Effects of gamma irradiated, cooked soy-, beef-, and soy/meat-based diets in rats

There is increased demand for microbiologically safe foods. Ionizing energy (referred to as radiation pasteurization or irradiation) is effective in r educing the level of pathogenic organisms such as Salmonella, Trichinae, an d Campylobacter which affect the health each year of many people. The irrad iation of phytate (IP6), known to bind essential minerals in beef, soy, and soy-extended beef, at an absorbed dosage of less than 4 kilogray (kGy) cau sed no difference (P > 0.05) in the level of IP3-6 compared with non-irradi ated samples. In a 3-wk study, 84 weanling rats (12 groups, 7 per group) co nsumed diets containing irradiated and non-irradiated soy, beef, and a soy- beef combination fed at 20% of the diet. There were no differences in liver and tibia mineral concentrations. Moreover, there was no measurable effect on body weight, feed efficiency, survival of experimental animals, nor on any of the 4 blood or 7 biochemical parameters measured. In addition, the p hytate:zinc and the [phytate x calcium]:zinc molar ratios of the diets were calculated as an estimation of potential zinc deficiency. Microbiological tests, performed both before and after irradiation, on the soy-extended mea t and meat patties used as dietary ingredients demonstrated a reduction in the bioload as a consequence of irradiation. Thus, irradiation at the dosag e described above had no negative nutritional effects, was unable to enhanc e hydrolysis of phytate yet reduced the number of microorganisms in the ani mal food.