Assessment of aflatoxins and heavy metals in Zingiber officinale (ginger) across the value chain in Kaduna and Oyo states, Nigeria and the use of probiotics for aflatoxin detoxification

Zingiber officinale (ginger) is a high-value crop with significant nutritional benefits, but it is susceptible to food hazards, including mycotoxins and heavy metals. Fifty-one ginger samples were collected along the value chain in Kaduna state (local government areas: Jaba, Kachia and Zango) and 44 samples obtained from markets in Oyo state (local government areas: Ibadan North, Ibadan North East, Ibadan North West, and Ibadan South West). The incidence of aflatoxins (B1, B2, G1, and G2) and heavy metals (mercury, cadmium, lead, copper, zinc, and chromium), as well as risk assessments, were determined. Half (50%) of the samples from Kaduna contained aflatoxins and all (100%) of the samples from Oyo State contained aflatoxins. On average, 18 to 60% of split dried samples and 17 to 83% of fresh from Kaduna exceeded 10 ng/g total aflatoxin concentration. In Oyo State 67 to 100% of the split dried samples exceeded 10 ng/g and 100% of both fresh and milled samples exceeded 10 ng/g total aflatoxins. The probable tolerable limit of mercury (0.572 mg/kg bw/day) exceeded the limit of 0.23 mg/kg bw/day from Kaduna samples, whereas others were within the tolerable limits. Lead, which has no defined tolerable daily intake, was not detected in Kaduna State samples. In Oyo State samples, lead was detectable with an estimated limit of 0.007 mg/kg bw/day whereas the others were within the limit. The estimated probable daily intake (PDI) of aflatoxin B1 was estimated at 4.1 µg/kg bw/day and 1.5 µg/kg bw/day from Oyo State and Kaduna state samples respectively. The provisional maximum tolerable daily intake (TDI) for aflatoxins is 2 µg/kg bw/day. The use of probiotics was explored for the detoxification of aflatoxin-spiked ginger samples (at 50 ng/g). Lactiplantibacillus plantarum ATCC 8014 (LP) and Lactobacillus helveticus ATCC 15009 (LH) reduced aflatoxin concentrations by 50% when used alone or together at the end of a 120-h incubation period. The study highlights the incidence and risk of exposure to multiple toxicants in ginger and the need for management of aflatoxins and heavy metals along the ginger value chain.