Saving the planet and reducing carbon footprints are all well and good, but cutting costs moves technology from “that’s nice” to “that’s for me.” By that measure, the use of compact, modular electron beam emitters is must-have technology for sterilizing beverage packaging.
Tzvi Avnery applied for his first of 22 patents surrounding low-power e-beam 12 years ago. Instead of relying on large pumps to create a vacuum inside a chamber, Avnery bundled an electron generator inside a permanently sealed chamber with an e-beam exit window. Ultra-thin titanium foil with a thickness of about 6 microns forms the window. The beauty of Avnery’s miniaturized design, besides cost magnitudes less than a conventional emitter, is the simplified maintenance. Instead of replacing filaments or exit windows periodically, users replace the entire unit, eliminating downtime and the need for maintenance personnel with expertise in vacuum and accelerator technology. And while beam intensity is insufficient to pasteurize food, it is effective at either forming chemical bonds or breaking them. This has helped the technology find commercial applications in drying and curing as well as sterilizing materials.
Firms like Baxter International and Johnson & Johnson have embraced e-beam to sterilize medical devices and pharmaceutical materials. Now Avnery’s firm, Advanced Electron Beams Inc. (AEB), is training its sites on food and beverage packaging. Eliminating chemicals and rinse water from the material-preparation process makes the case for sustainability, but lower operating costs are a more compelling argument for adoption. Helping to tell the economic and environmental story is Anne L. Testoni, director of marketing applications. Testoni joined AEB three years ago. She is the inventor or co-developer of eight patented analytical tools, most involving e-beam or X-ray to detect imperfections in semiconductor wafers. After earning undergraduate degrees in chemistry and mathematics at the University of Dayton, Testoni received a doctorate in chemical physics from Northwestern University.
FE: How does electron beam for package sterilization differ from e-beam for food pasteurization or sterilization?
Testoni: The high-energy systems to treat food are the size of a room and are housed in a large building, which means products have to be treated in a central location. If a slab of meat 6 inches thick is being treated, a large integrated dose of electrons needs to be delivered to penetrate it.
Our emitters are low energy and only penetrate to about 200 microns. Instead of shipping product to and from a facility, our customers put modular devices right on their processing lines. The units are small enough to integrate in an HVAC system to purify return air. We fabricate two sizes of emitters, with the larger unit measuring about 2 feet long and weighing about 40 lbs. They can be plugged into conventional industrial electrical service.
FE: How is it used in food and beverage?
Testoni: Three years ago, a customer outside the US began using e-beam to sterilize caps in an aseptic juice filler, as well as the air around the capping operation. Since then, we’ve applied the technology to pouches, PET containers and all types of equipment surfaces.
Typically we don’t sell emitters directly to end-users. We work with OEM partners such as Shibuya, which makes aseptic fillers, and PCT Engineered Systems. They integrate as many emitters as necessary to achieve the desired result. We built the first system to sterilize juice caps, but we prefer to focus on the box containing the emitter. The OEMs build the lamp; we supply the light bulb.
FE: How do you validate that a lethal dosage is delivered, particularly on a high-speed beverage line?
Testoni: Current, voltage and line speed are the only variables affecting lethality. That simplifies kill-rate monitoring, particularly in comparison with chemical treatment, such as hydrogen peroxide and peracetic acid (PAA). FDA officials like the fact that monitoring power validates that the machine is delivering the needed dose; the beam is either on or off. With chemical sanitizers, the concentration and coverage also must be monitored.
FE: Must workers wear radiation tags for safety monitoring?
Testoni: A sandwich of lead shielding less than an inch thick is all that’s necessary. That helps keep the system from becoming cumbersome.
Gamma rays are used in level measurement devices in bottling operations, and the radiation from the radioactive material in those devices is roughly equivalent to our emitters. Fill-level machines need to be registered and properly maintained, and proper decommissioning procedures must be followed. With e-beam, there is no residue or waste to deal with. When the emitter is at the end of its useful life, there’s a lot less paperwork to do.
FE: Does FDA accept e-beam sterilization for low-acid aseptic filling?
Testoni: No petitions for a commercial e-beam sterilization system have been submitted, though FDA officials are aware of the technology and have indicated they see no impediment to a letter of nonobjection. And we’ve been working with aseptic processing authorities to be sure validation requirements will be met.
We have our own challenge organism, Bacillus pumulis, that we’ve inoculated surfaces with to correlate electron dose and kill rate. A dose of 1.5 kiloGrays (kGy) delivers a 1 log reduction, while 10 kGy delivers a 6 log reduction in milliseconds. The FDA has accepted our dose response curve.
FE: A bottle enclosure is mostly two-dimensional. Is the beam powerful enough to sterilize a more complicated shape, such as a PET bottle?
Testoni: We’re working on a new emitter we call ITB, short for “in the bottle.” It’s the first time we’ve tried to put the device inside an object. We’re working through issues such as, what size opening should we be able to probe, how do we reach all the nooks and crannies in the bottle cavity, and how do we ensure that the bottle doesn’t slam into the emitter during the process? We’ve never made a beam this small. New optics and a lot of physics are involved.
We’re beginning to think the best way to do ITB is to hold the beam fixed and have bottles go up and down a cam. Multiple probes could be mounted on a star wheel on a filling line, with individual bottles accepting a probe as the wheel rotates. The process takes less than a second, and by using multiple probes, the system could keep up with the fastest filling lines on the market.
FE: How economical is the system?
Testoni: For high-speed cap and closure sterilization, the electrical use is 20% higher than with PAA, but there is no water or chemical demand, and no steam is needed to sterilize rinse water. We calculate the operating cost at $7 an hour with electron beam, compared to $47 an hour with a conventional system.
ITB sterilization looks even more attractive. Comparing two 90-head aseptic filling lines, we calculate that electrical demand would be significantly lower with e-beam. When you add in water, steam and chemical savings, the operating cost for e-beam works out to $45 an hour compared to $150 an hour for conventional PAA. A return on the capital investment could be delivered in nine months, and the equipment footprint is a lot smaller.