Characterization of the mechanical properties of high-moisture meat analogues using low-intensity ultrasound: Linking mechanical properties to textural and nutritional quality attributes.

Plant-based meat analogues offer possible alternatives to meat consumption. However, many challenges remain to produce a palatable meat analogue as well as to understand the roles of different processing steps and ingredients on both the texture and nutritional properties of the final product. The goal of this paper is to help with addressing these challenges by using a low-intensity ultrasonic transmission technique, both online and 24 h after production, to investigate high-moisture meat analogues made from a blend of soy and wheat proteins. To understand the ultrasonic data in the context of traditional characterization methods, physical properties (meat analogue thickness, density, peak cutting force) and protein nutritional quality attributes of the meat analogues were also characterized separately. The ultrasonic velocity was found to decrease with the feed moisture content and to be strongly correlated (r = 0.97) with peak cutting force. This strong correlation extends over a wide range of moisture contents from 58% to 70%, with the velocity decreasing from about 1730 m/s to 1660 m/s over this range. The protein quality was high for all moistures, with the highest amino acid score and in vitro protein digestibility being observed for the highest moisture content treatment. The accuracy of the ultrasonic measurements was enhanced by the development of an innovative non-contact method, suitable for materials exhibiting low ultrasonic attenuation, to measure the meat analogue thickness ultrasonically and in a sanitary fashion - an advance that is potentially useful for online monitoring of production problems (e.g., extruder barrel-fill and cooling-die temperature issues). This study demonstrates, for the first time, the feasibility of using ultrasonic transmission techniques to measure both velocity and sample thickness simultaneously and provide information in real time during production that is well correlated with some textural and nutritional attributes of meat analogues.

A PDMS-based broadband acoustic impedance matched material for underwater applications.

Having a material that is matched in acoustic impedance with the surrounding medium is a considerable asset for many underwater acoustic applications. In this work, impedance matching is achieved by dispersing small, deeply subwavelength sized particles in a soft matrix, and the appropriate concentration is determined with the help of Coherent Potential Approximation and Waterman & Truell models. We show experimentally the validity of the models using mixtures of Polydimethylsiloxane (PDMS) and TiO2 particles. The optimized composite material has the same longitudinal acoustic impedance as water and therefore the acoustic reflection coefficient is essentially zero over a wide range of frequencies (0.5-6 MHz). PDMS-based materials can be cured in a mold to achieve desired sample shape, which makes them very easy to handle and to use. Various applications can be envisioned, such the use of impedance-matched PDMS in the design and fabrication of acoustically transparent cells for samples, perfectly matched layers for ultrasonic experiments, or superabsorbing metamaterials for water-borne acoustic waves.

Bubbles in noodle dough: Characterization by X-ray microtomography.

Bubbles, found in a huge variety of food products, are known to afford desirable quality attributes, especially those related to texture, mouthfeel and taste. However, the presence of bubbles and their effects on wheat flour noodles is an aspect that has been, until now, largely overlooked, despite the positive and negative connotations of bubbly inclusions on Asian noodle quality. X-rays from a synchrotron source (Biomedical Imaging and Therapy facility at the Canadian Light Source) were used to rapidly and non-destructively acquire tomographic images of noodle dough. Appropriate image analysis protocols were used to determine the bubble size distribution, the orientation of bubbles, and their position within the dough sheet. The effect of processing (one or multiple lamination steps) on bubble properties in the dough that was subsequently sheeted (gradual elongation and reduction in thickness) was investigated. Bubble size distributions, well captured by lognormal distribution function, showed that the lamination process induced bubble entrapment and reduction in bubble size. Bubbles were found to be flat, elongated and oriented in the sheeting direction, this effect being less for doughs laminated ten times (90° rotations between lamination steps). Interestingly, a gradient in concentration of bubbles within the dough sheet was found from the noodle core to the sheet edges. Aging effects were also apparent. This first non-destructive study of bubbles in wheat-flour noodle dough provides a more complete knowledge of the dough sheet's internal structure, and how it originates via processing, and this has repercussions on the overall quality of Asian noodles.

