High Power Ultrasound Treatment Research Articles

High-Power Ultrasound (HPU) and Pulsed Electric Field (PEF) in the Hurdle Concept for the Preservation of Antioxidant Bioactive Compounds in Strawberry Juice-A Chemometric Evaluation-Part II.

In this work, the influence of high-power ultrasound (HPU) followed by pulsed electric field (PEF) in the hurdle concept (HPU + PEF) on the content of biologically active compounds (BACs) and antioxidant activity in strawberry juices stored at 4 °C/7 days was investigated. The HPU was performed with an amplitude of 25% and pulse of 50% during 2.5, 5.0 and 7.5 min, while the PEF was performed with an electric field strength of 30 kV cm-1 and frequency of 100 Hz during 1.5, 3 and 4.5 min. The results obtained indicate that the synergy of the mechanisms of action for technologies in the hurdle concept plays a critical role in the stability of BACs and antioxidant activity. Juices treated with HPU + PEF hurdle technology and kept at 4 °C for 7 days showed a statistically significant decrease in all BACs, antioxidant capacity and pH. Shorter HPU + PEF treatment times favored the preservation of BACs in juices. Regarding total phenolic compounds, flavonols, condensed tannins and antioxidant capacity, optimization of hurdle parameters showed that a shorter HPU treatment time of 2.5 min provided the best yield of these compounds. In summary, by optimizing and adjusting the parameters of the HPU/PEF technology, it is possible to produce functional strawberry juice.

Escherichia coli K-12 Transcriptomics for Assessing the Mechanism of Action of High-Power Ultrasound.

An investigation into the mechanisms of action on bacteria involving exposure to stress factors was conducted in this study. The effects of ultrasound on Escherichia coli K-12 MG1655 and its isogenic mutant, ∆gadW, under high power ultrasound treatments (26 kHz) were screened and identified by analysing their transcriptome differences between primary and secondary sequential treatments using RNA-Seq. This also helped to assess any developed protection for cells between different generations. According to our results, 1825 genes of all tested conditions were expressed, playing different roles in the cell. The expression of these genes is associated with DNA damage, cell membrane integrity, and also metabolic effects. The studied strains also showed different differential expressed genes (DEGs), with some genes being directly responsible for defence mechanisms, while others play an indirect effect due to cell damage. A gradual decrease in the expression of the genes, as we moved from just one cycle of ultrasound treatment to sequential treatment, was evident from a heat map analysis of the results. Overall, E. coli K-12 builds a self-protection mechanism by increasing the expression of genes involved in the respiration for increased growth, and production of flagellum and pili. It can be concluded that high power ultrasound is a technology that triggers several different defence mechanisms which directly link to E. coli.

Влияние сонохимического воздействия на свойства пшеничного крахмала

The food industry uses sonochemical treatment as part of emulsification, homogenization, and dispersion, as well as to modify viscosity and structure. Starch is one of the most common food ingredients, both as a raw material or a property-modifying additive. The research objective was to study the effect of sonochemical action on the structural and mechanical properties of wheat starch suspensions.
 The study involved suspension samples with 10% wheat starch. The suspension samples were treated with ultrasound using an ultrasonic device Volna-M model UZTA-1/22-OM or in an ultrasonic bath (22 kHz; 100, 150, 300, and 400 W). The treatment time was 15 and 30 min. The rheological, physical, and textural properties were recorded according to conventional methods before and after the treatment.
 The ultrasonic treatment caused mechanical damage to the starch, making it more accessible to moisture when heated. As a result, the structural, mechanical, and rheological properties of starch suspensions changed. All the studied suspensions had a non-Newtonian character. The ultrasonic treatment increased their consistency coefficient from 28.12 to 152.75 µPa·s. The gelatinization temperature of all experimental starch suspensions dropped from 63.4 to 61.0°C. The short high-power ultrasound treatment reduced the strength of gels to 1.25 N compared to that of native starch gel (4.28 N).
 In this research, the ultrasound treatment of wheat starch suspensions modified the structural, mechanical, and rheological profile of starch and proved able to replace some conventional starch modification procedures, i.e., chemical, physical, or enzymatic. The new approach can provide modified starches of a preset quality while reducing energy costs and processing time.

