August 17, 2016

Blue LEDs show potential for killing bacteria in juice

A team at the National University of Singapore, led by professor Yuk Hyun-Gyun and his former Ph.D. student, Vinayak Ghate, studied the use of blue LEDs to decontaminate unpasteurized orange juice from foodborne pathogens and reduce the incidence of foodborne outbreaks.

Figure shows the LED assembly used to decontaminate orange juice. Photo: Yuk Hyun-Gyun
Figure shows the LED assembly used to decontaminate orange juice. Photo: Yuk Hyun-Gyun

The team used LEDs of wavelength 460 nanometres (nm) to illuminate orange juice that was artificially contaminated with five strains of the foodborne pathogen Salmonella. It was observed that the LEDs could kill 99 to 99.999 percent of the Salmonella cells in the juice.

The team also studied different combinations of intensity and time, and concluded that a lower irradiance and a correspondingly longer illumination time produced a greater antibacterial effect. While a slight color change was observed in the juice after the illumination, the researchers believe that this change can be minimized by selecting an optimum temperature and light intensity.

The results of this study have important applications for the food industry. To date, the major method used for the preservation of unpasteurized juices has been refrigeration. However, refrigeration only stalls the growth of microorganisms and does not kill them, according to the researchers. LED technology can act as an alternative or a complementary intervention technology. In the future, LEDs could be incorporated into juice dispensers in food courts and even domestic blenders to enhance food safety.

While there have been papers published on the use of LEDs for food preservation by research groups in other parts of the world, these have resorted to the use of an exogenous photosensitizer to bring about bacterial inactivation. With increasing consumer resistance to food additives, the study by this group is promising as it does not use any additives.

Source: National University of Singapore