Suntans are bad for bacteria too! Exposure to UV irradiation kills off harmful bacteria in food

15 December 2003: The presence of E.coli bacteria, found in foods such as egg white and apple juice, is a major public health concern. The bacteria have, in the past, been inactivated by heat pasteurisation -- which can affect flavour and consistency. New evidence published in the Journal of Science of Food and Agriculture, however, suggests that UV irradiation may prove to be a better and more cost effective method of eliminating the risks posed by E. coli bacteria.

Researchers working in Canada discovered that an optimal UV irradiation system can be developed for individual food products, taking into account the UV transmittance of each product. With the optimal fluid depth and UV dose, significant decrease in active E. coli bacteria was observed in both apple juice and liquid egg white.

The UV rays inactivate E. coli bacteria by degrading their cell walls and DNA. These rays can be produced by high intensity fluorescent lamps, which are both cheap and readily available, making this method extremely efficient. The researchers also found that, in direct contrast to pasteurisation, the sensory quality of the food products following irradiation was not compromised, and that inactivation of the bacteria lasted for the entire shelf life of the product.

"UV irradiation offers a relatively inexpensive and effective means of inactivating some of the serious bacteria in food products," says Dr Michael Ngadi, co-author of the study. "We are able to design and operate systems that can process liquid products to satisfy regulatory requirements. The wonderful thing is that products can be processed at lower temperatures and therefore the fresh-like quality of the product can be maintained."

John Wiley & Sons. December 2003.