The engine of this transformation is acoustic cavitation. When high-intensity sound waves pass through a protein suspension, they force microscopic bubbles to form, grow, and then collapse violently. Each collapse creates a fleeting hot spot of extreme temperature and pressure, accompanied by intense shear forces, shock waves, and microjets of liquid. These micro-events last only microseconds, but they deliver enough localized energy to pry apart the hydrogen bonds, hydrophobic interactions, electrostatic contacts, and disulfide linkages that hold a protein in its compact native shape. Crucially, because the energy is deposited in tiny, transient zones, the bulk of the liquid barely warms, making ultrasound a genuinely non-thermal technology that preserves heat-sensitive nutrients.

The review, authored by Gulcin Yildiz of Igdir University and Gökçen Yıldız of Bursa Technical University, frames ultrasound not as a mere processing aid but as a multiscale structural engineering tool. At the molecular level, cavitation partially unfolds protein chains, exposing functional groups that were previously buried inside. At the supramolecular level, large aggregates are shattered into smaller assemblies, and protein–protein interaction networks reorganize. At the colloidal scale, particle sizes shrink, surface charges shift, and dispersion stability improves. These levels are not independent; they form a continuous cascade in which energy input at the smallest scale ultimately determines whether a protein solution flows, gels, foams, or emulsifies at the largest.

The practical payoffs are striking. In soy protein, combining pH-shifting with ultrasonication produced nano-aggregates of roughly 22 nanometers and lifted solubility from a dismal 1.49 percent to 82.73 percent. Hemp protein isolates treated with ultrasound showed about a 3.7-fold increase in solubility, while lentil proteins gained up to roughly 90 percent more solubility after sonication or thermosonication. Faba bean proteins fragmented from aggregates of 370 nanometers down to 187 nanometers, reaching solubilities above 89 percent, and combining ultrasound with alkaline pH-shifting pushed faba bean solubility from around 12 percent to more than 95 percent. Even mung bean proteins underwent a dramatic micro-to-nano transition, with particles shrinking from 10.37 micrometers to 484 nanometers, improving solubility, emulsification, and oil-holding capacity in the process.

Not every protein responds the same way, however. The review emphasizes that plant protein isolates are heterogeneous mixtures of distinct fractions: soy contains 7S β-conglycinin and 11S glycinin, pea contains vicilin, legumin, and convicilin, and cereals contribute glutelins, prolamins, and albumin–globulin fractions, each with its own structural stability and susceptibility to cavitation. Rice protein, in particular, is a tough case. Its compact, rigid assemblies resist ultrasound-induced unfolding, and meaningful gains require synergistic treatments such as alkaline or thermal assistance. When ultrasound was combined with alkali treatment, rice protein solubility increased by up to roughly 230-fold, one of the largest enhancements reported, but ultrasound alone delivered only modest changes compared with the dramatic responses seen in legumes.

Perhaps the most important conceptual contribution of the review is the idea of an optimal cavitation window. Moderate ultrasound doses promote controlled unfolding, exposing hydrophobic and sulfhydryl groups in ways that enhance interfacial adsorption, gelation, and digestibility. Push past that window, however, and the same exposed hydrophobic regions begin to find each other, driving reaggregation and functional decline. The authors trace this non-linearity to a temporal race: cavitation bubbles collapse in microseconds, but proteins relax and refold over much longer timescales. When sufficient recovery time exists between cavitation pulses, proteins settle into favorable, functional conformations. Under prolonged or continuous sonication, proteins are perturbed again before they can relax, accumulating unfolding and hydrophobic exposure until uncontrolled aggregation wins.

