Increase Of Ultrasonic Power Research Articles

Longitudinal torsional ultrasonic vibratory assistant milling of borosilicate glass material removal mechanism based on the thickness of undeformed chips

Borosilicate glass is an ideal material for microfluidic chip substrates due to its excellent light transmittance and stable chemical properties. However, it is also prone to brittle fracture during processing, making it a typical difficult-to-machine material. As an emerging processing technology, longitudinal torsional ultrasonic assistant milling (LTUVAM) can effectively reduce the surface damage of glass materials and improve the proportion of plastic removal of materials. The mechanism of LTUVAM of borosilicate glass was studied in this paper. Critical undeformed chip thickness (hc) is a key factor in achieving plastic material removal. At present, the influence of LTUVAM on the hc is not clear. Therefore, in this paper, the material-specific cutting energy model in the LTUVAM process was established to predict the hc. Firstly, the motion path of LTUVAM was analyzed, and the undeformed chip thickness model and the tool-workpiece separation rate model were established. Then, based on the above model, the material-specific cutting energy model was established according to the material removal principle. Finally, an LTUVAM orthogonal experiment was carried out to study the surface quality of the material. The experimental results showed that with the increase of ultrasonic power, the roughness and side damage area increased first and then decreased. With the increase of spindle speed, it showed that the roughness and side damage area decreased first and then increased. With the increase of feed per tooth, it showed that the roughness increased first and then decreased, and then increased, and the side damage area increased first and then decreased. Through the analysis of the experimental and model results, the increase of the separation rate between the tool and the workpiece contributes to the increase of the hc and the improvement of the processing quality.

Microstructure refinement, mechanical performances and degradability of biomedical Zn-2Cu alloy by ultrasonic melting and homogenization treatment

Zn alloys are deemed to be desired body implant materials because of their moderate degradation rate. In this paper, the microstructural evolution, mechanical performances, and degradability of Zn-2Cu alloy prepared by ultrasonic melt treatment (UMT) with different ultrasonic powers (0 W, 300 W, 600 W, and 900 W) were systematically studied. Under the condition of UMT, the coarse α-Zn grains of Zn-2Cu alloy were refined into fine equiaxed grains and the mean size was significantly decreased from 133.4 μm to 65.3 μm when the ultrasound power was enhanced. The precipitating CuZn5 phase was significantly refined from the coarse block into the spherical shape. Moreover, the fraction of the CuZn5 precipitates of the Zn-2Cu alloy was greatly reduced with the increase of ultrasonic power. Tensile tests showed that the ultimate tensile strength (UTS), yield strength (YS), and elongation (El) of Zn-2Cu alloy were remarkably enhanced to 203 MPa, 167 MPa, and 8.14 %, respectively, when the Zn-2Cu alloy melting was treated by 600 W power. It was found by electrochemical polarization test that the degradation rate of Zn-2Cu alloy treated by UMT with 0 W, 300 W, 600 W, and 900 W power in Hank’s solution was gradually decreased to 1.6312 mm/a, 1.3206 mm/a, 1.0992 mm/a, and 1.2832 mm/a, respectively. In addition, after the Zn-2Cu alloys were immersed in Hank’s solution for 30 days, the degradation rate of samples was summarized as 0 W alloy (0.472 mm/a) > 300 W alloy (0.436 mm/a) > 900 W alloy (0.412 mm/a) > 600 W alloy (0.398 mm/a). The studies verified that the UMT was a very valuable technology for preparing Zn-2Cu alloy, which can meet the requirement of mechanical properties and degradable rate as a promising implant material.