Effects of ultrasound treatment on muscle structure, volatile compounds, and small molecule metabolites of salted Culter alburnus fish

This study investigated the effects of ultrasound treatment on the quality of salted Culter alburnus fish. The results showed that with the increasing ultrasound power, the structural degradation of muscle fibers was intensified, and the conformation of myofibrillar protein was significantly changed. The high-power ultrasound treatment group (300 W) had relatively higher thiobarbiturate reactive substance content (0.37 mg malondialdehyde eq/kg) and peroxidation value (0.63 mmol/kg). A total of 66 volatile compounds were identified with obvious differences among groups. The 200 W ultrasound group exhibited fewer fishy substances (Hexanal, 1-Pentene-3-ol, and 1-Octane-3-ol). Compared with control group, ultrasound groups (200, 300 W) contained more umami taste-related amino peptides such as γ-Glu-Met, γ-Glu-Ala, and Asn-pro. In the ultrasound treatment group, L-isoleucine and L-methionine, which may be used as flavor precursors, were significantly down-regulated, while carbohydrates and its metabolites were up-regulated. Amino acid, carbohydrate, and FA (fatty acyls) metabolism products in salted fish were enriched by ultrasound treatment, and those products might ultimately be related to the taste and flavor of salted fish.

Optimization of A Procedure to Improve the Extraction Rate of Biologically Active Compounds in Red Grape Must Using High-Power Ultrasound

The primary focus in the production of quality red wine is the extraction of grape components, which can be achieved in a variety of ways. This work investigates the extraction yield of biologically active compounds from crushed Merlot grapes, as a result of ultrasound treatment applied before maceration, and optimizes the process parameters of a laboratory scale using response surface methodology (RSM) within a central composite design (CCD) model. The two factors whose response was studied were amplitude (A) % and treatment time (t), while the dependent variables were the total phenolic compounds (TPC), monomeric anthocyanins (MA), and antioxidant activity expressed as ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity. The results showed that the application of high-power ultrasound treatment to crushed grapes for a few minutes increased both the extraction rate of bioactive compounds and the antioxidant activity by a maximum of 12 times for the TPC, 14 times for the MA, 3.6 times for the FRAP value, and 18.77% for the DPPH. The optimized solution had an amplitude of 90% and a treatment time of 4 min and 24 s. The validation experiments yielded errors between—8.70% and 3.14%, confirming the proposed model. Thus, the RSM model is recommended as a tool to optimize a procedure for enhancing both the extraction rate of the bioactive compounds from grapes and the antioxidant properties of grape must. Our results demonstrate the ultimate benefits of using ultrasonic treatment on crushed grapes at the beginning of the winemaking process, as a highly effective technique for improving the extraction of high-value bioactive chemicals, with significant application potential.

High power ultrasound treatment of crushed grapes: Beyond the extraction phenomena

The treatment of white and red crushed grapes by high power ultrasounds (US) represents an emerging technology in winemaking. In 2019, it was officially recognized by OIV through the resolution n°616-2019, and it was also approved by European Union in January 2022. The US effect on extraction mechanisms was widely studied, but more researches are needed to better understand the ultrasound effect on some specific classes of grape compounds. This research aimed to highlight at laboratory scale some specific effects of ultrasounds on some key compounds of white and red grapes. The samples were sonicated at different frequency (20-30 kHz), time (1-10 min), and power (30-90%) technological conditions used in maceration, to obtain valuable information on potential technological transferability. Valuable results were obtained regarding the release of thiols from their precursors, and the reactivity changes of unstable proteins of white wines. The experimental trails on red grape varieties allowed a maintenance of free anthocyanins and no degradative effects were highlighted. Significant and valuable effects were determined also on the tannin polymerization, with an astringency decrease. The sonication treatment of crushed grapes showed several chemical effects that contribute to decreasing the winemaking inputs and preserving the wine quality. The process conditions must be managed related to grape variety and ripeness for a precision winemaking.

A Chemometric Investigation on the Functional Potential in High Power Ultrasound (HPU) Processed Strawberry Juice Made from Fruits Harvested at two Stages of Ripeness.

