Be aware of factors that affect antimicrobial action of electron beams.

Electron beam irradiation is a highly effective process for inactivating foodborne microorganisms and improving the microbial safety and shelf life of food. As with other types of ionizing radiation, such as gamma rays and x-rays, electron beam irradiation inactivates microorganisms by breaking molecular bonds in their DNA. Irradiation-induced damage to the 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.

Several factors affect the antimicrobial action of electron beam irradiation against foodborne bacteria. These include the irradiation dose, temperature, population and types of bacteria, the physiological state of the organism, the gaseous environment and the food preservation technique used.

Careful consideration of these factors is crucial for optimizing electron beam technology and destroying bacteria in food. The sequential application of certain food processing treatments, such as heat pasteurization, acidification, high pressure, bacteriocins and electron beam technology, should make it possible to use lower irradiation doses to inactivate foodborne bacteria.

In addition, good food manufacturing practices and proper sanitation can reduce microbial contamination. They also make it possible to inactivate the bacteria by using lower irradiation doses. This in turn minimizes negative changes that could occur in the desirable sensory characteristics of food. But also be aware that, depending on the amounts used, certain food additives with antioxidant properties may protect foodborne bacteria from the lethal effects of electron beam irradiation by scavenging free radicals. Also, the ability of foodborne bacteria to adapt to certain environmental stresses may enhance their ability to survive following irradiation treatment.

Further research is needed to determine the resistance of pathogenic bacteria to electron beam irradiation after they adapt to environmental stresses commonly encountered in food processing environments. This type of research can help processors in designing irradiation treatments that offer an extra margin of safety.

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].