The effect of temperature and ultrasonic power on the microstructure evolution of coal modified by clean fracturing fluid: An experimental study

Ultrasonic-assisted fracturing permeability enhancement technology offers several advantages, including a broad range of hydraulic fracturing permeability enhancement, microstructure modified by fracturing fluid, and ultrasonic promotion of gas desorption and extraction. This technology can significantly improve the efficiency of coalbed methane extraction and has broad application prospects. To investigate the effect of ultrasonic action power and temperature on the microstructure evolution of coal by using clean fracturing fluid, experiments were conducted using coal samples from a mine in Shenyang. The pore structure of these samples was analyzed by scanning electron microscopy (SEM) and mercury intrusion method (MIP), while the chemical microstructure was evaluated with energy dispersive spectroscopy (EDS), X-ray diffraction experiment (XRD) and Fourier transform infrared spectroscopy (FTIR). The results showed that ultrasonic treatment improved the pore structure characteristics and connectivity by facilitating chemical reactions between fracturing fluid and mineral impurities. Specifically, when the ultrasonic parameter was set at 600W-60 °C, the pore volume of coal samples increased by 26.09 %, tortuosity decreased by 31.81 %, pore fractal dimension increased by 3.93 %, permeability increased by 100.45 %, aromaticity increased by 16.69 %, and the degree of branching aliphatic side-chains increased by 108.70 %. Under the same ultrasonic power, the effective temperature for ultrasonic-assisted fracturing fluid treatment on coal rock was found to be 60 °C. Additionally, under the same temperature conditions, an increase in ultrasonic power resulted in significant enhancements in both pore structure parameters and chemical structure parameters in coal, showing a certain linear relationship. The research results enrich the theoretical system of coalbed methane mining and provide theoretical guidance for the field practice of this technology.

Microstructure evolvement and wear properties of Ni60-based coating by ultrasonic power-assisted laser cladding

Ultrasonic vibration is known to cause significant refinement of microstructure, the effect of ultrasonic power on grain size, grain orientation and Schmid factor by laser cladding in the Ni60/WC composite coating was studied systematically. Meanwhile, the effect of microstructure on wear properties and hardness was elucidated. The results show that the performance of the cladding layer is the best when the ultrasonic power is 600 W, which is due to the combined effect of ultrasonic cavitation and acoustic flow. The average grain diameter is refined from 28.36 μm to 23.02 μm, and the refinement range is 18.9%. The formation of low Angle grain boundaries (LAGBs) is promoted by ultrasound, and the dislocation density is increased. The texture strength of the coating is distributed over {100}, {110} and {111} surfaces, and the strength decreases from 12.307 to 5.447 The microhardness is increased by 16% (from 768.85HV1 to 896.95HV1), the wear mechanism gradually from adhesive to abrasive wear and the average friction coefficient decreases from 0.47 to 0.216 with the increase of ultrasonic power, which improve the wear resistance of the coatings. Based on the understanding of microstructure evolvement, the grain refinement mechanism effected by ultrasonic power was explained from the aspect of cavitation processes.

Ultrasonic-assisted nanofiltration separation recovering salvianolic acid B from ethanol wastewater

The transformation of salvianolic acid B brought on by heat treatment recovery of ethanol eluent, which is a difficult problem in pharmaceutical technology, affects the purity of raw material when the medicinal raw material salvianolic acid B is purified by resin. Ultrasonic-assisted nanofiltration separation (UANS) was first employed to improve efficiency of resource utilization by regulating rejection and separating salvianolic acid B and rosmarinic acid from organic pharmaceutical wastewater. The rejection was related to three variables: ultrasonic power, pH, and ethanol concentration. But there were differences in the effects of variables on the rejections of salvianolic acid B and rosmarinic acid. The rejections of rosmarinic acid and salvianolic acid B showed a decreasing trend with an increase in ultrasonic power or a decrease in pH; however, when the concentration of ethanol was increased from 5 % to 35 %, the salvianolic acid B rejection increased from 84.96 % to 96.60 % and the rosmarinic acid rejection decreased from 35.09 % to 17.51 %. On the basis of response surface methodology (RSM), the optimal UANS parameters for solution conditions involving different ethanol concentrations are as follows: 10 % ethanol solution (ultrasonic power 500 W and pH 6.15), 20 % ethanol solution (ultrasonic power 500 W and pH 6.54), and 30 % ethanol solution (ultrasonic power 460 W and pH 6.34). The molecular proportions of salvianolic acid B were 10.75 %, 7.13 %, and 8.27 % in 10 %, 20 %, and 30 % ethanol wastewater, while the molecular proportions of rosmarinic acid were 40.52 %, 33.83 %, and 69.87 %, respectively. And the recoveries of salvianolic acid B in 10 %, 20 %, and 30 % ethanol wastewater were 93.56 %, 95.04 %, and 97.30 %, respectively, while the recoveries of rosmarinic acid were 3.19 %, 2.27 %, and 0.56 %. The molecular proportion and the rejection are correlated exponentially. In comparison with conventional nanofiltration separation (CNS), UANS is able to resolve the conflict between rosmarinic acid and salvianolic acid B in pharmaceutical wastewater, as well as enhance resource recycling and separation efficiency to prevent pollution of the environment from pharmaceutical wastewater. Experiments using UANS at different power intensities suggest that the ultrasonic at a power intensity of 46–50 W/L and the power density of 0.92–1.00 W/cm2 may resolve the separation conflict between rosmarinic acid and salvianolic acid B. This work suggests that UANS may be a significant advancement in the field of ultrasonic separation and has several potential uses in the water treatment industry.

