Search

Fresh meat has a limited shelf life and is prone to spoilage. Drying serves as a common method for food preservation. Non-thermal techniques such as ultrasound treatment (US) can positively affect the drying processes and alter the final product. The study aimed to evaluate the impact of US pre-treatment on the hot air (HA) and freeze-drying (FD) of chicken breast meat and the quality of the dried products. US pre-treatment had a varied impact depending on the drying method used. The contact US method extended the HA drying time (about 50%) but improved water removal during FD (about 30%) compared to the untreated samples. Both methods resulted in low water content (<8.3%) and low water activity (<0.44). While rehydration properties (RR) and hygroscopicity (H) were not significantly affected by US pre-treatment in HA drying (about 1.35% and about 1.1, respectively), FD noticed differences due to shrinkage and porosity variations (RR: 2.4–3.2%, H: 1.19–1.25). The HA-dried samples exhibited notably greater tissue shrinkage and a darker surface color than the FD meat. Ultrasonic processing holds substantial potential in creating dried meat products with tailored characteristics. Hence, meticulous consideration of processing methods and parameters is of utmost importance. [ABSTRACT FROM AUTHOR]

Fresh meat has a limited shelf life and is prone to spoilage. Drying serves as a common method for food preservation. Non-thermal techniques such as ultrasound treatment (US) can positively affect the drying processes and alter the final product. The study aimed to evaluate the impact of US pre-treatment on the hot air (HA) and freeze-drying (FD) of chicken breast meat and the quality of the dried products. US pre-treatment had a varied impact depending on the drying method used. The contact US method extended the HA drying time (about 50%) but improved water removal during FD (about 30%) compared to the untreated samples. Both methods resulted in low water content (

The study of organic molecules in meteorite and return samples allows for the understanding of the chemistry that undergoes in our Solar System. The present work aims at studying ultrasound assisted extraction technique as effective extraction method for these molecules in extraterrestrial samples and analogs. Optimal conditions were selected from the investigation of ultrasonic frequency, irradiation duration and solvent effects on amino acids, nucleobases and dipeptides extraction yields from a model clay-rich mineral matrix. Optimal ultrasound-assisted extraction parameters were frequency of 20 kHz within 20 min irradiation time and methanol/water solvent ratio of 1. We then validated this protocol on Mukundpura and Tarda meteorite fragments and compared it to the reference extraction protocol used in astrobiology and based on 24 h extraction time at 100 °C in water We obtained similar quantitative results without any racemization with both methodologies.

Exploitation of polar resources and scientific research require efficient ice drilling technology. Thermal drilling is a common method for polar ice drilling, and is similar to the principle of ultrasonic assisted drilling; both are drilled by melting ice layers, but improving energy utilization has always been a challenge. In order to improve energy utilization and drilling efficiency, this paper proposes a method for ice drilling with ultrasonic frequency vibration. The mechanism of ultrasonic vibration drilling into ice was analyzed, the solid theoretical foundation for the application of ice melting efficiency under ultrasonic frequency vibration was determined and a series of indoor experiments were conducted. According to experimental data obtained, two conclusions were provided. First, different frequencies have distinct influence on power density, drilling speed and melting rate, and the optimum range excitation frequency for ultrasonic ice drilling is at least 30~32 kHz, under which the ice melting efficiency and drilling speed reached the peak value. Second, ultrasonic assisted drilling was verified to have the ability of improving the efficiency of ice breaking by comparing to thermal drilling under the same power density under 30 kHz. As an environmentally friendly and efficient drilling method, ultrasonic assisted ice drilling has great application prospects in the field of polar exploration. By using Ultrasonic assisted drilling, we demonstrate a strategy for a faster and more efficient drilling method, which is important for humankind.

The application of ultrasonic assisted extraction to extract seed oils for multifaceted food applications is discussed in this study. Seed oils, which are notable sources of health‐promoting characteristics and reservoirs of fatty acids and phytochemicals, are being targeted for effective extraction. Conventional techniques of oil extraction, including mechanical pressing and rendering, have limitations such as low extraction rate, high energy consumption, and low yield. In this context, ultrasonic assisted extraction is green and fast oil extraction technology with a greater extraction rate and low energy consumption. Ultrasound assisted oil extraction is mostly used technique since it is environmentally friendly and can be easily integrated with other extraction processes. Ultrasound‐aided extraction uses less solvent than traditional extraction methods. In this process, cavitation bubbles form in the solvent and burst, causing changes in pressure and temperature that expedite the mass transfer of solutes into solvent. The miscella, including the solvent and oil mixture, is then desolventized using evaporators, followed by steam‐stripping to remove the extracted oil. The current review paper discusses the characteristics of ultrasonic extractions for efficient oil extraction (extraction duration, ultrasound frequency, temperature, solvent employed, and ultrasound type). The conventional and non‐conventional oil extraction methods from sources have been examined in this article, in addition to the ultrasound assisted extraction. Along with traditional and advanced oil extraction techniques, the use of ultrasonication in conjunction with other cutting‐edge techniques is covered in this article. Practical applications: Ultrasound assisted oil extraction extracts oil from vegetables, oilseeds, and nuts by using a suitable carrier. The key parameters influencing ultrasound aided extraction of oilseed include particle shape and size, moisture content of seed, amount of solvent, and extraction time/temperature. The ultimate extraction yield is influenced by the extraction time, operating frequency, operational temperature, solvent type, and proportion, and ultrasonicator design. This technique consumes less energy and requires less maintenance. It is quite efficient and reliable. On this basis, ultrasound aided extraction may be utilized commercially to increase oil extraction rate from oil seeds. [ABSTRACT FROM AUTHOR]

