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Soria A.C.,Institute Fermentaciones Industriales | Corzo-Martinez M.,Institute Fermentaciones Industriales | Montilla A.,Institute Fermentaciones Industriales | Riera E.,Institute Fermentaciones Industriales | And 2 more authors.
Journal of Agricultural and Food Chemistry | Year: 2010

Preservation of the quality and bioactivity of carrots dehydrated by power ultrasound (US) under different experimental conditions including prior blanching has been evaluated for the first time by measuring the evolution of the Maillard reaction and the changes in soluble sugars, proteins, total polyphenols, antioxidant activity, and rehydration ability. This study also includes a comparison with a freeze-dried sample and data of commercial dehydrated carrots. The synergic effect of US and temperature (60°C) increased the dehydration rate of carrots (90% moisture loss in only 75 min) while still providing carrots with a level of 2-furoylmethyl-amino acids significantly lower than that of dehydrated commercial samples. Whereas a decrease in the content of reducing soluble sugars was observed with processing temperature, minor carbohydrates (scyllo- and myo-inositol and sedoheptulose) were rather stable, irrespective of the US dehydration parameters. Blanching significantly improved the rehydration ability of US-dehydrated carrots without increasing the loss of soluble sugars by leaching. As supported by the similarity of most quality indicators studied in both US-treated and freeze-dried carrots, the mild processing conditions employed in US dehydration gave rise to premium quality dehydrated carrots. © 2010 American Chemical Society.

Pardo L.,CSIC - Institute of Materials Science | Garcia A.,CSIC - Institute of Materials Science | De Espinosa F.M.,Institute Acustica | Brebol K.,Limiel ApS
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2011

The determination of the characteristic frequencies of an electromechanical resonance does not provide enough data to obtain the material properties of piezoceramics, including all losses, from complex impedance measurements. Values of impedance around resonance and antiresonance frequencies are also required to calculate the material losses. Uncoupled resonances are needed for this purpose. The shear plates used for the material characterization present unavoidable mode coupling of the shear mode and other modes of the plate. A study of the evolution of the complex material coefficients as the coupling of modes evolves with the change in the aspect ratio (lateral dimension/thickness) of the plate is presented here. These are obtained using software. A soft commercial PZT ceramic was used in this study and several shear plates amenable to material characterization were obtained in the range of aspect ratios below 15. The validity of the material properties for 3-D modeling of piezoceramics is assessed by means of finite element analysis, which shows that uncoupled resonances are virtually pure thickness-driven shear modes. © 2011 IEEE.

Dubus B.,CNRS Institute of Electronics, Microelectronics and Nanotechnology | Vanhille C.,Rey Juan Carlos University | Campos-Pozuelo C.,Institute Acustica | Granger C.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
Ultrasonics Sonochemistry | Year: 2010

The cavitation field generated by an ultrasonic horn at low frequency and high power is known to self-organize into a conical bubble structure. The physical mechanism at the origin of this bubble structure is investigated using numerical simulations and acoustic pressure measurements. The thin bubbly layer lying at horn surface is shown to act as a nonlinear thickness resonator that amplifies acoustic pressure and distorts acoustic waveform. This mechanism explains the self-stabilization of the conical bubble structure as well as the generation of shock wave and the focusing at very short distance. © 2010 Elsevier B.V. All rights reserved.

Vanhille C.,Rey Juan Carlos University | Campos-Pozuelo C.,Institute Acustica
Journal of Computational Acoustics | Year: 2010

This paper deals with the nonlinear propagation of ultrasonic pulses in a homogeneous medium in which a bubbly layer is placed. The medium we use is air bubbles in water. During the propagation of a pulse, the interaction of the acoustic field and bubbles vibration is assured via the coupling of a nonlinear differential system. The solution is tracked in the time domain by means of the SNOW-BL code. In the biphasic fluid, attenuation and nonlinear effects are due to the bubbles only. The study addresses to two applications: filter effects of the layer and nonlinear characterization of liquidgas mixtures. We study the filter effects (screen effect) a layer has for some frequency ranges present in the initial ultrasonic pulses, in the linear and nonlinear regimes, i.e. for low and high pressure amplitude. One (or several) simple layer is contemplated in numerical experiments with different bubble densities, bubble sizes, layer thicknesses, for different kinds of pulse. © 2010 IMACS.

