The core challenge is architectural. Many plant proteins fold into compact globular shapes stabilized by dense networks of hydrogen bonds, hydrophobic interactions, and disulfide linkages. These bonds provide stability but also bury the functional groups that proteins need to dissolve in water, stabilize emulsions, form foams, and create gel networks. The result is poor solubility, weak interfacial behavior, limited digestibility, and sensory performance that often falls short of animal proteins. The review emphasizes that these constraints operate across a hierarchy of scales, from the molecular conformation of secondary and tertiary structures to the microstructural organization of protein aggregates and the macroscopic properties of gel networks, and it is this multiscale organization that ultimately governs how plant proteins behave in complex food matrices.

Ultrasound processing has emerged as one of the most versatile tools for breaking through these structural barriers. Operating at frequencies between roughly 20 and 100 kilohertz, ultrasound triggers acoustic cavitation, a process in which microscopic bubbles form, grow, and collapse violently within liquid protein suspensions. Each bubble collapse generates localized shear forces, microjets, and shock waves that can disrupt protein aggregates and promote partial unfolding without the extensive thermal damage associated with conventional heating. The review highlights that these mechanical forces primarily target the non-covalent interactions stabilizing protein structure, weakening hydrogen bonds and hydrophobic associations that hold aggregates together.

The structural consequences are measurable and significant. Jambrak and colleagues demonstrated that ultrasound treatment altered the secondary structure of soy proteins, reducing the proportion of alpha-helical structures while increasing random coil configurations, which enhanced protein flexibility and improved solubility and emulsifying capacity. Li and co-workers reported that ultrasound reduced the particle size of pea protein aggregates from 831.6 to 346.7 nanometers under controlled conditions, with the resulting smaller particles exhibiting improved interfacial activity and producing more stable emulsions over time. Hu and colleagues observed that ultrasound treatment increased the availability of free sulfhydryl groups in soy protein isolates, promoting stronger gel formation and improved water-holding capacity. These molecular-level changes cascade upward: disrupted hydrogen bonds drive partial unfolding, which exposes previously buried hydrophobic residues and reactive groups, which then drive controlled aggregation or interfacial adsorption, ultimately determining the macroscopic solubility, emulsification, and gelation properties of the final food product.

Pulsed electric field processing operates through a fundamentally different mechanism. Short bursts of high-voltage electricity, typically between 5 and 50 kilovolts per centimeter with microsecond pulse durations, temporarily disrupt cell membranes through electroporation, creating nanoscale pores that facilitate the release of intracellular proteins without harsh solvents or severe thermal treatments. Barba and colleagues reported that PEF pretreatment improved protein extraction yields from plant materials by approximately 30 percent. Beyond its effects on cellular structures, PEF directly influences protein molecules by interacting with molecular dipoles and charged amino acid residues, causing polarization and reorientation that can disrupt hydrogen bond networks and modify the hydration layer surrounding proteins. The review offers a particularly elegant physical explanation for why alpha-helical segments are preferentially affected: the alpha-helix carries a substantial net dipole moment along its axis because the peptide-bond dipoles are aligned in the same direction, making these segments more strongly coupled to an externally applied electric field than beta-sheet segments, which leave a comparatively small net dipole.

Cold plasma treatment takes yet another approach, acting primarily at the protein surface rather than inducing extensive unfolding throughout the molecular structure. Plasma is a partially ionized gas containing energetic electrons, ions, ultraviolet photons, and reactive oxygen and nitrogen species. When these reactive species interact with exposed amino acid residues, they initiate oxidation-reduction reactions that modify protein side chains. Sulphur-containing amino acids such as cysteine and methionine are especially susceptible, forming sulfoxides, disulfide cross-links, or carbonyl derivatives. Misra and colleagues demonstrated that cold plasma treatment increased the emulsifying activity of soy protein isolates because the introduction of oxygen-containing groups enhanced protein surface polarity and interfacial adsorption. Segat and colleagues reported improved foaming capacity in plasma-treated wheat proteins, while Ji and colleagues showed enhanced solubility and dispersibility of plasma-treated peanut proteins. Because cold plasma modifies surfaces selectively, it allows fine control over interfacial behavior while minimizing structural degradation.