In sonochemistry, acoustic bubbles are a population of microreactors where hydrogen and oxidants are produced. Optimizing the effectiveness of sonochemical processes and, as a result, designing ultrasonic reactors for diverse uses, including hydrogen generation, requires determining the number density of acoustic microreactors. The number density of micro-bubbles during water sonolysis was determined in this study using a novel semi-empirical method developed (for the first time) using hydrogen sono-production. The technique is based on relying on the overall molar production rate of hydrogen (i.e. resulted from the sonicated solution) to the amount of hydrogen produced per a single collapsing bubble, either from its internal gas phase reaction (pyrolysis) or from both the bubble inside and its liquid shell (via H•+H•→H 2). The retrieved number density of bubbles varied between ∼108 to ∼1013 L−1 s−1 (depending on empirical conditions), showing an excellent order with that reported in the literature. As the frequency increased, the number of active bubbles increased, regardless of whether the number density is calculated through the amount of hydrogen formed inside the bubble or the total single-bubble yield (gas phase + liquid shell). However, a reduced number density was obtained as it was calculated via the total single-bubble yield, where this decrease goes up with the rise of ultrasound frequency (from 210 to 724 kHz) and the decrease of the liquid temperature. It has been deduced that hydrogen is mainly formed at the bubble's liquid shell (via H•+H•→H 2), particularly at higher frequency and cold liquid. [Display omitted] • Hydrogen sonoproduction was quantified and used for determining the bubbles number. • A full cavitation-based model was applied for predicting the H 2 's single bubble yield. • The H 2 -based technique relies the overall and the single bubble yield during sonication. • The bubbles' number density was ∼108 to ∼1013 L−1 s−1, depending on circumstances. • The number density increased with frequency increase and liquid temperature decrease. [ABSTRACT FROM AUTHOR]

The effects of power ultrasound (US) pretreatment on the preparation of soy protein isolate hydrolysate (SPIH) prepared at the same degree of hydrolysis (DH) of 12 % were measured. Cylindrical power ultrasound was modified into mono-frequency (20, 28, 35, 40, 50 kHz) ultrasonic cup coupled with an agitator to make it applicable for high density SPI (soy protein isolate) solutions (14 %, w/v). A comparative study of the alterations of the hydrolysates molecular weight, hydrophobics, antioxidants and functional properties change as well as their relation were explored. The results showed that under the same DH, ultrasound pretreatment decelerated the degradation of protein molecular mass and the decrease rate of the degradation lessened with the increase of ultrasonic frequency. Meanwhile, the pretreatments improved the hydrophobics and antioxidants properties of SPIH. Both surface hydrophobicity (H0) and relative hydrophobicity (RH) of the pretreated groups increased with the decrease of ultrasonic frequency. Lowest frequency (20 kHz) ultrasound pretreatment had the most improved emulsifying properties and water holding capacities, although decrease in the viscosity and solubility were found. Most of these alterations were correspondence toward the change in hydrophobics properties and molecular mass. In conclusion, the frequency selection of ultrasound pretreatment is essential for the alteration of SPIH functional qualities prepared at the same DH.

Sonodynamic antimicrobial chemotherapy (SACT), as a novel anti-infective program, has received tremendous attention due to its good tissue penetration depth and low invasion. Ultrasound (US) frequency was one of the important parameters for SACT. To investigate the influence of different US frequencies on sonodynamic antimicrobial activity of ciprofloxacin-capped gold nanoparticles (CIP:GNPs). C. albicans and E. coli were chosen as the action objects. The bacterial survival rate was used in the assessment index and measured by plate colony-counting methods. The reactive oxygen species (ROS) produced under US irradiation were detected by ROS fluorescence probe and used to analyze the sonodynamic antibacterial mechanism of CIP:GNPs following different US frequencies. High-frequency US combined with CIP:GNPs had a good synergistic antimicrobial impact on C. albicans , while medium-frequency US showed a strong effect on E. coli. Moreover, the mechanism research experiment proved that intracellular ROS levels were closely related to changes in US frequency, and significantly affected the synergistic activity of CIP:GNPs. The injury of E. coli appearance showed more sensitivity to the change of US frequency than that of C. albicans , but its action laws were relatively complicated and needed to be further studied. • High-frequency US combined with CIP:GNPs had a better synergistic antimicrobial activity on C. albicans than on E. coli a nd medium-frequency US combined with CIP:GNPs got a stronger antibacterial effect on E.coli than on C.albicans. • The influence of US frequency on the synergistic antimicrobial activity of CIP:GNPs were relatively complicated, but it largely related to the yields of intracellular ROS and the cellular structural damage caused by the acoustic cavitation. [ABSTRACT FROM AUTHOR]

An ultrasonic microreactor with rough microchannels is presented in this study for oil-in-water (O/W) emulsion generation. Previous accounts have shown that surface pits or imperfections localize and enhance cavitation activity. In this study cavitation bubbles are localized on the rough microchannels of a borosilicate glass microreactor. The cavitation bubbles in the microchannel are primarily responsible for emulsification in the ultrasonic microreactor. We investigate the emulsification mechanism in the rough microchannels employing high-speed imaging to reveal the different emulsification modes influenced by the size and oscillation intensity of the cavitation bubbles. The effect of emulsification modes on the O/W emulsion droplet size distribution for different surface roughness and frequency is demonstrated. The positive effect of the frequency on minimizing the droplet size utilizing a reactor with large pits is presented. We also demonstrate microreactor systems for a successful generation of miniemulsions with high dispersed phase volume fractions up to 20%. The observed emulsification mechanism in the rough microchannel offers new insights into the utility and scale-up of ultrasonic microreactors for emulsification.

Objectives: Sonication of explanted prosthesis constitutes an element of microbiological diagnostics. The aim of performing this procedure is to remove biofilm and to increase sensitivity of diagnostics. Ultrasound used for medical purposes are low-frequency and low-intensity. With this wide range of frequency which can be used in sonication process it is necessary to find the golden mean between biofilm dislodging and planktonic bacteria sparing. Materials and methods: The aim of this study was to determine the least harming low-intensity ultrasound frequency (35 kHz, 40 kHz or 53 kHz) used during sonication process with other parameters constant. Four bacteria species were examined: S. aureus, E. faecalis, E. coli, K. pneumoniae. Number of microbiological studies (n) for each group (g) counted 40 specimens (based on scheme 1 bacteria type – 4 groups, 40 studies each). Results: A detailed analysis of gathered data was conducted. Based on study findings following conclusions were drawn. Sonication has a significant and negative impact on survival of sonicated planktonic bacteria. Part of bacteria in planktonic state are damaged/killed by ultrasound, which is demonstrated by lower CFU count in sonicated samples versus control group. Conclusions: Optimal ultrasound frequencies for sonication of S. aureus, P. aeruginosa and E. coli are 35 kHz and 40 kHz. Ultrasound frequencies used in sonication process (35 kHz, 40 kHz, 53 kHz) of E. coli showed same impact on bacteria survival. It is crucial to perform further assessment of ultrasound parameters on clinical effects of sonication used in PJI diagnostics.

