If you see a symbol with a flower in the middle and a circle of dotted lines around it in the grocery store it means that food has been irradiated. Irradiation is the use of gamma rays or X-rays to kill most of the dangerous microorganisms, such as E. coli. There are arguments regarding whether this is good for you or not. Some groups say it alters the flavor and destroys nutrients others say studies show it to be safe. The FDA is considering removing the above labeling and allowing the use of the word pasteurized or similar terminology. With recent food safety scares it is an issue you'll have to decide on for yourself. For more information about the process copy this link into your browser bar.