Microstructural characterization of recycled Al–Mg–Si-based alloys upon the synergistic effect of ultrasonic technology (UT) and novel refiners

Ultrasound, as an efficient, clean, and safe processing technology, is widely used in industries. Grain refiners are widely used in the refinement of cast alloys. In this study, ultrasonic technology (UT) and Al–5Ti–1B refiner prepared by continuous rheological extrusion (CRE Al–5Ti–1B) were used to modify the recycled Al–Mg–Si-based alloy, and the microstructure and mechanical properties of the recycled Al–Mg–Si-based alloy were studied. The differences in porosity and grain refinement caused by ultrasonic power were discussed. Results showed that, increasing the ultrasonic power can effectively reduce the porosity of the recycled Al–Mg–Si-based alloy. The synergistic effect of UT and CRE Al–5Ti–1B refiner significantly refined α-Al grains and second phases. The increase of ultrasonic power can effectively cause deagglomeration while reducing the nucleation undercooling of α-Al, which promotes the refinement of the recycled Al–Mg–Si-based alloy and significantly improves the mechanical properties. The yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) of the recycled Al–Mg–Si-based alloy were 106 MPa, 210 MPa and 9.4%, respectively. When 0.2 wt% CRE Al–5Ti–1B refiner was added and the ultrasonic power was 150 W, the YS, UTS, and EL were improved by 12.8%, 28.8% and 228.4%, respectively.

Effects of Ultrasonic Treatment on Physical Stability of Lily Juice: Rheological Behavior, Particle Size, and Microstructure.

The aim of this study was to investigate the rheological properties, particle size distribution, color change, and stability of lily juice under different ultrasonic treatment conditions (152 W, 304 W, 456 W, 608 W, and 760 W). The results showed that the lily juice exhibited non-Newtonian shear thinning behavior, and the viscosity decreased with the increase in ultrasonic power. Under ultrasonic treatment conditions, there was no significant change in the pH value and zeta potential value of the samples. The content of cloudy value and total soluble solids (TSS) increased gradually. However, both the sedimentation components and centrifugal sedimentation rate showed a downward trend and an asymptotic behavior. In addition, high-power ultrasound changed the color index (L* value decreased, a* value increased), tissue structure, and particle distribution of the sample, and small particles increased significantly. To sum up, ultrasonic treatment has great potential in improving the physical properties and suspension stability of lily juice.

Regulation of Protein Flexibility and Promoting the Cod Protein Gel Formation Using Ultrasound Treatment.

In order to obtain a soft-textured protein gel suitable for the elderly, the cod protein gel was prepared by improving the protein flexibility under ultrasound treatment. It has been found that the increase in ultrasonic power, protein flexibility, particle size, ζ-potential, surface hydrophobicity, and α-helix content of preheated cod protein exhibited an increasing trend. The improvement of protein flexibility promoted uniformity and density of the gel network, water retention, and texture properties. The flexibility of preheated cod protein increased to 0.189, the water holding capacity of the gel reached up to 99.41%, and the hardness increased to 49.12 g, as the ultrasonic power level increased to 400 W. Protein flexibility was correlated well with the cohesiveness of the gel. The storage modulus (G') initially decreased and then increased during the heating-cooling process. The attractive forces forming between the flexible protein molecules during cooling in the ultrasound treatment groups promoted protein self-assembly aggregation and formed the cod protein gel. The gel obtained at 100-400 W could be categorized as Level 6─soft and bite-sized according to the International Dysphagia Diet Standardization Initiative (IDDSI) framework, indicating that the cod protein gel has potential as an easy-to-swallow diet for the elderly.