Background: The purpose of this study was to examine whether high‐frequency ultrasound toothbrushes have different effects on oral hygiene. Methods: Fifty first‐year dental hygiene students were randomly divided into three groups using ultrasound toothbrushes with different frequencies (1.6, 3.2 and 4.8 MHz) twice a day (3‐min sessions) for 8 weeks. Plaque index (PlI) and gingival index (GI) scores were assessed at 4 and 8 weeks. Results: Changes in GI scores from baseline to 8 weeks tended to differ among the groups (p = 0.0862). The GI was significantly lower in the 3.2 and 4.8 MHz groups at 8 weeks (3.2 MHz group: p < 0.01, 4.8 MHz group: p < 0.05). At 4 weeks, the GI was significantly lower in the 3.2 MHz group (p < 0.05) and tended to be lower in the 4.8 MHz group (p = 0.07). The PlI was significantly lower in the 3.2 MHz group at 8 weeks (p < 0.01) and tended to be lower in the 1.6 and 4.8 MHz groups (1.6 MHz: p = 0.07, 4.8 MHz: p = 0.05). In addition, the PlI was significantly lower in the 4.8 MHz group at 4 weeks (p < 0.05). No significant differences in the changes in any measurements were observed among the groups. Conclusions: The results of this study indicated that ultrasound toothbrushes with different frequencies probably have different effects on oral hygiene. However, it is difficult to conclude strongly that higher frequency ultrasound toothbrushes are more effective as there were some limitations. [ABSTRACT FROM AUTHOR]

A systematic study on the sonocrystallisation of ZIF-8 (zeolitic imidazolate framework-8) in a water-based system was investigated under different mixing speeds, ultrasound frequencies, calorimetric powers and sonication time. Regardless of the synthesis technique, pure crystals of ZIF-8 with high BET (Brunauer, Emmett and Teller) specific surface area (SSA) can be obtained in water after only 5 s. Furthermore, 5 s sonication produced even smaller crystals (~0.08 µm). The type of technique applied for producing the ZIF-8 crystals did not have any significant impact on crystallinity, purity and yield. Crystal morphology and size were affected by the use of ultrasound and mixing, obtaining nanoparticles with a more spherical shape than in silent condition (no ultrasound and mixing). However, no specific trends were observed with varying frequency, calorimetric power and mixing speed. Ultrasound and mixing may have an effect on the nucleation step, causing the fast production of nucleation centres. Furthermore, the BET SSA increased with increasing mixing speed. With ultrasound, the BET SSA is between the values obtained under silent condition and with mixing. A competition between micromixing and shockwaves has been proposed when sonication is used for ZIF-8 production. The former increases the BET SSA, while the latter could be responsible for porosity damage, causing a decrease of the surface area.

Purpose: To study the effects of ultrasound pretreatment at different frequencies and working modes, including mono frequency ultrasound (MFU) and dual-frequency ultrasound (DFU), on the degree of hydrolysis (DH) and angiotensin-I-converting enzyme (ACE) inhibitory effect of Stevia protein (SP). Methods: Protein from Stevia leaves was extracted by water (50 g suspended in 1000 mL). The hydrolysis of stevia protein extract (SPE) was carried out using alcalase at 5 % enzyme substrate (E/S) ratio. A study was then carried out to investigate its microstructure and morphology using scanning electron microscopy (SEM). Results: The results showed that ultrasound pretreatment did not increase DH of SP significantly (p > 0.05). However, the highest ACE inhibitory activity of stevia protein hydrolysate was obtained at DFU level (20/50 KHz). Overall, ultrasonic frequency mode had a significant influence on ACE inhibitory activity. Conclusion: The frequency selection of ultrasound pretreatment of SP is essential for the preparation of ACE inhibitory peptide. [ABSTRACT FROM AUTHOR]

• Sonication is a practical and effective method to dislodge biofilm and the associated bacteria from the surface of the implant. • Aim of this study was to determine the least harming low-intensity ultrasound frequency used during sonication process. • Low-frequency and low-intensity ultrasound has a negative influence on planktonic bacteria. • Ultrasound frequency has a great influence on bacteria viability. Sonication of explanted prosthesis constitutes an element of microbiological diagnostics. The aim of performing this procedure is to remove biofilm and to increase sensitivity of diagnostics. Ultrasound used in medical purposes are low-frequency and low-intensity. With this wide range of frequency which can be used in sonication process it is necessary to find the golden mean between biofilm dislodging and planktonic bacteria sparing. The aim of this study was to determine the least harming low-intensity ultrasound frequency (35 kHz, 40 kHz or 53 kHz) used during sonication process with other parameters constant. Four bacteria species were examined: S. aureus , E. faecalis , E. coli , K. pneumoniae. Number of microbiological studies (n) for each group (g) counted 40 specimens (based on scheme 1 bacteria type – 4 groups, 40 studies each). A detailed analysis of gathered data was conducted. Based on study findings following conclusions were drawn. Sonication has a significant and negative impact on survival of sonicated planktonic bacteria. Part of bacteria in planktonic state are damaged/killed by ultrasound, which is demonstrated by lower CFU count in sonicated samples versus control group. Optimal ultrasound frequencies for sonication of S. aureus , P. aeruginosa and E. coli are 35 kHz and 40 kHz. Ultrasound frequencies used in sonication process (35 kHz, 40 kHz, 53 kHz) of E. coli showed same impact on bacteria survival. It is crucial to perform further assessment of ultrasound parameters on clinical effects of sonication used in PJI diagnostics. [ABSTRACT FROM AUTHOR]

Numerous experimental studies have shown that the interaction of ultrasound with different cell membranes can result in a wide range of non-thermal effects on different cells or their membrane, including increased membrane permeability, ultrasonic cavitation in cells, and increased gene and drug delivery. However, the molecular mechanism for the interaction between ultrasound and cell membrane remains unclear. In this study, we model ultrasonic waves as cycles of alternating positive and negative pressure, and then use atomic molecular dynamics simulation to investigate how the applied ultrasound affects the structure of cell membranes and the corresponding molecular distribution of dissolved gas. We find that ultrasound energy is concentrated more effectively on the hydrophobic core of the membrane because it causes a strong oscillation of membrane thickness while producing a much weaker response in the surrounding water. In addition, our simulations reveal a substantial effect of the ultrasonic frequency on redistribution of dissolved gas molecules, and only an ultrasound with a long period can result in a significant gas redistribution. [ABSTRACT FROM AUTHOR]

