The review, led by researchers from Johns Hopkins Bloomberg School of Public Health and collaborators across Australia, Canada, South Africa, the United States, and the United Kingdom, followed Joanna Briggs Institute guidelines and the PRISMA-ScR reporting checklist. The team searched PubMed, Scopus, CINAHL, Embase, and Web of Science, supplemented by grey literature from organizations such as the World Health Organization and PATH, along with forward citation searching. From 7,030 records identified, 24 studies published between 2005 and 2025 met the inclusion criteria. Two independent reviewers screened and extracted data using Covidence software, evaluating each study against three domains: microbiological safety, preservation of nutritional and immunological components, and feasibility in low-resource and outbreak settings.

Flash-heating was originally developed more than two decades ago to give HIV-positive mothers in resource-limited settings a way to eliminate the risk of transmitting the virus through breastmilk. The method is deliberately low-technology. Fifty to one hundred twenty milliliters of expressed milk are placed in an uncovered 450-milliliter glass food jar, which is set inside a one-to-two-liter pan containing roughly 450 milliliters of water, with the water level standing two fingers above the milk line. The pan is heated over an electric hot plate or gas stove until the water reaches a rolling boil at 100 degrees Celsius, at which point the jar is immediately removed and rapidly cooled in a cool water bath. The approach is designed to approximate the conditions of high-temperature short-time pasteurization, the industrial standard that holds milk at 72 degrees Celsius for 15 seconds, but using only common household equipment.

The microbiological evidence assembled in the review is encouraging. Field and clinical studies demonstrated that flash-heating substantially reduces common bacterial contaminants of breastmilk, including Escherichia coli, Staphylococcus aureus, and Group B Streptococcus, organisms frequently introduced through handling or maternal mastitis. Although Staphylococcus aureus is relatively heat-tolerant, significant reductions in bacterial load were observed, though complete growth inhibition was not consistently achieved. On the viral side, flash-heating reduced HIV viral load in breastmilk, affecting both cell-free and cell-associated virus, a finding consistent with the known heat sensitivity of lipid-enveloped viruses. Laboratory studies of high-temperature short-time treatment, used as contextual evidence, indicate that most vegetative bacteria and enveloped viruses are readily inhibited at temperatures around 72 degrees Celsius, whereas non-enveloped viruses such as porcine parvovirus show marked heat resistance, suggesting that similar pathogens may be less susceptible to brief heat exposure.

Notably, the review uncovered a significant methodological gap: in half of the studies investigating flash-heating and pathogen inactivation, the temperature of the breastmilk itself was never directly measured. Instead, researchers assumed the milk had reached 72 degrees Celsius for 15 seconds based on the protocol. Temperatures achieved varied between studies, and contextual factors such as altitude and heating rates may influence the actual temperatures reached, potentially affecting pathogen inactivation. This variability complicates comparisons across the evidence base and underscores the need for standardized protocols with direct temperature monitoring.

On the nutritional side, the picture is largely reassuring. Flash-heating had no negative impact on total carbohydrates and fat content, and micronutrients including vitamins A, B1, B6, B12, and E were well preserved with little to no loss. Vitamin B2 retention ranged from 59 to 100 percent, vitamin C from 39 to 100 percent, and folate from 76 to 100 percent, depending on the specific procedure used. Total oligosaccharides, the largest sugar component of human milk and a critical fuel for the infant gut microbiome, were completely preserved. The one clear casualty was lipase activity, the enzyme important for fat digestion in infants, which was almost completely destroyed by heat treatment, as expected.

Immunological components fared less uniformly. Immunoglobulins IgA and IgG were preserved to a moderate degree, with retention ranging from 25 to 80 percent depending on peak temperature and the volume of milk heated. Cytokines IL-8 and IL-10 were well preserved, with retention approaching 100 percent. In contrast, lactoferrin concentrations dropped to between 16 and 30 percent of original levels, and lysozyme concentrations fell to between 21 and 60 percent. Interestingly, the bactericidal activity of both lactoferrin and lysozyme was relatively better preserved than their concentrations, with lactoferrin activity retention ranging from roughly 39 to 89 percent and lysozyme activity from 43 to 78 percent. Compared with high-temperature short-time pasteurization, flash-heating resulted in greater reduction of immune components overall, though at least one-third of most immunological factors remained intact.

