Light & Food Preservation
Consumers demand high-quality processed foods with minimal changes in nutritional and sensory properties. Nonthermal methods are considered to keep food quality attributes better than traditional thermal processing. Pulsed light (PL) is an emerging non-thermal technology for decontamination of food surfaces and food packages, consisting of short time high-peak pulses of broad-spectrum white light. It is considered an alternative to continuous ultraviolet light treatments for solid and liquid foods. This paper provides a general review of the principles, mechanisms of microbial inactivation, and PL treatments applications on foods. Critical process parameters that are needed to be optimized for better efficiency of PL treatments are also discussed. PL has considerable potential to be implemented in the food industry. However, technological problems need to be solved to avoid food overheating and achieve better penetration and treatment homogeneity. Besides, more extensive research is needed to understand how PL affects quality food attributes.
Nonthermal technologies are being applied in food processing as a viable alternative to thermal processing. Traditionally, most foods are thermally processed by subjecting them to temperatures between 60 °C for a few minutes and 100 °C for a few seconds. During this period, a large amount of energy is transferred to the food, which may trigger reactions that lead to undesirable changes or by-products formation. During nonthermal processing, food temperature is held below that achieved in thermal treatments. Thus, vitamins, essential nutrients, and flavors are expected to undergo minimal or no changes.
Pulsed light (PL) is used for the rapid inactivation of microorganisms on food surfaces, equipment, and food packaging materials. The terms high-intensity broad spectrum pulsed light and pulsed white light are synonymous with PL.
Inert-gas flash lamps generate intense and short pulses of ultraviolet (UV) light for microbial inactivation started during the late 1970s in Japan. In 1988, extensive experimentation carried out by PurePulse Technologies Inc. provided a pulsed light process called PureBright® to sterilize pharmaceuticals, medical devices, packaging, and water. The process's efficacy was tested against a broad range of microorganisms, including bacteria (vegetative cells and spores), fungi, viruses, and protozoa. However, the food industry adopted the technology only in 1996, when the Food and Drug Administration approved the use of PL technology for the production, processing, and handling of foods.
Description of PL
PL involves the use of intense pulses of short duration and a broad spectrum to ensure microbial inactivation on the surface of either foods or packaging materials. Electromagnetic energy is accumulated in a capacitor during fractions of a second and then released in the form of light within a short time (nanoseconds to milliseconds), resulting in an amplification of power a minimum of additional energy consumption (Dunn et al. 1995). Typically, the equipment used to produce PL comprises one or more adjustable xenon lamp units, a power unit, and a high-voltage connection that allows the transfer of a high current electrical pulse. As the current passes through the lamp unit's gas chamber, a short, intense burst of light is emitted. The light produced by the lamp includes broad-spectrum wavelengths from UV to near-infrared. The wavelength distribution ranges from 100 to 1,100 nm: UV (100–400 nm), visible light (400–700 nm), and infrared (700–1,100 nm). Pulses of light used for food processing applications typically emit 1 to 20 flashes per second at an energy density in the range of about 0.01 to 50 J cm−2 at the surface (Barbosa-Canovas et al. 1998).
Many fluids, such as water, have a high degree of transparency 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 will diminish the intensity of UV radiation's penetration. In an aqueous solution, the lower the transparency, the less effective the PL treatment. Liquids with high UV absorbance must be treated as a thin layer to reduce the liquid's radiation absorption. In this manner, the liquid's UV absorption is low, and bacteria are more likely to be subjected to lethal doses. The absorbance of clarified fresh juices and juices containing pulp varies considerably. Clarified apple juice has a low absorbance, with absorption coefficients about 11 cm−1, whereas absorbance of orange juice can achieve values close to 50 cm−1. A positive correlation between vitamin C content and the absorption coefficient of clear apple juices was observed.
PL is a novel non-thermal technology to inactivate pathogenic and spoilage microorganisms on foods. The significant microbial reductions in short treatment times, the limited energy cost of PL, the lack of residual compounds, and its great flexibility are some of the technique's major benefits. This method is clearly efficient in inactivating microorganisms in vitro, but its potential for real foods is still under investigation. Further studies need to be conducted to assess PL treatments' effects on food properties beyond safety and spoilage. There is a need for optimizing the critical process factors to achieve the target inactivation level for specific food applications without affecting quality. PL equipment with good penetration and short treatment times need to be designed for commercial purposes. Also, the applicability of PL treatments on an industrial scale needs to be compared with other nonthermal or conventional thermal processes.
