Ultrasonic Treatment Research Articles

Investigation on the loading rate dependence of electromechanical properties of graphene-cement composites under compressive loading

In this paper, the dependence of the electromechanical properties of graphene-cement composites on the loading rate is studied by combining experiment and theory. The graphene-cement composites are prepared using a wet dispersion technique combined with surfactant assist and ultrasonication treatment. Both monotonic and cyclic compressive experiments with different loading rates are conducted on the graphene-cement composites with different graphene contents to measure their mechanical, electrical and piezoresistive properties. The optimum dosage of graphene in cement matrix is about 0.05 wt%, which can increase the compressive strength by 35.7 % and 34.1 %, and decrease the electrical resistivity to 1.43 and 3.48 × 105 Ω•cm, respectively, after 14 and 28 d curing periods. The uniform dispersion of graphene with less layers endows the graphene-cement composites with very low percolation threshold of electrical conductivity (0.007 wt%), stable piezoresistive response, and good reproducibility. Furthermore, the mechanism of the loading rate on the strain sensing behavior is discussed, and a rate dependent theoretical model of resistance change is proposed to quantitatively predict the electromechanical responses. This study provides guidelines for the fabrication of highly strain-sensitive graphene-cement composites and the rate-dependent evaluation of their electromechanical properties in the fields of intelligent construction.

Bioinspired surface silicification of cellulose-mediated PVDF membranes for significantly enhancing superhydrophilicity and anti-oil adhesion toward ultrafast oil/water emulsion separation

Cellulose is a widely used hydrophilic material due to its rich hydrophilic hydroxyl groups. However, the presence of its lipophilic segment will affect the antifouling performance. Finding strategies to improve this problem has attracted considerable attention. In this work, a layer of silica was applied to a cellulose-deposited polyvinylidene fluoride membrane through a straightforward in-situ bionic silicification process of tetraethyl orthosilicate. The contact angle and oil droplet contact test proved that the high-hydrophilicity and underwater superoleophobicity of the silicified membranes were significantly enhanced. The surface structure and composition were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results of show that this improvement was mainly attributed to the presence of silicon hydroxyl groups, buried cellulose chains, and micro-nanostructures composed of cellulose and silica. The stable silica coating also provided protection for the polymeric membrane against degradation after water washing for 24 h, ultrasonic treatment (40 KHZ) for 10 min or exposure to different pH levels (pH=1, 4, 9 and 12) and saturated sodium chloride solution for 24 h. Furthermore, the silicified membrane showed outstanding oil adhesion resistance and permeation flux, enabling effective purification of different oil-in-water emulsions that were stabilized by emulsifiers. Notably, the membrane achieved a high oil removal rate (> 99.4 %) of various emulsions (toluene-in-water, cyclohexane-in-water, tetrachloroethane-in-water, soybean oil-in-water, toluene-in-salt solution, toluene-in-acid solution and toluene-in-alkaline solution emulsions). In particular, for toluene-in-water emulsions (oil droplets in the emulsion ranged from 58.77 nm to 615.1 nm), a significantly enhanced permeation flux (4777 L·m−2·h−1·bar−1) was obtained at 0.8 bar pressure. Even after multiple cycles of separation, the flux was higher than that of the unsilicified membrane. Overall, this approach is mild, simple, efficient, and easily scalable, making it an ideal method for producing superhydrophilic coatings with substantial application potential.