Effect of high-intensity ultrasound on the structural and functional properties of proteins in housefly larvae (Musca demestica)

Insect protein has gradually attracted wide attention from the international research community as a promising source of high-quality protein that can replace traditional protein sources. The larvae of the housefly, a prevalent and widespread species, contain high levels of protein with beneficial properties, namely, anti-fatigue, anti-radiation, and anti-aging functions, as well as liver protection and immunity enhancement. This work thoroughly examined the impact of high-intensity ultrasound (HIUS) on the structural and functional characteristics of housefly larval concentrate protein (HLCP). HLCP samples were sonicated for 20 min at a frequency of 20 kHz with varying energies (0, 100, 200, 300, 400, and 500 W). The findings demonstrated that sonication considerably altered the secondary and tertiary structures of HLCP but had no effect on molecular weight. With an increase in ultrasonic power, HLCP's particle size shrank, more hydrophobic groups were exposed, more free sulfhydryl groups were present, the solution's stability improved, and HLCP's solubility rose. In addition, HLCP's emulsification and foaming abilities were improved by HIUS treatment. It is anticipated that this study's findings will offer fresh insights into the implementation of HLCP in the food sector.

Microstructure and mechanical properties of SUS304 weldments manufactured by ultrasonic vibration assisted local dry underwater welding

To address the key manufacturing challenges such as severe columnar crystal growth trend and heterogeneous composition of molten pool, which caused by the rapid water cooling in local dry underwater welding (LDUW), the ultrasonic vibration assisted local dry underwater welding (U-LDUW) was innovatively proposed in this study. The phase structure and distribution, grain structure characteristic, microhardness, and tensile property of SUS304 weldments fabricated by LDUW and U-LDUW were investigated and compared comprehensively. The obtained results demonstrated that the stirring action on the molten pool was realized by the external ultrasonic vibration, which accelerated the ferrite morphology evolution from skeleton to lath, and more ferrites were remained in the austenite matrix. Compared with LDUW, the ultrasonic vibration facilitated to break the dendritic crystals, with the ultrasonic power of 800 W, the grain refinement was the maximum 32.1% and the proportion of the small-dimension (less than 20 µm) grains was increased from 53% to 67%. The ultrasonic vibration also contributed to the grain boundary transformation from low-angle to high-angle and increased the proportion of the recrystallized grains from 10% to 15%. With the increase of ultrasonic power, the microhardness, ultimate tensile strength, and elongation were increased first and then decreased, that of U-LDUW weldment were increased by 16.3%, 23.3% and 55.5% than that of LDUW. The results of this work provide a novel process method to enhance the comprehensive performance of LDUW weldments and expand the application of LDUW in repairing large-scale underwater structures.

Effect of ultrasonic power on degassing and microstructure of large-scale 7085 aluminum alloy ingots

In this work, five sets of large-scale 7085 Al alloy ingots (diameter 830 mm × length 3600 mm) were manufactured by introducing different ultrasonic powers (0–750 W) in the Direct-Chill (DC) casting process. The difference among the ultrasonic degassing, the α-Al grains, elemental segregation and eutectic phase with ultrasonic treatment were investigated. The results indicated that with the increase of ultrasonic power, the efficiency of ultrasonic degassing was gradually improved, which was decreased from 0.085 cm3/100 g to 0.056 cm3/100 g in ingot center part. The grain size was also dramatically refined, in which the grain refinement rate reached 38.2%, 42.8% with 550 W, 750 W power, respectively. The segregation of alloying elements (Zn, Mg, Cu) in the ingot was significantly suppressed, which the maximum positive deviations ∆C of Zn, Mg, and Cu were reduced by 59.5%, 55.9%, and 60.8%, respectively. In addition, the new Al14Cu2Fe3 (α−Fe) phase was the first to be discovered in the low power state and the coarse eutectic phase was more refined in the high power. The mechanisms of degassing, grain refinement and suppression of macroscopic segregation during ultrasonic casting were further revealed by calculating the acoustic energy density (I).

