Pre- and post-storage evaluation of nutritional profiles and aflatoxin contamination in maize, millet, and wheat in Oyo town

Cereal grains such as maize (Zea mays), millet (Pennisetum glaucum), and wheat (Triticum aestivum) are essential dietary staples in Nigeria, yet their nutritional quality and safety are often compromised by traditional storage practices. This study examined the impact of traditional storage on the nutritional quality and aflatoxin contamination of maize, millet, and wheat in Nigeria. Thirty grain samples (10 each) were collected, with one portion of each sample analysed immediately and the other stored for 7–8 months under traditional conditions. Proximate composition (protein, fat, ash, fibre, carbohydrate) and total aflatoxin levels were quantified using HPLC. Nutritional composition varied significantly (p < 0.05) between pre- and post-stored samples across all grains. Carbohydrate and protein contents generally declined after storage, while crude fibre and moisture showed variable trends. In maize, total aflatoxin content rose from 54.61 to 93.54 µg/kg pre-storage to 82.79–101.50 µg/kg post-storage. Millet ranged from 65.13 to 76.79 µg/kg to 81.89–99.24 µg/kg, while wheat increased from 56.22 to 58.20 µg/kg to 84.74–108.30 µg/kg. Aflatoxin B1 was the predominant toxin in all samples. These findings highlight the deterioration of nutritional quality and increased food safety risks in stored cereals, emphasising the need for improved storage systems, regular monitoring, and strict regulatory measures to safeguard consumer health.