Investigation of the flotation behavior and interaction characteristics of micro-fine quartz and magnesite in a dodecylamine system under ultrasonic treatment

Ultrasonic treatment, as an important surface modification method, profoundly affects the flotation behavior of minerals. This study examined the impact of ultrasonic treatment on the surface properties and flotation performance of magnesite and quartz in a dodecylamine (DDA) flotation system. Atomic force microscope detection results revealed that the surface roughness and roughness size of both magnesite and quartz increased after ultrasonic treatment. Flotation tests indicated that the recovery rates of magnesite and quartz were lower after ultrasonic treatment. At pH of 10 and DDA of 75 mg/L, ultrasonic treatment led to a 0.66%, 3.46%, and 0.33% decrease in the flotation recovery rates for three different magnesite particle sizes. Following ultrasonic processing, the flotation recovery rates for three different quartz particle sizes decreased by 8.48%, 30.76%, and 43.69%, in that order. X-ray photoelectron spectroscopy detection results showed an increased presence of characteristic Mg and Si sites on the surfaces of magnesite and quartz following ultrasonic treatment. DDA acted on the surfaces of the two minerals through electrostatic adsorption and hydrogen bonding adsorption and repelled the flotation of minerals owing to the same charge as characteristic sites, thereby reducing flotation recovery. Adsorption capacity tests and contact angle measurements demonstrated a decrease in DDA adsorption and contact angle on the surfaces of magnesite and quartz after ultrasonic treatment, explaining the reduced floatability. Extended Derjaguin–Landau–Verwey–Overbeek theoretical calculations indicated that before ultrasonic treatment, there was a repulsive energy between magnesite and fine-grained quartz particles. After ultrasonic treatment, the interaction energy between magnesite and fine quartz particles is mutual attraction.

Development and performance investigation of a novel ultrasonic-assisted non-contact membrane distillation process to prevent membrane fouling

A novel non-contact membrane distillation (NCMD) process is proposed that prevents membrane fouling by preventing direct physical contact between the feed and membrane. The feed channel of the NCMD module is equipped with an ultrasonic transducer that provides high-frequency mechanical oscillations to the feed film, which forms a fine mist of droplets and water column. Experiments are conducted to determine the feed height required to maximize the evaporation rate, and the effects of feed temperature, flow rate, and ultrasonic power on the permeation flux. The results reveal that the highest permeation flux occurs at a feed height of 20 mm, and an increase in the feed height and flow rate decreases the ultrasonic cavitation effect, while a higher feed temperature and ultrasonic power significantly increases the permeation flux. At the feed temperature of 60 °C, feed flow rate of 1.0 L/min, and ultrasonic current of 600 mA, the permeation flux is 6.3 kg/m2h, which is 8.4 times greater than that of the NCMD process without ultrasonic treatment. The corresponding specific energy consumptions with and without the ultrasonication are 647 and 6028 kWh/m3, respectively. Moreover, the long-term experimental results indicate that the proposed system is unaffected by high feed concentrations.

Effect and mechanisms of type, content, and dispersion method of flash graphene on the rheological behaviors of fresh cement pastes

Flash Joule heating provides a facile, low-carbon, and cost-effective method for upscale graphene production, benefiting the application of graphene in modifying cement-based materials. Understanding the effect and mechanisms of flash graphene (FG) type, content, and dispersion method on the rheological behaviors of cement-based materials is essential for designing and controlling cement-based materials in different application scenarios. Therefore, this study explored the rheological behaviors of cement pastes with 2 different types of flash graphene at 4 different content levels (namely 0.1 wt%, 0.2 wt%, 0.3 wt%, and 0.4 wt% of cement mass) using 3 different dispersion methods (namely water reducer dispersion with ultrasonic treatment, dry mixing with water reducer, and mechanical dispersion with water reducer). The results indicated that the addition of FG generally increases the yield stress and plastic viscosity of fresh cement pastes. The water reducer dispersion with ultrasonic treatment and nano-boron doping shows a good effect in dispersing FG. The influence mechanisms of FG on rheological behaviors of fresh cement pastes are a competition between exert replacement, agglomeration, lubrication, and adsorption effects.

Yield Difference between Different Cultivation Techniques under Ultrasonic Treatment Driven by Radiation Use Efficiency.