The functional consequences ripple through every property food scientists care about. Emulsifying activity improved by roughly 1.5 to 1.7 times in hemp protein, and pea proteins formed nanoemulsions around 198 nanometers with improved oxidative stability. Lentil proteins stabilized high internal phase emulsions with smaller droplets and better rheological stability, while faba bean proteins produced oil-in-water emulsions with droplets below 0.4 micrometers, suitable as clean-label emulsifiers. Gelation benefited too: moderate cavitation fostered dense, elastic networks stabilized by hydrophobic interactions, hydrogen bonding, and disulfide linkages, raising gel hardness, water-holding capacity, and storage modulus in soy, chickpea, mung bean, and faba bean systems. Excessive sonication, by contrast, produced porous, weak gels with poor viscoelasticity.

Nutrition stands to gain as well. By loosening protein structure and exposing cleavage sites, ultrasound makes plant proteins more accessible to digestive enzymes, enhancing gastrointestinal hydrolysis and the release of bioactive peptides with antioxidant and antihypertensive properties. Rice protein digestibility reached approximately 96.9 percent under optimized ultrasound-assisted pretreatment, and chickpea proteins showed increased enzymatic accessibility along with improved antioxidant activity and gut microbiota modulation. Ultrasound also strengthens protein–biopolymer interactions: sonicated proteins form more stable complexes with polysaccharides such as pectin and inulin, and covalent conjugates with polyphenols such as curcumin and chlorogenic acid, opening routes to encapsulation systems and functional ingredients with enhanced antioxidant activity.

The technology also pays dividends upstream. Ultrasound-assisted extraction disrupts cell walls, improves mass transfer, and boosts solvent penetration into protein-rich plant matrices, cutting extraction time, solvent use, and energy consumption relative to conventional methods. Hemp seed protein extraction yields rose up to 2.1-fold, chickpea protein recovery increased by up to 47.28 percent when ultrasound was combined with pulsed electric fields, and pumpkin seed proteins showed the highest yields under alkaline extraction assisted by ultrasound. The review cautions, though, that excessive cavitation during extraction can trigger aggregation, oxidation, or loss of nutritional quality, so the same optimal-window logic applies to recovery processes as to functional modification.

Scaling all of this from the laboratory bench to the factory floor remains the central challenge. The authors identify persistent obstacles, including a lack of standardization of ultrasound parameters across different systems, incomplete understanding of energy efficiency and heat dissipation at industrial scale, matrix-dependent variability in product functionality, and limited real-time monitoring of structural transitions during processing. Scale-up often produces non-uniform energy distribution, undermining reproducibility. Their roadmap for the future includes integrating ultrasound with complementary technologies such as pulsed electric fields, cold plasma, and high-pressure processing; developing in situ monitoring tools that track unfolding and aggregation as it happens; deploying multiscale computational modeling alongside advanced spectroscopy; and designing continuous-flow ultrasound reactors with improved acoustic uniformity. If those pieces come together, the same sound waves that once seemed a niche laboratory trick could become the precision instrument that turns humble peas, beans, and seeds into the next generation of high-performance plant-based foods.

Subject of Research: Ultrasound-assisted multiscale structural modification of plant proteins and its effects on functionality

Article Title: Ultrasound-assisted multiscale structural engineering of plant proteins: mechanisms and structure–property relationships

Article References: Yildiz, G., & Yıldız, G. (2026). Ultrasound-assisted multiscale structural engineering of plant proteins: mechanisms and structure–property relationships. Frontiers in Soft Matter, 6, Article 1893101. https://doi.org/10.3389/frsfm.2026.1893101

Image Credits: AI Generated

DOI: 10.3389/frsfm.2026.1893101

Keywords: plant proteins, ultrasound, acoustic cavitation, food processing, solubility, emulsification, gelation, digestibility, soy protein, pea protein, sustainable food, non-thermal processing

Intermetallic compounds are ordered alloys in which nickel and gallium atoms occupy fixed positions in a crystalline lattice, a configuration that endows the material with catalytic properties distinct from either element alone. Nickel-gallium phases have attracted sustained interest since researchers demonstrated nearly a decade ago that they can catalyze the synthesis of methanol from carbon oxides, and subsequent work has explored their use in deoxygenation reactions for upgrading biomass-derived compounds. The obstacle has always been manufacturing. Conventional routes require extended heating at elevated temperatures to drive gallium atoms into the nickel lattice and establish the ordered intermetallic structure, an energy-intensive process that also coarsens the microstructure and can limit the active surface area available for catalysis.

