Chapter 15: Biological Techniques

Gamma irradiation causes several types of biological changes in foods and food ingredients subjected to this technology. DNA is the major cellular target of ionizing radiation, and the resulting damage is responsible for the inactivation of microorganisms, inhibition of growth, and other degradative effects. Hence, analytical methods for the molecular damage to the DNA of foods themselves or of microorganisms usually associated, for the microbial load and diversity, and for the ability to germinate are being developed and applied as rapid, simple, and inexpensive procedures for screening irradiated foods, either qualitatively or for the estimation of the applied dose. The most commonly used biological methods for the detection of irradiated foods are Direct Epifluorescent Filter Technique/Aerobic Plate Count (DEFT/APC), the DNA comet assay, and the Limulus Amebocyte Lysate (LAL) test. These are currently standardized methods, but others are under development. Since biological changes are generally not radiation-specific, the biological methods detailed in this chapter are typically used for screening, and should subsequently be complemented by confirmative chemical or physical methods, such as the standard methods described in Chapters 13 and 14.