Discover how light-based technologies are used in food preservation to extend shelf life and maintain quality naturally and safely.
Consumers want processed foods that stay close to their original nutritional and sensory quality. Non-thermal methods can preserve these attributes better than conventional heat treatments. Pulsed light (PL), an emerging non-thermal technology, applies millisecond flashes of high-intensity, broad-spectrum white light to decontaminate food and packaging surfaces. It is being studied as an alternative to continuous ultraviolet treatments for both solid and liquid products. This review outlines the principles of PL, the mechanisms behind microbial inactivation, and current food applications. Key process parameters that must be optimized for reliable efficacy are also highlighted. PL shows promise for industrial adoption, yet technical hurdles—such as preventing localized overheating and improving light penetration and uniformity—remain. More data are also needed on how PL may influence food quality attributes.
Non-thermal technologies offer a processing route that keeps food temperatures lower than conventional pasteurization or sterilization. Traditional thermal treatments typically expose foods to 60 °C for minutes or near 100 °C for seconds, transferring enough energy to trigger reactions that can degrade vitamins, flavors, or pigments. By remaining below these temperatures, non-thermal techniques may better retain nutrients and sensory properties.
Pulsed light (PL) delivers rapid microbicidal flashes to food surfaces, equipment, and packaging. The terms "high-intensity broad-spectrum pulsed light" and "pulsed white light" are used interchangeably with PL.
Inert-gas flash lamps that emit intense, brief pulses of ultraviolet (UV) light were first used for microbial inactivation in Japan in the late 1970s. In 1988, PurePulse Technologies Inc. developed the PureBright® pulsed-light process to sterilize pharmaceuticals, medical devices, packaging, and water, demonstrating activity against bacteria (vegetative cells and spores), fungi, viruses, and protozoa. The food industry adopted the technology in 1996 after the U.S. Food and Drug Administration authorized its use for food production, processing, and handling.
Pulsed light (PL) delivers short, high-intensity flashes across a broad spectrum to inactivate microorganisms on food or packaging surfaces. Energy stored in a capacitor for fractions of a second is released as light within nanoseconds to milliseconds, amplifying power with minimal added energy (Dunn et al. 1995). A typical system contains adjustable xenon flash-lamp units, a power supply, and high-voltage connections that deliver rapid current pulses. As current crosses the lamp’s gas chamber, an intense flash is emitted, spanning roughly 100–1,100 nm: UV (100–400 nm), visible (400–700 nm), and near-infrared (700–1,100 nm). For food applications, lamps usually provide 1–20 flashes per second with surface energy densities of about 0.01–50 J cm⁻² (Barbosa-Cánovas et al. 1998).
Many fluids, such as water, are highly transparent to a broad range of wavelengths, including visible and UV light. Other liquids, such as sugar solutions and wines, exhibit more limited transparency. Increasing the number of solids reduces the depth to which UV radiation can penetrate. In an aqueous solution, lower transparency lessens the effectiveness of pulsed-light (PL) treatment. Liquids with high UV absorbance must be processed as a thin layer so that less radiation is absorbed by the liquid itself. This approach keeps UV absorption low, increasing the likelihood that bacteria receive a lethal dose. The absorbance of clarified fresh juices and pulpy juices varies considerably. Clarified apple juice has low absorbance, with absorption coefficients around 11 cm⁻¹, whereas orange juice can reach values close to 50 cm⁻¹. A positive correlation between vitamin C content and the absorption coefficient of clear apple juices has been observed.
PL is a novel non-thermal technology that can inactivate pathogenic and spoilage microorganisms on foods. Significant microbial reductions in short treatment times, low energy demand, absence of residual compounds, and processing flexibility are among its main advantages. The method is clearly efficient for microbial inactivation in vitro, yet its potential for real foods is still under investigation. Further studies are needed to evaluate PL effects on food properties beyond safety and spoilage. Optimizing critical process factors is necessary to achieve target inactivation levels for specific foods without compromising quality. Equipment offering better penetration and short treatment times must be designed for commercial use, and the industrial applicability of PL should be compared with other non-thermal or conventional thermal processes.