Experimental Study on Ultrasonic Cavitation Intensity Based on Fluorescence Analysis

The Ultrasonic cavitation effect has been widely used in mechanical engineering, chemical engineering, biomedicine, and many other fields. The quantitative characterization of ultrasonic cavitation intensity has always been a difficulty. Based on this, a fluorescence analysis method has been adopted to explore ultrasonic cavitation intensity in this paper. In the experiment of fluorescence intensity measurement, terephthalic acid (TA) was used as the fluorescent probe, ultrasonic power, ultrasonic frequency, and irradiation time were independent variables, and fluorescence intensity and fluorescence peak area were used as experimental results. The collapse of cavitation bubble will cause molecular bond breakage and release ·OH, and the non-fluorescent substance TA will form the strong fluorescent substance TAOH with ·OH. The spectra of the treated samples were measured by a F-7000 fluorescence spectrophotometer. The results showed that the fluorescence intensity and fluorescence peak area increased rapidly after ultrasonic cavitation treatment, and then increased slowly with the increase of ultrasonic power, which gradually increased with the increase of irradiation time. They first decreased and then increased with the increase of ultrasonic frequency from 20 kHz to 40 kHz. The irradiation time was the most influential factor, and the cavitation intensity of low frequency was higher overall. The fluorescence intensity and fluorescence peak area of the samples increased by 2–20 times after ultrasonic treatment, which could increase from 69 and 5238 to 1387 and 95451, respectively. After the irradiation time exceeded 25 min, the growth rate of fluorescence intensity slowed down, which was caused by the decrease of gas content and TA concentration in the solution. The study quantitatively characterized the cavitation intensity, reflecting the advantages of fluorescence analysis, and provided a basis for the further study of ultrasonic cavitation.

Promotion of hydrophobic-hydrophilic separation of coal gasification fine slag through ultrasonic pre-treatment

Coal gasification fine slag (CGFS) is a solid waste byproduct generated during the coal gasification process. However, the high content of residual carbon hinders its potential for resource utilization. The urgent need for an efficient carbon extraction and ash reduction technology is evident. Hydrophobic–hydrophilic separation (HHS) is a technology that enriches hydrophobic particles in the oil phase while hydrophilic particles are in the water phase by stirring, and the different hydrophobic particles are separated by the separation of the oil and water phases. The molecular dynamics simulations revealed that the adsorption of n-heptane onto the residual carbon surface occurred spontaneously and was primarily driven by van der Waals forces. Ultrasonic pre-treatment pulp could enhance the effect of HHS. The fluctuation in tailings ash did not exceed 2% while the concentrate ash was reduced from 31.81% to 18.93% with a continual increase in ultrasonic power. The application of ultrasonic treatment on CGFS facilitated the separation of Carbon-ash molten state, as well as the elimination of ash materials particles residing within the pores of the residual carbon matrix and on its surface. Notably, many residual carbon particles are concentrated in the particle size range of 0.045–0 mm. The heightened hydrophobicity exhibited by particles within this size range enhanced the capture of oil droplets, thereby promoting the efficiency of HHS. This research aims to provide technical support and theoretical foundation for utilizing ultrasonic pretreatment as a means to enhance the HHS efficiency of CGFS.

