Blue LEDs can preserve orange juice

15 Aug 2016. NUS food scientists proved the potential of blue light-emitting diodes (LEDs) in killing deadly bacteria in orange juice.

Food safety is a global concern, even to economically developed countries like Singapore. Of the different foods, fruit juices are easily contaminated with deadly bacteria during peeling. The bacteria can survive in juices sold at food establishments. There have been numerous cases of foodborne outbreaks that have been traced to fruit juices, especially unpasteurised juices.

A team led by Prof YUK Hyun-Gyun and his former Ph.D. student, Dr Vinayak GHATE, from the Food Science & Technology Programme at the Department of Chemistry in NUS aimed to develop a novel intervention using blue LEDs that would decontaminate unpasteurised orange juice from foodborne pathogens, and reduce the incidence of foodborne outbreaks.

The team used LEDs of wavelength 460 nanometres (nm) to illuminate orange juice that was artificially contaminated with five strains of the dangerous foodborne pathogen Salmonella. It was observed that the LEDs could kill 99 to 99.999% 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 colour change was observed in the juice after the illumination, the researchers believe that this change can be minimised 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 unpasteurised juices has been refrigeration. However, refrigeration only stalls the growth of microorganisms and does not kill them. 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 photosensitiser 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.


Figure shows the LED assembly used to decontaminate orange juice [Image Credit: Yuk HG].



Ghate V, Kumar A., Zhou W, Yuk HG.” Irradiance and temperature influence the antibacterial effect of 460-nanometer light-emitting diodes on Salmonella in orange juice.” Journal of Food Protection. 79(4) (2016) 553.