Microbial quality and Aflatoxin levels of sorghum grains (Sorghum bicolor) irradiated with gamma rays, low energy electron beam (LEEB) and high energy electron beam (HEEB)

Abstract

Sorghum grains (Sorghum bicolor) are used as food components for man as well as feed for animals. However, there have been reported cases of microbial contamination on sorghum grains. The present study investigated the comparative effects of gamma rays, low energy electron beam (LEEB) and high energy electron beam (HEEB) on the microbial quality and mycotoxin levels of sorghum grains. Sorghum grains were purchased from a local market in Accra, Ghana, and packaged in zip-lock bags. Samples were exposed to irradiation doses of 2, 4, 6, 8, and 10 kGy, and the un-irradiated sorghum grains served as control. For LEEB, the ILU-6 accelerator (250 keV) was used, and for HEEB ELEKTRONIKA 10-10 accelerator (9 MeV) was used. Gamma Chamber 5000 Co-60 source was used for gamma irradiation. Total viable counts, total coliforms, Bacillus cereus, Staphylococcus aureus, Salmonella spp, yeasts, and molds counts were determined using standard methods. Aflatoxins B1, B2, G1, and G2 were also evaluated. The presumptive yeast and molds were further analyzed using MALDI-TOF. All three sources of irradiation significantly reduced the microbial populations of the sorghum grains, and subsequently eliminated the microorganisms at high doses. However, at 10 kGy, total viable counts as well as yeasts and molds were still detected for LEEB. Aspergillus flavus was identified as an organism associated with the sorghum grains. The aflatoxin levels were below the detection limits. Gamma rays and HEEB were more effective than LEEB.