Blue light as a tool to decontaminate fresh produce

Last changed: 26 May 2021
Image of scientific poster. Author: Connor Lawrence

Connor Lawrence, Horticultural Science - Master´s Programme


Pathogenic bacteria are a threat to food safety and lead to large amounts of food waste; this is especially true for minimally processed produce. In order to decrease the threat of an outbreak and the significant losses in the fresh produce industry, researchers are working to implement safety hurdles. Visible light has been tested as a potential means to decontaminate multiple forms of bacteria for a wide variety of uses. This is due to the presence of photoreceptor proteins that lead to a concentration of reactive oxygen species when exposed to a high intensity of visible light. For Escherichia coli, some research has pointed to light within the blue spectrum as likely to cause reactive oxygen species build-up, and therefore damaging to the cell. However, bacterial stress can lead to a state of viable but not culturable bacteria; this would still present a threat to any hurdle This project used 400, 420, and 450 nanometers of light at varying intensities to measure the photodynamic inhibition of these wavelengths. 400 and 420 nanometers showed a decrease in culturable E. coli after 105 mJ/cm2, with 400 nanometers having the most inhibitory effect. The regrowth potential of E. coli was tested for 16 days at 4 C, as expected in a processing facility. Regrowth was apparent for all intensities and wavelengths, but the sample exposed to 400 nanometers at the highest intensity level (105.18 mJ/cm2) showed very little regrowth. The potential for blue light in fresh produce safety and minimal loss is promising.


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Image of scientific poster. Author: Connor Lawrence


About me

Connor Lawrence. Private photo.

Connor Lawrence

I came to SLU-Alnarp with a background in inorganic chemistry and the earth sciences, but after taking a Microbial Horticulture class as part of my masters, I was quickly hooked on the power of the microbiological world and its influence in food production. I sought out any opportunity to immerse myself deeper into this realm where bacteria play a significant role in something we take for granted—our access to food. This project, using blue light to decontaminate pathogenic E. coli excited me because it gave me the ability to apply a broad microbiological principal, the presence of photoreceptor proteins in bacteria, to a very specific food safety problem. It also addresses food waste and human health: two sustainability principles crucial for global well-being. In the future, I would like to continue to challenge myself to solve difficult problems such as this using interdisciplinary methods. And that’s something I have in common with light as a food safety hurdle: the future looks ‘bright!’