Dynamic sound scattering: Field fluctuation spectroscopy with singly scattered ultrasound in the near and far fields.

Dynamic sound scattering (DSS) is a powerful acoustic technique for investigating the motion of particles or other inclusions inside an evolving medium. In DSS, this dynamic information is obtained by measuring the field autocorrelation function of the temporal fluctuations of singly scattered acoustic waves. The technique was initially introduced 15 years ago, but its technical aspects were not adequately discussed then. This paper addresses the need for a more complete account of the method by describing in detail two different implementations of this sound scattering technique, one of which is specifically adapted to a common experimental situation in ultrasonics. The technique is illustrated by the application of DSS to measure the mean square velocity fluctuations of particles in fluidized suspensions, as well as the dynamic velocity correlation length. By explaining the experimental and analytical methods involved in realizing the DSS technique in practice, the use of DSS will be facilitated for future studies of particulate suspension dynamics and particle properties over a wide range of particle sizes and concentrations, from millimeters down to nanometers, where the use of optical techniques is often limited by the opacity of the medium.

Anderson Mobility Gap Probed by Dynamic Coherent Backscattering.

We use dynamic coherent backscattering to study one of the Anderson mobility gaps in the vibrational spectrum of strongly disordered three-dimensional mesoglasses. Comparison of experimental results with the self-consistent theory of localization allows us to estimate the localization (correlation) length as a function of frequency in a wide spectral range covering bands of diffuse transport and a mobility gap delimited by two mobility edges. The results are corroborated by transmission measurements on one of our samples.

Risk factors for bone pain among patients with cancer receiving myelosuppressive chemotherapy and pegfilgrastim.

PURPOSE: The purpose of this study was to evaluate risk factors for bone pain in patients receiving myelosuppressive chemotherapy and pegfilgrastim. METHODS: Individual patient data from 22 pegfilgrastim clinical trials were analyzed. Multivariable logistic regression models were used to evaluate risk factors associated with grade ≥2 bone pain and any grade bone pain in the first chemotherapy cycle and across cycles 1-6. RESULTS: Of the 1949 patients analyzed, 19 and 36 % had grade ≥2 and any grade bone pain, respectively, in cycle 1, and 28 and 51 % had grade ≥2 and any grade bone pain, respectively, across cycles 1-6. In cycle 1, history of bone pain (odds ratio (OR), 1.51; 95 % confidence interval (CI), 1.09-2.07) was associated with increased risk of grade ≥2 bone pain; age ≥65 years (versus <45 years; OR, 0.64; 95 % CI, 0.42-0.98), the European Union region (versus the USA region; OR, 0.32; 95 % CI, 0.20-0.52), colorectal cancer (versus breast cancer; OR, 0.14; 95 % CI, 0.05-0.41), and small-cell lung cancer (OR, 0.34; 95 % CI, 0.12-0.98) were associated with reduced risk of grade ≥2 bone pain. CONCLUSIONS: Potential risk factors for bone pain in patients receiving myelosuppressive chemotherapy and primary prophylactic pegfilgrastim identified in this study are younger age and history of bone pain. No other association with clinical factors and risk of bone pain was detected. Better understanding of risk factors for bone pain would be useful in identifying patients who may benefit from pain prevention strategies.

History of chronic comorbidity and risk of chemotherapy-induced febrile neutropenia in cancer patients not receiving G-CSF prophylaxis.

