑菌浓度（minimum inhibitory concentration, MIC）、抑菌生长曲线分析青钱柳多糖对细菌的抑菌效果，并从抑制效果最佳的受试菌菌体电导率、细胞蛋白和核酸含量、还原糖的释放、呼吸链脱氢酶活性、脂质过氧化程度、细胞内ATP含量、细胞外碱性磷酸酶活力的角度来揭示其抑菌机理。结果表明，青钱柳多糖对金黄色葡萄球菌（Staphylococcus aureus）、大肠杆菌（Escherichia coil）、单增李斯特氏菌（Listeria monocytogenes）和鼠伤寒沙门氏菌（Salmonella typhimurium）有明显的抑制作用，MIC分别为2、4、6、6 mg/mL，对枯草芽孢杆菌（Bacillus subtilis）的抑菌性不明显；对指示菌的电导率、蛋白质和核酸渗漏、还原糖释放、呼吸链脱氢酶活性、细菌脂质过氧化程度、菌体胞内ATP和胞外碱性磷酸酶（AKP）含量均有影响。以上现象表明，青钱柳多糖的抑菌性主要是破坏菌体细胞壁和细胞膜完整性，改变其通透性，使得胞内大小分子物质外泄，抑制了细胞的呼吸代谢和引起氧化损失，进而影响细胞的生长代谢或造成细胞死亡，达到抑菌效果。     

蒜油蛋黄酱稳定性及其流变学特性研究

对蛋黄酱稳定性的影响因素及其流变学特性进行了研究，确定了最佳生产工艺流程、配方组合及品质指标。     

刺五加多糖的提取及含量测定

探讨了经80℃热水提取、Sevag法除蛋白、乙醇分级沉淀等步骤提取刺五加多糖,并应用苯酚-硫酸法测定其含量。本法选取490nm为反应产物的测定波长,所测葡萄糖标准曲线相关系数r=0.99956,线性范围为5-22.5μg/mL,测得多糖的总收率为刺五加干重的0.54%。本法反应产物在160min内吸光度值稳定,RSD为1.22%,精密度良好,回收率为97.6%-102.8%。     

The rheology of colloidal and noncolloidal food dispersions

ABSTRACT:  Rheological data on a food together with data on its composition and structure or microstructure should lead to understanding the interrelationships between them. A number of foods are dispersions of solids in liquids, liquids in liquids, or gas in liquids. The dispersed particles may be colloidal in nature with dimensions < 10 μm, or larger noncolloidal particles (> 10 μm). For both colloidal and noncolloidal dispersions (either in dilute or concentrated regimes), several theoretical equations exist that provide insights into the role of key rheological parameters, such as particle volume fraction and size, interparticle forces, and fractal dimension on their viscosity, yield stress, and modulus. When theoretical models cannot be easily applied to foods with complex structures, structural analysis and structure-based models provide insight into the role of solids loading and interparticle bonding on rheological behavior. In this review, recent studies on colloidal and noncolloidal food dispersions in which theoretical models as well as structural analysis were employed are discussed.     

The preparation and physical characterisation of modified soybean polysaccharides

A novel and facile method for modification of soybean polysaccharides was applied. This involved a swelling water‐solvent exchange technique. A series of stearoylated soybean polysaccharides was prepared under homogeneous reaction conditions in an N,N‐dimethylformamide/lithium chloride system by reaction with stearoyl chloride using 4‐dimethylaminopyridine as catalyst and triethylamine as acid acceptor. At a reaction temperature of 80 °C and time of 30 min, approximately 1 mol of the soybean polysaccharides, when reacted with 3 mol of reagent, resulted in an 85% yield. The products were characterised by Fourier transform infrared spectroscopy (FT‐IR), elemental analysis and thermogravimetric analysis. It was found that the modified soybean polysaccharides had improved thermal stability and enhanced solubility in organic solvents compared with their unmodified counterparts. © 2002 Society of Chemical Industry