This work aimed to investigate the influence of high-power ultrasound (HPU) technology on the stability of bioactive compounds in strawberry juices obtained from fruits with different stages of ripeness (75% vs. 100%) and stored at 4 °C for 7 days. HPU parameters were amplitude (25, 50, 75, and 100%), pulses (50 vs. 100%) and treatment time (5 vs. 10 min). Amplitude and pulse had a significant effect (p ≤ 0.05) on all bioactive compounds except flavonols and hydroxycinnamic acids. The treatment duration of 5 min vs. 10 min had a significant positive impact on the content of anthocyanins, flavonols and condensed tannins, while the opposite was observed for total phenols, whereas no statistically significant effect was observed for hydroxycinnamic acids. The temperature changes during HPU treatment correlated positively with almost all HPU treatment parameters (amplitude, pulse, energy, power, frequency). Optimal parameters of HPU were obtained for temperature changes, where the highest content of a particular group of bioactive compounds was obtained. Results showed that by combining fruits with a certain ripeness and optimal HPU treatment, it would be possible to produce juices with highly preserved bioactive compounds, while HPU technology has prospects for application in functional food products.

Modification in structural, physicochemical, functional, and in vitro digestive properties of kiwi starch by high-power ultrasound treatment

Kiwi starch (KS) is a fruit-derived starch; in order to improve its processing performance and increase its added value, it is necessary to modify KS to enhance the positive attributes and to enlarge its application. In this study, KS was modified by high-power ultrasound treatment (HUT) to reveal the relationship between the structure and function of KS with different treatment powers (0, 200, 400, and 600 W) and different treatment times (0, 10, 20, and 30 min). The results showed that HUT destroyed the granular morphology of KS, formed holes and cracks on the surface, and reduced the particle size and the short-range molecular order of KS. After different HUTs, the apparent amylose content (AAC), swelling power (SP), water solubility index (WSI), viscosity and setback value (SB) of KS were significantly increased, while the gelatinization temperature was significantly decreased. In addition, HUT significantly reduced the content of rapidly digestible starch (RDS) and slowly digestible starch (SDS), while it significantly enhanced the content of resistant starch (RS) (64.08–72.73%). In a word, HUT as a novel physical modification method for KS, enlarged its application, and fulfilled different demands of a starch-based product, which introduces another possibility for kiwi fruit further processing.

Combined pulsed electric field and high-power ultrasound treatments for microbial inactivation in oil-in-water emulsions

The impact of individual and combined pulsed electric field (PEF) and high power ultrasound (HPU) on the inactivation of different microorganisms in emulsions was investigated. The highest inactivation level using PEF was 2.6, 1.2 and 0.1 log-cycles for Escherichia coli, Aspergillus niger and Bacillus pumilus, respectively, achieved at the highest energy level and temperature (152.3–176.3 kJ/kg and 25 °C). HPU led to the highest reduction (5.4, 4.3 and 0.3 log-cycles for E. coli, A. niger and B. pumilus, respectively) after the longest treatment time studied (3 min). PEF (152.3–176.3 kJ/kg) followed by HPU (3 min) was found to be the most effective sequence, leading to synergistic effects (6.6 and 1.0 log-cycles for A. niger and B. pumilus, respectively), compared to the individual treatments. PEF-HPU is a promising hurdle technology with which to inactivate vegetative bacteria or fungal spores in emulsions. However, limited inactivation was achieved for bacterial spores.

A Review on High-Power Ultrasound-Assisted Extraction of Olive Oils: Effect on Oil Yield, Quality, Chemical Composition and Consumer Perception.