[Display omitted] • This paper constitutes a step forward in ultrasonic extraction of biomolecules from clays rich sample and meteorites. • It presents a fast and efficient ultrasonic extraction compared to highly energy and time-consuming hot water extraction. • The proof of concept has been made extracting amino acids and nucleobases from meteorites. The study of organic molecules in meteorite and return samples allows for the understanding of the chemistry that undergoes in our Solar System. The present work aims at studying ultrasound assisted extraction technique as effective extraction method for these molecules in extraterrestrial samples and analogs. Optimal conditions were selected from the investigation of ultrasonic frequency, irradiation duration and solvent effects on amino acids, nucleobases and dipeptides extraction yields from a model clay-rich mineral matrix. Optimal ultrasound-assisted extraction parameters were frequency of 20 kHz within 20 min irradiation time and methanol/water solvent ratio of 1. We then validated this protocol on Mukundpura and Tarda meteorite fragments and compared it to the reference extraction protocol used in astrobiology and based on 24 h extraction time at 100 °C in water We obtained similar quantitative results without any racemization with both methodologies. [ABSTRACT FROM AUTHOR]

Abstract This work was aimed at studying the effect of different ultrasound frequencies (20, 44, 98, 142 kHz) and ultrasound powers (10, 20, 30 W) on lactose nucleation. For this purpose, lactose solutions (25% w/v) with traces of whey proteins (0.3%) were sonicated 300 s. Crystallization was induced by reducing the temperature from 30 to 15 °C, which increased the absolute supersaturation of lactose (C α - C αs) from 0.19 to 8.25 g 100 g−1. The nucleation of lactose was monitored by light scattering. Results showed that application of ultrasound (US) modified both, the molecular-attachment frequency to form new nuclei (k) and the induction time. The ultrasound effect on lactose nucleation varied depending on the US-frequency or power applied. The most noticeable changes were observed at 44 kHz (11.13 J mL−1) since the number of nuclei formed (a) raised, the k -value increased to 0.1482 s−1, and the induction time decreased to 15 s. Highlights • In non-sonicated crystallization, nucleation of lactose was slow with few nuclei. • Lactose nucleation was most affected at 44 kHz of ultrasound frequency and 20 W • Crystallization at 44 kHz accelerated the nucleation and reduced the induction time. • Crystallization at 20 W increased the nuclei and lowered the induction time. • The whey proteins modified the nucleation of lactose in sonocrystallization. [ABSTRACT FROM AUTHOR]

• This study used ultrasound instantaneous frequency for evaluating the clinical severity of DMD. • Clinical measurements were performed for validations. • The accuracy to characterize the walking function of patients was 91.76%. • The proposed method benefits future DMD evaluation and management. Duchenne muscular dystrophy (DMD) results in loss of ambulation for the patients. Ultrasound attenuation correlates with fat content in muscles, resulting in changes in signal frequency. The Hilbert–Huang transform (HHT) allows time–frequency analysis with high time–frequency resolution. This study explored the feasibility of using the instantaneous frequency (IF) obtained from the HHT to diagnose the walking function of patients with DMD. Eighty-five participants (12 control and 73 patients with DMD) underwent a standard-care ultrasound examination of the gastrocnemius to acquire raw image data for ultrasound B-mode and IF calculations, which were compared with the DMD stage using Pearson correlation and receiver operating characteristic (ROC) curve analyses. With increasing DMD stage, the median IF decreased from 7.25 to 7.01 MHz (the correlation coefficient r = −0.73; the probability value p < 0.0001). The area under the ROC curve was 0.97 when using ultrasound IF to discriminate between ambulatory and nonambulatory patients (accuracy: 91.76%; sensitivity: 93.75%; and specificity: 90.57%). The study reveals that ultrasound IF has great potential in DMD evaluation and management. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of process conditions as well as ultrasound and microwave pretreatments on shrinkage of potato strips during deep-fat frying process. Ultrasound pretreatment was performed at frequencies of 28 and 40 kHz and microwave pretreatment was conducted at powers of 3 and 6 W/g on the potato slices. Then, the frying process was done at 150, 170 and 190°C for 1, 2, 3 and 4 min. According to the results, ultrasound pretreatment significantly reduced the shrinkage of potato strips. However, microwave pretreatment resulted in a significant increase in the samples shrinkage. In addition, frying time as an important process factor had a significant effect on shrinkage; such that by increasing time, shrinkage was increased. Moreover, the results showed that temperature effect on shrinkage is not significant. Furthermore, six models were presented in order to predict shrinkage considering the process conditions and for the models constants, multivariate models were obtained based on multivariate regression analysis as a function of process conditions (ultrasound frequency, microwave power and process temperature).

It is well known that edible oil consumption and saturated fat intake in high amount are individually associated with important health problems such as obesity, coronary heart disease, and cancer. In recent years, ultrasound application prior to deep-fat frying has been proposed as an innovative emerging technology to reduce oil uptake. The objective of this study was to investigate the influence of various ultrasound frequency-time combinations on quality characteristics of potato strips during deep-fat frying. Results indicated that the potato strips subjected to ultrasonic waves at the frequency of 40 kHz for 30 min, exhibited the highest moisture diffusivity, resulting in the highest reduction in oil uptake (23.18%) among all the samples. Additionally, the ultrasound combined frequencies of 28 kHz (for 20 min) and 40 kHz (for 10 min) showed the best performance in reducing the shrinkage of fried products. Moreover, ultrasound frequency of 40 kHz for 30 min and also combined frequencies of 28 kHz (for 15 min) and 40 kHz (for 15 min) increased the apparent density of samples. In summary, by considering proper ultrasound frequency-time combinations, ultrasound application before deep-fat frying can be a promising approach to decrease oil uptake and shrinkage of fried potato strips. [ABSTRACT FROM AUTHOR]

The use of ultrasound in cutting plastics, synthetic fabrics, and polymer films is considered. A practical configuration is outlined, and the benefits of ultrasound in cutting are presented. The influence of the parameters in ultrasonic cutting on the productivity and the quality of the machined polymer is analyzed. [ABSTRACT FROM AUTHOR]

Ultrasound technology has been successfully demonstrated for several food processing and preservation applications. The majority of food processing applications reported refer to liquid foods. Ultrasound has been applied to solid foods in some niche applications, e.g., tenderization of meat, mass transfer applications, and drying. Similar to any other technology, ultrasound also has some positive and negative effects on food quality depending on the application and processing conditions employed. This chapter outlines various applications of ultrasound to food and its effect on food and nutritional quality. [ABSTRACT FROM AUTHOR]