Ohmic heating, which the review carefully distinguishes as an electro-thermal rather than strictly non-thermal technology, passes alternating electric current directly through the food material, generating heat internally through electrical resistance. Unlike conventional heating, where thermal energy transfers gradually from external surfaces inward, ohmic heating produces rapid and uniform volumetric heating throughout the entire food matrix. This minimizes temperature gradients and prevents localized overheating, allowing greater control over protein denaturation and aggregation behavior. Sakr and Liu observed that ohmic heating promoted more homogeneous protein unfolding and network formation compared with conventional thermal methods, with the resulting protein gels exhibiting improved water-holding capacity, elasticity, and structural stability. The review notes that this controlled heating approach is particularly valuable for developing plant-based meat analogues and high-moisture protein systems where uniform network formation is essential for replicating the fibrous texture of animal muscle tissue.

One of the most striking findings of the review is that no single set of processing parameters is optimal across all plant protein sources. Soy and pea proteins are dominated by 7S vicilin and 11S legumin globulins, with the more loosely associated 7S fraction unfolding and solubilising more readily than the disulfide-rich 11S fraction under identical ultrasound treatment. Oat protein, dominated by a compact, highly disulfide-stabilised 12S globulin with unusually high thermal and structural stability, requires substantially higher ultrasound intensities to achieve comparable particle-size reduction and solubility gains. Wheat gluten proteins, being prolamins rather than globulins, respond to ultrasound primarily through changes in disulfide crosslink density and aggregate structure rather than through classical alpha-helix-to-beta-sheet transitions, since their native structure already contains little ordered secondary structure. Faba bean globulins occupy an intermediate position, sharing the 7S/11S architecture of legumes but with a subunit composition that produces a somewhat lower unfolding threshold and a correspondingly higher risk of re-aggregation if treatment is not carefully controlled.

The review also sounds a cautionary note about overprocessing. Beyond a defined favourable range, the same mechanisms that improve functionality at moderate intensity begin to cause functional deterioration. At high acoustic intensities, water sonolysis generates hydroxyl and other free radicals that oxidise newly exposed free sulfhydryl groups back into disulfide bonds, promoting irreversible protein re-aggregation rather than continued unfolding. Excessive cold plasma exposure can over-oxidise surface amino acid residues, producing carbonylation and cross-linking reactions that stiffen the protein surface and reduce interfacial activity. Once excessive aggregation has occurred, the resulting dense aggregates can become less accessible to digestive proteases than either the native protein or the moderately processed form, producing an inverted U-shaped relationship between processing intensity and digestibility. The point at which structural modification becomes detrimental is technology- and protein-source-specific, and is generally reached well before complete protein unfolding or maximal cavitation intensity.

Looking forward, the review identifies computational modelling and machine learning as critical tools for optimizing non-thermal protein processing. Molecular dynamics simulations allow researchers to observe atomic-level structural changes in proteins subjected to mechanical stress, electric fields, or pressure variations, providing insights into how protein folding patterns respond to different processing environments. Machine learning algorithms such as artificial neural networks and random forest models can identify relationships between processing parameters and functional outcomes that may not be evident through conventional statistical analysis, predicting how variations in ultrasound intensity, treatment time, or PEF strength influence solubility, emulsifying capacity, and gel strength. The integration of real-time sensors with machine learning algorithms enables adaptive process control, where processing parameters are adjusted dynamically based on incoming data to ensure consistent product quality despite variations in raw materials. As the review concludes, the most energy-efficient operating point for a given technology is generally the same moderate-intensity window that avoids overprocessing, meaning that energy efficiency and functional quality are not competing objectives but are, in practice, optimised together, bringing the food industry closer to producing plant-based products that are nutritionally balanced, environmentally sustainable, and appealing to consumers.