The objective of this review is to illustrate the state of the art in high-power ultrasound (HPU) application for olive oil extraction with the most recent studies about the effects of HPU treatment on oil yield, quality, chemical composition, as well as on the consumer’s perception. All the examined works reported an increase in oil yield and extractability index through the use of HPU, which was ascribed to reduced paste viscosity and cavitation-driven cell disruption. Olive oil legal quality was generally not affected; on the other hand, results regarding oil chemical composition were conflicting with some studies reporting an increase of phenols, tocopherols, and volatile compounds, while others underlined no significant effects to even slight reductions after HPU treatment. Regarding the acceptability of oils extracted through HPU processing, consumer perception is not negatively affected, as long as the marketer effectively delivers information about the positive effects of ultrasound on oil quality and sensory aspect. However, only a few consumers were willing to pay more, and hence the cost of the innovative extraction must be carefully evaluated. Since most of the studies confirm the substantial potential of HPU to reduce processing times, improve process sustainability and produce oils with desired nutritional and sensory quality, this review points out the need for industrial scale-up of such innovative technology.

Combination of supercritical CO2 and high-power ultrasound for the inactivation of fungal and bacterial spores in lipid emulsions

For the first time, this study addresses the intensification of supercritical carbon dioxide (SC-CO2) treatments using high-power ultrasound (HPU) for the inactivation of fungal (Aspergillus niger) and bacterial (Clostridium butyricum) spores in oil-in-water emulsions. The inactivation kinetics were analyzed at different pressures (100, 350 and 550 bar) and temperatures (50, 60, 70, 80, 85 °C), depending on the microorganism, and compared to the conventional thermal treatment. The inactivation kinetics were satisfactorily described using the Weibull model.Experimental results showed that SC-CO2 enhanced the inactivation level of both spores when compared to thermal treatments. Bacterial spores (C.butyricum) were found to be more resistant to SC-CO2 + HPU, than fungal (A.niger) ones, as also observed in the thermal and SC-CO2 treatments. The application of HPU intensified the SC-CO2 inactivation of C.butyricum spores, e.g. shortening the total inactivation time from 10 to 3 min at 85 °C. However, HPU did not affect the SC-CO2 inactivation of A.niger spores. The study into the effect of a combined SC-CO2 + HPU treatment has to be necessarily extended to other fungal and bacterial spores, and future studies should elucidate the impact of HPU application on the emulsion’s stability.

Ultrasonic-assisted supercritical CO2 inactivation of bacterial spores and effect on the physicochemical properties of oil-in-water emulsions

A combined supercritical carbon dioxide and high power ultrasound treatment (SC-CO2 + HPU) to inactivate spores while minimizing the physicochemical changes in emulsions was investigated. The inactivation kinetics were obtained for Bacillus subtilis, Bacillus pumilus and Geobacillus stearothermophilus spores and the effect of the treatment conditions on the quality of the emulsions was explored using response surface methodology. The treatment for 20 min at 95 °C and 350 bar was effective at inactivating B. subtilis and B. pumilus. Treated emulsions showed, in general, minimal changes in density and good stability, although the pH decreased and the droplet size increased. The treatment at 600 bar, 95 °C and 12.5 min permitted satisfactory B. subtilis and B. pumilus inactivation with minimal physicochemical changes in the emulsions. Therefore, the use of SC-CO2 + HPU could be a viable alternative for the preservation of emulsions using temperatures lower than those of thermal treatments.

Assessment of the olive oil extraction plant layout implementing a high-power ultrasound machine

The objective of this study is to assess the effects of installation and operation of a high-power ultrasound machine (HPU) for the treatment of olive paste by using ultrasound technology in order to evaluate the best way installation and the best definition of the operating conditions of the machine. The study was conducted installing in an industrial olive oil mill a continuous processing ultrasound machine, which used a frequency of 20 kHz able to work at 3200 kg h−1 as feed capacity. Checking of performance has been carried out by the assessment of the different operating and process conditions, assessing in particular the impact of the ultrasound treatment before and after the malaxation phase on performance indicators of the continuous olive oil plant (plant extractability, olive paste rheological characteristic) and on selected chemical properties of the olive oil extracted (quality parameters, antioxidant content, and volatile profiles). In the tested conditions, high-power ultrasound treatment did not produce significant effect on the legal parameters (free acidity, peroxide index and spectrophotometric indexes), while a significant increase in the content of phenolic compounds was generally observed; higher enhancements were more evident when the high-power ultrasound treatment was carried out before the malaxation phase.