Ultrasonic treatment and optimal cultivation techniques are both conducive to the high yield of super rice in South China. Many previous studies have shown that the increase in intercepted photosynthetically active radiation (IPAR) and radiation use efficiency (RUE) is an important reason for high rice yield. Field experiments were conducted over two years to evaluate the effects of IPAR and RUE on the yield under different treatments (CK: conventional cultivation technique without ultrasonic treatment; T1: conventional cultivation technique with ultrasonic treatment; T2: super rice-specific cultivation technique without ultrasonic treatment and T3: super rice-specific cultivation technique with ultrasonic treatment), with two representative rice varieties, Wufengyou-615 (WFY) and Jingnongsimiao (JNSM) during the late seasons of rice cultivation in South China. The super rice-specific cultivation technique and the ultrasonic treatment could significantly increase the yield, which was significantly (p < 0.01) and positively correlated with panicle number, grain-filling rate, and aboveground total dry weight. The higher grain yield depended more highly on higher RUE in the mid-tillering stage and maturity stage. The results of multiple-regression models also showed that the contributions of IPAR and RUE to yield were significant (p < 0.01). Conclusively, IPAR and RUE contributed a lot to yield progress of super rice in both super rice-specific cultivation techniques with fewer times of topdressing and ultrasonic treatment in South China. It is worth further studying how to reasonably improve the RUE of high-RUE varieties through other means.

Synchronous ultrasonic impact assisted laser cladding CoCrFeNiMo high entropy alloy coating: Microstructure and wear property

Synchronous ultrasonic impact treatment (UIT) is proposed to enhance the microstructure and wear property of laser cladded CoCrFeNiMo high entropy alloy (HEA) coatings on 45 steel. FCC phase with minor tetragonal σ phase and rhombic η phase are form in both conventional and UIT treated coatings. Due to the plastic deformation and high-frequency vibrations induced by UIT, dislocation interactions lead to recrystallization process at the top region coating. With the application of UIT, the columnar grains at top region of the coating transform into fine equiaxed grains owing to recrystallization. The fragmentation of dendrites occurs in the middle region of the coating, resulting in reduced dendrite arm spacing. The results also show the defects, such as pores and microcracks, are effectively eliminated within the coating. Microhardness and wear property of the coating are remarkably enhanced owing to fine-grain strengthening and second-phase strengthening. The average friction coefficient decreases from 0.56 for the conventional sample to 0.49 for the UIT treated sample, and the wear mechanism evolved from a combination of abrasive, fatigue, and oxidized wear to predominantly fatigue and oxidized wear. It indicates that synchronous ultrasonic impact assisted laser cladding is a potential method to fabricate high-performance HEA coatings.

The Effect of Ultrasound Treatment on the Structural and Functional Properties of Tenebrio molitor Myofibrillar Protein.

The objective of this study was to explore the impacts of various ultrasonic powers (0, 300, 500, 700, and 900 W) on the structure and functional attributes of the myofibrillar protein (MP) of Tenebrio molitor. As the ultrasonic intensity escalated, the extraction efficiency and yield of the MP rose, while the particle size and turbidity decreased correspondingly. The reduction in sulfhydryl group content and the increase in carbonyl group content both suggested that ultrasonic treatment promoted the oxidation of the MP to a certain extent, which was conducive to the formation of a denser and more stable gel network structure. This was also affirmed by SEM images. Additionally, the findings of intrinsic fluorescence and FTIR indicated that high-intensity ultrasound significantly altered the secondary structure of the protein. The unfolding of the MP exposed more amino acid residues, the α-helix decreased, and the β-helix improved, thereby resulting in a looser and more flexible conformation. Along with the structural alteration, the surface hydrophobicity and emulsification properties were also significantly enhanced. Besides that, SDS-PAGE demonstrated that the MP of T. molitor was primarily composed of myosin heavy chain (MHC), actin, myosin light chain (MLC), paramyosin, and tropomyosin. The aforementioned results confirmed that ultrasonic treatment could, to a certain extent, enhance the structure and function of mealworm MP, thereby providing a theoretical reference for the utilization of edible insect proteins in the future, deep-processing proteins produced by T. molitor, and the development of new technologies.