Subject of Research: Food Science and Soft Matter

Article Title: Multiscale structural modulation of plant proteins via ultrasound and electro-physical processing: from extraction to functional food matrices

Article References: Majeed, N., Younis, K., & Yousuf, O. (2026). Multiscale structural modulation of plant proteins via ultrasound and electro-physical processing: from extraction to functional food matrices. Frontiers in Soft Matter, 6, Article 1881300. https://doi.org/10.3389/frsfm.2026.1881300

Image Credits: AI Generated

DOI: 10.3389/frsfm.2026.1881300

Keywords: plant proteins, ultrasound, pulsed electric fields, cold plasma, ohmic heating, non-thermal processing, food structure, sustainable food systems, protein functionality, multiscale, structural, modulation

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

The appeal of PEF lies in what it avoids. Conventional pasteurization of fruit and vegetable juices relies on intense heat, which effectively eliminates pathogens and spoilage organisms but simultaneously degrades vitamins, polyphenols, flavonoids, and carotenoids, the very compounds that make juices attractive to health-conscious consumers. PEF works differently. When microbial cells are exposed to an electric field strength above roughly 10 kV/cm for micro- to millisecond durations, a phenomenon called electroporation occurs: the cell membrane, normally an insulating barrier, develops pores as the transmembrane potential exceeds a critical threshold. If the pores reseal, the cell survives, injured but alive. If they fail to reseal, the cell dies. The new study tackles both outcomes head-on, quantifying not just how many cells die but how many are left in that dangerous middle state of sub-lethal injury.

The experimental setup was deliberately designed to mimic industrial conditions. The team used a continuous-flow PEF system, the EPULSUS-BM1A-12 pulse generator, pumping juice at 6 liters per hour through a treatment chamber with parallel titanium electrodes separated by a 0.4-centimeter gap. Square-wave pulses of 4 microseconds were applied at a field strength of 20 kV/cm, with repetition frequencies ranging from 4 to 78 Hz. This produced treatment times between 0 and 112.3 microseconds and total specific energies from 0 up to 139.2 kJ/kg, with outlet temperatures held between 20 and 55.8 degrees Celsius, well below what conventional pasteurization would require. Three juices with sharply different chemistries served as the test matrices: acidic pomegranate juice at pH 3.1, moderately acidic tomato juice at pH 4.4, and nearly neutral carrot juice at pH 6.1, each with distinct conductivity and soluble solids content.

Four microbial strains were put through this gauntlet: two strains of Escherichia coli, the laboratory strain K12 and the foodborne isolate FAM 21843 originally recovered from raw milk cheese, and two strains of the spoilage yeast Saccharomyces cerevisiae, AD1890 isolated from fruit and 130.0014 from the food industry. The results met and in some cases exceeded the benchmark that matters most for commercialization. The U.S. Food and Drug Administration requires a 5-log reduction, meaning a 100,000-fold decrease in the most resistant foodborne pathogen, before PEF can be approved for commercial juice pasteurization. In pomegranate and carrot juices, both E. coli strains achieved greater than 5-log reductions at the highest treatment intensities. Tomato juice proved more challenging, yielding reductions above 3.85 logs, a shortfall the authors attribute to its intermediate acidity and composition.

One of the most technically important aspects of the study is its modeling approach. Traditional kinetic modeling proceeds in two stages: a primary model is fitted to each survival curve individually, and then the resulting parameters are linked to process variables through a secondary model. This stepwise procedure propagates errors and wastes information. Instead, the researchers fitted primary and secondary models simultaneously to the full dataset, combining a log-linear primary model with a second-order polynomial secondary model that describes how the maximum specific inactivation rate, k-max, depends on total specific energy. The polynomial captures three things at once: a baseline inactivation constant C1, a linear sensitivity coefficient C2, and a quadratic coefficient C3 that accounts for nonlinear acceleration or deceleration of killing as energy accumulates. Model performance was excellent, with regression coefficients ranging from 0.965 to 0.998 across all twelve strain-juice combinations.