Anderson, J. G., Rowan, N. J., MacGregor, S. J., Fouracre, R. A., & Farish, O. (2000). Inactivation of food-borne enteropathogenic bacteria and spoilage fungi using pulsed-light. IEEE Transactions on Plasma Science, 28(1), 83–88. doi:10.1109/27.842870.
Baka, M., Mercier, J., Corcruff, R., Castaigne, F., & Arul, J. (1999). Photochemical treatment to improve storability of fresh strawberries. Journal of Food Science, 64, 1068–1072. doi:10.1111/j.1365–2621.1999.tb12284.x.
Barbosa-Canovas, G. V., Pothakamury, U. R., Palou, E., & Swanson, B. G. (1998). Nonthermal preservation of foods pp. 139–161. New York: Marcel Dekker.
Barka, E. A. (2001). Protective enzymes against reactive oxygen species during ripening of tomato (Lycopersicon esculentum) fruits respond to low amounts of UV-C. Australian Journal of Plant Physiology, 28, 785–791.
Bialka, K. L., & Demirci, A. (2007). Decontamination of Escherichia coli O157:H7 and Salmonella enterica on blueberries using ozone and pulsed UV-light. Journal of Food Science, 72(9), 391–396. doi:10.1111/j.1750–3841.2007.00517.x.
Bialka, K. I., & Demirci, A. (2008). Efficacy of pulsed UV-light for the decontamination of Escherichia coli O157:H7 and Salmonella enterica on raspberries and strawberries. Journal of Food Science, 00(0), 1–7.
Bialka, K. I., Demirci, A., & Purl, V. M. (2008). Modeling the inactivation of Escherichia coli O157:H7 and Salmonella enterica on raspberries and strawberries resulting from exposure to ozone or pulsed UV-light. Journal of Food Engineering, 85(3), 444–449. doi:10.1016/j.jfoodeng.2007.08.007.
Bintsis, T., Litopoulou-Tzanetaki, E., & Robinson, R. (2000). Existing and potential applications of ultraviolet light in the food industry — A critical review. Journal of the Science of Food and Agriculture, 80, 637–645. doi:10.1002/(SICI)1097–0010(20000501)80:6<637::aid-jsfa603>3.0.CO;2–1</637::aid-jsfa603>.
Cantos, E., Espin, J. C., & Tomas-Barbaran, F. A. (2002). Postharvest stilbene enrichment of red and white table grape varieties using UVC irradiation pulses. Journal of Agricultural and Food Chemistry, 50, 6322–6329. doi:10.1021/jf020562x.
Chung, S. Y., Yang, W., & Krishnamurthy, K. (2008). Effects of pulsed UV-light on peanut allergens in extracts and liquid peanut butter. Journal of Food Science, 73(5), 400–404. doi:10.1111/j.1750–3841.2008.00784.x.
Dhallewin, G., Schirra, M., Manueddu, E., Piga, A., & Ben-Yehoshua, S. (1999). Scoparone and scopoletin accumulation and ultraviolet-C induced resistance to postharvest decay in oranges as influenced by harvest date. Journal of the American Society for Horticultural Science, 124, 702–707.
Dong, Y. H., Mitra, D., Kootstra, A., Lister, C., & Lancaster, J. (1995). Postharvest stimulation of skin color in Royal-gala apple. Journal of the American Society for Horticultural Science, 120, 95–100.
Dunn, J. (1996). Pulsed light and pulsed electric field for foods and eggs. Poultry Science, 75(9), 1133–1136.
Dunn, J., Bushnell, A., Ott, T., & Clark, W. (1997). Pulsed white light food processing. Cereal Foods World, 42, 510–515.
Dunn, J. E., Clark, R. W., Asmus, J. F., Pearlman, J. S., Boyer, K., Painchaud, F., et al. (1989). Methods for the preservation of foodstuffs. US Patent number 4871559.
Dunn, J. E., Clark, R. W., Asmus, J. F., Pearlman, J. S., Boyer, K., Painchaud, F., et al. (1991). Methods for the preservation of foodstuffs. US patent number 5034235.
El Ghaouth, A., Wilson, C. L., & Callahan, A. M. (2003). Induction of chitinase, beta-1,3-glucanase, and phenylalanine ammonia-lyase in peach fruit by UV-C treatment. Phytopathology, 93, 349–355. doi:10.1094/PHYTO.2003.93.3.349.
