ANALYTICAL APPROACH
Detecting Irradiated
% FOODS: Use of Hydroxyl Radical (ifBIOMARKERS Lisa R. Karam and Michael G. Simic National Institute of Standards and Technology Ionizing Radiation Division Building 245/C214 Gaithersburg, MD 20899
Recent legislation in the United States has increased the probability of using ionizing radiation for preserving food. The possible increased use of food irra diation in this country, in addition to current use of the technique in other countries, makes it important to devel op a method whereby the extent of irra diation of foods can be determined. Both opponents and proponents of this particular food-processing tech nique support postirradiation dosime try (PID) as a way to measure the ex tent of changes in irradiated products. To prevent tampering and alteration of the dosimeters, the best postirradiation dosimeters are those that are in herent in the product exposed to the ionizing radiation. Therefore detection of the intermediates and subsequent products arising from the interaction of ionizing radiation with biomolecules in foods should be a viable means by which the irradiated status of a food sample can be determined. To be use ful as biomarkers, however, the prod ucts formed by irradiation must be de tectable by routine analytical methods, This article not subject to U.S. Copyright Published 1988 American Chemical Society
formed exclusively by ionizing radia tion (unless formation from alternate methods can be readily determined), and stable for the duration of the ex pected shelf life of the food product.
Method development At the National Institute of Standards and Technology (formerly the National Bureau of Standards), we are develop ing ways to identify the irradiated sta tus of meats and shellfish. These proce dures, based on the detection of certain radiolytic intermediates (e.g., free radi cals in bone and hard tissue, detected by electron spin resonance) and prod ucts (in protein, detected by mass spec trometry), require sensitive analytical techniques because such substances exist in trace amounts. Using boneless chicken as a model for PID in meat, we solved several challenging analytical problems. An advantage of using irradiation to preserve foods is that, at the dose levels used, the sample is essentially indistin guishable from its nonirradiated coun terpart. This is particularly true of fresh meats, which, at an exposure dose of
