Enzymatic detoxification of the fumonisin mycotoxins during dry milling of maize

Fumonisin esterase FumD (EC 3.1.1.87), FUMzymeg (R) (BIOMIN, Austria), effectively detoxifies fumonisin B mycotoxins (FB) by hydrolysis and removal of the tricarballylic acid groups. The current study evaluated FumD detoxification of total FB (FBT) in commercial maize utilising an experimental dry milling plant by introducing the enzyme during the kernel conditioning stage. Total FB and the hydrolysed product of FB1, HFB1, in maize and milling products were determined by LC-MS/MS. During maize conditioning of 4 h 10 min substantial FB1 hydrolysis was achieved between 1 and 4 U FumD/100 g maize. Complete conversion into HFB1 was delayed and only achieved at the highest enzyme concentration (32 U/100 g maize) reaching a 1:1 M conversion ratio. Dry milling of maize containing 3.29 +/- 0.20 mu mole FBT/ kg (2354 +/- 140 mu g/kg) in the absence of FumD, resulted in a 2.5-fold increase in the FBT concentration in total hominy feed (8.34 +/- 0.22 mu mol/kg) (5979 +/- 158 mu g/kg) compared to the levels that prevail in Super (0.52 +/- 0.07 mu mol/kg) (347 +/- 48 mu g/kg) and Special (1.70 +/- 0.01 mu mol/kg) (1213 +/- 8 mu g/kg) maize meal, and Semolina (1.07 +/- 0.14 mu mol/kg) (765 +/- 100 mu g/kg) milling products. Introduction of FumD (40 U/kg) mainly impacted the total hominy feed product (germ + hominy milling fractions), constituting up to 30% of the reconstituted whole maize. A 99% reduction in FBT was obtained in total hominy feed, 48% in Semolina, 7% in Special maize meal, whereas no reduction was recorded in Super maize meal. FB1 reduction rates depend on the contamination level, kernel moisture and the diffusion rate from inner kernel layers to the kernel surface/aqueous interface. Risk modelling in children and adults indicated that FumD-treated whole maize and the resultant Semolina milling product intended for human consumption reduces the risk of exposure to FBT. However, no reduction in the exposure risk was observed when considering the Super and Special maize meal milling products. FB reduction in total hominy feed could open up new applications, such as its dietary incorporation as a source of fibre, minerals and bioactive plant constituents in maize-based food. In addition, the animal feed industry and subsistence maize farming communities using rudimentary milling processes, could also benefit.