The new approach replaces heat with mechanical energy delivered at the microscale. When ultrasound propagates through a liquid, it alternately compresses and stretches the medium, and if the acoustic pressure amplitude is sufficient, microscopic cavities nucleate, grow, and collapse violently in a phenomenon known as acoustic cavitation. The collapse of a cavitation bubble concentrates acoustic energy into a vanishingly small volume, generating transient local temperatures of thousands of degrees and enormous pressures, along with intense microjets and shock waves that impinge on nearby solid surfaces. Materials chemists have exploited these effects for decades to accelerate reactions and clean or activate surfaces, but the new study adds a crucial control knob: how readily cavitation bubbles attach to and attack the metal surface in the first place.

That knob is surface roughness, and the team tunes it with an electrochemical etch that could hardly be simpler. By polarizing the nickel in an electrolyte, hydrogen gas is generated at the surface, and the streams of evolving bubbles scour the metal, gradually texturing it into a landscape of pits and protrusions. The researchers allowed this hydrogen bubble etching to proceed for intervals ranging from zero to five minutes, producing a graded series of nickel surfaces whose roughness increased with etching time. Roughness matters for two reasons simultaneously. First, it governs how well liquid gallium wets the nickel, because a rougher surface offers more crevices for the liquid metal to infiltrate and more contact area across which gallium atoms can diffuse toward the nickel lattice. Second, it dictates where cavitation bubbles preferentially nucleate, since gas trapped in surface cavities acts as a seed for the acoustic bubbles that deliver the mechanical hammering.

Once a textured nickel substrate was immersed in liquid gallium and subjected to low-power ultrasound at 40 degrees Celsius, intermetallic layers formed with remarkable speed. Cross-sectional microscopy revealed a clear and initially intuitive trend: the thickness of the nickel-gallium layer grew as the etching time increased, peaking at samples etched for two minutes, where the intermetallic reached 8.2 micrometers. Beyond that optimum, however, the trend reversed. On the most aggressively textured surfaces, etched for five minutes, the cavitation became so intense that the freshly formed intermetallic layer could not withstand the mechanical assault and began to fragment and peel away from the substrate. The authors attribute this to cavitation-induced exfoliation, a self-limiting destruction in which the very bubbles that accelerate alloying also tear the product loose once the surface crosses a roughness threshold.

This non-monotonic relationship between roughness, cavitation efficiency, and layer integrity is the conceptual heart of the paper. It converts surface preparation into a genuine synthesis variable rather than a mere pretreatment. Too smooth, and gallium wets poorly while cavitation nucleates sparsely, leaving the alloying sluggish. Too rough, and the reaction runs hot and fast but destroys its own product. Somewhere in between lies a window in which wettability and cavitation intensity are jointly optimized, and the two-minute etch sits squarely inside it. The finding echoes earlier observations that cavitation can be positioned selectively on appropriately patterned surfaces, but it extends that principle from controlling where bubbles form to controlling how much intermetallic compound ultimately accumulates.

The practical payoff was evaluated in an electrochemical reaction of enormous contemporary relevance: the hydrogen evolution reaction, the cathodic half of water splitting that underpins green hydrogen production. Testing in one molar sodium hydroxide, a standard alkaline electrolyte, the team measured Tafel slopes, which describe how rapidly the current density increases as overpotential is applied and serve as a proxy for reaction kinetics. The optimized nickel-gallium surface etched for two minutes delivered a Tafel slope of 70.6 millivolts per decade, substantially lower than the 116.7 millivolts per decade recorded for pristine nickel under identical conditions. A lower Tafel slope means less additional voltage is needed for each tenfold increase in current, translating directly into improved energy efficiency. The treated electrode also maintained its performance over extended operation, indicating that the intermetallic layer is not merely an active but fragile coating.

