Rheological behaviour of fruit and milk-based smoothies

Two of the most important food attributes for today´s fast-moving lifestyle are convenience and healthiness [1-2]. Fast-moving lifestyle specifically affects to elderly people, who are prone to bad-nutrition due to their dental status reducing the consumption of fruits and vegetables [3]. Smoothies are blended beverages, and good examples of convenient and healthy foods for helping to reduce this problem. So, they are gaining increasing market leverage in the beverage sector. Texture and rheological behaviour of foods can determine their acceptability. Therefore, added to nutritious features, smoothies must also account with outstanding mechanical properties. Stability of the products is also a main quality, which can be gained adding a small amount of stabiliser to beverage formulations. But, to avoid opposite effects, stabilisers addition should ameliorate the product texture.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Heat transfer enhancement using nanofluids in the compression exchanger in a solar Stirling engine

In this paper a improvement in the heat exchange of a solar Stirling engine during the compression phase was studied. The viability of using nanoparticles as ceramic oxide (Al2O3 in water) at different concentrations instead of conventional refrigerants (water or air) was evaluated. Since these systems could behave as non- Newtonian fluids the dynamic viscosity was measured, as well as other thermophysical properties. The results showed that the convective heat transfer coefficient could raise one order of magnitude respect to the conventional heat transfer fluids at moderately volume fractions (over 0.15).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Characterization and thermophysical properties of rutile and alumina nanofluids

The characterization in relation to shape and particle size of alumina and rutile suspensions was performed. The intrinsic viscosity exhibited the presence of nonspherical aggregates in both suspensions although TEM images showed non monodisperse spherical shape of alumina particles. DLS indicated the existence of particle aggregates for both systems. In all cases, the increase in thermal conductivity with respect to the base fluid is verified. The thermal conductivities obtained experimentally were compared with three mathematical models, which yielded lower values than those measured. From rheological measurements and by means of the Peclet number defined in colloidal suspensions, values of thermal conductivity were also proposed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Electrorheological behaviour of flour/olive oil dough

• Changes in flow properties upon the application of an electrical field can be evaluated using of electrorheological techniques. • The fact that it had shown successful to reduce the fat content [1] has aimed us to explore potential benefits resulting from the wide use of this technique in food science. • It was claimed long time ago that the integration of this technique in food processing should translate into the development of new products [2]. • A study on the influence of the solid content and temperature on the steady viscous flow electrorheological behavior of wheat flour/olive oil dough has been made. • The overall conclusion is that this system is electrorheological positive, i.e. the yield stress increases with the electric field.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Activation energy in particle suspensions

Assuming that the molar activation energy in a fluid is interpreted as a measure of the potential energy barrier required for the molecular movement [1], the viscosity of a fluid depends on the actual size of the molecules, and the presence of solid particles in a suspension increases the dissipation of energy when the system flows, therefore it is expected that the viscosity of the suspension is higher than that of the pure solvent at a given temperature. The dependence of the viscosity of some silica/glycol suspensions with the temperature can be fitted using an empirical function analogous to the Arrhenius equation, ln⁡η=E/RT-ln⁡C, where η is the viscosity, C is a system-dependent constant, E is the molar activation energy for the viscous flow, T is the absolute temperature and R is the gas universal constant. When the temperature of the suspension decreases two effects are observed. First, larger aggregates of particles are formed due to the reduction of the thermal agitation and, second, the number of links among the molecules of the liquid phase increases. These two effects give place to a higher increase in the viscosity with the temperature compared to the pure solvent. Assuming that a higher viscosity value is due to a smaller free volume available for the molecular movement, and taking into account that the free suspension volume is limited only to the liquid fraction [2], it should be expected that the viscosity of the suspension is less sensitive to temperature than that of the pure solvent. In this work the dependence on the temperature of the viscosity values of the silica/glycol suspensions is compared to that of the liquid media. The results have shown a lower activation energy when the solid volume fraction increases, which has been explained with a scheme that assumes that the particle links are less sensitive to thermal energy absorption than the joining bonds among the solvent molecules. Our conclusion is that, for a given mechanical energy applied to the system, the thermal energy absorbed by the system is mainly used in the rupture of bonds between the solvent molecules. This study can be useful to understand the mechanisms that govern the differences in the activation energy values found between samples of foods, in which many factors are connected with sample composition [3]. [1] Briscoe B, Luckham P, Zhu S. Rheological properties of poly (ethylene oxide) aqueous solutions. J Appl Polym Sci 70 (1998) 419-429. [2] Shenoy AV. Rheology of filled polymer systems. Kluwer Acad Pub, 1999, The Netherlands. [3] Alvarez MD, Canet W. Time-independent and time-dependent rheological characterization of vegetable-based infant purees. J Food Eng 114 (2013) 449-464.Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tech