Use of high-power ultrasound combined with supercritical fluids for microbial inactivation in dry-cured ham

The aim of this study was to analyze the application of supercritical carbon dioxide combined with high-power ultrasound (SC-CO2 + HPU) and the use of a saline solution (SS; 0.85% NaCl) on the microbial inactivation and the quality of dry-cured ham. The effect of temperature, pressure and treatment time was studied using RSM. Physicochemical analyses were carried out after the treatments and during refrigerated storage (30 days / 4 °C). The most significant inactivation of Escherichia coli (3.62 ± 0.20-log CFU/g) was obtained using the SC-CO2 + HPU + SS (25 MPa, 46-°C and 10-min), with temperature being the most important process variable. Fat content showed a significant (p < 0.05) reduction (46%) after the SC-CO2 + HPU treatment. The breakage of the muscle fibers, the disorganization in the myofibrils, as well as the enlargement of the interfibrillar spaces led to the ham softening (avg 26.5%). No significant (p > 0.05) changes in color, texture or pH were found during storage. Thus, ultrasonic-assisted SC-CO2 could be used, in combination or not with SS, to improve the shelf of dry-cured ham. Industrial relevanceSupercritical carbon dioxide (SC-CO2) inactivation technology has been shown to be highly efficient at reducing different bacteria in liquid media with minimum effect on food quality. This technology is barely applied to solid products and its use is limited by the long processing times and reduced inactivation capacity. The application of high-power ultrasound (HPU) leads to a shorter process time. This technology is useful for the inactivation of ham microbiota and inoculated E.coli. A liquid medium surrounding the treated solid can enhance microbial inactivation for the purposes of improving the effect of ultrasound cavitation, while only minimally affecting the quality of the samples (color, texture, fat and moisture contents).

High Power Ultrasound Treatments of Red Young Wines: Effect on Anthocyanins and Phenolic Stability Indices.

Polyphenols, especially anthocyanins, play an important role on red wine sensory qualities and their evolution during storage. High Power Ultrasound (HPU) has been recognized as one of the most promising technologies which can be applied in winemaking processes for several purposes, and it is recently officially approved for crushed grapes treatments. The effect of ultrasound amplitude (41 and 81%) and treatment time (1, 3, and 5 min) has been studied on anthocyanins, flavan-3-ols, tannins, polymerized pigments, HCl index, and the color intensity of two finished red young wines. Anthocyanins and phenols compounds were not degraded with an increase in amplitude and sonication time, and the chromatic properties of the selected wines were preserved. Amplitude and ultrasound time were also evaluated considering their effect on evolution of anthocyanin content and phenolic stability indices during the first thirty days of storage. The higher level of amplitude (81%) induced a higher percentage decrease in tannins, 15% and 40% after 15 and 30 days of storage, respectively, compared to untreated wine which did not show a significant change during storage. HPU shows a possible chemical effect on the evolution of some analytical indices during bottling maturation, but their effectiveness could be strictly linked with the initial phenolic profile and ratios between polyphenol classes.

The ultrasound application does not affect to the thermal properties and chemical composition of virgin olive oils

In this work, the effects of high power ultrasound treatment (40 kHz) on virgin olive oil (VOO) for different times (0, 15, 30 min) were studied, in order to verify if extent modifications in their chemical composition and thermal properties. The effects of the different ultrasound treatments on VOOs were determined considering the following parameters: quality index (free acidity, K232 and K270), lipid profile (fatty acids and triglycerides composition) minor components (phenols, tocopherols, pigments and volatiles) and thermal properties (crystallization and melting) by Differential Scanning Calorimetry (DSC).During the ultrasound treatments, bubbles growth was present in the VOO due to the phenomenon of cavitation and a slight increase of the temperature was observed. In general, the ultrasound treatments did not cause alterations on VOO parameters evaluated (oxidation state, lipid profile, minor components and thermal profiles). However, a slight decrease was observed in some volatile compounds.

Non-thermal pasteurization of lipid emulsions by combined supercritical carbon dioxide and high-power ultrasound treatment.