The result is notable partly because liquid gallium and its alloys have become one of the most fashionable platforms in materials science, prized for a low melting point near room temperature, metallic conductivity, and a fluidity that allows them to flow, deform, and react in ways solid metals cannot. Recent studies from other groups have harnessed ultrasound to drive liquid metals into contact with reactive solids, dramatically accelerating the reaction of aluminum with water and even fracturing biometals through liquid metal layers inserted into multilayer coatings. The present work extends that emerging toolkit in a different direction, using ultrasound not to smash a material apart but to build an ordered alloy on demand, and using a cheap electrochemical pretreatment to dial in the outcome.

For catalyst designers, the implications are twofold. Synthetically, the protocol offers intermetallic compounds under mild conditions, avoiding furnace treatments that consume energy and can degrade fine structures, and offering a turnaround time of a quarter hour that makes systematic composition and thickness screening far more practical. Mechanistically, the study demonstrates that wettability and acoustic cavitation can be co-engineered through a single geometric parameter, suggesting that similar roughness-based control could transfer to other liquid-metal-solid combinations beyond nickel and gallium. The work was supported by the Natural Science Foundation of Shandong Province and several provincial research and development programs, reflecting the region’s investment in advanced light alloy technology and aluminum recycling, fields where liquid metal processing knowledge is directly transferable.

Challenges remain before the method matures beyond the laboratory. The intermetallic layers were grown on planar nickel substrates, and scaling to the high-surface-area porous electrodes favored in industrial electrolyzers will require confirming that cavitation and wetting behave comparably inside complex three-dimensional architectures. The balance between layer growth and cavitation-induced exfoliation is also inherently delicate, and real-world electrodes must tolerate far harsher current densities and gas evolution than laboratory tests impose. Even so, the demonstration that a two-minute bubble etch can more than halve the kinetic penalty of a hydrogen-evolving electrode, achieved with a household temperature, a beaker of gallium, and a modest ultrasonic source, is the kind of result that invites rapid replication. If roughness-engineered cavitation proves general, the slow, hot furnaces that have guarded the intermetallic catalysts may soon find themselves increasingly idle.

Subject of Research: Ultrasound-assisted synthesis of nickel-gallium intermetallic surfaces for electrocatalysis

Article Title: Ultrasound-driven rapid synthesis of Ni–Ga intermetallic surfaces modulated by electrolytic surface texturing under mild conditions

Article References: Bi, X., Guo, X., Xu, X., Song, W., Yao, S., Yang, X., Jia, S., Shi, D., Huo, Y., Zhao, J., & Dai, H. (2026). Ultrasound-driven rapid synthesis of Ni–Ga intermetallic surfaces modulated by electrolytic surface texturing under mild conditions. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13838-x

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13838-x

Keywords: nickel-gallium intermetallics, ultrasound, acoustic cavitation, liquid gallium, surface texturing, hydrogen bubble etching, electrocatalysis, hydrogen evolution reaction, Tafel slope, surface wettability, materials synthesis, alkaline water splitting

The review, authored by Rina Yu, Sin-Young Park, Prabhathma Yasasvi Rathnayake, and colleagues at Chungnam National University, Kongju National University, and the Korea Institute of Materials Science, systematically compares how different ultrasound systems and thermal conditions inactivate microbes in milk and milk-derived drinks. The authors frame their analysis around a simple but consequential observation: the antimicrobial power of ultrasound varies enormously depending on the equipment configuration, the processing parameters, and, crucially, how much heat is generated or deliberately added during treatment. By sorting the literature into three processing modes, cavitation-driven non-thermal ultrasound, ultrasound with natural temperature rise, and thermally assisted ultrasonic treatment, the review provides one of the clearest pictures yet of where sound-based pasteurization stands on the path from laboratory bench to dairy plant floor.

