Using Radio Frequency to Target Microbial Pathogens

“A brand recall is death,” says Arthur de Cordova, CEO and Co-founder of Ziel.

Cannabis flower has to pass microbial testing before it can be sold, and the options for getting it there fall into two families. Ionizing radiation and Non-Ionizing radiation. Ionizing radiation, meaning gamma, X-ray, and e-beam; these penetrate the flower and kill mold and pathogen DNA while removing electrons from the atoms and molecules of the flower, and that molecular change nullifies the natural integrity of the flower. Radio frequency is the non-ionizing alternative. It is a thermal process that harnesses the moisture already inside the bud, and it leaves the organoleptic qualities essentially unchanged.

From Food to Cannabis

Ziel did not start in cannabis. The company commercialized radio frequency technology developed at the University of California, Davis in 2008, under the name RF Biocidics, and spent its early years pasteurizing tree nuts before adding seeds, dates, and prunes.

“Ten years ago, we were approached by a large operator out of Colorado,” Arthur says. “They had just been notified by the state authority that they were going to implement microbial testing.” Nothing on the market addressed the problem, and the equipment Ziel had was built for a different scale entirely.

“Being in the food space, our machines require these long radio frequency tunnels with conveyor belts that process 2,000 lb an hour, which weren’t particularly suitable for cannabis,” Arthur explains. “So, we developed a machine that would carry out batch processes.”

That first-generation unit is still in operation after ten years. In 2023 Ziel launched its successor at MJBizCon, and that machine is the RFX, which replaced the APEX 7 and was built on the lessons of a decade of APEX 7 commercial operation. Reconditioned APEX 7 units are still available, and Ziel says they carry the same throughput and efficacy as the current generation machine. Ziel machines now run on five continents, and on the cannabis side that means the US and Canada along with the European medical markets, including Portugal, Germany, and North Macedonia.

Testing in the US

Microbial testing in Europe and the US work differently, and the US is the more complicated of the two. Cannabis is not federally legal, so there are no standardized testing requirements, and each state has developed its own guidelines on maximum allowable microbial content.

Three pathogens are tested in essentially every state: Aspergillus, Salmonella, and E. coli. Past those three, each state adds what it wants, whether that is total yeast and mold count, total aerobic count, coliforms, or bile-tolerant gram-negative bacteria. Washington, Massachusetts, New Mexico, New York, Illinois, and Ohio are among the states requiring the BTGN test. Canada requires it too.

So Ziel tailors the batch process to each cultivator’s bioburden and state’s requirements. “If a grower comes to us saying that they are going to grow in Colorado, we have recipes for those specific microbials,” Arthur says. “If someone is in Michigan, we review the regulations and provide the grower with the appropriate decontamination recipes.”

The process itself is straightforward to run. The operator loads flower into a Ziel-compliant bag and places the bag in the machine; an electromagnetic field forms, and the radio waves reach the moisture at the center of the bud rather than treating the surface. Heat does the work. So it has to be controlled.

“To kill the most heat-tolerant pathogens, the temperature may need to reach 95 degrees Celsius,” Arthur explains. “However, it doesn’t need to remain at that temperature for long. Our machine reaches it for a split second, ensuring the targeted microbes are destroyed while preserving product integrity.” The SOP then calls for the bag to be opened as soon as it leaves the machine and the flower transferred to a second bag, so the temperature drops quickly.

An RFX cycle averages 14 minutes and treats 1.3 to 2.5 kg, roughly 2.8 to 5.5 lb, which works out to about 160 lb across an eight-hour shift at around 16 cents of electricity per pound. Arthur has put the radio frequency process at five times faster than performing the same process with an X-ray machine. X-ray equipment also has to be cooled, requiring the same amount of downtime as machine uptime, and needs chiller hardware installed alongside it, while the RFX runs 24 hours a day.

The Techniques Now Have a Standard Behind Them

One thing has changed since this post first ran. In May 2025, ASTM International published D8575-25, the Standard Guide for Techniques to Lower Microbial Load of Post-Harvest Inflorescence of Cannabis and Hemp, the first standard guide for microbial control in post-harvest cannabis and hemp.

Ziel’s VP of Scientific and Regulatory Affairs, Parastoo Yaghmaee, was one of the experts who helped with the research behind it. She joined ASTM International in 2020, after the Cannabis Committee, D37, was established, and in 2021 the subcommittee formed to develop the guide. Each expert wrote the technology they knew best. Parastoo took radio frequency. The guide describes gamma and e-beam, ozone, UV, non-ionizing radio frequency, and less common options such as steam pasteurization, and it does not specifically endorse any of them. That is what a guide is for.

Testing in Europe

Europe runs the opposite model. The EU oversees medical cannabis, cultivation happens in GACP-validated facilities, and post-harvest processing happens in GMP-validated facilities. Testing standards are country mandated, based on Pharmacopoeia standards.

Ziel reached a milestone here in May 2024, when its partner Portocanna, a medical cannabis processor in Portugal, received GMP validation for decontaminating cannabis flower with Ziel radio frequency technology. It was the first EU GMP approval for radio frequency microbial control in cannabis, and Portocanna runs a 3,000 sqm EU GMP-certified facility with 25 proprietary cultivars registered to its name.

It is worth being precise about what that covers. Holding GACP and GMP validation does not make a specific machine GMP-certified, because a GMP-validated facility applies to the documented equipment and the corresponding SOPs of that facility. “Our units installed in European GMP facilities have all received their GMP certification,” Arthur explains. “When we collaborate with European growers, we also provide GMP documentation to streamline their GMP application process; it’s a standard procedure for equipment in the pharmaceutical industry.”

There is a second consideration in Europe that rarely gets raised at trade shows. Germany’s AMRadV rules require an operator to license every cannabis strain treated with ionizing radiation before that strain can be sold, at approximately €5,000 per cannabis cultivar, with a typical approval timeline of 6–12 months and potentially up to 18 months. Radio frequency carries no such requirement.

Underneath every one of those decisions sits a record of what the machine did. “We are data-driven people,” says Arthur. “All the machine data from cycles run in our machines is recorded and saved in the cloud. We then reconcile that data against the returned Certificates of Analysis.”

The dashboard was built for strain variability, since not every cultivar responds the same way to a kill step. One may be more sensitive to decarboxylation. Another may fail state testing at settings that clear everything else in the room. The dashboard shows which strains are more prone to mold and pathogens, monitors SOP adherence, and can predict when a product will fail testing, and recipes get adjusted per cultivar when a pattern appears. Flower held at 8 to 12% moisture passes microbial compliance testing more than 99% of the time.

“We are well prepared for what’s to come in the EU,” Arthur points out. “We are investing more resources there to better serve the European medical cannabis space with safe and organic-compliant decontamination solutions.”