Cytotoxic and mutagenic effects of irradiated substrates and food material

Abstract

The lethal effects of both ionizing and non-ionizing radiations have many potentially important applications in food technology. To capitalize on this use, a pre-requisite is the clear establishment of the absence of undesirable secondary effects in the irradiated material. Commencing from the study of Stone, Wyss and Haas(150) who found that U.V.-irradiated substrate itself induces mutations in Staphylococcus aureus, numerous studies have been carried out to ascertain whether cytotoxic effects occur when unirradiated biological test systems are cultured or fed with irradiated media or food. In such studies, adverse physiological (growth retardation and inhibition), cytological (mitotic inhibition and chromosome aberrations) and genetical (forward and reverse mutations) effects have been observed in a wide range of test systems, ranging from bacteriophages to human cells. These adverse effects are very small in frequency of occurrence compared to those observed when the test systems are exposed directly to radiation. Consequently, they can be demonstrated primarily by statistical comparisons with the control populations. The yield and longevity of the cytotoxic principle generated in irradiated media are dose-dependent. On the other hand, the genetic effects do not show any well defined relationship with dose and also vary even within the same test organism such as Drosophila melanogaster. In media containing glucose, the glucose component seems particularly prone to the effects of radiation with reference to the production of cytotoxic and mutagenic secondary products. In some systems, the addition of catalase neutralized the cytotoxic effects, while in others, the effects were not influenced by catalase. It seems likely that hydrogen peroxide plays an important intermediate role in the formation of various toxic derivatives. The available data suggest that hydrogen peroxide, glyoxal, formic acid, hydroxyalkyl peroxides, histidine-peroxide adduct and deoxycompounds may act as the toxic and mutagenic agents in different systems. The bulk of the data now available in this field relate to somatic effects. The genetic data gathered in Drosophila melanogaster are conflicting, while in E. coli there is conclusive evidence of the mutagenic effects of irradiated media. In order to understand fully the bearing of these findings on human nutrition, data from critical genetic experiments in mice are urgently needed.