Alkaline cooking (nixtamalisation) and the reduction in the in vivo toxicity of fumonisin-contaminated corn in a rat feeding bioassay

Abstract

Nixtamalisation is a widely used food processing method in which whole kernel corn is cooked and steeped in alkaline water. It reduces the amount of fumonisin B1 (FB₁) that can be detected after cooking. However, the fate of FB₁ during nixtamalisation is not fully understood and potentially toxic reaction products, including matrix-associated “masked” FB₁ forms that are not detected by routine analytical methods might remain in nixtamalised corn. To assess how nixtamalisation of whole kernel corn affects fumonisin toxicity, male rats were fed diets containing low, mid or high levels of uncooked (LU, MU, HU) or alkaline cooked (LC, MC, HC) FB₁-contaminated corn for 3 weeks. The control diet contained uncontaminated corn only. Apoptotic kidney lesions of the type caused by FB₁ were not found in the LC or MC groups. Lesions in the group fed HC were minimal and less severe than those found in the rats fed LU, MU or HU. Furthermore, significantly increased sphinganine and sphingosine concentrations indicative of FB₁ exposure were found in the kidneys of the rats given LU, MU or HU. Concentrations were also elevated, but to a lesser extent, in rats fed HC, whereas sphinganine and sphingosine concentrations in rats given LC or MC did not differ from the control group. FB₁ concentrations in the LC (0.08 mg kg⁻¹), MC (0.13 mg kg⁻¹) and HC (0.37 mg kg⁻¹) diets were markedly reduced compared with their LU (1.8 mg kg⁻¹), MU (3.5 mg kg⁻¹) and HU (4.2 mg kg⁻¹) counterparts as determined by HPLC (n =  1 analysis/diet). Taken together, the findings show that nixtamalisation is an effective cooking method for reducing the potential toxicity of FB₁ contaminated corn.

Keywords:

• nixtamalisation (alkaline cooking)
• fumonisins
• toxicity
• in vivo bioassay

Acknowledgements

The authors thank S. Cunningham, M. Vongkunthong, J. Showker and C. Wray for their expert technical assistance. Mention of a trademark, proprietary name or vendor does not imply its approval by the US Department of Agriculture (USDA) to the exclusion of others that may be equally suitable. The authors declare no conflict of interest.