The survival curves themselves were anything but the simple straight lines that early PEF studies reported. Those earlier log-linear observations, the authors note, likely reflected limited inactivation levels below 4 logs achieved at low field strengths or short durations. At the intensities tested here, the curves were distinctly multiphasic. In pomegranate juice, the E. coli strains showed concave downward kinetics, a slow initial decline that accelerated sharply after 47.12 microseconds of treatment. In carrot juice, the pattern inverted: a pronounced shoulder of resistance persisted up to about 44.64 microseconds, followed by a rapid collapse in viability beyond 61.92 microseconds. Tomato juice produced near log-linear behavior with slight tailing. The yeast strains followed similar matrix-dependent patterns, with S. cerevisiae showing particularly sharp sensitivity in tomato juice beyond 38.48 microseconds of treatment.

Statistical analysis of the fitted parameters revealed a satisfying hierarchy of effects. The linear coefficient C2 did not differ significantly across any strain or juice, suggesting a conserved, universal linear response of microbial populations to increasing energy input. In contrast, the baseline inactivation constant C1 and the quadratic coefficient C3 both varied significantly, clustering strains into distinct statistical groups. E. coli K12 in pomegranate juice showed one of the highest baseline inactivation rates, while S. cerevisiae 130.0014 in carrot juice showed the lowest. Notably, E. coli FAM 21843 displayed no matrix dependence in its baseline rate, meaning its initial susceptibility to PEF was unaffected by which juice it was suspended in. The predicted inactivation rates climbed steeply for all strains at total specific energies above 80 kJ/kg, with S. cerevisiae 130.0014 showing the highest rate at high energies in pomegranate and tomato juices, marking it as the most energy-sensitive organism tested.

Strain heterogeneity, the bane of predictive food microbiology, showed up in the details. The two E. coli strains behaved nearly identically across all juices, with one exception: in the most acidic matrix, pomegranate juice, FAM 21843 proved more resistant than K12, showing a 1.71-log reduction versus K12’s 2.36-log reduction at 72.32 kJ/kg. Among the yeasts, AD1890 was consistently more resistant than 130.0014 at high energy levels, a pattern that echoes earlier findings from the same laboratories under high-pressure processing and ultrasound, hinting at cross-resistance to multiple preservation stresses in the AD1890 strain. Sub-lethal injury, assessed by plating on selective versus nonselective media, was minimal in tomato and carrot juices but pronounced in pomegranate juice at medium energy levels, where the gap between counts on the two media widened, indicating a pool of membrane-damaged cells that could potentially recover during storage.

Crucially for consumers, the treatment left the juices’ nutritional chemistry untouched. Measurements of total phenolic content, total flavonoid content, total orthodiphenol content, and CUPRAC antioxidant capacity showed no statistically significant differences between untreated and PEF-treated samples for any of the three juices. This aligns with prior reports that PEF preserves anthocyanins in pomegranate juice, carotenoids in tomato juice, and antioxidant capacity in carrot juice, sometimes through twelve weeks of refrigerated storage. The combination of FDA-relevant microbial reductions and intact bioactive compounds is precisely the value proposition that has kept PEF on the industry’s wish list for decades.

The study’s authors are candid about what remains to be done. Future models should explicitly account for strain and matrix variability, other quality attributes such as color, volatile compounds, and flavor deserve investigation, and the capital cost of PEF equipment remains a significant barrier to widespread adoption. But the message of this work is clear and commercially resonant: under realistic continuous-flow conditions, total specific energy is the master variable controlling microbial inactivation by PEF, a well-fitted polynomial model can predict it across organisms and juices, and the technology can deliver pathogen-killing performance without sacrificing the antioxidants that sell fresh juice in the first place.

