Calorimetric method for measuring high ultrasonic power using water as a heating material

Modeling and Optimization of Ultrasound-Assisted Extraction of Bioactive Compounds from Allium sativum Leaves Using Response Surface Methodology and Artificial Neural Network Coupled with Genetic Algorithm

This study explains the effect of ultrasound on the extraction of the bioactive compounds from garlic (Allium sativum L.) leaf powder. The experiment was carried out by varying the ultrasound amplitude (30-60%), treatment time (5-15 min), and ethanol concentration (40-60%) required to obtain the maximum extraction yield of total phenol content (TPC), total flavonoid content (TFC), and antioxidant activity. Rotatable central composite design (RCCD) provided experimental parameter combinations in the ultrasound-assisted extraction (UAE) of garlic leaf powder. The values of extraction yield, TPC, TFC, and antioxidant activity for the optimized condition of RSM were obtained at 53% amplitude, 13 min of treatment time, and 50% ethanol concentration. The values of the target compounds predicted at this optimized condition from RSM were 32.2% extraction yield, 9.9 mg GAE/g TPC, 6.8 mg QE/g TFC, and 58% antioxidant activity. The ANN-GA optimized condition for the leaf extracts was obtained at 60% amplitude, 13 min treatment time, and 53% ethanol concentration. The predicted values of optimized condition obtained by ANN-GA were recorded as 32.1738% extraction yield and 9.8661 mg GAE/g, 6.8398 mg QE/g, and 58.5527% for TPC, TFC, and antioxidant activity, respectively. The matured leaves of garlic, if not harvested during its cultivation, often go waste despite being rich in antioxidants and phenolic compounds. With the increased demand for the production of value-added products, the extraction of the bioactive compounds from garlic leaves can resolve waste management and potential health issues without affecting the crop yield through the process for high-end use in value addition.

The Impact of High-Intensity Ultrasound-Assisted Extraction on the Structural and Functional Properties of Hempseed Protein Isolate (HPI)

Hempseed protein has become a promising candidate as a future alternative protein source due to its high nutritional value. In the current study, hempseed protein isolate (HPI) was obtained using ultrasonic-assisted extraction with the aim to improve the functionality of HPI via protein structure modification. The solubility of HPI could be improved twofold under 20 kHz ultrasound processing compared to conventional alkaline extraction-isoelectric point precipitation. The protein solubility was gradually enhanced as the ultrasonic power improved, whereas excessive ultrasound intensity would cause a decline in protein solubility. Ultrasonic processing was found to have beneficial effects on the other functionalities of the extracted HPI, such as emulsifying and foaming properties. This improvement can be ascribed to the physical effects of acoustic cavitation that changed the secondary and tertiary structures of the protein to enhance surface hydrophobicity and decrease the particle size of the extracted protein aggregates. In addition, more available thiols were observed in US-treated samples, which could be another reason for improved functionality. However, the results of this study also revealed that prolonged high-power ultrasound exposure may eventually have a detrimental impact on HPI functional properties due to protein aggregation. Overall, this study suggests that high intensity ultrasound can enhance the functionality of HPI, which may ultimately improve its value in HPI-based food products.

Mechanisms for removal of gaseous toluene in headspace using sonophysical and sonochemical effects at the gas-liquid interface

We developed a new method for removing gaseous substances by using high frequency (200 kHz) ultrasonic irradiation of water, and the effects of ultrasonic irradiation on gas-phase toluene were evaluated quantitatively for the first time. The removal ratio of gaseous toluene increased with increasing ultrasonic power, but the reaction was inhibited by the addition of radical scavengers, indicating that ultrasonic irradiation not only accelerated the dissolution of gaseous toluene but also induced toluene decomposition. The contribution made by OH radicals to the decomposition of gaseous toluene at the gas-liquid interface was confirmed by the difference in removal ratios between addition of KI and addition of tert-butyl alcohol. The toluene removal mechanism was investigated by studying the logarithmic plots for toluene concentration at specified times. The results of this study clearly showed the promotion of gaseous toluene dissolution and the reaction via OH radicals at the gas-liquid interface by sonophysical and sonochemical effects with both effects contributing to the removal of gaseous toluene. Furthermore, the total organic carbon concentration in the aqueous phase increased with increasing reaction time, indicating that the toluene degradation products were trapped and decomposed into low-molecular-weight organic compounds in the aqueous phase.