The ultrasonic welding of dissimilar plastics is considered. This process depends on the diffusion of molecules to the surface of polymers at temperatures corresponding to the viscoplastic state. The weldability of a pair of dissimilar plastics depends on the compatibility of their acoustic properties, assessed in terms of the density and viscosity of the melts. [ABSTRACT FROM AUTHOR]

The effects of ultrasound pretreatment with different frequencies and working modes, including mono-frequency ultrasound (MFU), dual-frequency ultrasound (DFU) and tri-frequency ultrasound (TFU), on the degree of hydrolysis (DH) of rice protein (RP) and angiotensin-I-converting enzyme (ACE) inhibitory activity of RP hydrolysate were investigated. Ultraviolet–visible (UV) spectroscopy, fourier transform infrared (FTIR) spectroscopy, surface hydrophobicity and scanning electron microscopy (SEM) of RP pretreated with ultrasound were measured. The results showed that ultrasound pretreatment did not increase DH of RP significantly ( p > 0.05). However, all the ultrasound pretreatment increased the ACE inhibitory activity of RP hydrolysate significantly ( p < 0.05). The MFU of 20 kHz showed higher ACE inhibitory activity compared to that of other MFU. The ACE inhibitory activity of sequential DFU was higher than that of simultaneous with the same frequency combination. Sequential TFU of 20/35/50 kHz produced the highest increase in ACE inhibitory activity in contrast with other ultrasound frequencies and working modes. All the results under ultrasound pretreatment showed that ultrasound frequencies and working modes were of great effect on the ACE inhibitory activity of RP. The changes in UV–Vis spectra and surface hydrophobicity indicated the unfolding of protein and exposure of hydrophobic groups by ultrasound. The FTIR analysis showed that all the ultrasound pretreatment with different frequencies and working modes decreased α -helix, β -turn content and increased β -sheet, random coil content of RP. The SEM results indicated that ultrasound pretreatment resulted in the deformation of RP. In conclusion, the frequency selection of ultrasound pretreatment of RP is essential for the preparation of ACE inhibitory peptide. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effect of ultrasonic frequencies and drying time on fatty acid profiles of beef jerky samples possessing different microbial compositions. Beef slices were cured using curing solutions formulated both with and without Lactobacillus sakei . Curing was carried out for 18 h at 4 °C prior to hot air drying at 60 °C for 4 h. Jerky samples from both treatment groups were then subjected to ultrasonic frequencies of 25 kHz, 33 kHz and 45 kHz for 30 min. Beef jerky samples were subsequently analysed for fatty acid profile using Gas Chromatography. In the present study, beef slices showed a high level of MUFAs, which accounted for 45.6–53.8%, followed by the SFAs (36.3–47.8%) and PUFAs (4.8–13.7%), respectively. Results demonstrated a significant effect of beef jerky processing on fatty acid profile. Various correlation analyses showed that changes in fatty acid profiles were significantly affected by individual and/or interactive effects of L. sakei , drying time and ultrasonic frequency. [ABSTRACT FROM AUTHOR]

• Emulsification mechanism in a microreactor with rough microchannels is reported. • Influence of cavitation bubble size on emulsification and droplet breakup is visually confirmed. • Influence of frequency on the emulsion droplet size is highlighted. • Optimal setup for miniemulsion generation is demonstrated. An ultrasonic microreactor with rough microchannels is presented in this study for oil-in-water (O/W) emulsion generation. Previous accounts have shown that surface pits or imperfections localize and enhance cavitation activity. In this study cavitation bubbles are localized on the rough microchannels of a borosilicate glass microreactor. The cavitation bubbles in the microchannel are primarily responsible for emulsification in the ultrasonic microreactor. We investigate the emulsification mechanism in the rough microchannels employing high-speed imaging to reveal the different emulsification modes influenced by the size and oscillation intensity of the cavitation bubbles. The effect of emulsification modes on the O/W emulsion droplet size distribution for different surface roughness and frequency is demonstrated. The positive effect of the frequency on minimizing the droplet size utilizing a reactor with large pits is presented. We also demonstrate microreactor systems for a successful generation of miniemulsions with high dispersed phase volume fractions up to 20%. The observed emulsification mechanism in the rough microchannel offers new insights into the utility and scale-up of ultrasonic microreactors for emulsification. [ABSTRACT FROM AUTHOR]

Objective: to investigate the relationship between frequency of ultrasounds and birthplace preference. Study design: retrospective case-control study with the number of ultrasounds as the exposure and the pregnant woman's preference to give birth in a low-technology setting (midwifery-led unit or home) or a high-technology setting (obstetric unit) as the primary outcome. Sample and Setting: low-risk primigravid women receiving antenatal care at a central London academic medical centre. Measurements: antenatal ultrasound frequency; birthplace preference at the initial pregnancy appointment (T1) and at the commencement of labour (T2); demographic data including ethnicity, index of multiple deprivation, age, and body mass index. Findings: 1100 cases were reviewed. Women received an average of 4.03 ultrasounds during their pregnancy (SD=1.96, range 2-14). The frequency of ultrasounds for women who had a low-technology T2 birthplace preference was significantly lower than for those who had a high-technology T2 birthplace preference (t=2.98, df=1098, p=0.003, r=0.1), and women who had a constant low-technology birthrate preference had significantly less ultrasounds than other women (F (3,644)=3.475, p=.02). However, within a logistic regression the frequency of ultrasound was not associated with T2 birthplace preference, after controlling for T1 birthplace preference. Key conclusions: the findings of this investigation suggest that a preference made early in pregnancy is a greater predictor of birthplace preference than exposure to antenatal ultrasounds. Implications for practice: further research is required to inform interventions that would encourage lowrisk pregnant women to select a low-technology place of birth. [ABSTRACT FROM AUTHOR]