The physics behind ultrasonic pasteurization is striking. A transducer converts electrical energy into acoustic energy, sending longitudinal pressure waves through the liquid. These waves create alternating regions of compression and rarefaction, and in the rarefaction phase the liquid is literally torn apart, forming microscopic bubbles. At sufficiently high acoustic amplitudes, these bubbles undergo inertial cavitation: they expand rapidly and then collapse violently. The collapse generates localized hotspots with temperatures estimated to reach up to 5,500 degrees Celsius and pressures up to 50,000 kilopascals, conditions that exist for only fractions of a microsecond but are enough to wreak havoc on nearby microorganisms. The asymmetric collapse of bubbles produces shockwaves, microjets, and microstreaming currents that physically batter bacterial cell walls and membranes, tearing open structures that would otherwise protect the cell.

But the physical assault is only half the story. The extreme conditions inside collapsing bubbles also split water vapor into hydrogen and hydroxyl radicals, reactive oxygen species that penetrate bacterial cells through membrane pores and attack intracellular biomolecules. Hydroxyl radicals can cleave the DNA double helix, induce base modifications, and trigger lipid peroxidation in the phospholipid bilayer by reacting with polyunsaturated fatty acids. The result is oxidative degradation of proteins, lipids, polysaccharides, and nucleic acids, culminating in cell death. A related phenomenon, sonoluminescence, in which collapsing bubbles emit light across a broad spectrum, can further amplify microbial inactivation when a photocatalytic sonosensitizer is present, because the emitted light excites the sensitizer and generates additional reactive species. Together, these mechanical and chemical mechanisms make cavitation a genuinely multi-pronged antimicrobial weapon rather than a single-mode killer.

The review emphasizes that not all ultrasound equipment delivers this weapon equally well. Probe-type systems, in which a sonotrode is immersed directly in the sample, concentrate energy intensely at the tip and deliver the highest power intensity. Bath-type systems, which use sandwich transducers mounted on tank walls and rely on water as a coupling medium, suffer from attenuation of the ultrasound in the water, resulting in power intensity roughly one hundred times lower than probe systems. Both configurations irradiate from a single direction, producing non-uniform energy distribution within the treated volume. Continuous-flow systems, a newer development, address this weakness by circulating the product through a treatment zone, and some cylindrical designs generate ultrasonic energy in a 360-degree pattern, giving circulating milk stronger and more uniform exposure. These systems also allow operators to tune flow rate and number of treatment cycles alongside the usual power, amplitude, and frequency settings, a flexibility that matters greatly for industrial scale-up.

The experimental record assembled in the review shows how strongly outcomes depend on thermal conditions. Under controlled room-temperature conditions, where cooling systems or ice baths suppress heating, ultrasound alone achieves moderate inactivation. Mudgil and colleagues found that treating camel milk with probe-type ultrasound at 160 watts and 20 kilohertz for ten minutes reduced total aerobic bacteria by approximately 4.16 log CFU per milliliter, Staphylococcus species by 3.40 log, and lactic acid bacteria by 1.50 log. Chouliara’s group reported roughly 2 log reductions in total viable and psychrotrophic counts in milk after sixteen minutes at 200 watts and 24 kilohertz without added heat. In a Kinnow whey beverage, fifteen minutes of 400-watt, 20-kilohertz treatment cut total aerobic bacteria by about 1 log and molds and yeasts by 1.61 log. These are meaningful reductions, but they fall short of what regulators demand.

When the natural temperature rise of ultrasound is allowed to accumulate rather than suppressed, the numbers improve dramatically. Treating raw milk with probe-type ultrasound at 19 kilohertz and 475 watts for 158 seconds raised the temperature to 54 degrees Celsius and reduced mesophilic bacteria by about 2.6 log and lactic acid bacteria by 2.1 log. More strikingly, Shamila-Syuhada and colleagues showed that raw milk treated at 200 watts and 24 kilohertz for fifteen minutes reached 60 degrees Celsius at the higher amplitude tested, and at that point reductions of approximately 8 log CFU per milliliter were recorded for Staphylococcus aureus, Listeria monocytogenes, Salmonella Typhimurium, E. coli, Pseudomonas fluorescens, and two Lactobacillus species. Scudino’s team demonstrated the same principle through energy density: 1 kilojoule per milliliter raised raw milk to only 34 degrees Celsius with no detectable bacterial reduction, 3 kilojoules per milliliter reached 55 degrees Celsius and achieved a 1.8 log reduction, and 5 kilojoules per milliliter pushed the temperature to 76 degrees Celsius, delivering a 4 log reduction in just over four minutes. In chocolate milk, an energy density of 3 kilojoules per cubic centimeter at 400 watts and 19 kilohertz produced a 3.56 log reduction with a final temperature of only 42 degrees Celsius.

