After a few years’ hiatus, pulsed light has re-emerged as a purification and sterilization tool for food and beverage manufacturers, beginning with packaging applications.

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