The feasibility data, drawn almost entirely from the HIV context, offer a glimpse of how the technique performs in real households. In Tanzania, 51.4 percent of HIV-infected mothers who received home-based infant feeding counseling initiated flash-heating over a six-month period, practicing it for an average of 9.6 weeks regardless of age, religion, parity, or education. In rural Zimbabwe, 20 HIV-infected mothers adopted the method for a mean duration of 4.5 months with nurse support, achieving peak milk temperatures of 79.3 to 80.5 degrees Celsius. The technique was implemented using readily available household materials, including glass jars, aluminum pans, cups, and common fuels such as kerosene and charcoal, with heated water often reused for cooking or bathing. Reported barriers included difficulties with expressing breastmilk, fuel shortages, conflicting guidance from health workers, and limited familiarity with heating practices, while facilitators included peer counselor support, household backing from husbands, low-cost materials, and perceived benefits for infant health.

The authors emphasize that the choice in an outbreak is not between flash-heating and a risk-free alternative, but between flash-heating and the known, well-documented risks of commercial milk formula and other substitutes in low-resource settings. Breastmilk retains a wide range of bioactive components even after heat treatment that are absent from artificial substitutes, including hundreds of oligosaccharides and prebiotic sugars that support commensal gut bacteria, inhibit pathogen adhesion, and modulate immune responses. Formula feeding, by contrast, makes infants susceptible to pathogen colonization through disruption of the intestinal mucosa. Global guidance from the World Health Organization and the Operational Guidance on Infant and Young Child Feeding in Emergencies already prioritizes mother’s own expressed milk and donor human milk before commercial substitutes, yet gaps remain in operationalizing these frameworks when breastfeeding is interrupted by outbreaks.

Looking forward, the review calls for research on a broader range of outbreak-relevant pathogens, including Ebola virus, cytomegalovirus, and Zika virus, along with standardized protocols defining heating duration, target temperature, and acceptable variability. Simple, low-cost tools such as thermometers placed directly in the milk, or calibrated devices like the FoneAstra and PiAstra monitors already shown to be effective, could support consistent application. Future work must also examine the full operational pathway, from safe expression and heating through post-heating handling and storage, with particular attention to the risk of recontamination after treatment. Long-term safety, clinical outcomes, infant growth, and effects on the gut microbiota remain unexplored. Strengthening this evidence base, the authors conclude, will be essential to support clear, context-sensitive public health recommendations that keep human milk at the center of infant feeding, even in the most challenging outbreak conditions.

Subject of Research: Flash-heating of expressed breastmilk as a low-cost pasteurization method for pathogen inactivation and nutrient preservation during infectious disease outbreaks

Article Title: A scoping review of microbiological safety, bioactive components, nutrient retention, and feasibility of flash-heating expressed breastmilk: exploring potential use during infectious disease outbreaks

Article References: Natalia, H., Guzman, C., Borg, B., Chase, J., Coutsoudis, A., Israel-Ballard, K., Gribble, K., Koniz-Booher, P., & Ververs, M. (2026). A scoping review of microbiological safety, bioactive components, nutrient retention, and feasibility of flash-heating expressed breastmilk: exploring potential use during infectious disease outbreaks. Frontiers in Nutrition, 13, Article 1926806. https://doi.org/10.3389/fnut.2026.1926806

Image Credits: AI Generated

DOI: 10.3389/fnut.2026.1926806

Keywords: flash-heating, breastmilk, pasteurization, infectious disease outbreaks, pathogen inactivation, immunoglobulins, human milk oligosaccharides, HIV, infant feeding, low-resource settings, emergency nutrition, scoping review

The Academy did not stop at advising families to avoid raw dairy. It renewed its call for a ban on the sale and distribution of raw milk and raw milk products, including raw cheeses, arguing that their consumption increases the risk of life-threatening infections. The policy statement also directly confronts one of the most persistent marketing claims surrounding raw milk: that it offers superior health benefits compared with pasteurized products. According to the Academy, those claims are not supported by scientific evidence. Pasteurization, a process of heating and then cooling milk that has been in use for more than a century, dramatically reduces the risk of infection without stripping away the nutritional value that families rely on from dairy.

The numbers behind the Academy’s concern are striking. Lead author Adam J. Ratner, MD, MPH, FAAP, noted that nearly half of illnesses caused by raw dairy consumption occur in people under the age of 20, and that a significant share of those cases are in children under 5. These illnesses, he emphasized, can be severe and can lead to life-threatening complications. The vulnerability of young children is not incidental: their immune systems are still developing, their body weight is small relative to the dose of pathogen they may ingest, and complications such as severe dehydration from diarrheal illness or kidney failure from certain strains of E. coli can escalate quickly in pediatric patients.