Modifying physicochemical properties, rheology, and creaming stability of milk fat globule and membrane through ultrasound treatment

The healthy benefits of milk fat globules and membrane (MFGs/MFGM) ingredients are increasingly recognized in the dairy industry. In this research, we examined the effects of ultrasonic treatment on the physicochemical and rheological properties, as well as the emulsions stability of MFGs/MFGM derived from bovine raw milk. Fresh milk was subjected to sonication at frequencies of 20 kHz and 40 kHz, either individually or simultaneously, for durations of 5 min or 15 min, using work/rest cycles of 5 s on and 3 s off. Bovine milk, without any treatment, served as the control. Regardless of the intensity difference, ultrasonic treatment for 5 min resulted in more pronounced changes in the regions of Amide Ⅱ (1600–1500 cm−1), Amide Ⅲ (1500–1200 cm−1), and fingerprint region (1200–1900 cm−1) compared to both the 15 min treatments and control MFGs/MFGM. Principal component analysis (PCA) conducted on the entire spectra, as well as in the regions of Amide Ⅰ, Amide Ⅱ, and the fingerprint spectra, clustered the 5 min treatment distinctly from the control and MFGs/MFGM ultrasonically treated for 15 min. MFGs/MFGM samples following 20 kHz and 40 kHz synchronous treatment for 15 min exhibited lower absorbance bands at 1727–1726 cm−1, whereas a higher content at 1740 cm−1 was observed compared to control MFGs/MFGM. Additionally, a more significant reduction in the intramolecular β-sheet content in 20 + 40 kHz/ 15 min treatment was observed. According to the sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) patterns, a diminished intensity of Periodic Acid Schiff 6/7 (PAS 6/7) bands was observed across all the MFGs/MFGM. Ultrasonic treatment retained more caseins while reducing the β –LG levels compared to the controls, enhancing the stability of MFGs/MFGM, except in MFGs/ MFGM subjected to 20 and 40 kHz simultaneously treated for 15 min. The irregular sphericity of fat globules was noted particularly in MFGs/MFGM treated at 20 kHz independently or in combination with 40 kHz for 15 min. According to the confocal laser scanning microscopy (CLSM), ultrasonic treatment facilitated the binding of caseins or whey proteins to the MFGs surface and induced flocculation of membrane proteins. Hierarchical cluster analysis (HCA) heat map further underscored the impact of ultrasonic treatments on the structural and compositional changes, as well as rheology and emulsions stability, of MFGs/MFGM.

Effect of Fe Element and Ultrasonic Vibration on the Microstructure and Mechanical Properties of the Cu-TiB2 Composites

Cu-(Fe-Ti)-TiB2 composites were prepared by in situ reaction and vacuum casting with and without ultrasonic vibration. The evolution of the microstructure and mechanical properties of the composite with the variation in Fe element was analyzed. The import of Fe elements could purify the matrix after in situ reaction and the formation of a nanoprecipitated phase, thus improving the strength of Cu-Fe-Ti-TiB2 composites. Meanwhile, compared with the traditional casting process, the Cu-Fe-Ti-TiB2 composites with ultrasonic vibration treatment exhibit uniform TiB2 particle distribution and better properties. The tensile strength and uniform elongation of the composite with a Fe content of 0.7 wt.% reached 511 MPa and 6.02%, increasing by 14.3% and 318% compared to the unalloyed composite, respectively. The tensile strength and uniform elongation of Cu-0.7Fe-Ti-TiB2 composite with ultrasonic vibration treatment increased to 533 MPa and 7.16%, respectively. The TiB2 microscale particles and Fe2Ti nanoscale precipitates with uniform distribution effectively impeded dislocation movement and recrystallization, which improved the tensile strength and stability at elevated temperatures.