Subject of Research: Kinetic modeling of microbial inactivation in fruit and vegetable juices treated with pulsed electric fields

Article Title: Kinetic Modeling of Microbial Inactivation in Juices Treated With Pulsed Electric Fields (PEF): A Comparative Study on Microbial Heterogeneity and Food Matrix Effects

Article References: Lytras, F., Psakis, G., Xuereb, M., Lia, F., Gatt, R., Raso, J., & Valdramidis, V. (2026). Kinetic Modeling of Microbial Inactivation in Juices Treated With Pulsed Electric Fields ( PEF ): A Comparative Study on Microbial Heterogeneity and Food Matrix Effects. Food Science & Nutrition, 14(10), Article e72408. https://doi.org/10.1002/fsn3.72408

Image Credits: AI Generated

DOI: 10.1002/fsn3.72408

Keywords: pulsed electric fields, food safety, microbial inactivation, kinetic modeling, juice processing, electroporation, non-thermal processing, Escherichia coli, Saccharomyces cerevisiae, sublethal injury, antioxidants, food matrix effects

The motivation behind the work is a genuine public health problem. Raw meat-based diets, particularly those fed to pets, retain their natural nutritional profile and palatability but carry inherent zoonotic risks in the shared living environments of animals and their owners. Regulatory bodies including the U.S. Food and Drug Administration and the American Veterinary Medical Association have warned about pathogen-contaminated raw pet food, yet conventional thermal sterilization destroys the very qualities that make raw diets appealing. High hydrostatic pressure offers an alternative: it transmits pressure uniformly through a product regardless of shape or size, works on sealed packages to prevent recontamination, has regulatory approval in major markets, and preserves heat-sensitive nutrients and flavors.

The study’s experimental design was deliberately broader than most previous work. Earlier investigations typically tested a narrow pressure range of 200 to 400 megapascals and examined either microbial safety or physicochemical quality in isolation. Here, pork samples were artificially contaminated with multiple strains of Escherichia coli, Bacillus cereus, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus, reaching initial populations of roughly 10^5 to 10^8 colony-forming units per gram. Vacuum-sealed samples were then treated in an industrial high-pressure sterilizer maintained at 21 degrees Celsius internally, creating a graduated pressure-time matrix that had never been systematically evaluated for raw pork intended for pet food.

The microbial results were striking and strongly pressure-dependent. Treatment at 500 megapascals for fifteen minutes produced the most pronounced inactivation across all organisms, and Salmonella Typhimurium and Listeria monocytogenes were reduced to below the detection limit during subsequent refrigerated storage. The mechanism is physical rather than chemical: compressive forces deform cell membranes and walls, increase membrane permeability, disrupt intracellular ion balance, dissociate ribosomes, and inactivate enzymes, ultimately collapsing cellular homeostasis. Pressures above 100 megapascals alter the phospholipid bilayer itself, impairing nutrient transport and energy metabolism.

Not every pathogen surrendered equally easily, however, and the species-specific patterns proved scientifically revealing. Although gram-positive bacteria are generally considered more pressure-resistant thanks to their thicker peptidoglycan layers, Listeria monocytogenes, despite being gram-positive, was completely eliminated under the harshest conditions, while Staphylococcus aureus showed the highest resistance of all organisms tested. Staphylococcus possesses a thick, highly cross-linked peptidoglycan layer of roughly 20 to 40 nanometers, and in the most intense treatment group its counts actually increased during storage, suggesting recovery and regrowth from sublethal injury. Bacillus cereus and E. coli also remained detectable under most conditions, with Bacillus spores protected by a multilayered structure that distributes pressure and maintains a dehydrated core stabilized by calcium-dipicolinic acid complexes.

