Evidence of low-density water to high-density water structural transformation in milk during high-pressure processing

The objective of this research was to check whether the observed low-density water (LDW) to high-density water (HDW) transformation does take place or not in a complex aqueous system like those involved in high pressure processing of food. In-situ measurements of speed-of-sound up to 640 MPa were used for this purpose. After validation of the methodology in liquid water at 25 ºC, LDW-to-HDW transformation was also evidenced in sodium caseinate solution and milk samples. The transformation pressure was always observed at 275 MPa. Since water plays a key role in most biochemical transformations, the occurrence of a LDW-HDW transition should be taken into account for understanding the complex component interactions in milk and other related systems under pressure. Industrial relevance: Opportunities exist for the industry to use pressure as a tool for texturing dairy products. Process parameter choice to obtain a given texture is tricky due to the complexity of milk component interactions under pressure. As a main component in foods, water structural transformation under pressure should not be ignored by experts in the fieldThis work has been funded by the Spanish Ministry of Science and Innovation under project MALTA-Consolider Ingenio 2010 (CSD2007-00045), by the Spanish Ministry of Economy and Competitiveness under projects AGL2012-39756-C02-01/ALI, CTQ2015-67755-C2-1-R and MAT2015-71070-REDC, and by GRUPOS UCM 910481Peer reviewe

Caracterización multianalítica de meteorito marciano NWA2975 mediante CF-LIBS, fluorescencia de rayos X y espectroscopía Raman

La caracterización isotópica y elemental de los meteoritos de Marte ha permitido determinar la cronología de los procesos de formación del planeta y avanzar en la comprensión de su evolución biogeoquímica e hidrológica. Los meteoritos más abundantes son las rocas de origen ígneo, como las shergottitas. Los estudios petrológicos y geoquímicos previos del meteorito Northwest Africa 2975 (NWA 2975), revelaron que se trata de una roca volcánica de grano medio, entre subofítica y granular, compuesta predominantemente por piroxenos (57,3 vol.%) y plagioclasa (38,3 vol. %) completamente enmascarados con fases opacas (2,7 vol.%) y fosfatos (1,7 vol.%) [1]. El instrumento SuperCam a bordo del rover Perseverance (misión MARS 2020 de la NASA) está equipado con técnicas atómicas y moleculares (incluyendo LIBS y Raman) para la detección y análisis a distancia de muestras geológicas en la superficie del Planeta Rojo. La capacidad de estas técnicas se ha demostrado ampliamente en la caracterización de rocas, minerales y suelos en varias misiones espaciales. En el presente trabajo, se analizó un fragmento del meteorito NWA 2975 mediante un sistema de micro-LIBS con el objetivo de revelar su composición química elemental. Debido a la heterogeneidad intrínseca de la muestra, se analizaron diferentes posiciones de su superficie. El análisis cuantitativo de los elementos principales (Si, Al, Fe, Mg, Mn, Ca y O) y de otros elementos menores se llevó a cabo utilizando la metodología Calibration-Free [2]. Los resultados sugieren la presencia de piroxenos como principal componente mineral en las posiciones inspeccionadas, aunque también se pueden encontrar otras fases minerales como la plagioclasa. La información extraída del análisis LIBS se ha comparado con la de fluorescencia de rayos X (XRF) y la espectroscopia Raman. El uso combinado de diferentes técnicas espectroscópicas ha permitido obtener una mejor interpretación de los resultados composicionales.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Aqueous solutions of tris(1,2-diaminoethane)cobalt(III) chloride and tris(1,3-diaminopropane)cobalt(III) chloride atT = 278.15 K. Enthalpy of dilution

The enthalpies of dilution of aqueous solutions of {Co(en)3}Cl3and {Co(tn)3}Cl3(where en = 1,2-diaminoethane andtn = 1,3-diaminopropane) have been measured up to m = 1 mol · kg − 1at T = 278.15 K and atmospheric pressure with an isoperibol calorimeter by the long-jump method. Relative apparent molar enthalpies Lφ,mhave been extracted from an empirical polynomial of the molality square root. Previously reported data at T = 298.15 K are compared with the new experimental dilution results. A noticeable decrease in Lφ,mwas observed at every experimental concentration when temperature diminished from 298.15 K to 278.15 K. An inversion in the relative layout for the Lφ,mcurves of aqueous {Co(en)3}Cl3and {Co(tn)3}Cl3was also found.This research was supported by DGESIC (M.E.C., Spain) under Research ProjectNo.: PB98-0832.Peer reviewe

Graphite under non-hydrostatic conditions.