Quantitative prediction of minced chicken gel strength under ultrasonic treatment by NIR spectroscopy coupled with nonlinear chemometric tools evaluated using APaRPs

Achieving the ideal gel strength is essential for desired texture in minced chicken products. This study developed a rapid, non-destructive method using near-infrared (NIR) spectroscopy and nonlinear chemometric modeling to predict minced chicken gel strength under ultrasonic treatment. Initially, minced chicken samples were subjected to high-intensity ultrasound for 0–50 min. This was followed by heat-induced gelation. Gel strength was conventionally measured, and NIR spectra were collected. Nonlinearity between gel strength and spectral data was confirmed using augmented partial residual plots (APaRPs). Subsequently, nonlinear support vector machine (SVM) and extreme learning machine (ELM) models were developed using full NIR spectra and variable selection methods, including uninformative variable elimination (UVE), competitive adaptive reweighting (CARS), and genetic algorithms (GA). GA proved most effective for enhancing model performance, achieving the highest predicted coefficient of determination (Rp2 = 0.8772) with the ELM model, demonstrating potential for rapid, non-destructive prediction of minced chicken gel strength quality.

Predicting fatigue life and crack growth rate of TC4 titanium alloy based on PINN before and after ultrasonic impact treatment

This study conducted fatigue crack growth rate (FCGR) experiments on TC4 titanium alloy specimens under different stress ratios (R=0.06, 0.1, 0.5) before and after ultrasonic impact treatment (UIT) conditions. Based on this, a Physics-Informed Neural Network (PINN) model was employed to predict the FCGR of TC4 titanium alloy. As a control group, the traditional Walker FCGR formula was fitted using experimental data. The results indicate that the stress ratio R does not significantly affect the FCGR of TC4 titanium alloy. Under the same range of stress intensity factor (ΔK), the FCGR (da/dN) decreases with increasing R. The FCGR prediction established by the PINN model can well reflect the nonlinear characteristics of the crack growth process rate. The coefficient of determination R2 for fitting the experimental data reached above 0.9900, generally higher than the 0.9545 of the Walker formula. Although the degree of dispersion increased after UIT, the PINN model demonstrated stable prediction accuracy compared to the Walker formula. In addition, when calculating the fatigue crack growth life using the cycle-by-cycle method, the PINN model also exhibits stable prediction accuracy compared to the Walker formula, and this advantage becomes more apparent with increased data dispersion.

Open-slit circular tube piezoelectric ultrasonic transducer with longitudinal bending mode conversion

Abstract A new type of longitudinal bending mode conversion ultrasonic transducer is designed by compounding a sandwich type piezoelectric ultrasonic transducer, amplitude transformer and Open-slit circular tube radiator. The radiator is made of a circular tube cut into a number of curved plates along the axis, and the two ends are thin disc end caps. The electromechanical equivalent circuit model of the transducer is established and its frequency equation is derived. The vibration performance of the transducer is studied by using the equivalent circuit method and the finite element method. The results show that: the new structure design and the longitudinal vibration sandwich piezoelectric ultrasonic transducer can effectively stimulate the two ends of the slit circular tube radiator to produce first-order bending vibration, and the curved plate to produce high-order bending vibration, so as to achieve high efficiency, uniform and all-round ultrasonic radiation. The research results are expected to be applied in ultrasonic treatment of large volume liquid such as ultrasonic wastewater treatment, ultrasonic algae removal and ultrasonic chemical reaction.

Aerobic oxidative desulfurization of model mixtures under ultrasonic treatment

Aerobic oxidative desulfurization of model mixtures under ultrasonic treatment

Effect of vacuum combined with ultrasound on color protection of pomegranate juice