Unpasteurized milk is a well-documented carrier of some of the most dangerous foodborne pathogens known to medicine. The policy statement lists Listeria, E. coli, Salmonella, Campylobacter, and Brucella among the serious organisms transmitted through raw dairy. Each of these bacteria can cause hospitalization, life-threatening illness, miscarriage, or death, and the risks are concentrated in young children, pregnant people, and individuals with weakened immune systems. Listeria monocytogenes is particularly formidable because it can grow even at refrigerator temperatures, meaning contaminated dairy stored properly in a home kitchen can still become more dangerous over time. Salmonella and Campylobacter are among the most common causes of bacterial gastroenteritis worldwide, while Shiga toxin-producing E. coli can trigger hemolytic uremic syndrome, a condition that destroys red blood cells and can cause kidney failure in children.

Pregnant people face especially high stakes from foodborne infection. The policy statement notes that the incidence of listeriosis is estimated to be 12 to 14 times higher during pregnancy than in the general population, a reflection of the immune changes that pregnancy induces. Listeria infection during pregnancy can result in miscarriage, stillbirth, premature delivery, or severe illness in newborns, outcomes that make even a low probability of contamination unacceptable from a public health standpoint. Because Listeria can cross the placenta, a mother may experience mild or even unnoticed symptoms while the fetus suffers devastating consequences. This asymmetry between maternal illness and fetal harm is a central reason obstetric and pediatric guidelines consistently single out unpasteurized dairy as a food to avoid entirely during pregnancy.

The most consequential update in the new statement concerns H5N1, the highly pathogenic avian influenza virus that has swept through poultry populations globally and, beginning with the 2024 United States dairy cattle outbreak, demonstrated an ability to infect cows. The Academy highlights emerging evidence that H5N1 may represent a new and potentially serious risk associated with raw milk. Research indicates the virus can be transmitted from infected dairy cattle into milk, where it can reach high concentrations and remain detectable in refrigerated raw milk for up to five weeks. That persistence is unusual and troubling: a virus surviving for more than a month in a chilled, nutrient-rich medium has ample opportunity to reach consumers, especially in distribution chains that lack pathogen testing.

During the 2024 U.S. dairy outbreak, infectious H5N1 virus was detected in nearly one-quarter of raw milk samples in affected areas. To date, there are no confirmed human cases of H5N1 infection resulting from the consumption of raw milk, and the Academy is careful to state this. Nevertheless, it characterizes the virus as a credible, emerging threat. The distinction between documented transmission and credible risk is important in virology: influenza viruses are capable of crossing species barriers, and the mammary gland infections observed in dairy cattle established a novel route by which a respiratory pathogen of birds could contaminate a staple food. Pasteurization, which inactivates influenza viruses effectively, closes that route for conventional dairy, but no such barrier exists for raw products.

The regulatory landscape in the United States remains fragmented. Despite the well-documented health risks, the sale and distribution of raw milk products remain legal in at least 27 states. Raw milk is defined as milk obtained from cows, goats, or sheep that has not undergone pasteurization, the heating process designed to eliminate harmful bacteria and other pathogens. Federal law prohibits the interstate sale of raw milk for human consumption, but intrastate sales fall under state jurisdiction, producing a patchwork in which a family’s exposure to raw dairy risk depends largely on geography. The Academy’s renewed call for a ban on sale and distribution is aimed squarely at this patchwork, arguing that voluntary warnings have not eliminated a preventable source of severe illness.

The scientific case for pasteurization rests on both microbiology and nutrition. The process typically involves heating milk to a temperature sufficient to inactivate vegetative bacterial pathogens and enveloped viruses, followed by rapid cooling to slow the growth of any surviving organisms. Decades of comparative studies have found no meaningful nutritional deficit in pasteurized milk relative to raw milk; the proteins, calcium, and vitamins that make dairy a dietary staple survive the treatment essentially intact. What pasteurization removes is the microbial load, including organisms that may be present even in milk from healthy-appearing animals, since udder infections and fecal contamination during milking can introduce pathogens without any visible sign. Co-author Mark R. Corkins, MD, FAAP, addressed the perception gap directly, saying that parents may choose raw milk because they have heard it is healthier or more natural, but that the scientific evidence tells a different story. Pasteurized dairy products, he said, provide the same essential nutrients without exposing children and families to preventable infections from dangerous bacteria and viruses, and for infants, children, and pregnant people they are clearly the safest choice.