BACKGROUND: Chemotherapy-induced febrile neutropenia (FN) is a clinically important complication that affects patient outcome by delaying chemotherapy doses or reducing dose intensity. Risk of FN depends on chemotherapy- and patient-level factors. We sought to determine the effects of chronic comorbidities on risk of FN. DESIGN: We conducted a cohort study to examine the association between a variety of chronic comorbidities and risk of FN in patients diagnosed with six types of cancer (non-Hodgkin lymphoma and breast, colorectal, lung, ovary, and gastric cancer) from 2000 to 2009 who were treated with chemotherapy at Kaiser Permanente Southern California, a large managed care organization. We excluded those patients who received primary prophylactic granulocyte colony-stimulating factor. History of comorbidities and FN events were identified using electronic medical records. Cox models adjusting for propensity score, stratified by cancer type, were used to determine the association between comorbid conditions and FN. Models that additionally adjusted for cancer stage, baseline neutrophil count, chemotherapy regimen, and dose reduction were also evaluated. RESULTS: A total of 19 160 patients with mean age of 60 years were included; 963 (5.0%) developed FN in the first chemotherapy cycle. Chronic obstructive pulmonary disease [hazard ratio (HR) = 1.30 (1.07-1.57)], congestive heart failure [HR = 1.43 (1.00-1.98)], HIV infection [HR = 3.40 (1.90-5.63)], autoimmune disease [HR = 2.01 (1.10-3.33)], peptic ulcer disease [HR = 1.57 (1.05-2.26)], renal disease [HR = 1.60 (1.21-2.09)], and thyroid disorder [HR = 1.32 (1.06-1.64)] were all associated with a significantly increased FN risk. CONCLUSIONS: These results provide evidence that history of several chronic comorbidities increases risk of FN, which should be considered when managing patients during chemotherapy.

Observation of infinite-range intensity correlations above, at, and below the mobility edges of the 3D Anderson localization transition.

We investigate long-range intensity correlations on both sides of the Anderson transition of classical waves in a three-dimensional disordered material. Our ultrasonic experiments are designed to unambiguously detect a recently predicted infinite-range C0 contribution, due to local density of states fluctuations near the source. We find that these C0 correlations, in addition to C2 and C3 contributions, are significantly enhanced near mobility edges. Separate measurements of the inverse participation ratio reveal a link between C0 and the anomalous dimension Δ2, implying that C0 may also be used to explore the critical regime of the Anderson transition.

Recurrent scattering and memory effect at the Anderson localization transition.

We report on ultrasonic measurements of the propagation operator in a strongly scattering mesoglass. The backscattered field is shown to display a deterministic spatial coherence due to a remarkably large memory effect induced by long recurrent trajectories. Investigation of the recurrent scattering contribution directly yields the probability for a wave to come back close to its starting spot. The decay of this quantity with time is shown to change dramatically near the Anderson localization transition. The singular value decomposition of the propagation operator reveals the dominance of very intense recurrent scattering paths near the mobility edge.

Influence of internal interfacial area on nanosecond relaxation of wheat gluten proteins as probed by broadband ultrasonic spectroscopy.

Understanding interactions between interfaces and biopolymers in complex industrially processed materials of plant origin will allow for their better utilization. Wheat flour doughs are one such material whose industrial use strongly depends on such interactions due to their effect on the mechanical properties of the dough. To date, mechanical characterizations of dough have been limited to a narrow range of frequencies. Here, ultrasonic spectroscopy measurements over a very broad frequency range are used to show that a fast volumetric relaxation occurs in dough; the nanosecond timescale of the relaxation is associated with ultrasonic stress-induced changes in the secondary structure of gluten proteins. Interestingly, there is a four-fold difference in the speed of this relaxation phenomenon in doughs mixed in air (where substantial internal interfacial area exists) compared to those mixed under vacuum (where bubbles are absent). Given the large internal interfacial area in dough, the amphiphilic proteins residing at gas bubble interfaces significantly alter the high-frequency mechanical response of this important material.

Probing thermal transitions and structural properties of gluten proteins using ultrasound.