• Hydrogen production by methanol sono-pyrolysis was computationally analyzed. • An accurate model was developed for H 2 production from methanol sono-conversion. • Hydrogen yields were substantially increased with methanol addition at low dosage. • Hydrogen yielding and CH 3 OH conversion decreased with frequency increase. • The H 2 yield is ideal at an acoustic intensity of 1 W/cm2 and liquid temp. of 20-30 °C. A comprehensive numerical investigation was conducted to analyze the effect of ultrasound frequency (213-1000 kHz), ultrasonic intensity (0.7-1.5 W/cm²) and medium temperature (293.15-333.15 K) on the production of hydrogen from methanol decomposition inside acoustic bubbles (methanol sono-conversion). The adopted model was firstly compared with some reference data. It was found that in the absence of methanol (in the presence of methanol), the bubble temperature, hydrogen production (and methanol conversion) are decreased monotonously with an increase in frequency. The maximal bubble temperature is slightly impacted by the presence of methanol under ultrasonic frequencies that are equal to or greater than 515 kHz. In addition, the yield of H 2 is larger in the presence of methanol, regardless of the utilized frequency. Between 213 to 355 kHz, methanol conversion and hydrogen production are most efficient. Both H 2 production and CH 3 OH degradation are accelerated under an ideal acoustic intensity of 1 W/cm2. At a liquid temperature of 303.15 K, a turning point in bubble temperature may be noticed in the absence of methanol, and at a liquid temperature of 323.15 K, the highest hydrogen production can be achieved. Hydrogen production and methanol conversion are most efficient at liquid temperatures between 293.15 and 303.15 K. Graphical Abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an experimental study of the ultrasonic degradation of organic pollutants in terms of the effect of ultrasonic frequency (40–380–850–1000kHz). The removal efficiency of two endocrine disrupting compounds [17β-estradiol (E2) and 17α-ethinylestradiol (EE2)] is investigated using laboratory scale ultrasonic baths at low power intensities. Higher ultrasonic frequencies were found to be more effective for pollutant degradation with 850kHz the best: 9.0×10−1 mg/kWh for E2 and 6.8×10−1 mg/kWh for EE2 at initial concentrations of 1ppm. Additionally, the removal of p-nitrophenol was investigated under the same conditions, as a dosimetry reaction for estimating the hydroxyl radical production, key component in organic pollutant removal. In order to describe the overall phenomena occurring inside the reactor and to predict the apparent hydroxyl radical production, a simulation algorithm is proposed. It incorporates the solution of ODE systems that embodies bubble dynamics, heat and mass transfer through the bubble wall and chemical reactions in the gas–vapor phase for an initial bubble nuclei population. The experimental degradation measures of p-nitrophenol over the range of frequencies studied were found to be comparable with the model results of hydroxyl radicals produced during the sonication treatment. [Copyright &y& Elsevier]

The aim of the present work was to demonstrate the possibility of selective detection of nanoparticle contrast agents (NPCAs) on diagnostic echographic images by exploiting the second harmonic component they introduce in the spectra of corresponding ultrasound signals, as a consequence of nonlinear distortion during ultrasound propagation. We employed silica nanospheres (SiNSs) of variable diameter (160 nm, 330 nm, and 660 nm) dispersed in different volume concentrations (range 0.07-0.8%) in agarose gel samples that were automatically scanned through a digital ecograph using narrow-band ultrasound pulses at 6.6 MHz and variable mechanical index (MI range 0.2-0.6). In the first part of the study, the intensity peaks of four different spectral components of the backscattered signal were considered: fundamental (detected in correspondence of the incident ultrasound frequency), subharmonic (detected at half of the fundamental frequency), ultra harmonic (detected at 1.5 times the fundamental frequency), and second harmonic (detected at twice the fundamental frequency). Subsequently, based on the experimental results of the first part of the study and on our recently reported findings, the focus was moved to a detailed comparison between subharmonic and second harmonic trend, which were determined as a function of nanoparticle composition, sample concentration, and MI. The experiments were also repeated on different agarose samples, containing SiNSs covered by an outer shell of smaller magnetic nanoparticles, made of either iron oxide (IO) or FePt-IO nanocrystals. Obtained results show that this new ultrasound-based method for NPCA imaging has a detection sensitivity similar to that of our previously introduced subharmonic-based technique in the presence of 330-nm SiNSs, but performs significantly better in the detection of both the types of “dual mode” NPCAs. The fact that the reported detection method was optimized for identification of 330-nm SiNSs (a sort of “ideal” size for the development of novel tumor-targeting NPCAs) and that the magnetically coated particles are detectable also through magnetic resonance imaging makes the presented second harmonic ultrasound method a valuable solution for the introduction of new protocols for multimodal molecular diagnoses employing only nonionizing radiations. [ABSTRACT FROM PUBLISHER]

Abstract: At high ultrasound frequencies, active bubble structures are difficult to capture due to the decrease in timescale per acoustic cycle and size of bubbles with increasing frequencies. However the current study demonstrates an association between the spatial distribution of visible bubbles and that of the active bubble structure established in the path of the propagating acoustic wave. By monitoring the occurrence of these visible bubbles, the development of active bubbles can be inferred for high frequencies. A series of still images depicting the formation of visible bubble structures suggest that a strong standing wave field exists at early stages of wave propagation and weakens by the increase in the attenuation of the acoustic wave, caused by the formation of large coalesced bubbles. This attenuation is clearly demonstrated by the occurrence of a force which causes bubbles to be driven toward the liquid surface and limit standing wave fields to near the surface. This force is explained in terms of the acoustic streaming and traveling wave force. It is found that a strong standing wave field is established at 168kHz. At 448kHz, large coalesced bubbles can significantly attenuate the acoustic pressure amplitude and weaken the standing wave field. When the frequency is increased to 726kHz, acoustic streaming becomes significant and is the dominant force behind the disruption of the standing wave structure. The disruption of the standing wave structure can be minimized under certain pulse ON and OFF ratios. [Copyright &y& Elsevier]

Abstract: Influence of ultrasound (US) on various unit operations in leather processing has been studied with the aim to improve the process efficiency, quality, reduce process time and achieve near-zero discharge levels in effluent streams as a cleaner option. Effect of US on substrate (skin/leather) matrix as well as substances used in different unit operations have been studied and found to be useful in the processing. Absorption of US energy by leather in process vessel at different distances from US source has been measured and found to be significant. Effect of particle-size of different substances due to sonication indicates positive influence on the diffusion through the matrix. Our experimental results suggest that US effect is better realized for the cases with pronounced diffusion hindrance. Influence of US on bioprocessing of leather has been studied and found beneficial. Attempts have also been made to improve the US aided processing using external aids. Operating US in pulse mode operation could be useful in order to reduce the electrical energy consumption. Use of US has also been studied in the preparation of leather auxiliaries involving mass-transfer resistance. Preliminary cost analysis carried out for ultrasound-assisted leather-dyeing process indicates scale-up possibility. Therefore, US application provide improvement in process efficiency as well as making cleaner production methods feasible. Hence, overall results suggest that use of US in leather industry is imminent and potential viable option in near future. [Copyright &y& Elsevier]

