Gamma irradiation effects on the microbial content in commercial bee pollen used for bumblebee mass rearing

Abstract

Bee pollen is a valuable natural product and by its nutritional composition is important for the development of insects of agricultural interest. In this work, we determined whether gamma irradiation can minimize the risk of microbial contamination of commercial bee pollen used for the mass rearing of bumblebees. Bee pollen samples were treated with target doses of 0, 2, 5, 7 and 9 kGy of gamma radiation emitted by a 60Co source and then analyzed for microbial content. Neither fungi nor coliform bacteria were detected in samples irradiated at 5 kGy or higher. Yeasts and aerobic bacteria were not detected in the samples irradiated at 7 kGy or higher (<10 CFU/g). Bacterial species capable of sporulation were most resistant to gamma irradiation and were identified. Taxonomic analysis indicated that the genus Bacillus, represented by fourteen species, was the most common, followed by Paenibacillus with six species. Our results strongly suggest that gamma irradiation is a useful treatment to assure the maintenance of acceptable food quality for bumblebee mass rearing.