The policy statement was developed through the Academy’s standard process, in which statements written by medical experts reflect the latest available evidence and undergo several rounds of peer review before approval by the AAP Board of Directors and publication in Pediatrics. It will be featured during a presentation on October 5 at the AAP 2026 National Conference and Exhibition in San Diego, where Dr. Ratner is scheduled to discuss the policy during a Meet the Red Book session at the San Diego Convention Center. For families navigating conflicting claims about raw dairy, the Academy has also published a consumer-facing resource, “Raw Milk: What Parents Need to Know About the Risk,” through its HealthyChildren.org platform. The core message of the updated guidance is unambiguous: whatever the appeal of raw milk on the shelf, the pathogens it can carry, from Listeria and E. coli to a potentially pandemic-capable influenza virus, are preventable hazards, and pasteurization remains one of the most effective and time-tested public health interventions in the food supply.

Subject of Research: Health risks of unpasteurized (raw) milk and dairy products for children and pregnant people, including emerging H5N1 avian influenza contamination

Article Title: American Academy of Pediatrics warns of dangers in consuming raw milk, dairy products

Article References: American Academy of Pediatrics warns of dangers in consuming raw milk, dairy products. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: raw milk, pasteurization, American Academy of Pediatrics, H5N1 avian influenza, foodborne illness, Listeria, E. coli, Salmonella, pregnancy, children's health, dairy cattle, public health policy

The enzyme, named BWbg1, belongs to a class of proteins known as beta-galactosidases, which catalyze the cleavage of lactose, the disaccharide sugar that makes up a large fraction of the solids in milk, into its two component monosaccharides, glucose and galactose. Beta-galactosidases have long occupied a central place in dairy biotechnology because they support two distinct and commercially significant applications. The first is the production of low-lactose and lactose-free milk and dairy goods for the large population of people who cannot properly digest lactose. The second is the synthesis of galacto-oligosaccharides, or GOS, through transgalactosylation reactions in which the enzyme, instead of simply splitting lactose, stitches galactose units together into short chains that humans cannot digest but that beneficial gut bacteria eagerly consume.

What makes BWbg1 stand out in a crowded field of known beta-galactosidases is its thermal profile. The purified enzyme exhibits maximum activity at 80 degrees Celsius and at a neutral pH of 7, a combination that immediately distinguishes it from the mesophilic enzymes traditionally used in dairy processing. It also demonstrates impressive resilience, retaining more than 72 percent of its activity after six hours of incubation at 55 degrees Celsius. For industrial operators, these are not merely laboratory curiosities. Elevated operating temperatures increase the initial productivity of enzymatic reactions, improve the solubility of substrates such as concentrated lactose solutions, and dramatically reduce the risk of contamination by spoilage and pathogenic microorganisms, which struggle to proliferate at temperatures that the enzyme tolerates with ease.

The path to BWbg1 illustrates the power of functional metagenomic screening, a technique that has become one of the most productive strategies in modern bioprospecting. Rather than trying to culture the microorganisms from the As Burgas hot spring, an approach that would capture only a small fraction of the community because most environmental microbes resist laboratory cultivation, the researchers extracted the collective DNA of the entire microbial ecosystem and cloned it into a metagenomic library. They then screened that library for clones exhibiting beta-galactosidase activity, allowing the function of the gene itself, rather than any prior knowledge of the organism that carried it, to guide the discovery. Sequence analysis of the protein encoded by the recovered gene revealed that BWbg1 belongs to glycoside hydrolase family 35, a well-characterized group of enzymes, yet its properties proved distinctive enough to warrant the label of novelty.

The enzyme’s performance in GOS synthesis is arguably its most commercially compelling feature. Working with a concentrated lactose solution of 40 percent weight per volume at 70 degrees Celsius, BWbg1 converted the substrate into a product mixture containing up to 48 percent galacto-oligosaccharides by weight over a four-hour reaction. That yield, achieved at a temperature at which most conventional enzymes would rapidly denature, positions BWbg1 as a serious candidate for industrial prebiotic production. GOS are among the most widely added prebiotics in infant formula and functional foods, valued for their ability to selectively stimulate the growth of beneficial bacteria such as Bifidobacteria in the gut. A thermostable enzyme that can sustain high-yield synthesis at 70 degrees Celsius offers manufacturers both faster throughput and a substantially lower microbial contamination risk during extended production runs.