Fixed frequency ultrasound (FFU), cyclic-sweeping frequency ultrasound (CSFU), and random-sweeping frequency ultrasound (RSFU) with the identical central frequency were constructed, and their effects on enzymatic hydrolysis and structural characteristics of rice protein (RP) were studied. FFU and RSFU enhanced the degree of hydrolysis (DH) and the angiotensin-I converting enzyme (ACE) inhibitory activity of RP hydrolysate significantly. CSFU increased the ACE inhibitory activity but had no significant effect on DH. The molecular weight distribution results showed that FFU and RSFU promoted the conversion of the hydrolysate to low molecular weight peptides (1000–2000 and 200–1000 Da). Meanwhile, FFU, CSFU, and RSFU pretreatment improved the surface hydrophobicity index H 0 from 397.53 to 464.23, 436.37, and 477.6, respectively. Circular dichroism spectra indicated that the three ultrasonic frequency modes decreased α-helix but increased random coil content. Ultraviolet–visible spectra and atomic force microscopy showed that the three ultrasound frequency modes caused the exposure of hydrophobic groups and reduced the particle size, respectively. Therefore, the innovative ultrasonic frequency modes modified the structural characteristics of RP and enhanced the ACE inhibitory activity of its hydrolysate. • Three frequency modes of one ultrasonic generator were constructed. • FFU, CSFU, and RSFU enhanced the DH and ACE inhibitory activity of RP hydrolysate. • Random-sweeping frequency ultrasound increased the ACE inhibitory activity most. • The enzymolysis effect of RP could be associated with the protein structure changes. [ABSTRACT FROM AUTHOR]

Abstract: The sonochemical efficiency of a cylindrical sonochemical reactor has been investigated as a function of frequency and liquid height. The irradiation frequencies were 45, 129, 231 and 490kHz. The liquid height was varied from 10 to 700mm. The sonochemical efficiency of the cylindrical reactor was evaluated by potassium iodide (KI) dosimetry and calorimetry. In our study, the sonochemical efficiency depended on the frequency and liquid height; further, the plots of sonochemical efficiency against liquid height exhibit one or two peaks for each frequency. The sonochemical efficiency up to the first peak increased monotonically with the logarithm of the frequency, and the liquid height for the first peak was inversely proportional to the frequency. From these results, the optimum frequency for a sonochemical reactor can be determined if the liquid height is specified for scale-up of the sonochemical reactor. [Copyright &y& Elsevier]

Abstract: Algae bloom in source water causes high chemical consumption and deteriorates water quality in waterworks. This paper studied the ultrasonic removal of Microcystis aeruginosa. The results showed that algae cells could be effectively removed by sonication and gas vesicle collapse was the main mechanism. The ultrasonic algae removal followed the first order reaction with a rate constant of 0.023min−1 (80W, 80kHz). Higher ultrasound frequency benefited algae removal; the algae removal rate constant was 0.114min−1 at 1320kHz and 0.0224min−1 at 20kHz (80W). Higher ultrasound power also accelerated algae removal; the algae removal rate constant was 0.023min−1 at 80W and 0.007min−1 at 32W (80kHz). However, high ultrasound power and long irradiation caused microcystins to increase. 80W, 80kHz sonication for 5min increased the extracellular microcystins concentration from 0.87μg/L to 3.11μg/L. Sound frequency had little impact on the microcystins release. The chlorophyll a concentration initially decreased and then stabilized after 5min of sonication. [Copyright &y& Elsevier]

Abstract: Over the past few decades, ultrasonography has been used intermittently as a non-invasive, diagnostic tool for evaluating a variety of conditions in aquatic organisms. There has been a recent upsurge in scientific articles in which ultrasound images were used as a diagnostic tool, and the predominant use was to evaluate gender and other reproductive issues. Ultrasonography equipment is available in a variety of configurations, but we are unaware of any published literature that evaluates the efficacy of the various probe types for diverse uses (e.g., anatomical and physiological examinations). In this paper, we compare striped bass ovary volume and fecundity data based on ultrasonic images produced by probes with different frequencies and array types and offer considerations for determining which frequency or array type best facilitates various potential applications. Both the 3.5/5.0MHz and the 6.0/8.0MHz probes were equally effective in determining striped bass sex, but not for determining ovary volume. The 3.5/5.0MHz curved array probe offered the best resolution of female striped bass ovaries. However, ovary area measurements had to be performed in the field because the curved images were incompatible with the image analysis software used in the lab. The 6.0/8.0MHz linear array probe provided only partial images of ovaries in striped bass>850mm, and estimates of ovary area were based on several scanned and recorded images. However, the 6.0/8.0MHz linear array probe has the advantage of a field scan, which can be recorded and later calibrated to computer image analysis software in the lab. Careful consideration of the type of animal and parts of its anatomy to be imaged as well as the image acquisition and processing circumstances should be undertaken to ensure that the ultrasonic imaging technology used is appropriate to the task. [Copyright &y& Elsevier]

The study focussed on the effect of ultrasonic frequency and co-pollutants on dechlorination and toxicity reduction of a toxic model pollutant, i.e. 2,3,5-trichlorophenol (TCP). The effect of ultrasonic frequency on TCP degradation and chloride formation was studied at 41, 206, 360, 618, 1068, and 3217 kHz. Most efficient ultrasonic dechlorination was achieved at 360 kHz. The degradation of TCP and adsorbable organic halogens followed pseudo-first-order rate kinetics. Toxicity in the bioluminescence test increased during the initial sonication period, indicating the temporary formation of more toxic reaction products. Subsequently, toxicity was significantly reduced. Dehalogenation efficiency decreased in the presence of the hydrophobic radical scavenger t-butanol, whereas hydrophilic co-pollutants such as acetate or glucose did not interfere with ultrasonic dechlorination and toxicity reduction. After ultrasonic pre-treatment, a fast biodegradation of the remaining organic pollutants was observed. In conclusion, the results demonstrate the potential of integrated ultrasonic/biological approaches for the treatment of wastewaters containing toxic pollutants. [Copyright &y& Elsevier]