Electron paramagnetic resonance of sonicated powder suspensions in organic solvents

The chemical effects of the acoustic cavitation generated by ultrasound translates into the production of highly reactive radicals. Acoustic cavitation is widely explored in aqueous solutions but it remains poorly studied in organic liquids and in particular in liquid/solid media. However, several heterogeneous catalysis reactions take place in organic solvents. Thus, we sonicated trimethylene glycol and propylene glycol in the presence of silica particles (SiO₂) of different sizes (5-15 nm, 0.2-0.3 µm, 12-26 µm) and amounts (0.5 wt% and 3 wt%) at an ultrasound frequency of 20 kHz to quantify the radicals generated. The spin trap 5,5-dimethyl-1-pyrrolin-N-oxide (DMPO) was used to trap the generated radicals for study by electron paramagnetic resonance (EPR) spectroscopy. We identified the trapped radical as the hydroxyalkyl radical adduct of DMPO, and we quantified it using stable radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a quantitation standard. The concentration of DMPO spin adducts in solutions containing silica size 12-26 µm was higher than the solution without particles. The presence of these particles increased the concentration of the acoustically generated radicals by a factor of 1.5 (29 µM for 0.5 wt% of SiO₂ size 12-26 µm vs 19 µM for 0 wt%, after 60 min of sonication). Ultrasound produced fewest radicals in solutions with the smallest particles; the concentration of radical adducts was highest for SiO₂ particle size 12-26 µm at 0.5 wt% loading, reaching 29 µM after 60 min sonication. Ultrasound power of 50.6 W produced more radicals than 24.7 W (23 µM and 18 µM, respectively, at 30 min sonication). Increased temperature during sonication generated more radical adducts in the medium (26 µM at 75 °C and 18 µM at 61 °C after 30 min sonication). Acoustic cavitation, in the presence of silica, increased the production of radical species in the studied organic medium.

Ultrasound-assisted hydration of finger millet (Eleusine Coracana) and its effects on starch isolates and antinutrients

Finger millet (Eleusine Coracana) is rich in nutrients and minerals. The iron and calcium contents are comparatively higher than other cereal crops. Finger millet also has some antinutrients such as tannins and phytates, that needs to be removed for maximum health benefits. Traditionally, these antinutrients are removed by the hydration process. The conventional hydration process is time cumbersome and often results in poor quality grains. Ultrasonication during hydration of finger millet could reduce the processing time and antinutrient content in finger millet. The ultrasound amplitude, treatment time, and grain to water ratio during hydration were optimized. An ultrasound amplitude of 66%, treatment time of 26 min, and a grain to water ratio of 1:3 resulted in best desirability parameters with a reduction in phytate and tannin contents of the finger millet by 66.98 and 62.83%, respectively. Ultrasonication during hydration increased the water binding capacity and solubility of the finger millet starch. XRD study of the starch isolates confirmed the increased crystallinity of the particles. FESEM of the starch isolates also confirmed that ultrasound-assisted hydration of finger millet resulted in the desired size reduction and homogeneous distribution of starch particles. The optimized ultrasound-assisted hydration could be adopted and scaled up for bulk processing of finger millets.

Continuous and pulsed ultrasound pectin extraction from navel orange peels

Pectin is a valuable product (up to 30 $kg^-1) that makes-up 20-30% of an orange's peel. The commercial extraction is lengthy (up to 6h) and energy intensive as it requires heating aqueous solutions (60-100 °C). Ultrasound speeds up the extraction process reducing processing time by macroscopic and microscopic mixing by acoustic cavitation. We adopted an ultrasonic horn to deliver a rated power of 500W at amplitudes of 20%, 40%, and 60% with and without pulsation to extract pectin from waste orange peels. These correspond to power densities of 0.08Wml^-1, 0.16Wml^-1 and 0.24Wml^-1, respectively. The extractions operated at a pH of either 2 or 3. The experimental data agree with the fitted values from the statistical model (R²=95.5%). The model confirms our predictions that yield increases with amplitude/power density and decreasing pH. The highest yield was (11%) at a pH of 2 and with continuous ultrasonic irradiation at a power density of 0.24Wml^-1. There is only a 1.3% difference between this datum and pulse ultrasound mode (1 s on/1 s off) at the same conditions - a Student's t test confirmed that there was no significant difference in yield between continuous and pulse mode. However, pulsing is more efficient in that it consumes less than half the energy of continuous operation (80kJ vs. 190kJ).