Sancho-Knapik D.,CSIC - Centro de Investigación y Tecnología Agroalimentaria | Gomez Alvarez-Arenas T.,Institute Acustica | Peguero-Pina J.J.,CSIC - Centro de Investigación y Tecnología Agroalimentaria | Gil-Pelegrin E.,CSIC - Centro de Investigación y Tecnología Agroalimentaria
Journal of Experimental Botany | Year: 2010

The implementation of non-destructive methods for the study of water changes within plant tissues and/or organs has been a target for some time in plant physiology. Recent advances in air-coupled ultrasonic spectroscopy have enabled ultrasonic waves to be applied to the on-line and real-time assessment of the water content of different materials. In this study, this technique has been applied as a non-destructive, non-invasive, non-contact, and repeatable method for the determination of water status in Populus×euramericana and Prunus laurocerasus leaves. Frequency spectra of the transmittance of ultrasounds through plant leaves reveal the presence of at least one resonance. At this resonant frequency, transmittance is at its maximum. This work demonstrates that changes in leaf relative water content (RWC) and water potential (Ψ) for both species can be accurately monitored by the corresponding changes in resonant frequency. The differential response found between both species may be due to the contrasting leaf structural features and the differences found in the parameters derived from the P-V curves. The turgor loss point has been precisely defined by this new technique, as it is derived from the lack of significant differences between the relative water content at the turgor loss point (RWCTLP) obtained from P-V curves and ultrasonic measurements. The measurement of the turgor gradient between two different points of a naturally transpiring leaf is easily carried out with the method introduced here. Therefore, such a procedure can be an accurate tool for the study of all processes where changes in leaf water status are involved.

Carcel J.A.,Polytechnic University of Valencia | Garcia-Perez J.V.,Polytechnic University of Valencia | Mulet A.,Polytechnic University of Valencia | Rodriguez L.,Polytechnic University of Valencia | Riera E.,Institute Acustica
Physics Procedia | Year: 2010

Grape stalks and olive leaves present high amount of phenolic compounds with antioxidant properties. The extraction of these compounds may be considered a way to increase in value both agro-food by-products. Ultrasound is widely applied in extraction due to its effects (cavitation, microstirring or sponge effect) over the process. The goal of this work was to address the application of ultrasound on the antioxidant extraction of olive leaves and grape stalk. For that purpose, the extraction of antioxidant compounds from grape stalks and olive leaves, previously dried at 100 °C, were carried out using a ethanolic solution (80 % v/v) at 60 °C. Extractions were carried out with (US; 30 kHz; 600W)) and agitation (AG) without ultrasound application. In the AG experiments, the solution was agitated with a stirrer. Samples were obtained at different extraction time (10, 30, 60, 120, 180, 240, 360, 480 and 1440 min) and their antioxidant capacity was measured using FRAP method. The Naik model was used to model the extraction kinetics, being identified the antioxidant capacity of extracts at the equilibrium (Yeq) and the initial velocity of extraction (Yeq/B). For grape stalks, the antioxidant capacity of extracts at the equilibrium (Yeq) and the initial velocity of extraction (Yeq/B) were higher in AG experiments than in US experiments. In the olive leaves extractions, the Yeq/B was of the same order for both treatments but Yeq was significantly higher for US experiments. The different influence of ultrasound for both by-products can be explained from their different geometry and structure.