The physicochemical consequences of pressure treatment were equally systematic. As pressure and holding time increased, water-holding capacity, shear force, and pH all rose above control values, while moisture and protein contents increased and fat and ash decreased. The researchers attribute these shifts to pressure-induced denaturation and reorganization of myofibrillar proteins. The non-covalent bonds that maintain protein structure, including ionic bonds, hydrogen bonds, and hydrophobic interactions, are voluminous and unstable under pressure, so when secondary and tertiary structures collapse, myosin partially unravels and exposes polar and charged groups that bind water. The resulting compact protein network traps moisture in a gel-like matrix but also cross-links myosin aggregates, making crack propagation difficult and increasing mechanical strength, which explains the higher shear force.

Color changes followed a nuanced pattern tied to the pigment myoglobin and to light-scattering physics. Lightness increased with pressure and time, redness peaked in the 300 megapascal groups before falling again at 500 megapascals, and yellowness was highest in the 500 megapascal, five-minute group. Previous research has shown that dramatic pressure-induced color changes in meat generally appear only above roughly 400 to 600 megapascals, leaving color largely preserved at lower intensities. The observed paleness here is attributed more to protein denaturation and microstructural changes that enhance light scattering than to straightforward myoglobin oxidation, a combined effect rather than a single pigment transformation.

Oxidation and spoilage chemistry told a two-sided story. Thiobarbituric acid reactive substances, a marker of lipid oxidation, rose with pressure and time, reaching their highest values in the 500 megapascal, fifteen-minute group and climbing further during storage. Pressures between 300 and 700 megapascals disrupt phospholipid membranes and expose lipids to oxygen and pro-oxidants, while structural changes in heme proteins can release iron ions that catalyze oxidative chain reactions. In contrast, volatile basic nitrogen, an indicator of protein decomposition and spoilage, was suppressed by treatment, with the 500 megapascal, five-minute group showing the lowest increase rate during storage at just 13.24 percent compared with 111.72 percent in the mildest group. Microbial inactivation and pressure-induced enzyme inactivation both limit the production of ammonia and volatile amines.

Correlation analysis tied the whole picture together. Pressure and holding time correlated negatively with all tested microorganisms, redness, and volatile basic nitrogen, while water-holding capacity, shear force, pH, lightness, yellowness, and lipid oxidation correlated positively, all consistent with cumulative pressure-induced effects on membranes, myofibrils, myoglobin, and enzymes. The authors conclude that while high hydrostatic pressure effectively inactivated Salmonella and Listeria, enhanced water retention, and suppressed spoilage markers, it also produced a paler appearance, increased lipid oxidation, and failed to achieve complete microbial elimination, with pressure-tolerant organisms surviving or recovering.

The practical takeaway is that pressure treatment should not be deployed as a stand-alone solution. The researchers recommend integrated hurdle strategies, combining pressure with salt addition, antimicrobial agents, optimized packaging, and strict refrigerated storage management, to push microbial safety further while preserving quality. For a food industry increasingly interested in minimally processed products, the study provides something rare: a complete pressure-time map showing exactly where pathogen reduction ends and quality degradation begins, at least for raw pork. As demand for raw pet food and clean-label meats grows, that map may prove one of the most useful tools yet for producers navigating the delicate balance between safety and freshness.

Subject of Research: Effects of high hydrostatic pressure processing on microbial inactivation and physicochemical quality of raw pork

Article Title: Application of high hydrostatic pressure on the microbial and physicochemical characteristics of pork

Article References: Baek, U.-B., & Kim, H.-Y. (2026). Application of high hydrostatic pressure on the microbial and physicochemical characteristics of pork. Food Science of Animal Resources, 46(1), Article 73. https://doi.org/10.1007/s44463-026-00091-8

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00091-8

Keywords: high hydrostatic pressure, food safety, pork, microbial inactivation, non-thermal processing, Salmonella, Listeria monocytogenes, lipid oxidation, myofibrillar protein, water-holding capacity, raw pet food, food science

