Innovative Dairy Preservation Techniques: Ohmic Heating to PEF

Conventional pasteurization has served the dairy industry well for over a century, but it comes with a trade-off: heat. High temperatures, while effective at killing pathogens, can degrade heat-sensitive vitamins, denature whey proteins, alter flavor, and reduce the nutritional value of milk. Consumers today increasingly demand minimally processed products that retain their fresh-like nutritional and sensory characteristics – and that demand is driving a wave of innovative preservation technologies. From ohmic heating and microwave processing to pulsed electric fields and ultraviolet light, these novel techniques are redefining what it means to safely preserve dairy.

Why traditional thermal processing falls short 🔗

Standard pasteurization methods – whether low-temperature long-time (LTLT) at 63°C for 30 minutes or high-temperature short-time (HTST) at 72°C for 15 seconds – are highly effective at eliminating pathogens. But the heat involved causes measurable collateral damage. The high temperatures applied during conventional heat treatments lead to significant nutritional and sensory losses in milk, such as degradation of vitamins, denaturation of whey proteins, lactose isomerization, decreased calcium bioavailability, and undesirable changes in color, flavor, and texture. Beyond quality, conventional thermal processing also carries negative economic and environmental aspects, including high maintenance costs, low overall efficiency, high water consumption, and significant greenhouse gas emissions. Novel preservation techniques aim to solve these exact problems.

Thermal alternatives: heating smarter, not hotter 🔗

Not all novel techniques are non-thermal. Several innovative methods still use heat – but apply it in far more precise and efficient ways, reducing the thermal damage to the product.

Ohmic heating 🔗

Ohmic heating is an innovative thermal processing method that uses alternating current to heat food products. Electrodes are inserted into the food, and the electric current passes through the product, causing it to heat up internally. Unlike conventional heating where the food surface heats first and the core lags behind, ohmic heating heats the entire product simultaneously and uniformly. It can be used for ultra-high temperature (UHT) sterilization of foods, including those containing large particles up to 2.5 cm that are difficult to sterilize by other means.

The added benefit of ohmic heating is that the electric field itself appears to play a role in killing microbes beyond just heat alone. Research has demonstrated that the electric field of ohmic heating has an additional effect on microbial destruction, meaning the time and temperature required for bacterial inactivation is reduced, thereby minimizing the negative heat effects of pasteurization on food products. According to a review published in Springer’s Food Engineering Reviews, the first industrial application of ohmic heating appeared as far back as 1920, designed specifically to heat milk in continuous flow – and modern advances have significantly expanded its capabilities since then.

Inductive heating 🔗

Inductive heating uses electromagnetic fields to generate heat within the milk itself, rather than through direct contact with a heated surface. This approach delivers rapid and uniform heating without an external heat source in direct contact with the product. The result is energy-efficient processing that minimizes localized overheating and helps retain nutritional and sensory attributes of the milk.

Microwave and radio frequency processing 🔗

Both microwave (MW) and radio frequency (RF) processing use electromagnetic waves to generate internal heat within milk. These technologies allow for rapid volumetric heating, which means the milk reaches target temperatures faster and more uniformly than in conventional systems, reducing the total heat exposure time. Compared with traditional thermal sterilization methods, microwave sterilization is distinguished by rapid and uniform heating, which facilitates the inactivation of pathogens while maximizing the preservation of the food’s nutritional and sensory attributes. Radio frequency heating has also been studied specifically for milk, with research showing effects on quality, safety, and shelf life that are favorable when compared to conventional heat treatment.

Non-thermal techniques: preservation without the heat penalty 🔗

Non-thermal preservation methods are the more radical departure from tradition. These techniques inactivate microorganisms at or near ambient temperatures, largely eliminating the heat-related damage to milk quality.

Ultraviolet (UV) light 🔗

Ultraviolet light, particularly UV-C radiation (wavelengths of 200-280 nm), works by attacking microbial DNA directly. UV-C radiation can be considered an effective method for inactivating pathogenic and spoilage microorganisms in milk and dairy products by forming lesions in DNA and causing damage to cellular enzyme activity and cytoplasmic membrane integrity.

One practical advantage is that UV treatment does not require chemicals, generates no residues, and has low installation and running costs. Shortwave UV light has excellent germicidal properties that can destroy a variety of microbial pathogens – including bacteria, fungi, molds, yeasts, and viruses – with minimal energy use and without the undesirable effects of heat treatment. UV light has even found a unique secondary application in dairy: UV-treated pasteurized cow’s milk was authorized as a novel food in European markets, as UV radiation results in an increase in vitamin D3 concentrations through conversion of 7-dehydrocholesterol to cholecalciferol. The main limitation for liquid milk is its optical opacity – UV light does not penetrate deeply into opaque liquids – which has led to the development of turbulent flow-through reactor designs to maximize exposure.

Pulsed light technology 🔗

Pulsed light (PL) technology takes UV application a step further. Instead of continuous UV radiation, it delivers intense, very short bursts of broad-spectrum white light (including UV-C). Pulsed UV light is produced by accumulating energy in a capacitor and releasing it in short duration pulses in the order of nanoseconds, greatly magnifying the power output, making it more effective at inactivating pathogens than continuous UV light. Pulsed light is applicable mainly in reducing the microbial population on the surface of packaging materials, food products, and other surfaces, extending shelf life and improving product quality. Research has confirmed its effectiveness against pathogens like E. coli O157:H7, Listeria monocytogenes, and Salmonella in milk with minimal taste degradation.