Rheological study of the aggregation state of alumina nanofluids

Se adjunta una comunicación, aunque se han publicado tres comunicaciones más.The presence of alumina solid particles in aqueous phase induces a change in the viscosity of the suspension from Newtonian to non- Newtonian flow. Besides, the presence of solid particles is adequate for the use as a heat exchanger fluid. The effect of nanoparticle size on thermal properties of nanofluids is still today a question, which is far from being answered. In this respect, the results reported in the literature are contradictory [1], probably due to the formation of aggregates when particles are dispersed in the liquid phase. Regarding to the nanoparticle shape influence in thermal conductivity, cylinders and spheres have been considered as the more effective in heat transfer. Spherical nanoparticles of alumina, which is one of the most investigated nanofluid, dispersed in water were used in this study. TEM images showed a mean average diameter of 50 nm. However, DLS measurements showed monodispersed particles of 260 nm. Very recently [2], the relationship between shear rheology and aggregation state of suspensions has been reviewed. Mechanical and physical properties of the resultant materials depend on shape, size and size distribution, which are considered determining parameters in the formation of particle aggregates. The steady shear flow (figure 1) has shown that these clusters, when they are at rest, are formed by highly branched aggregates that erode when shear rate increases, until a suspension of individual particles is achieved. These results are in good agreement with the intrinsic viscosity obtained by Money and Krieger-Dougherty models. In both cases, these values are far from the 2.5 corresponding to spherical particles. The temperature effects were also taken into account.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Experimental assessment of thermal and rheological properties of coconut oil-silica as green additives in drilling performance based on minimum quantity of cutting fluids

Conventional metal working fluids are prepared from petroleum based mineral oils with toxic, carcinogenic, non- biodegradable and unsustainable additives, which can cause serious environmental contamination and health risks to operators. Formulations with non-toxic emulsifiers and natural additives such as vegetable oils are currently being considered for further development and use of non-toxic tribological products. This study is concerned with the thermal and flow properties of a cutting fluid (taladrine, T) mixed with a phase change material (PCM) coconut oil (CO) in a proportion of 1:9 (CO-0.1T) and hydrophilic silica in 0.01, 0.03 and 0.05 vol fractions. The thermal properties were evaluated by differential scanning calorimetry (DSC) and thermal conductivity measurements while the flow properties were assessed by viscosity temperature curves. The addition of solid particles has demonstrated an enhancement of the thermal conductivities with small differences in the latent heat. The microstructure of the suspensions was established from the DSC cooling dynamic ther- mogram and the rheological measurements. These results were confirmed by the images of optical polarized microscopy in which plate-like needles were observed. The suspension of 0.03 silica in CO-0.1T demonstrated an adequate gel strength and produced a reduction of 11 ◦C in drilling performance. A Minimum Quantity of Cutting Fluid (MQCF) of 2 g as an alternative for dry machining and flood cooling. It also prevented evaporative loss and removed metal chips, as a high viscosity complex fluid. In this work the use of phase change materials filled with solid particles as a way of sustainable eco-friendly toxic waste removal in drilling was justified.Funding for open access charge: Universidad de Málag