The review, conducted according to PRISMA guidelines and published in September 2026, searched ScienceDirect, Scopus, and Web of Science for studies published between January 2015 and June 2025. From 327 initial records, the researchers screened 218 full-text articles and ultimately distilled 52 studies that directly addressed UV-C treatment of fresh apples, minimally processed fresh-cut apples, and apple juice. The bibliometric analysis reveals a field that has grown steadily and shifted geographically. Spain leads the world with 11 publications, followed by the United States with 9 and China with 7, and the journal Food Control stands out as the dominant venue, contributing nine articles over the decade. Publication activity peaked in 2015, 2020, and 2021, a rhythm the authors link to real-world shocks: a deadly listeriosis outbreak tied to caramel apples in the United States in 2014 and 2015, and heightened food safety anxieties during the COVID-19 pandemic.

The science behind the technology is deceptively simple. Ultraviolet light spans wavelengths from 100 to 400 nanometers, and the UV-C band, from 100 to 280 nanometers, is the most germicidal because microbial DNA absorbs photons most efficiently in this range, peaking near 260 nanometers. Conventional low-pressure mercury lamps emit roughly 85 percent of their energy at 253.7 nanometers, almost perfectly matching that absorption maximum. When photons strike microbial DNA, they forge pyrimidine dimers, kinks in the genetic strand that block replication and render pathogens harmless. The US Food and Drug Administration has approved UV-C at 254 nanometers as an alternative to thermal pasteurization for juices, provided processors achieve a 5-log reduction, meaning a 99.999 percent kill of target pathogens.

But microbes fight back. Many organisms repair UV damage through photoreactivation, which requires light between 300 and 500 nanometers, or through light-independent nucleotide excision repair. This is where combining UV-C with other treatments, so-called hurdle technology, becomes powerful. Mild heat between 50 and 60 degrees Celsius fluidizes bacterial membranes and disables DNA repair machinery, producing synergistic lethality. In one study, adding the antimicrobial dimethyl dicarbonate before combined UV-C and heat treatment at 55 degrees achieved a 5-log reduction of E. coli in apple juice in just 1.8 minutes, cutting processing time and dose requirements by 44 percent.

On fresh apples themselves, the results are striking. Because apple skins are relatively smooth and less hydrophobic than those of berries or melons, radiation reaches microorganisms more directly. Researchers recorded reductions of 2.9 log units for E. coli O157:H7 and 1.6 log units for Listeria monocytogenes on apple surfaces after applying just 0.92 kilojoules per square meter. Low doses also trigger hormesis, a beneficial stress response in the fruit itself: irradiated apples showed increased phenolic compounds and antioxidant activity while maintaining firmness, soluble solids, and acidity through weeks of storage. Even more remarkably, UV-C fluences of 8.8 and 35.1 kilojoules per square meter degraded patulin, the dangerous mycotoxin produced by P. expansum, eliminating 99.9 percent of the contaminant at the higher dose.

Apple juice presents a tougher optical problem. The liquid is extraordinarily opaque to UV-C, with transmission below 0.01 percent, and 90 percent of radiation is absorbed within the first 0.67 millimeters. Suspended solids, fibers, pigments, and polyphenols scatter and soak up photons, shielding microbes in the liquid’s depths. Industry solutions rely on thin-film reactors that pass juice through gaps of just 2 to 3 millimeters, or on Dean vortex technology, which uses helical tube geometry to create secondary flows that continuously cycle particles toward the lamp. With these engineering fixes, studies report up to 5-log reductions of heat-resistant Alicyclobacillus acidoterrestris spores and significant kills of spoilage yeasts, alongside shelf-life extensions of at least three weeks.