Quantitative characterization and influencing factors analysis of dual-frequency ultrasonic cavitation intensity based on fluorescence analysis

Ultrasonic cavitation assisted processing technology has been widely used in machinery, chemistry, biology, food, and other fields. Compared with single-frequency ultrasonic cavitation, dual-frequency ultrasonic shows unique advantages such as cavitation bubbles imploding more strongly, breaking cavitation shielding, and reducing cavitation threshold. It has higher ultrasonic cavitation intensity and has received more extensive attention. However, the quantification of cavitation intensity enhanced by dual-frequency ultrasonic is a complex problem. This paper quantitatively characterized the cavitation intensity using fluorescence analysis method. The results showed that the samples fluorescence indexes after ultrasonic cavitation increased to 1.68–10.60 times. The dual-frequency ultrasonic could significantly enhance the cavitation intensity. The smaller frequency differences and lower-frequency combination (20+30 kHz) led to the maximum fluorescence index differences of 117.6 and 6677.3. The effect of dual-frequency ultrasonic on cavitation intensity was further enhanced accompanied by the increase of ultrasonic power, and the extension of irradiation time leaded to a higher fluorescence index, which was due to the accumulation of ·OH. The ultrasonic mode had the most significant impact on cavitation intensity. This study analyzed the cavitation intensity enhanced by dual-frequency ultrasonic quantitatively, which provided a basis for further research and utilization of dual-frequency ultrasonic cavitation.

Effect of ultrasound power on HCl leaching kinetics of impurity removal of aphanitic graphite

This study aimed to investigate the effect of ultrasonic power and temperature on the impurity removal rate during conventional and ultrasonic-assisted leaching of aphanitic graphite. The results showed that the ash removal rate increased gradually (∼50 %) with the increase in ultrasonic power and temperature but deteriorated at high power and temperature. The unreacted shrinkage core model was found to fit the experimental results better than other models. The Arrhenius equation was used to calculate the finger front factor and activation energy under different ultrasonic power conditions. The ultrasonic leaching process was significantly influenced by temperature, and the enhancement of the leaching reaction rate constant by ultrasound was mainly reflected in the increase of the pre-exponential factor A. Ultrasound treatment improved the efficiency of impurity mineral removal by destroying the inert layer formed on the graphite surface, promoting particle fragmentation, and generating oxidation radicals. The poor reactivity of hydrochloric acid with quartz and some silicate minerals is a bottleneck limiting the further improvement of impurity removal efficiency in ultrasound-assisted aphanitic graphite. Finally, the study suggests that introducing fluoride salts may be a promising method for deep impurity removal in the ultrasound-assisted hydrochloric acid leaching process of aphanitic graphite.

Ultrasound improves the physicochemical and foam properties of whey protein microgel.

Whey protein microgel (WPM) is an emerging multifunctional protein particle and methods to improve its functional properties are continuously being explored. We developed a method to prepare WPM by heat-induced self-assembly under different ultrasound power (160, 320, 480, and 640 W/cm2) and characterized the particle size, surface hydrophobicity, disulfide bond, viscosity, and foam properties of WPM. Ultrasound increased the particle size of WPM-160 W to 31 μm. However, the increase in ultrasound power gradually reduced the average particle size of samples. The intrinsic fluorescence spectrum showed that ultrasound unfolded the structure of whey protein and exposed more hydrophobic groups, which increased the surface hydrophobicity of WPM. In addition, infrared spectroscopy suggested ultrasound decreased the α-helix content of WPM, implying an increase in the flexibility of protein molecules. The disulfide bond of WPM was broken by ultrasound, and the content of the-SH group increased correspondingly. The rheology indicated that the apparent viscosity decreased with the increase of ultrasonic power. Compared with the control, the ultrasonicated WPM displayed higher foam ability. Ultrasound improved the foam stability of WPM-160 W but destroyed the foam stability of other samples. These results suggest that proper ultrasound treatment can improve the physicochemical and foam properties of WPM.