Ortuno C.,Polytechnic University of Valencia | Perez-Munuera I.,Polytechnic University of Valencia | Puig A.,Polytechnic University of Valencia | Riera E.,Institute Acustica | Garcia-Perez J.V.,Polytechnic University of Valencia
Physics Procedia | Year: 2010

Power ultrasound application on convective drying of foodstuffs may be considered an emergent technology. This work deals with the influence of power ultrasound on drying of natural materials addressing the kinetic as well as the product's microstructure. Convective drying kinetics of orange peel slabs (thickness 5.95 ± 0.41 mm) were carried out at 40 °C and 1 m/s with (US) and without (AIR) power ultrasound application. A diffusion model considering external resistance to mass transfer was considered to describe drying kinetics. Fresh, US and AIR dried samples were analyzed using Cryo-SEM. Results showed that drying kinetics of orange peel were significantly improved by the application of power ultrasound. From modeling, it was observed a significant (p<0.05) increase in both mass transfer coefficient and effective moisture diffusivity. The effects on mass transfer properties were confirmed from microestructural observations. In the cuticle surface, the pores were obstructed by wax components scattering, which evidence the ultrasonic effects on the interfaces. The cells of the flavedo were compressed and large intercellular air spaces were generated in the albedo facilitating water transfer through it.

Gonzalez I.,Institute Acustica | Fernandez L.J.,IKERLAN - IK4 | Gomez T.E.,Institute Acustica | Berganzo J.,IKERLAN - IK4 | And 2 more authors.
Sensors and Actuators, B: Chemical | Year: 2010

A new polymer microchip is presented in this paper for separation and particle sorting in flowing suspensions. It includes a microchannel where a fluid-sample containing particles flows in parallel with another liquid. The working principle is based on an ultrasonic actuation on the cross-section of the chip, which behaves as a multilayer system. That part of the wave established within the channel includes a node of pressure strategically located within the collector fluid path, where the target particles collected to be extracted from their host sample. The use of a polymer as the constitutive material of the chip, new in this type of devices, allows a channel width somewhat larger than a quarter of a wavelength, which does not fit any of the conventional models but it represents an intermediate situation. The device has been fabricated by standard SU-8 photolithography using PMMA as substrate. In the experiments, polystyrene particles of 20 μm in diameter have been extracted from aqueous suspensions containing 6-μm sized particles by a strategic application of ultrasonic waves. A high efficiency of particle separation, over 95%, at different concentrations and flow rates, prove the feasibility of the device to carry out sorting processes on flowing suspensions. © 2009 Elsevier B.V. All rights reserved.

A method that combines transmission of air-coupled ultrasound pulses through solid plates and amplitude and phase spectral analysis is presented. In particular, the method analyzes the first thickness resonance of the plates. The purpose is to determine, simultaneously, velocity and attenuation coefficient of the ultrasounds in the material and the thickness of the plate. This is especially useful when thickness can not be measured independently. The method is successfully applied to soft membranes, biological samples and FRP composites. © 2009 Elsevier B.V. All rights reserved.

Gallego-Juarez J.A.,Institute Acustica
Physics Procedia | Year: 2010

Although the application of ultrasonic energy to produce or to enhance a wide variety of processes have been explored since about the middle of the 20th century, only a reduced number of ultrasonic processes have been established at industrial level. However, during the last ten years the interest in ultrasonic processing has revived particularly in industrial sectors where the ultrasonic technology may represent a clean and efficient tool to improve classical existing processes or an innovation alternative for the development of new processes. Such seems to be the case of relevant sectors such as food industry, environment, pharmaceuticals and chemicals manufacture, machinery, mining, etc where power ultrasound is becoming an emerging technology for process development. The possible major problem in the application of high-intensity ultrasound on industrial processing is the design and development of efficient power ultrasonic systems (generators and reactors) capable of large scale successful operation specifically adapted to each individual process. In the area of ultrasonic processing in fluid media and more specifically in gases, the development of the steppedplate transducers and other power generators with extensive radiating surface has strongly contributed to the implementation at semi-industrial and industrial stage of several commercial applications, in sectors such as food and beverage industry (defoaming, drying, extraction, etc), environment (air cleaning, sludge filtration, etc...), machinery and process for manufacturing (textile washing, paint manufacture, etc). The development of different cavitational reactors for liquid treatment in continuous flow is helping to introduce into industry the wide potential of the area of sonochemistry. Processes such as water and effluent treatment, crystallization, soil remediation, etc have been already implemented at semi-industrial and/or industrial stage. Other single advances in sectors like mining or energy have also to be mentioned. The objective of this paper is to review some recent developments in ultrasonic processing to show the present situation and the prospective progresses of high-power ultrasonics as an innovative technology in many industrial sectors.

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