Zn-Co-CeO2 vs. Zn-Co Coatings: Effect of CeO2 Sol in the Enhancement of the Corrosion Performance of Electrodeposited Composite Coatings

Electrodeposition and characterization of novel ceria-doped Zn-Co composite coatings was the main goal of this research. Electrodeposited composite coatings were compared to pure Zn-Co coatings obtained under the same conditions. The effect of two ceria sources, powder and home-made sol, on the morphology and corrosion resistance of the composite coatings was determined. During the electrodeposition process the plating solution was successfully agitated in an ultrasound bath. The source of the particles was found to influence the stability and dispersity of plating solutions. The application of ceria sol resulted in an increase of the ceria content in the resulting coating and favored the refinement from cauliflower-like morphology (Zn-Co) to uniform and compact coral-like structure (Zn-Co-CeO2 sol). The corrosion resistance of the composite coatings was enhanced compared to bare Zn-Co as evidenced by electrochemical impedance spectroscopy and scanning Kelvin probe results. Zn-Co doped with ceria particles originating from ceria sol exhibited superior corrosion resistance compared to Zn-Co-CeO2 (powder) coatings. The self-healing rate of artificial defect was calculated based on measured Volta potential difference for which Zn-Co-CeO2 (sol) coatings exhibited a self-healing rate of 73.28% in a chloride-rich environment.

Sonochemical activity in ultrasonic reactors under heterogeneous conditions

Due to its physical and chemical effects, ultrasound is widely used for industrial purposes, especially in heterogeneous medium. Nevertheless, this heterogeneity can influence the ultrasonic activity. In this study, the effect of the addition of inert glass beads on the sonochemical activity inside an ultrasonic reactor is investigated by monitoring the formation rate of triiodide, and the ultrasonic power is measured by calorimetry and by acoustic radiation. It was found that the sonochemical activity strongly depends on the surface area of the glass beads in the medium: it decreases above a critical area value (around 10^-2 m²), partly due to wave scattering and attenuation. This result is confirmed for a large range of frequencies (from 20 to 1135 kHz) and glass beads diameters (from 8-12 µm to 6 mm). It was also demonstrated that above a given threshold of the surface area, only part of the supplied ultrasonic power is devoted to chemical effects of ultrasound. Finally, the acoustic radiation power appears to describe the influence of solids on sonochemical activity, contrary to the calorimetric power.

Effect of ultrasonic frequency and surfactant addition on microcapsule destruction

In a previous study, we found that cavitation bubbles cause the ultrasonic destruction of microcapsules containing oil in a shell made of melamine resin. The cavitation bubbles can be smaller or larger than the resonance size; smaller bubbles cause Rayleigh contraction, whereas larger bubbles are not involved in the sonochemical reaction. The activity in and around the bubble (e.g., shear stress, shock wave, microjet, sonochemical reaction, and sonoluminescence) varies substantially depending on the bubble size. In this study, we investigated the mechanism of the ultrasonic destruction of microcapsules by examining the correlations between frequency and microcapsule destruction rate and between microcapsule size and cavitation bubble size. We evaluated the bubbles using multibubble sonoluminescence and the bubble size was changed by adding a surfactant to the microcapsule suspension. The microcapsule destruction was frequency dependent. The main cause of microcapsule destruction was identified as mechanical resonance, although the relationship between bubble size and microcapsule size suggested that bubbles smaller than or equal to the microcapsule size may also destroy microcapsules by applying shear stress locally.

