C. Gallegos

Development of new green lubricating grease formulations based on cellulosic derivatives and castor oil

Environmentally friendly lubricating greases may be produced by solely replacing the mineral base oil for vegetable oil. However, the substitution of traditional metallic soaps by biodegradable and renewable thickeners is, up to now, much less considered. This work is focused on the development of new oleogels, using castor oil and cellulose derivatives, which could be potentially used as biodegradable lubricating greases. Thermal and thermo-rheological behaviours of these materials were characterised by means of TGA analysis and SAOS measurements, in order to evaluate the evolution of oleogel microstructure with temperature. Moreover, both roll-stability and leakage tendency standard tests, usually performed in the grease industry, were used to evaluate the mechanical resistance of each sample. The evolution of biogrease linear viscoelasticity functions with frequency is quite similar to that found for traditional lithium lubricating greases. However, the influence of temperature on biogreases linear viscoelasticity functions is less important than that found for traditional greases. In general, the biogrease samples studied show both slightly lower mechanical stability and higher leakage tendency than traditional lubricating greases. The use of a blend of ethyl and methyl cellulose as thickener provides a mechanical stability comparable to that found for commercial greases.

Linear viscoelastic properties of sucrose ester-stabilized oil-in-water emulsions

This paper deals with the influence of composition [sucrose ester SE and oil O concentrations] and temperature on the linear viscoelasticity properties of highly concentrated oil-in-water emulsions, using a hydrophilic sucrose palmitate as emulsifier. Different oil-in-water emulsions were prepared using a sucrose palmitate (SE=1–5 wt %) with a hydrophilic–lipophilic balance of 15, sunflower oil (O=60–80 wt %) and water. Oscillatory measurements were carried out in the linear viscoelasticity region. The relaxation time spectra of the emulsions were calculated using regularization techniques and were fitted to an empirical model proposed by Reference 1996. The results obtained are explained on the basis of the relationship among linear viscoelasticity properties, droplet size distribution, and characteristics of the continuous phase. Thus, an increase in sucrose palmitate concentration produces higher values of the linear viscoelasticity functions and a broader plateau region in the relaxation time spectrum...

Influence of composition of emulsifier blends on the rheological properties of salad dressing-type emulsions

This paper deals with the influence that composition of emulsifier blends exerts on the rheological properties of low-in-fat salad dressing-type emulsions. Binary blends of egg yolk and different types of amphiphilic molecules (low-molecular weight and macromolecules) were used in several proportions to stabilize emulsions by keeping constant the total amount of emulsifier. The different emulsifiers added to egg yolk were pea protein, sodium caseinate, polyoxyethylene(20)-sorbitan monolaurate (Tween 20) and sucrose distearate. Steady state flow tests and small-amplitude oscillatory measurements within the linear viscoelasticity region were carried out. Rheological tests were complemented with droplet size distribution measurements and observation of physical stability against creaming of these emulsions. It was pointed out that rheological properties, droplet size and physical stability of the emulsions studied depended on the weight ratio of emulsifiers in the binary blends, although the emulsifier total concentration remained constant, as well as the nature of the substance blended with egg yolk. These results have been explained on the basis of the relationship among rheological properties, droplet size distribution, continuous phase characteristics and interactions among different emulsifier molecules.

Non-linear viscoelasticity modeling of tomato paste products

Abstract This paper deals with the characterization and modeling of the non-linear rheological properties of tomato paste samples manufactured under different conditions (sieve pore size and breaking temperature). With this aim, flow measurements, dynamic linear viscoelastic and linear and non-linear stress relaxation tests have been carried out on the above-mentioned tomato paste samples. Different geometries with smooth and serrated surfaces have been used to optimize the viscous flow measurements and avoid wall-depletion phenomena. The viscous flow properties of tomato paste samples depend on water insoluble solids (WIS) content and particle size, which may be highly influenced by processing conditions. In general, viscosity follows a power-law relationship with tomato paste water insoluble content and particle diameter. A factorable non-linear viscoelasticity model, the Wagner integral equation, predicts the non-linear rheological response of these products under shear fairly well. The time-dependent part of this model is described by a continuous linear relaxation spectrum, calculated from regularization techniques. The use of the Soskey–Winter damping function provides the best predictions of the viscous flow curves.

Influence of Tomato Paste Processing on the Linear Viscoelasticity of Tomato Ketchup

Tomato paste is used as an ingredient for the manufacture of tomato ketchup. This paper deals with the influence that some tomato paste processing variables (finisher screen opening and breaking temperature) and tomato variety exert on the linear viscoelastic properties of tomato ketchup. Two tomato varieties (H-282 and H-282F) were used. H-282 is a commercial variety whilst H-282F is a variety with a lower content in polygalacturonase (PG). Dynamic viscoelastic tests and particle size distribution measurements were carried out. Viscoelastic properties of tomato ketchup were mainly related to their mean volume diameter, tomato paste water-insoluble solids content (that depended on the tomato paste processing) and tomato variety.