Elmnasser, N., Guillou, S., Leroi, F., Orange, N., Bakhrouf, A., & Federighi, M. (2007). Pulsed-light system as a novel food decontamination technology: A review. Canadian Journal of Microbiology, 53, 813–821. doi:10.1139/W07–042.
Elmnasser, N., Dalgalarrondo, M., Orange, N., Bakhrouf, A., Haertlé, T., Federighi, M., et al. (2008). Effect of pulsed-light treatment on milk proteins and lipids. Journal of Agricultural and Food Chemistry, 56, 1984–1991. doi:10.1021/jf0729964.
Fine, F., & Gervais, P. (2004). The efficiency of pulsed UV light for microbial decontamination of food powders. Journal of Food Protection, 67, 787–792
Food and Drug Administration. (, 2000). Kinetics of microbial inactivation for alternative food processing technologies: pulsed light technology. Available at: http://vm.cfsan.fda.gov/∼comm/ift-puls.html. Accessed 2 May 2008.
Gómez-López, V. M., Devlieghere, F., Bonduelle, V., & Debevere, J. (2005a). Factors affecting the inactivation of microorganisms by intense light pulses. Journal of Applied Microbiology, 99, 460–470. doi:10.1111/j.1365–2672.2005.02641.x.
Gómez-López, V. M., Devlieghere, F., Bonduelle, V., & Debevere, J. (2005b). Intense light pulses decontamination of minimally processed vegetables and their shelf-life. International Journal of Food Microbiology, 103, 79–89. doi:10.1016/j.ijfoodmicro.2004.11.028.
Gómez-López, V. M., Ragaert, P., Debevere, J., & Devlieghere, F. (2007). Pulsed light for food decontamination: A review. Trends in Food Science & Technology, 18, 464–473. doi:10.1016/j.tifs.2007.03.010.
Guerrero-Beltrán, J. A., & Barbosa-Cánovas, G. V. (2004). Review: Advantages and limitations on processing foods by UV light. Food Science and Technology International, 10, 137–147. doi:10.1177/1082013204044359.
Hillegas, S. L., & Demirci, A. (2003). Inactivation of Clostridium sporogenes in clover honey by pulsed UV-light treatment. Agricultural Engineering International, V. Manuscritp FP 03 009.
Hiramoto, T. (1984). Method of sterilization. US Patent number 4464336.
Hollósy, F. (2002). Effects of ultraviolet radiation on plant cells. Micron, 33, 179–197. doi:10.1016/S0968–4328(01)00011–7.
Hoornstra, E., de Jong, G., & Notermans, S. (2002). Preservation of vegetables by light. In Conference frontiers in microbial fermentation and preservation (pp. 75–77). The Netherlands: Wageningen.
Jun, S., Irudayaraj, J., Demirci, A., & Geiser, D. (2003). Pulsed UV-light treatment of cornmeal for inactivation of Aspergillus niger spores. International Journal of Food Science & Technology, 38, 883–888. doi:10.1046/j.0950–5423.2003.00752.x.
Koutchma, T. (2008). UV light for processing foods. Ozone: Science & Engineering, 30, 93–98. doi:10.1080/01919510701816346.
Koutchma, T., Keller, S., Parisi, B., & Chirtel, S. (2004). Ultraviolet disinfection of juice products in laminar and turbulent flow reactors. Innovative Food Science & Emerging Technologies, 5, 179–189. doi:10.1016/j.ifset.2004.01.004.
Krishnamurthy, K., Demirci, A., & Irudayaraj, J. (2004). Inactivation of Staphylococcus aureus by pulsed UV-light sterilization. Journal of Food Protection, 67, 1027–1030.
Krishnamurthy, K., Demirci, A., & Irudayaraj, J. M. (2007). Inactivation of Staphylococcus aureus in milk using flow-through pulsed UV-light treatment system. Journal of Food Science, 72(7), M233–M239. doi:10.1111/j.1750–3841.2007.00438.x.
Krishnamurthy, K., Tewari, J. C., Irudayaraj, J., & Demirci, A. (2008). Microscopic and spectroscopic evaluation of inactivation of Staphylococcus aureus by pulsed UV light and infrared heating. Food and Bioprocess Technology. doi:10.1007/s11947–008–0084–8.
Lagunas-Solar, M. C., Piña, C., MacDonald, J. D., & Bolkan, L. (2006). Development of pulsed UV light processes for surface fungal disinfection of fresh fruits. Journal of Food Protection, 69(2), 376–384.