PURPOSE: To probe the thermal and structural properties of gluten proteins using ultrasound. METHODS: A new ultrasonic approach for characterizing the quality of wheat gluten proteins is described. Low frequency (50 kHz) longitudinal ultrasonic velocity, v L, measurements were performed on gluten samples extracted from three wheat flours differing in protein content and in wheat endosperm hardness. RESULTS: At room temperature, v L for gluten extracted from soft flowers (Fielder) was found to be (870 ± 92) m/s, while for gluten extracted from extra strong flours (Glenlea) it was found to be (1,940 ± 90) m/s. In the second set of experiments, which aimed at probing thermal properties of gluten proteins, the variation in the numerical value of v L propagating in the wet gluten was found to be substantial (about 1,000 m/s) when the temperature of the gluten was raised from 20 to 90 °C, and also when gluten from different flour types was investigated. A continuous structural phase transition was observed, which was different for glutens extracted from different flours. Upon cooling, the velocity also varied depending on wheat type. CONCLUSIONS: These experiments demonstrate that ultrasonic velocity measurements can be used as a selection tool and study changes in properties of wheat proteins, particularly the thermal transitions that are critical to the quality of end products such as noodles, pasta, and bread. It was also shown that v L is sensitive to gluten class (strength or protein content), showing the potential of such measurements as an early-generation selection tool in wheat breeding programs.

A statistical approach to direct density of states measurements in disordered systems.

A statistical method for measuring the modal density of elastic waves through direct mode counting in strongly scattering disordered systems is presented. To illustrate this approach, the results of ultrasonic experiments in a highly porous sintered glass bead network are reported. This method is shown to yield a reliable and robust measurement of the density of states, enabling mode-counting techniques to be applied to increasingly complex systems, where modal overlap and sensitivity to experimental conditions have previously hampered definitive results.

Experimental and theoretical evidence for subwavelength imaging in phononic crystals.

We show experimentally and theoretically that super resolution can be achieved while imaging with a flat lens consisting of a phononic crystal exhibiting negative refraction. This phenomenon is related to the coupling between the incident evanescent waves and a bound slab mode of the phononic crystal lens, leading to amplification of evanescent waves by the slab mode. Super resolution is only observed when the source is located very near to the lens, and is very sensitive to the location of the source parallel to the lens surface as well as to site disorder in the phononic crystal lattice.

Transmission of ultrasound through a single layer of bubbles.

We investigate, both experimentally and theoretically, the effect of coupling between resonant scatterers on the transmission coefficient of a model system of isotropic scatterers. The model system consists of a monodisperse layer of bubbles, which exhibit a strong monopole scattering resonance at low ultrasonic frequencies. The layer was a true 2D structure obtained by injecting very monodisperse bubbles (with radius a approximately 100 microm) into a yield-stress polymer gel. Even for a layer with a low concentration of bubbles (areal fraction, n pi a(2), of 10-20%, where n is the number of bubbles per unit area), the ultrasonic transmission was found to be significantly reduced by the presence of bubbles (-20 to -50 dB) and showed a sharp minimum at a particular frequency. Interestingly, this frequency did not correspond to the resonance frequency of the individual, isolated bubbles, but depended markedly on the concentration. This frequency shift is an indication of strong coupling between the bubbles. We propose a simple model, based on a self-consistent relation, which takes into account the coupling between the bubbles and gives good agreement with the measured transmission coefficient.

Ultrasonic investigation of the effect of vegetable shortening and mixing time on the mechanical properties of bread dough.

Mixing is a critical stage in breadmaking since it controls gluten development and nucleation of gas bubbles in the dough. Bubbles affect the rheology of the dough and largely govern the quality of the final product. This study used ultrasound (at a frequency where it is sensitive to the presence of bubbles) to nondestructively examine dough properties as a function of mixing time in doughs prepared from strong red spring wheat flour with various amounts of shortening (0%, 2%, 4%, 8% flour weight basis). The doughs were mixed for various times at atmospheric pressure or under vacuum (to minimize bubble nucleation). Ultrasonic velocity and attenuation (nominally at 50 kHz) were measured in the dough, and dough density was measured independently from specific gravity determinations. Ultrasonic velocity decreased substantially as mixing time increased (and more bubbles were entrained) for all doughs mixed in air; for example, in doughs made without shortening, velocity decreased from 165 to 105 ms(-1), although superimposed on this overall decrease was a peak in velocity at optimum mixing time. Changes in attenuation coefficient due to the addition of shortening were evident in both air-mixed and vacuum-mixed doughs, suggesting that ultrasound was sensitive to changes in the properties of the dough matrix during dough development and to plasticization of the gluten polymers by the shortening. Due to its ability to probe the effect of mixing times and ingredients on dough properties, ultrasound has the potential to be deployed as an online quality control tool in the baking industry.