International audienc

An experimental device for accurate ultrasounds measurements in liquid food at high pressure

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Speed of sound in liquid water from (253.15 to 348.15) K and pressures from (0.1 to 700) MPa

Water thermodynamic properties are available as standards through the IAPWS-95 formulation of the equation of state. Among these properties, speed of sound is very useful for calibrating devices and for obtaining derived properties. However, the values of speed of sound calculated in the range (200 to 700) MPa are more uncertain than desirable, due to a lack of accurate experimental data above 200 MPa. The aim of this work is to provide a complete set of accurate speed of sound results in water covering the pressure range mentioned above. Speed of sound was determined by the multiple reflections method between (0.1 and 700) MPa at temperatures from (253.15 to 348.15) K. Estimated uncertainties at a confidence level of 95 % range between (0.22 and 0.32) % over the whole pressure range. These new results may help to improve the reference database for future parametrizations of the equation of state for water. © 2011 American Chemical Society.Peer Reviewe

Role of water structure on the high pressure micellization and phase transformations of sodium dodecanoate aqueous solutions

The aim of this work is to study the micelle formation and possible subsequent transformations of sodium dodecanoate aggregates in aqueous solutions at pressures up to 700 MPa. This pressure range is much larger than in most available studies on surfactant solutions and allows for evaluating the possible effect of the low-density to high-density water transformation on the aggregative behavior of the surfactant. The speed-of-sound and attenuation coefficient were determined at 298.15 K as a function of pressure at concentrations up to 0.13 mol kg-1 in water. The speed-of-sound behavior with concentration is maintained up to pressures around 350 MPa. The attenuation coefficient, initially insensitive to pressure, exhibits a sudden increase around 250 MPa, reaching a maximum around 350 MPa and a plateau above 500 MPa in the case of the highest studied surfactant concentrations. From the analysis of the changes observed in these properties, it was possible to extend the concentration-pressure phase diagram of sodium dodecanoate at constant temperature. Some peculiarities found were: (1) the critical micellar concentration reaches a maximum around 170 MPa, (2) the micellar phase disappears above 400 MPa, (3) a phase transformation starts around 250 MPa, setting the solubility limit of the surfactant at concentrations around 0.06 mol kg-1 in this pressure region, and (4) further transformations occur between 350 and 500 MPa. We discuss in length the possibility that such transformations might be driven by structural changes linked to the so-called low-density-water to high-density-water transition. © 2014 American Chemical Society.This work has been supported by MICINN/MINECO through Projects CSD2007-00045 and CTQ2012-38599-CO2-02 and by Comunidad de Madrid through Project QUIMAPRES S2009/PPQ-1551.Peer Reviewe

Effects of high pressure on unsaturated fatty acids

The objective of this study is to investigate the effects of high pressure processing on the molecular structure of some unsaturated fatty acids. Samples of elaidic acid, linoleic acid, ZE and EE conjugated linoleic acid are treated at 293 or 333 K at pressures up to 700 MPa. It is observed that the adiabatic heat generated from compression is able to bring the sample temperature above 373 K after 700 MPa. These relatively extreme conditions are of great interest for food sterilization, but they may induce undesirable change in fatty acid quality characteristics. To check for structural changes, Raman spectra of the samples are analysed after treatments. The comparison with Raman spectra of samples kept at atmospheric pressure shows that pressure induces some conformational changes at the hydrocarbon skeleton in solid samples, while the liquid ones remain unchanged. No cis/trans isomerization occurs, but gauche conformers are likely to be present.Peer Reviewe