Lamikanra, O., Kuenemon, D., Ukuku, D., & Bett-Garber, K. L. (2005). Effect of processing under ultraviolet light on the shelf life of fresh-cut cantaloupe melon. Journal of Food Science, 70(9), C534–C539.
Shama, G. (1992). Ultraviolet irradiation apparatus for disinfecting liquids of high ultraviolet absorptivities. Letters in Applied Microbiology, 15, 69–72. doi:10.1111/j.1472–765X.1992.tb00727.x.
Shama, G. (2007). Process challenges in applying low doses of ultraviolet light to fresh produce for eliciting beneficial hormetic responses. Postharvest Biology and Technology, 44, 1–8. doi:10.1016/j.postharvbio.2006.11.004.
Sharma, R. R., & Demirci, A. (2003). Inactivation of Escherichia coli O157:H7 on inoculated alfalfa seeds with pulsed ultraviolet light and response surface modeling. Journal of Food Science, 68, 1448–1453. doi:10.1111/j.1365–2621.2003.tb09665.x.
Shuwaish, A., Figueroa, J. E., Silva, J. L. (2000). Pulsed light treated prepackaged catfish fillets. IFT Annual Meeting, 10–14 June 2000, Dallas, USA.
Smith, W. L., Lagunas-Solar, M. C., & Cullor, J. S. (2002). Use of pulsed ultraviolet laser light for the cold pasteurization of bovine milk. Journal of Food Protection, 65(9), 1480–1482.
Takeshita, K., Shibato, J., Sameshima, T., Fukunaga, S., Isobe, S., Arihara, K., et al. (2003). Damage of yeast cells induced by pulsed light irradiation. International Journal of Food Microbiology, 85, 151–158. doi:10.1016/S0168–1605(02)00509–3.
Tonon, F., & Agoulon, A. (2003). Lumiere pulse, principe et application au cas des solutions liquids. Industries Agro-alimentaires, la conservation de demain, 4e edition, 20 November 2003, Talence, France.
Turtoi, M., & Nicolau, A. (2007). Intense light pulse treatment as an alternative method for mold spores destruction on paper-polyethylene packaging material. Journal of Food Engineering, 83, 47–53. doi:10.1016/j.jfoodeng.2006.11.017.
Uesugi, A. R., Woodling, S. E., & Moraru, C. I. (2007). Inactivation kinetics and factors of variability in the pulsed light treatment of Listeria innocua cells. Journal of Food Protection, 70(11), 2518–2525.
Wang, T., MacGregor, S. J., Anderson, J. G., & Woolsey, G. A. (2005). Pulsed ultra-violet inactivation spectrum of Escherichia coli. Water Research, 39, 2921–2925. doi:10.1016/j.watres.2005.04.067.
Wekhof, A. (2000). Disinfection with flash lamps. PDA Journal of Pharmaceutical Science and Technology, 54, 264–276.
Wekhof, A. (2003). Sterilization of packaged pharmaceutical solutions, packaging and surgical tools with pulsed UV light. In: Proceedings of the Second International Congress UV Technologies, 9–11 July 2003, Vienna, Austria.
Wekhof, A., Trompeter, F. J., & Franken, O. (2001). Pulse UV disintegration (PUVD): A new sterilization mechanism for packaging and broad medical-hospital applications. In: Proceedings of the First International Conference on Ultraviolet Technologies, 14–16 June 2001, Washington, DC, USA.
Woodling, S. E., & Moraru, C. I. (2005). Influence of surface topography on the effectiveness of pulsed light treatment for the inactivation of Listeria innocua on stainless-steel surfaces. Journal of Food Science, 70(7), M345–M351. doi:10.1111/j.1365–2621.2005.tb11478.x.
Wright, J. R., Summer, S. S., Hackney, C. R., Pierson, M. D., & Zoecklein, B. W. (2000). Efficacy of ultraviolet light for reducing Escherichia coli O:157:H7 in unpasteurized apple cider. Journal of Food Protection, 63(5), 563–567.
Wuytack, E. Y., Phuong, L. D. T., Aertsen, A., Reyns, K. M. F., Marquenie, D., De Ketelaere, B., et al. (2003). Comparison of sublethal injury induced in Salmonella enterica serovar typhimurium by heat and by different nonthermal treatments. Journal of Food Protection, 66, 31–37.