On-Demand Sonochemical Synthesis of Ultrasmall and Magic-Size CdSe Quantum Dots in Single-Phase and Emulsion Systems

The sonochemical synthesis of CdSe quantum dots (QDs) in a single-liquid bulk phase and in an emulsion-based system is presented. Reactions utilized cadmium oleate and trioctylphosphine selenide precursors and were monitored as a function of sonication time under controlled temperature conditions to isolate the effects of cavitation from those of bulk temperature changes. QD synthesis was found to be slow in the single-phase liquid system (i.e., 1-octadecene) but greatly accelerated in the dispersed system (i.e., emulsions of 1-octadecene in ethylene glycol). It is hypothesized that the emulsion system increases the cavitation efficiency while also delivering acoustic energy in closer proximity to the precursor molecules. The capacity of CdSe production in the emulsion system was found to be 3.8 g/(L h), which is comparable to the typical hot-injection synthesis of CdSe QDs and can likely be further optimized. While the single-phase solvent system was found to produce ultrasmall QDs that exhibit broadband white-light emission, the emulsion system was found to produce well-defined magic-size clusters (MSCs) with photoluminescence quantum yield as high as 34%. Differences in synthesis rate and product properties from the emulsion and single-phase systems were probed by X-ray diffraction, electron microscopy, UV-visible (vis) and photoluminescence spectroscopy, and small-angle X-ray scattering (SAXS). Finally, precise temporal control of the QD synthesis was demonstrated via on-off cycling of the ultrasound waves.

The Sonophotocatalytic Degradation of Pharmaceuticals in Water by MnOx-TiO2 Systems with Tuned Band-Gaps

Advanced oxidation processes (AOPs) are technologies to degrade organic pollutants to carbon dioxide and water with an eco-friendly approach to form reactive hydroxyl radicals. Photocatalysis is an AOP whereby TiO2 is the most adopted photocatalyst. However, TiO2 features a wide (3.2 eV) and fast electron-hole recombination. When Mn is embedded in TiO2, it shifts the absorption wavelength towards the visible region of light, making it active for natural light applications. We present a systematic study of how the textural and optical properties of Mn-doped TiO2 vary with ultrasound applied during synthesis. We varied ultrasound power, pulse length, and power density (by changing the amount of solvent). Ultrasound produced mesoporous MnOx-TiO2 powders with a higher surface area (101–158 m2 g−1), pore volume (0-13–0.29 cc g−1), and smaller particle size (4–10 µm) than those obtained with a conventional sol-gel method (48–129 m2 g−1, 0.14–0.21 cc g−1, 181 µm, respectively). Surprisingly, the catalysts obtained with ultrasound had a content of brookite that was at least 28%, while the traditional sol-gel samples only had 7%. The samples synthesized with ultrasound had a wider distribution of the band-gaps, in the 1.6–1.91 eV range, while traditional ones ranged from 1.72 eV to 1.8 eV. We tested activity in the sonophotocatalytic degradation of two model pollutants (amoxicillin and acetaminophen). The catalysts synthesized with ultrasound were up to 50% more active than the traditional samples.

Ultrasound pre-treatment prior to unripe banana air-drying: effect of the ultrasonic volumetric power on the kinetic parameters

Aiming to decrease the water content during the air-drying process of unripe banana slices, ultrasound (US) pre-treatments (25 °C) for 20 and 25 min at 9.38 and 25.63 W/L ultrasonic volumetric power were evaluated. Air-drying was performed at 50 and 60 °C for 360 min. Unripe banana slices pretreated at 25.63 W/L did not improve water migration, under either air-drying temperature, while slices pretreated at 9.38 W/L resulted in an increase in water effective diffusivity of 4.8 and 13.7% at 20 min US + air-drying at 50 °C and 25 min US + air-drying at 60 °C, respectively. The drying time saving of 7% and 9%, respectively, was achieved, showing that these treatments were alternative for processing unripe banana slices. Thus, ultrasound and air-drying operational parameters required accurately defined to achieve desirable results. Experimental data were adjusted to four models and the Midilli model resulted in the best experimental data fit, with r ² > 0.9988, RMSE < 0.0873 and χ² < 0.00996.