A technological revolution is now underway in the light sources themselves. Ultraviolet light-emitting diodes, or UV-LEDs, are displacing mercury lamps with compelling advantages: they switch on instantly rather than requiring up to 30 minutes to stabilize, last more than 100,000 hours compared with 4,000 to 10,000 for lamps, resist breakage, and contain no mercury, a toxic metal whose disposal is increasingly restricted under the international Minamata Convention. Intriguingly, LEDs at wavelengths near 277 nanometers have inactivated P. expansum spores more effectively than traditional 253.7-nanometer lamps, and 222-nanometer far-UV sources outperformed 254 nanometers against E. coli O157:H7 in juice, possibly because their spectra overlap better with microbial action spectra or because they damage viral proteins faster.

The economics are equally persuasive. Recent analyses suggest UV-C consumes only 6 to 8 percent of the energy of conventional thermal, ohmic, microwave, or high-pressure treatments, and continuous UV-C systems use roughly 39 percent of the energy of thermal pasteurization. Because it is a dry disinfection method, it eliminates the vast wastewater streams generated by chlorine washing, and its low capital cost makes it accessible to small-scale juice producers who could never afford high-pressure processing equipment. Treated juices also retain more flavor, color, and vitamin C than heat-pasteurized counterparts, adding commercial value. Combined approaches amplify the benefits: UV-C with ultrasound achieved a 5-log kill of E. coli O157:H7 in juice in 51.5 minutes versus 77.5 minutes for ultrasound alone, while UV-C paired with peracetic acid completely inactivated E. coli O157:H7 and Listeria on apples in just 5 minutes without harming color or firmness.

Regulation, however, lags behind the science. The United States explicitly permits UV-C at 254 nanometers under 21 CFR Part 179.39, but the European Union has no framework for non-ionizing UV decontamination of food; EU Regulation 2017/2470 restricts UV-C approval to vitamin D enrichment of mushrooms, bread, yeast, and milk. This regulatory asymmetry, the review’s authors argue, hampers trade and slows adoption in a major apple-producing region. They call for internationally harmonized dose standards, validated protocols, and industrial-scale trials to close persistent gaps in the literature, where exposure conditions vary wildly between studies and real processing environments remain underexplored.

The verdict after ten years of research is that UV-C radiation stands as one of the most promising sustainable tools in the apple supply chain, capable of replacing or complementing chlorine while boosting, rather than stripping, the fruit’s natural defenses. Excessive doses do carry risks, from cell membrane rupture and browning to accelerated oxidation, so precision matters. But with LEDs making the technology cheaper, safer, and more flexible than ever, and with consumer demand for minimally processed, additive-free food only growing, the invisible light that unzips microbial DNA may soon be as standard in apple processing as refrigeration itself.

Subject of Research: Use of ultraviolet C radiation for sanitizing fresh apples, minimally processed apples, and apple juice

Article Title: Global Overview of the Use and Effectiveness of Ultraviolet C Technology in Fresh, Minimally Processed Apples and Apple Juice Over the Last 10 Years

Article References: Silva, M. D. P. E., de Azevedo, C. R., Coelho, C. C. D. S., Belas, J. P. R., Soares, A. G., Rosenthal, A., & Freitas‐Silva, O. (2026). Global Overview of the Use and Effectiveness of Ultraviolet C Technology in Fresh, Minimally Processed Apples and Apple Juice Over the Last 10 Years. Food Science & Nutrition, 14(9), Article e72316. https://doi.org/10.1002/fsn3.72316

Image Credits: AI Generated

DOI: 10.1002/fsn3.72316

Keywords: UV-C radiation, apples, apple juice, food safety, Listeria monocytogenes, Penicillium expansum, patulin, UV-LEDs, hurdle technology, non-thermal processing, bibliometric review, food decontamination

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: Yu, R., Park, S.-Y., Rathnayake, P. Y., Yeo, S. E., Nam, C., Cho, H. U., Baek, K. H., & Yong, H. I. (2026). A review of ultrasonic pasteurization in milk and milk-based beverages using different ultrasound systems and thermal conditions: from mechanistic insights to regulatory challenges. Food Science of Animal Resources, 46(1), Article 90. 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