Green sport-bottle caps are depicted passing a xenon vapor lamp and reflector in a pulsed light decontamination chamber. Source: Claranor SA.

Sustainable manufacturing practices are well and good, but when new technologies help lower costs by expending fewer resources, business people sit up and take notice. Using low-power electron-beam emitters to sterilize packaging material instead of hydrogen peroxide, for example, doesn’t simply reduce water use, it lowers operating cost by a factor of seven (see “E-beam makes a comeback,” Food Engineering, March 2009).

The same economies work in favor of cleaning with pulsed light. Japanese scientists pioneered the use of short, intense bursts of light for decontamination 40 years ago, and US defense contractor Maxwell Technologies funded the first commercialization effort in the 1990s. By 2000, though, venture partner Tetra Pak and Maxwell’s PurePulse division had concluded the technology was too expensive for food applications, and development stalled.

Pulsed light soon acquired a French accent. The now-defunct firm Solsys successfully deployed systems that decontaminate bottle closures at Nestlé Waters plants in the Philippines and Saudi Arabia. A group of Solsys alums, including R&D services director Christophe Riedel, formed Claranor SA in 2004. The Manosque, France-based firm has installed seven systems and, more importantly, has built a scientific team to refine the technology and validate its efficacy in packaging material sterilization and surface pasteurization of solid foods.

Educated as a food engineer with a focus on physics, microbiology, food chemistry and packaging, Riedel serves as a liaison between Claranor’s researchers and scientists, investors and food and beverage clients. In his role as marketing and sales manager, he recently discussed the technology with Food Engineering at Claranor’s booth at the Anuga FoodTec trade show in Cologne, Germany.  


FE: Describe how a pulsed light system functions.

Riedel: The key elements are the capacitor and electronics racks and the cabinet housing the xenon vapor arc lamp and reflectors. Electricity is accumulated in the capacitor and converted to 3,000 volts of luminous energy. When the current flows, it creates a pulsed flash lasting 300 microseconds (one-millionth of a second). The wavelengths range from 200 to 1,100 nanometers. Though only 300 joules, the short duration means the amount of light energy involved is equivalent to one megawatt.


FE: How do light pulses purify or sterilize?

Riedel: There is both a photochemical and a photothermic effect. UVC light and other technologies also are effective at disrupting a microorganism’s DNA, causing a photochemical effect that leads to death. The photothermic effect enhances the effectiveness of pulsed light. The temperature difference between the inside and outside of a living cell causes cell deformation and rupturing. The theory is that the differential between the surface heat delivered by the flash and the cell’s internal temperature causes denaturing.

Although the temperature at the surface can reach 160˚ (320˚ F), pulsed light is considered a heat-free process that does not cause chemical modification. If the lamp’s heat was absorbed, it would incinerate microorganisms. In an experiment, light was pulsed through transparent film, and the temperature on either side remained the same. A black spot was then placed on the film, and the light burned through the film.


FE: How has Claranor advanced the art?

Riedel: For two years, the focus was on standardizing the electronics, which were a big cost problem initially. Our technical director has an extensive background in laser-light pulsing. That led us to an electronics firm that standardized the racks that control the pulsed light, the cooling system and the material being treated, and helped reduce machine cost by 50%. The life of the lamp has been extended by a factor of four, to 10 million flashes.

The charging of the capacitor was a limitation, and that has been increased to five per second, with additional improvements expected. Aseptic log reductions greater than five have been achieved with two lamps and two flashes on sport caps, preform necks and films.


FE: How big is the system’s footprint?

Riedel: The optical cabinet is quite compact. It is positioned adjacent to equipment where the purified material is applied. It can be located up to 7 meters from the capacitor; beyond that, the form of the pulse would change as it passes through the high-voltage cord, limiting the flash’s effectiveness.

Maintaining sterility after treatment is crucial. We have partnered with firms to integrate ultra-clean or aseptic zones between the cabinet and capping machine. In the US, Fowler Products Co. integrated the pulsed light system into a capper that came on line in California in June. Capping machines used to be regarded as mechanical devices, but microbiology and hygiene are big concerns now.


FE: Replacing hydrogen peroxide and water to sterilize packaging material also is accomplished with low-power e-beam emitters. Is e-beam a competing technology?

Riedel: I consider it a complementary technology. The development work Advanced Electron Beams is doing for in-the-bottle sterilization is very interesting and not something pulsed light currently can do because of the shadow effect when the flash comes from outside the bottle. On the other hand, pulsed light is simpler to use, less expensive to operate and more effective for sterilizing or decontaminating caps. And protecting workers from the very intense light flashes is much easier than protecting them from electron beams.

Our objective is not to be a general solution but to target applications that bring the most benefit to manufacturers. We are focused on niche applications with the highest probability of commercial acceptance. Pilot equipment is available at several research labs, including Campden and Chorleywood in the UK, for companies interested in testing additional applications.  


FE: What regulatory issues exist in applying pulsed light to food?

Riedel: In the European Union, regulation EC 258/97 requires proof that new technologies don’t significantly alter the nutritional value or chemical composition of food. We have demonstrated to French regulators that there is no chemical change to the proteins and fats with pulsed light, and they have granted us a partial exemption. Once an EU country acknowledges a technology is relatively benign, no toxicology or clinical studies are necessary, and it becomes fairly easy to get approval in other EU countries.

In the US, the National Food Lab in Dublin, CA, has evaluated the technology for food processing. Based on NFL’s findings, we believe the FDA would issue a letter of no objection. And in 1996, PurePulse secured FDA acknowledgement of the effectiveness of pulsed light in controlling microorganisms on food and packaging surfaces.


FE: How is the global economy impacting new technologies that address sustainable manufacturing concerns?

Riedel: Sustainability remains very topical in Europe, with high consumer interest influencing buying decisions. The bonuses paid to managers and directors often are tied to reduced water consumption or improved safety for workers. But if your technology increases a company’s costs, that is a problem. New methods can’t cost more than conventional techniques. Fortunately, pulsed light reduces cost and, with packaging materials, eliminates chemical use.


FE: What other food applications are likely for pulsed light?

Riedel: Commercial evaluation of an inline system with 13 lamps for salmonella treatment of eggs got underway in 2008. Clear liquids are good candidates, and extensive lab testing on decontamination of fruits and vegetables has been conductive.

An American firm approached us about using pulsed light in hot fill. A thick bottle is required when filling liquids heated to 88°-90° (190°-194° F). If pulsed light is used to decontaminate the preform neck and the closure, a bottle with 1-3 grams less material can be used. Based on 160 million bottles a year on a high-speed line, the savings would be 10 times greater than the pulsed light’s cost, not including chemical and water-reduction savings.