Supercritical carbon dioxide (SC-CO2) is a novel method for food pasteurization, but there is still room for improvement in terms of the process shortening and its use in products with high oil content. This study addressed the effect of high power ultrasound (HPU) on the intensification of the SC-CO2 inactivation of E. coli and B. diminuta in soybean oil-in-water emulsions. Inactivation kinetics were obtained at different pressures (100 and 350bar), temperatures (35 and 50°C) and oil contents (0, 10, 20 and 30%) and were satisfactorily described using the Weibull model. The experimental results showed that for SC-CO2 treatments, the higher the pressure or the temperature, the higher the level of inactivation. Ultrasound greatly intensified the inactivation capacity of SC-CO2, shortening the process time by approximately 1 order of magnitude (from 50 to 90min to 5-10min depending on the microorganism and process conditions). Pressure and temperature also had a significant (p<0.05) effect on SC-CO2+HPU inactivation for both bacteria, although the effect was less intense than in the SC-CO2 treatments. E. coli was found to be more resistant than B. diminuta in SC-CO2 treatments, while no differences were found when HPU was applied. HPU decreased the protective effect of oil in the inactivation and similar microbial reductions were obtained regardless of the oil content in the emulsion. Therefore, HPU intensification of SC-CO2 treatments is a promising alternative to the thermal pasteurization of lipid emulsions with heat sensitive compounds.

An Overview of Effects Induced by Pasteurization and High-Power Ultrasound Treatment on the Quality of Red Grape Juice.

In juice processing, ultrasound treatment has been tested as a potential alternative to conventional thermal methods to inactivate microorganisms and to enhance the nutritional status of juice. In this study, the impact of pasteurization and high-power ultrasound treatment on the quality of red grape juice was investigated in terms of the content of bioactive compounds such as phenolic compounds and l-ascorbic acid as well as regarding the microbiological and physicochemical properties. The grape juice was subjected to pasteurization (80 °C, 2 min) as well as to ultrasound treatment with an amplitude of 50 and 70% for 5 and 10 min. The results indicated the same level of total phenolic content for pasteurized and sonicated samples for 10 min with an amplitude of 70%, while the highest level of l-ascorbic acid was recorded for sonicated samples with an amplitude of 70% for 10 min. pH of sonicated samples decreased with amplitude and treatment time while total soluble solids and titratable acidity increased with amplitude and time. Moreover, the results indicated the usefulness of juice sonication to enhance the inactivation of microorganisms. Thus, the high-power ultrasound treatment might represent a viable technique to replace the conventional thermal treatment in grape juice processing.

Effects of single- and dual-frequency ultrasound on the functionality of egg white protein

The effects of high-power ultrasound (HP-US) treatment with different frequencies, temperatures, and durations on the physicochemical and structural properties of untreated and HP-US-treated egg white protein (EWP) were evaluated. Results indicated that the solubility of EWP was significantly improved after HP-US treatment, especially under the continuous dual frequency of 20/40 kHz. The foaming capacity of the EWP also depended on the treatment frequency, temperature, and duration, and foaming stability increased considerably in the HP-US-treated EWP compared with the untreated one. The particle size of the HP-US-treated EWP greatly decreased compared with that of untreated EWP. Results of low-field nuclear magnetic resonance analysis indicated that more water molecules were trapped in the EWP gel structure as free water after HP-US treatment. Therefore, the green technology of HP-US treatment can improve the physicochemical properties of EWP because of its sonochemical effect on the molecular conformation of EWP.

Low-frequency, high-power ultrasound treatment at different pressures for olive paste: Effects on olive oil yield and quality.

Ultrasound technology was employed to test its action on the extraction of olive oil at the industrial scale. Because of its mechanical effects, ultrasound waves were applied to the olive paste, between the crushing and malaxing operations. Comparative experiments were performed between traditional extraction processes and the innovative extraction process, with the addition of the ultrasound treatment. Different levels of pressure were tested on olive paste, using four different olive cultivars. Pressure level played an important role in olive oil extractability. When ultrasound was subjected to olive paste with a pressure of about 3.5 bar, there was a significant increase of extractability compared to the traditional process. On the other hand, there was no significant effect between ultrasound treatment and traditional technology on extractability when ultrasound at a pressure level of 1.7 bar was used.