Rheological behavior of a commercial milk-based sauce

• The acceptation of semisolid foods by consumers is greatly determined by their rheological properties. • Sauces are semisolid foods and, in general, show viscoplastic and shear-thinning viscous flow behaviours. On the other hand, viscoelastic properties are specifically significant in the handling and quality control tasks. • As temperature changes cause alterations in physical and chemical properties of food components, which influence in texture, stability, taste, etc., a better understanding of the influence of this parameter on milk-based sauces would allow improve product quality.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

ABCG2 transporter plays a key role in the biodistribution of melatonin and its main metabolites

[EN] The ATP-binding cassette G2 (ABCG2) is an efflux transporter expressed in the apical membrane of cells from a large number of tissues, directly affecting bioavailability, tissue accumulation, and secretion into milk of both xenobiotics and endogenous compounds. The aim of this work was to characterize the role of ABCG2 in the systemic distribution and secretion into milk of melatonin and its main metabolites, 6-hydroxymelatonin, and 6-sulfatoxymelatonin. For this purpose, we first showed that these three molecules are transported by this transporter using in vitro transepithelial assays with MDCK-II polarized cells transduced with different species variants of ABCG2. Second, we tested the in vivo effect of murine Abcg2 in the systemic distribution of melatonin and its metabolites using wild-type and Abcg2−/− mice. Our results show that after oral administration of melatonin, the plasma concentration of melatonin metabolites in Abcg2−/− mice was between 1.5 and 6-fold higher compared to the wild-type mice. We also evaluated in these animals differences in tissue accumulation of melatonin metabolites. The most relevant differences between both types of mice were found for small intestine and kidney (>sixfold increase for 6-sulfatoxymelatonin in Abcg2−/− mice). Finally, melatonin secretion into milk was also affected by the murine Abcg2 transporter, with a twofold higher milk concentration in wild-type compared with Abcg2−/− lactating female mice. In addition, melatonin metabolites showed a higher milk-to-plasma ratio in wild-type mice. Overall, our results show that the ABCG2 transporter plays a critical role in the biodistribution of melatonin and its main metabolites, thereby potentially affecting their biological and therapeutic activity.SIPublicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

Analysis of the interaction between tryptophan-related compounds and ATP-binding cassette transporter G2 (ABCG2) using targeted metabolomics

ATP-binding cassette transporter G2 (ABCG2) is involved in the secretion of several compounds in milk. The in vitro and in vivo interactions between tryptophan-related compounds and ABCG2 were investigated. The tryptophan metabolome was determined by liquid chromatography-tandem mass spectrometry in milk and plasma from wild-type and Abcg2-/- mice as well as dairy cows carrying the ABCG2 Y581S polymorphism (Y/S) and noncarrier animals (Y/Y). The milk-to-plasma ratios of tryptophan, kynurenic acid, kynurenine, anthranilic acid, and xanthurenic acid were higher in wild-type mice than in Abcg2-/- mice. The ratio was 2-fold higher in Y/S than in Y/Y cows for kynurenine. In vitro transport assays confirmed that some of these compounds were in vitro substrates of the transporter and validated the differences observed between the two variants of the bovine protein. These findings show that the secretion of metabolites belonging to the kynurenine pathway into milk is mediated by ABCG2.SIThis study was supported by the research projects AGL2015-65626-R (MINECO/FEDER, UE) and RTI2018-100903-B-I00 (AEI/FEDER, UE), predoctoral grants from the Ministry of Economy, Industry, and Competitiveness (BES-2016-077235 grant to AMGL), and grants from the Spanish Ministry of Education, Culture, and Sport (FPU14/05131 grant to DGM). Funding was also obtained from a research contract for OJP from the Spanish Health Institute Carlos III (CPII16/00027