Thermally assisted ultrasound, combining acoustic cavitation with deliberately applied mild heat, offers perhaps the most pragmatic route to regulatory compliance. Van Hekken and colleagues applied continuous-flow ultrasound at dual frequencies of 16 and 20 kilohertz and 1,200 watts to raw milk held at 54 degrees Celsius for fourteen minutes, achieving reductions of 3.36 log in total mesophilic bacteria and 4.88 log in psychrotrophic bacteria, whereas the same treatment at 42 degrees Celsius showed no bactericidal effect at all. In human milk, bath-type ultrasound at 60 degrees Celsius reduced Staphylococcus aureus by approximately 4.58 log, while treatment at 20 degrees Celsius had no effect. The synergy arises because mild heat weakens the protective function of the bacterial cell envelope and increases cavitation efficiency, making cells simultaneously easier to rupture mechanically and more vulnerable to radical attack.

Yet the review is candid about the obstacles standing between these promising numbers and commercial reality. Under the Codex Alimentarius, any validated milk pasteurization technology must achieve at least a 5 log CFU per milliliter reduction of non-spore-forming pathogenic bacteria, and only a handful of ultrasound studies have crossed that threshold using ultrasound alone. Pushing intensity high enough to meet the standard risks damaging the product: ultrasound-generated radicals promote lipid oxidation and create volatile compounds responsible for metallic, burnt, and rubbery off-flavors in treated milk. There are also safety concerns specific to the equipment itself, since probe erosion can release metallic particles into the product and ultrasound accelerates electrochemical corrosion of stainless steel in the presence of chlorides. The authors argue that the future lies in continuous-flow systems suitable for large-scale processing, hurdle combinations of ultrasound with mild heat, pulsed electric fields, ultraviolet treatment, or natural antimicrobials, and real-time digital process control that can hold both microbial safety and sensory quality within tight tolerances.

What emerges from the review is not a verdict but a roadmap. Ultrasound is safe, non-toxic, relatively inexpensive to build, and well suited to liquid foods, and its antimicrobial mechanisms are now well characterized at the cellular level. The decisive variable is heat: whether it is suppressed, harvested, or deliberately supplied determines whether ultrasound is a gentle quality-preserving treatment or a genuine pasteurization technology. As consumer demand grows for fresh-flavored, minimally processed dairy, and as outbreaks linked to pasteurization failures continue to surface, the pressure to validate sound-based alternatives will only intensify. The next few years of equipment engineering and regulatory data generation will determine whether the dairy industry’s next pasteurizer hums rather than hisses.

Subject of Research: Ultrasonic pasteurization of milk and milk-based beverages using different ultrasound systems and thermal conditions

Article Title: A review of ultrasonic pasteurization in milk and milk-based beverages using different ultrasound systems and thermal conditions: from mechanistic insights to regulatory challenges

Article References: A review of ultrasonic pasteurization in milk and milk-based beverages using different ultrasound systems and thermal conditions: from mechanistic insights to regulatory challenges. (n.d.). https://doi.org/10.1007/s44463-026-00105-5

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00105-5

Keywords: ultrasound, pasteurization, milk, dairy, acoustic cavitation, food safety, microbial inactivation, non-thermal processing, reactive oxygen species, continuous-flow ultrasound, foodborne pathogens, dairy processing