Linear and non-linear viscoelasticity of low-in-cholesterol mayonnaise / Viscoelasticidad lineal y no lineal de mayonesas con bajo contenido en colesterol

Five different mayonnaise products were prepared with constant composition except for the type of egg product used. The linear viscoelastic functions were superposed using a time-temperature su perposition method and the shift-factor showed an Arrhenius-like temperature dependence. The ther mal susceptibility was found to be higher for processed-egg-containing mayonnaise and when egg yolk was used instead of whole egg as the emulsifier. Transient flow curves always showed a stress overshoot, but a stress undershoot was found for whole-egg-containing emulsions at high shear rates. Processed yolk gave rise to higher storage modulus values than did native yolk. This effect lost sig nificance when yolk was diluted by native egg white. Mayonnaise made from egg yolk was always more viscous and did not show a stress undershoot in transient flow. The non-linear relaxation modulus was factorized as the product of the linear relaxation modulus and the damping function. Hence, the Wagner model was able to predict the transient flow of these emulsions fairly well. However, this model failed at low shear rates. This fact may be explained on the basis of wall-slip phenomena.

Nutritional Aspects of Dysphagia Management

This chapter describes the nutritional aspects of dysphagia management by starting with the definition of these two conditions (dysphagia and malnutrition) that share three main clinical characteristics: (a) their prevalence is very high, (b) they can lead to severe complications, and (c) they are frequently underrecognized and neglected conditions. From an anatomical standpoint, dysphagia can result from oropharyngeal and/or esophageal causes; from a pathophysiological perspective, dysphagia can be caused by organic or structural diseases (either benign or malignant) or diseases causing impaired physiology (mainly motility and/or perception disorders). This chapter gathers up-to-date information on the screening and diagnosis of oropharyngeal dysphagia, the consequences of dysphagia (aspiration pneumonia, malnutrition, and dehydration), and on the nutritional management of dysphagic patients. Concerning this last topic, this chapter reviews the rheological aspects of swallowing and dysphagia (including shear and elongational flows) and its influence on the characteristics of the enteral nutrition for dysphagia management (solid/semisolid foods and thickened liquids; ready-to-use oral nutritional supplements and thickening powders), with special focus on the real characteristics of the bolus after mixing with human saliva.

Droplet-size distribution and stability of commercial injectable lipid emulsions containing fish oil

PURPOSE The droplet size of commercial fish oil-containing injectable lipid emulsions, including conformance to United States Pharmacopeia (USP) standards on fat-globule size, was investigated. METHODS A total of 18 batches of three multichamber parenteral products containing the emulsion SMOFlipid as a component were analyzed. Samples from multiple lots of the products were evaluated to determine compliance with standards on the volume-weighted percentage of fat exceeding 0.05% (PFAT(5)) specified in USP chapter 729 to ensure the physical stability of i.v. lipid emulsions. The products were also analyzed to determine the effects of various storage times (3, 6, 9, and 12 months) and storage temperatures (25, 30, and 40 °C) on product stability. Larger-size lipid particles were quantified via single-particle optical sensing (SPOS). The emulsions droplet-size distribution was determined via laser light scattering. RESULTS SPOS and light-scattering analysis demonstrated mean PFAT(5) values well below USP-specified globule-size limits for all the tested products under all study conditions. In addition, emulsion aging at any storage temperature in the range studied did not result in a significant increase of PFAT(5) values, and mean droplet-size values did not change significantly during storage of up to 12 months at temperatures of 25-40 °C. CONCLUSION PFAT(5) values were below the USP upper limits in SMOFlipid samples from multiple lots of three multichamber products after up to 12 months of storage at 25 or 30 °C or 6 months of storage at 40 °C.

The role of human saliva on the elongational properties of a starch-based food product

In the medical context of swallowing disorders, human saliva may play an essential role, affecting the rheological properties of starch-based thickened products, due to the effect of the alpha-amylase, a protein enzyme naturally present in saliva. The aim of this work was to compare the effect of three different salivary solutions on the uniaxial properties of a starch-based food product (SBFP). Extensional rheology properties of SBFP after addition of solution containing a commercial alpha-amylase, mechanically stimulated saliva, or in-vivo stimulated whole human saliva, were measured by using a CaBER (Capillary Break-up Extensional Rheometer) device. Extensional and oscillatory shear results for the different types of salivary solutions were then analysed. These results showed that in-vivo stimulated whole human saliva provides an increased SBFP elasticity, while the alpha-amylase dramatically decreases its viscoelastic functions in oscillatory shear. The results obtained also suggest that mechanically stimulated saliva and alpha-amylase aqueous solutions do not offer adequate information concerning the real extensional properties of the bolus when blended with whole human saliva.

Linear viscoelastic behaviour of oil-in-water food emulsions stabilised by tuna-protein isolates

This work deals with the manufacture of oil-in-water food emulsions stabilised by tuna proteins. The influence of protein and oil concentrations on the linear viscoelastic properties and microstructure of these emulsions was analysed. Stable emulsions with suitable linear viscoelastic response and microstructural characteristics were formulated with 70 wt.% oil and, at least, 0.25 wt.% tuna protein. Similarly, emulsions with oil concentrations between 45 and 70 wt.% were prepared using 0.50 wt.% protein. All these emulsions showed a predominantly elastic response in the linear viscoelastic region and a well-developed plateau region in its mechanical spectrum. Rheological and droplet size distribution results pointed out an extensive droplet flocculation, due to interactions among emulsifier molecules located at the oil–water interface of adjacent droplets. As a result, the linear viscoelastic behaviour was controlled by protein–protein interactions, allowing the use of the plateau modulus to successfully normalise both the storage and loss moduli as a function of frequency onto a master curve, irrespective of the selected emulsion formulation.