Mesoscopic phase statistics of diffuse ultrasound in dynamic matter.

Temporal fluctuations in the phase of waves transmitted through a dynamic, strongly scattering, mesoscopic sample are investigated using ultrasonic waves, and compared with theoretical predictions based on circular Gaussian statistics. The fundamental role of phase in diffusing acoustic wave spectroscopy is revealed, and phase statistics are also shown to provide a sensitive and accurate way to probe scatterer motions at both short and long time scales.

Characterizing a model food gel containing bubbles and solid inclusions using ultrasound.

Ultrasonic spectroscopy is used to characterize a model aerated food system consisting of agar gel in which both bubbles and polystyrene beads are embedded. By exploiting the distinct frequency dependence of each inclusion's acoustic resonances, it is demonstrated that the sizes of the bubbles and beads can be measured by ultrasound even when the size distributions are so similar that these inclusions are difficult to distinguish in optical images. While these results demonstrate the potential for applying ultrasonic spectroscopy to evaluate any soft heterogeneous material in which both bubbles and solid inclusions are present, the technique is especially relevant for functional foods, in which solid functional ingredients must be incorporated without degrading the aerated structure of the food and causing unacceptable quality impairment.

Focusing of sound in a 3D phononic crystal.

We present a combined experimental and theoretical study of phonon focusing phenomena in a pass band above the complete band gap in a 3D phononic crystal. Wave propagation was found to depend dramatically on both frequency and incident direction. This propagation anisotropy leads to very large negative refraction, which can be used to focus a diverging ultrasonic beam into a narrow focal spot with a large focal depth. The experimental field patterns are well explained using a Fourier imaging technique, based on the 3D equifrequency surfaces calculated from multiple scattering theory.

Field fluctuation spectroscopy in a reverberant cavity with moving scatterers.

We report a study of transient ultrasonic waves inside a reverberant cavity containing moving scatterers. We show that the elastic mean free path and the dynamics of the scatterers govern the evolution of the autocorrelation of acoustic wave field. A parallel is established between these results and a closely related technique, diffusing acoustic wave spectroscopy. Excellent agreement is found between experiment and theory for a moving stainless steel ball in a water tank, thereby elucidating the underlying physics, and a potential application, fish monitoring inside aquariums, is demonstrated.

Diffusing acoustic wave spectroscopy.

We have developed a technique in ultrasonic correlation spectroscopy called diffusing acoustic wave spectroscopy (DAWS). In this technique, the motion of the scatterers (e.g., particles or inclusions) is determined from the temporal fluctuations of multiply scattered sound. In DAWS, the propagation of multiply scattered sound is described using the diffusion approximation, which allows the autocorrelation function of the temporal field fluctuations to be related to the dynamics of the multiply scattering medium. The expressions relating the temporal field autocorrelation function to the motion of the scatterers are derived, focusing on the types of correlated motions that are most likely to be encountered in acoustic measurements. The power of this technique is illustrated with ultrasonic data on fluidized suspensions of particles, where DAWS provides a sensitive measure of the local relative velocity and strain rate of the suspended particles over a wide range of time and length scales. In addition, when combined with the measurements of the rms velocity of the particles using dynamic sound scattering, we show that DAWS can be used to determine the spatial extent of the correlations in the particle velocities, thus indirectly measuring the particle velocity correlation function. Potential applications of diffusing acoustic wave spectroscopy are quite far reaching, ranging from the ultrasonic nondestructive evaluation of the dynamics of inhomogeneous materials to geophysical studies of mesoscopic phenomena in seismology.