Investigate resistance of bacteria to E-beam technology.

Electron-beam (E-beam) irradiation involves the use of an electron gun to send high-speed electrons into a food. The electrons smash into molecules in the food as well as bacteria, damaging their DNA. This is a fairly new technology. Until 2000, almost all food irradiated in the United States came from facilities using radioactive cobalt-60.

E-beam irradiation is highly effective for inactivating foodborne microorganisms, and in this manner can improve the microbial safety and shelflife of food. As with other types of ionizing radiation, such as gamma rays and x-rays, E-beam irradiation inactivates microorganisms by breaking molecular bonds in their DNA.

Irradiation-induced damage to DNA is caused by the direct deposition of energy in the bacterial cell or by the production of free radicals from the radiolysis of water. The antimicrobial action of E-beam irradiation against foodborne bacteria can be impacted by several factors, including irradiation dose, temperature, population and types of bacteria, the physiological state of the organism, the gaseous environment and the preservation method.

So it's important to carefully consider these factors in order to optimize the application of this technology and destroy bacteria in food. The sequential application of certain food processing treatments, including heat pasteurization, acidification, high pressure and bacteriocins--and E-beam technology--allows us to use lower irradiation doses to inactivate the bacteria.

Good food manufacturing practices and proper sanitation can reduce microbial contamination, and this also makes it possible to inactivate bacteria using lower irradiation doses. This in turn minimizes negative changes in the desirable sensory characteristics of food.

Depending on the level used, certain food additives with antioxidant properties may protect foodborne bacteria from the lethal effects of E-beam irradiation by scavenging free radicals. Also, the ability of foodborne bacteria to adapt to certain environmental stresses may enhance their ability to survive irradiation treatment.

Further research is needed to determine the resistance of foodborne pathogenic bacteria to E-beam irradiation following their adaptation to environmental stresses commonly encountered in food processing environments. Results of this type of research can help food processors in designing irradiation treatments with an extra margin of safety against pathogenic bacteria.

Further information. Aubrey Mendonca, Department of Food Science and Human Nutrition, Iowa State University, 3399 Food Sciences Building, Ames, IA 50011; phone: [phone]; fax: [phone]; email: [e-mail].