AbstractPomegranate juice is prone to color fission during processing and storage due to the instability of anthocyanins, resulting in significant economic losses. This study aims to inhibit the browning of pomegranate juice during processing using the combined technology of vacuum and ultrasound for maintaining its color as much as possible. Pomegranate juice was treated with vacuum (0.5 MPa) and ultrasound (300, 600, 900, 1200, and 1500 W; 15, 20, 25, 30, and 35 min), respectively, to investigate the effects on the color, antioxidant capacity, anthocyanin/polyphenol content, and polyphenol oxidase activity of pomegranate juice. The results showed that the combined treatment of vacuum and ultrasound had a better effect on improving the total anthocyanin content of pomegranate juice than vacuum or ultrasound treatment alone. Vacuum combined with ultrasound can reduce the browning during pomegranate juice processing, increasing browning inhibition rates by 46.01% and 46.19%; reduce the activity of PPO enzyme and increase the inhibition rate of PPO enzyme activity by 35.58%; maintain a high total phenolic content, increasing the total phenolic content of pomegranate juice by 29.27% and 33.79%, respectively; and improve the ABTS scavenging rates by 2.89% and 1.92%, and increase DPPH scavenging rates by 1.35% and 3.01%. Moreover, vacuum ultrasound treatment had no significant effect on the odor of pomegranate juice. Vacuum combined with ultrasonic treatment is beneficial for protecting the color of pomegranate juice and improving its antioxidant performance during the processing. Therefore, combined technology of vacuum and ultrasound would be a promising method for future food processing.Practical applicationsThis study provides a simple and novel method for protecting the color of pomegranate juice during processing. The combination of vacuum and ultrasound has a certain protective effect on the color of pomegranate juice during processing, and also provides new ideas for color protection research.

Characterization of ultrasonic-assisted antifungal film loaded with fermented walnut meal on Rosa roxburghii Tratt during near-freezing temperature storage.

Fermented walnut meal (FW) has antifungal activity against Penicillium victoriae, a fungus responsible for Rosa roxbughii Tratt spoilage. This study characterized and applied ultrasonic-assisted antifungal film loaded with FW to preserve R. roxbughii Tratt during near-freezing temperature (NFT). Results showed that O2 and CO2 transmission rates decreased by 80.02% and 29.05%, respectively, and antimicrobial properties were improved with ultrasound at 560W for 5min and 1% FW. Fourier transform infrared spectroscopy and X-ray diffraction results revealed ultrasound improved hydrogen bonds and inductive effect via ─NH, ─OH, and C═O bonds. The addition of FW led to the formation of CMCS-GL-FW polymer via C═O bond. Thermogravimetric analysis and transmission electron microscope results demonstrated thermal degradation process was decomposed by ultrasound, and the internal structure of P. victoriae was accelerated by the addition of FW. Compared to the U-CMCS/GL group, the vitamin C content, peroxidase, and catalase activities of U-CMCS/GL/FW were enhanced by 4.24%, 8.52%, and 14.3% during NFT (-0.8 to -0.4°C), respectively. Particularly, the fungal count of the U-CMCS/GL/FW group did not exceed 105 CFU g-1 at the end of storage, and the relative abundance of P. victoriae decreased to 0.007%. Our findings provide an effective route for agricultural waste as natural antifungal compounds in the active packaging industry. PRACTICAL APPLICATION: In this study, the barrier and antimicrobial properties of film were successfully improved by ultrasonic treatment and loaded fermented walnut meal. The ultrasonic-assisted antifungal film loaded with fermented walnut meal effectively delayed the degradation of nutrients and reduced microbial invasion of Rosa roxburghii Tratt. These results provide a theoretical basis for the application of agricultural waste in the food packaging industry.

Research on influence factors of small punch test to evaluate the mechanical properties of gradient nanostructured material

Abstract The influence factors of small punch test (SPT) were investigated to evaluate the mechanical properties of gradient nanostructured (GNS) materials. The gradient nanostructure was prepared on the top layer of S30408 austenitic stainless steel by ultrasonic impact treatment (UIT). The mechanical properties of the GNS material were obtained using SPT and correlated with those obtained by standard tensile tests. The results indicate that, when the specimen thickness is 0.5 mm, the sphere diameter is 2.4 mm, the punch velocity is 0.5 mm min−1, and the gradient nano-grained layer is placed face-on in the mold, the GNS material exhibits better plastic deformability. The SPT specimen achieves better bearing capacity, and the mechanical properties of the GNS material obtained by SPT are more accurate. The yield strength and tensile strength of the GNS material were also evaluated by analytical and empirical methods in SPT. The error is approximately 10% compared with the standard tensile test results, which is within the allowable range.

