Occurrence of aflatoxins and aflatoxin-producing fungi in ofada rice (Oryza sativa–Oryza glaberrima blend) sold in Lagos markets: food safety implications

Abstract

Ofada rice is an indigenous variety of rice predominantly grown and consumed in Nigeria. Similar to other cereals, it is susceptible to fungal and mycotoxin contamination.  This study investigates the occurrence of aflatoxins and aflatoxin-producing fungi in ofada rice and its food safety risks. Three hundred grams (300 g) of ofada rice were purchased from each of four (4) different markets in Lagos: Victoria Island, Ajah, Mushin and Mile 12 markets, using simple random sampling within each market. Samples were pooled into composites per market. One half (150 g) was cooked while the remaining half (150 g) was uncooked. Five (5) grams each were analysed for the presence of aflatoxin using the LC-MS/MS technique. One gram (1 g) each was used for fungal isolation using Sabouraud Dextrose Agar (SDA).Molds isolated were identified as Aspergillus flavus (2 different strains), Aspergillus tritili and Penicillium sp. SGE33. LC-MS/MS results showed that aflatoxin levels in both cooked and uncooked ofada rice were below reporting limit of <1ppb. Low levels of aflatoxins in ofada rice in this study, irrespective of the presence of toxigenic Aspergillus species, indicate that this cereal is generally safe for consumption, as it poses no food safety or public health risks.