Occurrence of fumonisins in selected maize meal marketed to consumers in Harare, Zimbabwe
MetadataShow full item record
Mycotoxins are secondary metabolites secreted by filamentous fungi. The fungi produce toxic chemicals which affect animals, plants and humans. Several researchers have reported the presence of high fumonisin concentrations in Zimbabwean maize. The detected fumonisin levels could have a deleterious effect on human health, such as oesophageal and liver cancers. Hundreds of mycotoxins are known to date and fumonisins are regarded the types that most affect cereal grains. A survey was conducted to determine the measures taken by 5 major Harare millers to mitigate fumonisin contamination in the maize meal. Levels of fumonisin contamination among the 5 millers’ four different types of maize meal were assessed and linked to the mitigation measures each individual miller is taking to reduce fumonisin levels in maize meal. The survey results showed that all the millers knew very little about fumonisins. However, measures, such as vetting maize grains for weevils, monitoring moisture levels and removing old grain from the silos were being taken to mitigate the effects of fumonisin contamination of the maize grains. The prevalence of fumonisins in Harare marketed maize meal was investigated in 72 randomly selected samples. Fumonisin B1 and fumonisin B2 were extracted from maize meal with methanol and water (3:1, v/v) using ultrasonic extraction. These were injected into an LC-MS system following centrifugation. All the fumonisins eluted at 7.2 to 7.8 minutes. Fumonisin B1 (FB1) was detected in all analysed samples at mean concentrations ranging between 61.45 µg/kg and 265.79 µg/kg. Fumonisin B2 (FB2) was detected in only 56.9 % of the samples analysed, with a range between 13.72 µg/kg and 76.93 µg/kg. The highest total fumonisin mean concentration (FB1+FB2) was detected in maize meal with maize bran added to it (342.72 µg/kg), while the least total fumonisin mean concentration was detected in maize meal with wheat bran added to it (61.45 µg/kg). All the samples analysed had fumonisin levels within the maximum tolerable limit (MTL) of 1000 µg/kg (EC, 2007). However, the average probable daily intake (PDMI) of fumonisins ranged between 0.82 and 4.57 µg/kg body weight/day. Maize meal with maize bran added and Roller meal had fumonisin concentrations above the regulatory limit of 2 µg/kg body weight/day proposed by the World Health Organisation. The high frequency of fumonisins consumed daily in the two types of maize meal pose health risks to consumers. There is need for constant screening of foods so as to regulate fumonisin levels. The screening would help alleviate the risk of succumbing to esophageal cancer and other ailments that are a result of fumonisin contamination.