Effect on High-Intensity Fields of a Tough Hydrophone With Hydrothermal PZT Thick-Film Vibrator and Titanium Front Layer

A novel tough hydrophone was fabricated by depositing hydrothermally synthesized lead zirconate titanate polycrystalline film on the back-side surface of a titanium plate. Our developed tough hydrophone resisted damage in a high-pressure field (15 MPa) at a focal point of a sinusoidal continuous wave driven by a concave high-intensity focused ultrasound (HIFU) transducer with up to 50 W of power input to the sound source. The hydrophone was suitable for the HIFU field, even though the hydrophone has a flat-shape tip of 3.5 mm diameter, which is slightly larger than the wavelength of a few megahertz. In this paper, experiments are performed to assess the effect on the HIFU field of changing the shape of the tough hydrophone, with the aim of developing a tough hydrophone. The spatial distribution of the acoustic bubbles around the focal point was visualized by using ultrasonic diagnostic equipment with the tough hydrophone located at the focal point of the HIFU transducer. From the visualization, the trapped acoustic bubbles were seen to arise from the standing wave, which implies that the acoustic pressure is reduced by this cloud of acoustic bubbles that appeared during hydrophone measurement. Although cavitation and acoustic bubbles may be unavoidable when using high-intensity ultrasound, the estimated result of evaluating acoustic fields without misunderstanding by acoustic bubbles can be obtained by the aid of visualizing bubbles around the tough hydrophone.

Size of Sclerosing Foams Prepared by Ultrasound, Mechanical Agitation, and the Handmade Tessari Method for Treatment of Varicose Veins

OBJECTIVES

Sclerotherapy is a therapeutic method used in the treatment of varicose veins and works by occluding damaged blood vessels with a chemical solution. Foam sclerotherapy is an attractive treatment because the results are more effective than those obtained by using liquid sclerosants. However, serious neurologic complications, which are likely related to air embolism, have been reported after treatment with foams generated by the handmade method (Tessari technique) most often used clinically. We present an alternative ultrasonic technique for preparation of sclerosing foams to treat varicose veins.

METHODS

Three methods of foam generation were compared: ultrasound, mechanical agitation, and Tessari techniques.

RESULTS

Optical microscopic analyses showed that low-frequency ultrasound can generate foams with smaller bubble distributions compared to those produced by handmade and mechanical agitation methods: 98% of the bubble population was less than 55 ± 10 μm for sonicated foams (mean ± SD, 19 ± 1.8 μm; maximum bubble size, <138.3 ± 32.5 μm), 196.7 ± 38.2 μm for mechanically agitated foams (mean, 37.1 ± 10.6 μm; maximum bubble size, <350 ± 70.9 μm), and 211.7 ± 20.8 μm for handmade foams (mean, 30.8 ± 3.8 μm; maximum bubble size, <445 ± 32.8 μm).

CONCLUSIONS

Low-frequency ultrasonic foam generation yields smaller bubbles and more uniform size distributions than other investigated methods. These properties may reduce serious adverse events reported for sclerotherapy of varicose veins, increasing the safety of foam treatment.

Effect of reaction temperature on the size and morphology of scorodite synthesized using ultrasound irradiation

Synthesis of scorodite (FeAsO₄·2H₂O) using dynamic action agglomeration and the oxidation effect from ultrasound irradiation was investigated. The effect of different reaction temperatures (90, 70, 50, and 30°C) on the size and morphology of scorodite particles synthesized under O₂ gas flow and ultrasound irradiation was explored because the generation of fine bubbles depends on the solution temperature. At 90°C, the size of scorodite particles was non-homogeneous (from fine particles (<1μm) to large particles (>10μm)). The oxidation-reduction potential (ORP) and yield at 90°C showed lower values than those at 70°C. The scorodite particles, including fine and non-homogeneous particles, were generated by a decrease in the oxidation of Fe(II) to Fe(III) and promotion of dissolution caused by the generation of radicals and jet flow from ultrasound irradiation. Using ultrasound irradiation in the synthesis of scorodite at low temperature (30°C) resulted in the appearance of scorodite peaks in the X-ray diffraction (XRD) pattern after a reaction time of 3h. The peaks became more intense with a reaction temperature of 50°C and crystalline scorodite was obtained. Therefore, ultrasound irradiation can enable the synthesis of scorodite at 30°C as well as the synthesis of large particles (>10μm) at higher temperature. Oxide radicals and jet flow generated by ultrasound irradiation contributed significantly to the synthesis and crystal growth of scorodite.