Perhaps the most surprising finding, however, concerns what happens when the enzyme is exposed to heat before it is asked to work. The researchers observed a remarkable heat activation effect: after two hours of incubation at 65 degrees Celsius, BWbg1’s ability both to hydrolyze lactose and to produce GOS was enhanced rather than diminished. This behavior has direct implications for how the enzyme could be deployed in real dairy plants. Milk destined for the market is routinely pasteurized, and the two dominant methods are HTST, high-temperature short-time pasteurization, and VAT, the older vat pasteurization approach that uses lower temperatures over longer holding periods. The study demonstrated that BWbg1 retains its activity after both HTST and VAT pasteurization of commercial milk, and that the heat activation it experiences during these treatments actually improves its subsequent performance on the lactose in the milk.

This compatibility with pasteurization regimes is a genuinely practical advantage. In current industrial practice, lactose hydrolysis is typically performed as a separate step after pasteurization, requiring additional equipment, time, and careful hygiene controls. An enzyme that can be added to milk, survive the pasteurization step itself, and then go on to work more effectively afterward could allow manufacturers to merge two processing stages into one streamlined operation. The enzyme’s tolerance of the exact thermal conditions used to make milk safe for consumers means that the same heat treatment that protects public health simultaneously primes the biocatalyst for action, a coincidence of process requirements that enzyme engineers usually struggle to achieve by design.

Equally noteworthy is the enzyme’s behavior at the opposite end of the temperature scale. The study reports that BWbg1 remains capable of hydrolyzing lactose from commercial milk and producing GOS even at 8 degrees Celsius, a temperature within the range of standard refrigerated storage. This cold activity opens the door to applications in which milk is treated during chilled logistics or storage, extending the enzyme’s usefulness well beyond the hot processing floor. A single biocatalyst that functions productively from refrigeration temperatures up to 80 degrees Celsius spans a thermal range that few, if any, commercially established beta-galactosidases can match, and it gives process designers an unusual degree of freedom in choosing where and when in the production chain to deploy it.

The broader significance of the work lies in what it says about the untapped enzymatic wealth of extreme environments. Hot springs have long been recognized as reservoirs of thermostable proteins, because the microorganisms adapted to life at elevated temperatures must maintain enzymes that keep their structure and function under conditions that would destroy the proteins of ordinary organisms. Yet the vast majority of these thermophilic communities remain genetically uncharacterized, and functional metagenomics offers a way to access their catalytic repertoire without ever growing a single cell in the laboratory. The As Burgas spring, flowing through a geologically active region of Galicia, proved to be a productive hunting ground, and the researchers suggest that BWbg1’s versatility, spanning lactose hydrolysis, GOS synthesis, pasteurization compatibility, and cold-temperature activity, makes it a strong candidate for industrial application.

For consumers, the practical outcome of such research is tangible. Lactose intolerance affects a substantial share of the global population, and demand for lactose-free dairy continues to climb, while the market for prebiotic ingredients that support gut health grows in parallel. An enzyme that can serve both markets, converting milk into a digestible product for one consumer group and into a GOS-enriched functional food for another, addresses two major trends in food science with a single biocatalyst. As the team’s results demonstrate, the answer to some of the dairy industry’s most persistent processing challenges may have been waiting all along in the steaming waters of a Spanish hot spring, encoded in the genomes of microbes no one has ever cultured.

Subject of Research: A thermostable GH35 beta-galactosidase from a hot spring metagenome for lactose hydrolysis and galacto-oligosaccharide production in milk

Article Title: A novel thermostable beta-galactosidase for low-lactose and galacto-oligosaccharide-rich milk

Article References: DeCastro, M.-E., Becerra-Fernández, M., Rodríguez-Belmonte, E., & González-Siso, M.-I. (2026). A novel thermostable beta-galactosidase for low-lactose and galacto-oligosaccharide-rich milk. Applied Microbiology and Biotechnology. https://doi.org/10.1007/s00253-026-14045-z

Image Credits: AI Generated

DOI: 10.1007/s00253-026-14045-z

Keywords: beta-galactosidase, metagenomics, thermostable enzyme, galacto-oligosaccharides, lactose-free milk, hot spring, bioprospecting, dairy biotechnology, prebiotics, pasteurization, GH35, transgalactosylation

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