Pulsed X-rays 🔗

Pulsed X-ray technology applies short bursts of ionizing radiation to inactivate microorganisms in dairy products. Similar in principle to pulsed light but using higher-energy ionizing radiation, pulsed X-rays can penetrate packaging and liquid matrices more deeply than UV light. The U.S. Food and Drug Administration has identified pulsed X-rays among the alternative food processing technologies being evaluated for microbial inactivation, recognizing that alternative mechanisms of microbial destruction may require different kinetic models than those used for thermal processing. While still largely at the research stage for dairy applications, pulsed X-ray technology holds potential for surface and package decontamination.

Oscillating magnetic fields (OMF) 🔗

Oscillating magnetic fields are among the non-thermal processes that have been developed for dairy preservation. By inactivating bacteria at near-ambient temperatures, these processes keep food’s sensory and nutritional quality while preventing thermal degradation of food components. OMF works by exposing the food to rapidly alternating magnetic fields, which disrupt microbial cellular functions. Oscillating magnetic fields were recognized as an emerging non-thermal technology that retains the nutritional quality of food – including vitamins, minerals, and essential flavors – while consuming less energy than thermal processing. Though still an emerging tool in the dairy space, OMF is considered part of the broader toolkit of electromagnetic non-thermal preservation strategies.

Ultrasound energy 🔗

Ultrasound consists of the propagation of sound waves greater than 20 kHz through air, liquid, or solid media, generating cycles of high and low pressure; in liquid media, it leads to the cavitation of microbubbles. It is this acoustic cavitation – the violent collapse of microscopic bubbles – that physically disrupts and destroys microbial cells. Ultrasound has a dual role in dairy: it can serve as a homogenization tool as well as a preservation treatment. Ultrasound-assisted processing facilitates the extraction of bioactive compounds and simultaneously minimizes changes to the nutritional content of the food product.

Research published in MDPI’s Foods journal confirms that when ultrasound is combined with downstream pasteurization technologies like PEF, microwaves, or high hydrostatic pressure, the sequential treatment improves both the microbiological safety and the shelf-life extension of the milk compared to either method alone.

Pulsed electric fields (PEF): the leading non-thermal contender 🔗

Among all the novel preservation techniques discussed, pulsed electric fields (PEF) have attracted the most extensive research attention – and with good reason. Among all nonthermal technologies, PEF treatment is considered one of the most promising and versatile, with a wide variety of applications ranging from liquid or semisolid foods to solid foods for all sorts of purposes.

PEF treatment consists of exposing food to electrical fields between electrodes within a treatment chamber, which can improve the preservation of fresh-like products such as milk. The mechanism is called electroporation: the electrical breakdown of the microbial cell membrane causes it to act as a capacitor filled with a dielectric medium, and the resulting membrane rupture inactivates the microorganism, without the thermal load of conventional pasteurization.

How PEF works 🔗

The essential standard of the PEF technique is the utilization of small pulses of elevated electric fields within the period of micro to milliseconds, with field strengths ranging from 10-80 kV/cm. In this method, pulsed electrical current is transmitted to the product located between a pair of electrodes, and the applied high voltage produces an electric charge that results in destruction of microorganisms. Post-treatment, the food is aseptically packed and stored under refrigeration.

PEF and milk quality 🔗

One of PEF’s most compelling advantages is what it does not do to the milk. PEF-treated milk shows significant retention of major nutrients such as proteins, minerals, and vitamins, with minimal effect on texture, taste, and color, as well as maintained fat globule structural stability. PEF also enhances the technological properties of milk proteins – including solubility, gelation, and emulsification – without causing significant structural changes.

When combined with mild heating (below pasteurization temperatures), PEF performance improves substantially. Combining PEF with mild heating has been explored as an alternative processing technology to enhance the safety and preserve the quality of fresh milk and milk products, achieving 3 to 6 log₁₀ cycle reductions in microbial load and a drastic impact on enzyme activity. Research on goat milk has confirmed that employing PEF as a pre-heating process significantly reduces the heating energy requirements in thermal treatment by approximately three times, resulting in substantial water vapor conservation and reducing the workload and costs associated with boilers.

Challenges to PEF commercialization 🔗

Despite its promise, PEF is not yet mainstream in dairy processing plants. Several factors such as high capital investment, changes to conventional layouts of milk processing plants, and requirements to optimize PEF conditions for specific product applications have prevented the industry from more widely investing in PEF equipment. Additionally, issues related to regulatory aspects, toxicity risks, and consumer acceptance need to be addressed. These remain active areas of research and policy discussion worldwide.

The bigger picture: hurdle technology and hybrid approaches 🔗

Increasingly, researchers and dairy processors are moving toward combining multiple preservation techniques – an approach known as hurdle technology. The integration of multiple technologies promises synergistic benefits in both quality and safety. Furthermore, using digital tools such as big data analytics and artificial intelligence will fine-tune processing methods, ensuring reliable nutritional quality. For example, applying ultrasound for homogenization followed by PEF or microwave pasteurization delivers better microbial reduction and better quality retention than either method alone. Scientific literature has documented the performance of ohmic heating, microwaves, radio frequency, high pressure, pulsed electric field, and ultrasound collectively – highlighting their effectiveness in destroying microorganisms, inactivating enzymes, and avoiding damage to milk components during storage.

The dairy industry is at an inflection point. As consumer preferences, sustainability goals, and food safety standards all intensify simultaneously, the shift from purely thermal to smart, combined, and minimally invasive preservation is not a matter of if – but when. Each of the novel techniques outlined here offers a distinct mechanism of microbial inactivation, specific advantages, and specific constraints. The future of dairy preservation will likely not rest on any single technology, but on the intelligent combination of several.

What do you think? As dairy producers face pressure to reduce energy use and deliver more nutritious products, which of these novel preservation techniques do you think is most ready for wide-scale commercial adoption – and what would it take to get there? If you were designing a dairy processing facility today, would you invest in a non-thermal technology like PEF, or would you opt for an improved thermal approach like ohmic heating?

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