Simultaneous extraction, optimization, and analysis of flavonoids and polyphenols from peach and pumpkin extracts using a TLC-densitometric method

Background

The use of medicinal plants has been reported throughout human history. In the fight against illnesses, medicinal plants represent the primary health care system for 60 % of the world’s population. Flavonoids are polyphenolic compounds with active anti-microbial properties; they are produced in plants as pigments. Quercetin, myricetin, and rutin are among the most well-known and prevalent flavonoids in plants, with an antioxidant activity capable of decreasing the oxidation of low density lipoproteins [LDLs]. To date, this research is the first of its kind to employ a coupled thin-layer chromatography (TLC) and a densitometric quantification method with a Box-Behnken design (BBD) response surface methodology (RSM) for optimization of ultrasonic-assisted extraction and determination of rutin and quercetin from peach and ellagic acid and myricetin from pumpkin fruits.

Results

The effect of process variables (extraction temperature (°C), extraction power (%) and extraction time (min)) on ultrasound-assisted extraction (UAE) were examined by using BBD and RSM. TLC followed by Quantity-One™ (BioRad) image analysis as a simple and rapid method was used for identification and quantification of the compounds in complex mixtures. The results were consistent under optimal conditions among the experimental values and their predicted values. A mass spectrometry (MALDI-TOF MS) technique was also used to confirm the identity of the natural products in the TLC spots resolved.

Conclusion

The results show that the coupled TLC-densitometric methods & BBD can be a very powerful approach to qualitative and quantitative analysis of; rutin and quercetin from peach extracts; and ellagic acid and myricetin contents from pumpkin extracts.

Beating the blues: is there any music in fighting cyanobacteria with ultrasound?

The hypothesis that cyanobacteria can be controlled by commercially available ultrasound transducers was tested in laboratory experiments with cultures of the cyanobacteria Anabaena sp., Cylindrospermopsis raciborskii and Microcystis aeruginosa and the green alga Scenedesmus obliquus that were grown in the absence or presence of ultrasound (mix of 20, 28 and 44 kHz). The Scenedesmus experiment also included a treatment with the zooplankton grazer Daphnia magna. Chlorophyll-a and biovolume-based growth of Anabaena was significantly lower in ultrasound exposed cultures than in controls. Particle based growth rates were higher in ultrasound treatments. Filaments were significantly shorter in ultrasound exposed cultures reflecting filament breakage. Photosystem II efficiency was not affected by ultrasound. In Cylindrospermopsis chlorophyll-a based growth rates and photosystem II efficiencies were similar in controls and ultrasound treatments, but biovolume-based growth was significantly lower in ultrasound exposed cultures compared to controls. Despite biovolume growth rates of the filamentous cyanobacteria were reduced in ultrasound treatments compared to controls, growth remained positive implying still a population increase. In Microcystis and Scenedesmus growth rates were similar in controls and ultrasound treatments. Hence, no effect of ultrasound on these phytoplankton species was found. Ultrasound should not be viewed "environmental friendly" as it killed all Daphnia within 15 min, releasing Scenedesmus from grazing control in the cultures. Based on our experiments and critical literature review, we conclude that there is no music in controlling cyanobacteria in situ with the commercially available ultrasound transducers we have tested.

Inactivation of bacteria and yeast using high-frequency ultrasound treatment

High-frequency (850 kHz) ultrasound was used to inactivate bacteria and yeast at different growth phases under controlled temperature conditions. Three species of bacteria, Enterobacter aerogenes, Bacillus subtilis and Staphylococcus epidermidis as well as a yeast, Aureobasidium pullulans were considered. The study shows that high-frequency ultrasound is highly efficient in inactivating the bacteria in both their exponential and stationary growth phases, and inactivation rates of more than 99% were achieved. TEM observation suggests that the mechanism of bacteria inactivation is mainly due to acoustic cavitation generated free radicals and H2O2. The rod-shaped bacterium B. subtilis was also found to be sensitive to the mechanical effects of acoustic cavitation. The study showed that the inactivation process continued even after ultrasonic processing cessed due to the presence of H2O2, generated during acoustic cavitation. Compared to bacteria, the yeast A. pullulans was found to be more resistant to high-frequency ultrasound treatment.