Ultrasonic treatment of aerosol jet printed traces

Ultrasonic treatment of aerosol jet printed traces

Effect of Ultrasonic Treatment on Residual Stress and Mechanical Properties of AISI 304 Stainless Steel Welding

Abstract AISI 304 stainless steel has low thermal conductivity and a high linear expansion coefficient; conventional welding with this material produces coarse grains and poor joint tensile properties. To address the problems inherent in conventional 304 stainless steel welding, an ultrasonic transducer was brought into contact with a base metal and treated with ultrasonic vibration during welding. The residual stress distribution, microstructure, and mechanical properties of the welded joint were then analyzed. The results showed that under the combined action of thermodynamics and the dynamics caused by ultrasonic treatment, the flow performance of the molten pool was enhanced, heat was transferred from the high-temperature region to the low-temperature region, and the metal elements were constantly diffused during the crystallization of the molten pool. Thus, the transformation rate of columnar crystals to equiaxed crystals was accelerated, the proportion of equiaxed crystals increased, and the grains became refined. Compared with conventional welding, the microstructure of the 304 stainless steel welded joints was better after the introduction of ultrasonic vibration, and its tensile residual stress was significantly lower. The improvement in the microstructure of the weld improved its mechanical properties, and the hardness of the weld zone increased significantly, which was close to that of the base metal. After the ultrasonic treatment, the increase in the equiaxed crystals and the refinement in the grains effectively improved the quality of the welded joints so that the tensile strength of the welded joints was higher than that of conventional welded joints. Under the condition of the same ultrasonic vibration frequency and power, the tensile strength of welded joints with 2-mm steel plate exhibited a notable increase, which was 13 %.

Effect of Ultrasound and Osmotic Dehydration as Pretreatments on the Infrared Drying of Banana Slices.

There is a growing interest in foods with added nutritional value and extended shelf life. This study investigates the use of infrared technology in the drying of banana slices to improve their stability and quality by minimizing moisture content and water activity. The drying experiments were carried out at a temperature of 70 °C, using the following pretreatments: ultrasound-assisted (UA) immersion in water for 20 and 30 min, osmotic dehydration (OD) and ultrasound-assisted osmotic dehydration (UAOD) for 20, 30 and 40 min. The osmotic process consisted of immersing the samples in the isomaltulose solution (40.0 g/100 g deionized water) for 60 min. All mathematical models used to describe the drying process showed a good fit with high R2 values (>0.98) and low value of the relative mean error E (%), the sum of squared error and the root mean squared error. The Fick's diffusion coefficient (D eff) was higher for the samples previously treated with ultrasound for 20 and 30 min. The ultrasonic treatment resulted in shorter drying times with a reduction in average time of up to 29 %. OD was not efficient in reducing drying time, resulting in samples with lower drying rates. The samples treated with ultrasound showed less isotropic shrinkage and better color parameters. The osmotic process resulted in samples with greater rehydration capacity. The impregnation of a carbohydrate with low glycemic index in banana slices was achieved by the osmotic pretreatment, resulting in a new food product with attractive nutritional properties. This advancement represents not only a significant step in the development of functional foods, but also a major innovation in terms of processing technologies. The OD was combined with infrared drying, a method known for its superior drying rates, high heat transfer coefficient and energy efficiency. The synergy of these promising techniques not only shortens the processing times but also ensures more uniform dehydration of food products, resulting in end products that not only maintain but also optimize their nutritional value. These advances offer innovative solutions to improve food quality and also minimize environmental impact through low-energy technologies such as ultrasound and infrared treatment.