The aim of this experimental trial was to study the effect of ultrasound application on the lipolysis in adipose tissue. Rats were administered to pentobarbital (Nembutal) anesthesia and their abdomens were shaved. Rat abdomen was subjected to 24 kHz–1 MHz ultrasound for 10 min to investigate frequency and power-intensity dependency for fat mobilization. Blood was taken from the tail vein to estimate plasma free fatty acids (FFA). For frequency dependency two regions around 100 kHz and 300–500 kHz were effective for fat mobilization. For power-intensity dependency, effective regions were found to be from 24 to 1090 kHz. In the effective regions on frequency and power-intensity, application of ultrasound caused increases in plasma FFA and norepinephrine concentration of extra-cellular fluid of perirenal adipose tissue. These results suggest that ultrasound application stimulates fat mobilization through a local increase in norepinephrine secretion under the conditions of effective frequency and intensity. [Copyright &y& Elsevier]

This study investigated the impacts of ultrasound-assisted osmotic dehydration (UOD) with different frequency (40 kHz, 80 kHz, 40 + 80 kHz) and intensity (25 W/L, 50 W/L, 75 W/L) on the kinetics of mass transfer, phenolic losses and the antioxidant properties of apple cubes (8 mm). The mass transfer efficiency of solid gain (SG) was greater under dual-frequency (β = 0.413) than 40 kHz (β = 0.707) and 80 kHz (β = 0.793) under the same intensity. Moreover, the mass transfer efficiency of SG under 75 W/L 40 kHz UOD was higher than that of 25 W/L and 50 W/L UOD based on β values. Notably, the loss of phenolic content under 75 W/L UOD (18.9 %) was substantially higher than that of the 25 W/L UOD treatment (1.2–1.8 %). A UOD treatment of 50 W/L and 40 + 80 kHz is recommended to optimize mass transfer efficiency and phenolic retention of dehydrated apple cubes. • Increasing ultrasound intensity accelerated mass transfer during osmotic dehydration. • Dual-frequency ultrasound treatment showed higher mass transfer efficiency than single-frequency. • Chlorogenic acid leached out from apple cubes during osmotic dehydration. • Increasing ultrasound intensity accelerated phenolic degradation and leaching. • Phenolic retention was higher under UOD with dual than with single frequency. [ABSTRACT FROM AUTHOR]

• ZIF-8 synthesis under different mixing speeds, US frequencies, powers and time. • ZIF-8 crystals were formed after 5 s of reaction time. • Sonication produced smallest crystals with an average size of 80 nm. • Varying frequency and power did not significantly affect the crystal properties. • Ultrasound has both positive and negative impact on crystal properties. A systematic study on the sonocrystallisation of ZIF-8 (zeolitic imidazolate framework-8) in a water-based system was investigated under different mixing speeds, ultrasound frequencies, calorimetric powers and sonication time. Regardless of the synthesis technique, pure crystals of ZIF-8 with high BET (Brunauer, Emmett and Teller) specific surface area (SSA) can be obtained in water after only 5 s. Furthermore, 5 s sonication produced even smaller crystals (~0.08 µm). The type of technique applied for producing the ZIF-8 crystals did not have any significant impact on crystallinity, purity and yield. Crystal morphology and size were affected by the use of ultrasound and mixing, obtaining nanoparticles with a more spherical shape than in silent condition (no ultrasound and mixing). However, no specific trends were observed with varying frequency, calorimetric power and mixing speed. Ultrasound and mixing may have an effect on the nucleation step, causing the fast production of nucleation centres. Furthermore, the BET SSA increased with increasing mixing speed. With ultrasound, the BET SSA is between the values obtained under silent condition and with mixing. A competition between micromixing and shockwaves has been proposed when sonication is used for ZIF-8 production. The former increases the BET SSA, while the latter could be responsible for porosity damage, causing a decrease of the surface area. [ABSTRACT FROM AUTHOR]

This study endeavored to develop a method to evaluate the effect of ultrasound frequency on soybean protein extraction. In the ultrasonic frequencies range from 20 to 52 kHz, 28, 35, and 45 kHz were predicted to be the resonance frequencies in the ultrasound-assisted extraction (UAE) process of soybean protein by simulating the acoustic field distribution. The absolute sound pressure and the relative standard deviation could be well-coordinated via frequency regulation. The extraction experiment of soybean protein showed that the extraction rate was improved significantly (p < 0.05) with the aid of ultrasound. The extraction effect was optimal at 28 kHz and the extraction rate was improved to 73.35 g/100 g from 46.09 g/100 g of control under the same condition. The structure of the extracted protein was analyzed by the spectrum to further explore the mechanism of the effect of ultrasonic frequency. Spectral analysis showed that 20, 28, and 35 kHz had a significant influence on the structure of protein molecules. Therefore, acoustic field simulation can be used as one effective method for selecting ultrasonic frequency, which could help to optimize equipment and improve efficiency. • An acoustic field simulation model of a custom-made ultrasound was established. • The distribution of the acoustic field at 20, 28, 35, 40, and 50 kHz was visualized. • The highest extraction rate of soybean protein was achieved at 28 kHz. • Spectral analysis verified the validity of the simulation indirectly. [ABSTRACT FROM AUTHOR]

The effect of ultrasound thawing with different frequencies and working modes, including mono-, dual- and tri-frequency, on the physicochemical quality, water holding capacity, microbial evaluation, microstructure, as well as moisture migration and distribution of quick-frozen small yellow croaker (Larimichthys polyactis) were evaluated. The results showed that the quality of samples thawed by sequential ultrasound working modes was higher than that of the simultaneous ultrasound and mono-frequency ultrasound working modes. Specifically, the samples thawed by combined dual-frequency sequential ultrasound (DSEU) at 20/40 kHz was close to fresh samples, which had better physicochemical quality (higher hardness, springiness, resilience, chewiness and lower TVB-N values, TBARS values, K-values), water-holding capacity (lower thawing loss and cooking loss), and microstructure, higher immobilized water content, lower free water content, and less microbial colonies, compared with other ultrasonically thawed samples. Therefore, the DSEU at 20/40 kHz can improve the quality of the samples better than other thawing methods. • Multi-frequency ultrasound was used to thaw quick-frozen small yellow croaker. • Product quality was improved by dual-frequency sequential ultrasound (DSEU) thawing. • The DSEU 20/40 kHz was the best frequency combination when thawing quick-frozen fish. • The samples thawed by DSEU at 20/40 kHz can retain more immobilized water content. • The moisture migration and distribution affect the quality of the sample. [ABSTRACT FROM AUTHOR]