Changes in the structure of polysaccharides under different extraction methods

Changes in the structure of polysaccharides under different extraction methods

Ultrasound‐assisted hot air drying characteristics of Phyllanthus emblica

AbstractThe ultrasound‐assisted hot air drying characteristics of Phyllanthus emblica was investigated in this paper. The effects of hot air temperature (60°C, 65°C, 70°C, and 75°C), ultrasonic pretreatment time (2, 4, 6, and 8 min), and ultrasonic power (200, 250, 300, and 350 W) on the drying rate, energy consumption, color change, and rehydration rate were evaluated and compared. It was found that the drying rate of Phyllanthus emblica increased with the hot air temperature. The drying time of Phyllanthus emblica with ultrasonic pretreatment was reduced by 10.0%, 25.0%, 21.4%, and 9.0% at 60°C, 65°C, 70°C, and 75°C, respectively. However, the hot air drying was not proportionally promoted by the increase of ultrasonic power or the extension of pretreatment time. Only an appropriate ultrasonic power or pretreatment time can not only improve the drying rate and rehydration rate, but also reduce the energy consumption and the total color change of the dried samples. A new drying model that considered the influences of hot air temperature, pretreatment time, and ultrasonic power was developed to fit the drying process. The results showed that the new model can accurately predict the hot air drying process of Phyllanthus emblica with and without ultrasonic pretreatment.Practical applicationsPhyllanthus emblica contains a variety of nutrients and has various biological activities. However, the harvest period and shelf life of Phyllanthus emblica is very short, and the fruit is prone to mildrew and browning after picking, which in turn leads to the loss of its nutritional and economical value. Thus, for the long‐term preservation of Phyllanthus emblica, drying techniques are needed. In the food industry, hot air drying is widely used due to its low cost and easy operation; however, it also has some disadvantages such as long drying time, the oxygen‐rich drying environment. These shortcomings lead to a low quality of dried materials. Ultrasonic pretreatment before hot air drying can improve drying efficiency without adversely affecting the drying quality of the material. In recent years, ultrasonic pretreatment before food drying has become a research hotspot.

Walnut Protein Isolate-κ-Carrageenan Composite Gels Improved with Synergetic Ultrasound-Transglutaminase: Gelation Properties and Structure

Walnut protein is a kind of natural, high-quality plant protein resource. However, its high content of gluten, strong hydrophobicity and poor gelation ability have greatly limited its development and utilization in gel products. It was found in this experiment that ultrasonic power combined with transglutaminase (TGase) had a significant effect on the gel properties of the walnut protein isolate (WNPI)-κ-carrageenan (KC) complex. The results showed that the gel strength of the WNPI-KC complex first increased and then decreased with the increase in ultrasonic power (0-400 W). WNPI-KC composite gel had the best texture properties, rheological properties, water-holding capacity (99.41 ± 0.76%), swelling ratio (2.31 ± 0.29%) and thermal stability (83.22 °C) following 200 W ultrasonic pretreatment. At this time, the gel network was more uniform and much denser, and the water molecules were more tightly bound. Further, 200 W ultrasonic pretreatment could promote the transformation of α-helices to β-folds in protein molecules, improve the fluorescence intensity, increase the content of free sulfhydryl groups and enhance the intermolecular forces. The experimental results could provide technical support for the development of walnut protein gel food.

Effect of Ultrasonic Pretreatment on Radio Frequency Vacuum Drying Characteristics and Quality of Codonopsis pilosula Slices

In this paper, the effects of ultrasonic pretreatment on the drying kinetics, bioactive components (polysaccharides, total phenols, total flavonoids and antioxidant), qualitative characteristics (color index, lobetyolin and syringin) and microstructure of Codonopsis pilosula during radio frequency vacuum drying (RFVD) were studied. The average drying rate curve showed that the whole drying process could be divided into three stages: accelerating period, constant drying rate period and falling drying rate period. Deff values ranged from 6.61425 to 9.46745 × 10−8. Analysis of the drying rate constants revealed that different conditions of pretreatment were effective in increasing the drying rate. Ultrasonic pretreatment has a positive effect on the retention of polysaccharide content; low frequency favors retention of total phenols, flavonoids and syringin; and with the increase in ultrasonic time and ultrasonic power, the antioxidant capacity was higher than that without ultrasonic treatment. Ultrasonic pretreatment significantly improved color and microstructure. In summary, the pretreatment condition of ultrasonic frequency 20 kHz and power 60 W for 30 min is suitable, which provides a certain reference for the application of ultrasonic pretreatment technology in RFVD of Codonopsis pilosula slices.