Submitted to: Multicrop Aflatoxin and Fumonisin Elimination and Fungal Genomics Workshop-The Peanut Foundation
Publication Type: Abstract Only
Publication Acceptance Date: October 14, 2007
Publication Date: October 22, 2007
Citation: Burns, T.D., Snook, M.E., Mitchell, T.R., Riley, R.T., Voss, K.A. 2007. Effect of nixtamalization with and without corn matrix on the concentration and toxicity of fumonisins in Fusarium verticillioides culture material.. Multicrop Aflatoxin and Fumonisin Elimination and Fungal Genomics Workshop-The Peanut Foundation. October 22 - 24, 2007. Atlanta, GA. Interpretive Summary: Abstract - no summary required.
Technical Abstract: Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium verticillioides and F. proliferatum. It is common in corn and is found in corn-based foods. FB1 causes equine leukoencephalomalacia in horses, pulmonary edema in swine, kidney and liver toxicity and cancer in laboratory rodents, and neural tube defects (NTD, a type of serious birth defect) in mice. Its impact on human health is not certain, however, there is evidence suggesting that FB1 and other fumonisins are risk factors for neural tube defects and cancer in populations that are dependent on corn as a diet staple. Minimizing exposure is therefore desirable. Nixtamalization is the cooking method for making masa and tortillas. It involves cooking and steeping in alkaline water and has been shown to reduce FB1 concentrations in cooked products, by a combination of extraction into the cooking liquid and conversion of FB1 to hydrolyzed FB1 (HFB1). There is evidence that FB1 can also bind to food matrix components so that it is not detectable by routine analytical methods. If this occurs during nixtamalization, the amount of reduction achieved could be overestimated and potential toxicity of the cooked products underestimated. To address this possibility, F. verticillioides culture material (CM) was nixtamalized as is (NCM) or after being mixed with ground corn (NCMC). Additional portions of the CM were sham nixtamalized under non-alkaline conditions either alone (SCM) or with the corn (SCMC). The materials were then compared in a bioassay using kidney toxicity as the critical endpoint. Toxicity was assessed by microscopic examinations and by quantification of tissue sphinganine (Sa) and Sa 1- phosphate (biomarkers of fumonisin exposure) from rats that had been fed CM equivalent weights of the CM, NCM, NCMC, SCM or SCMC for up to three weeks. Control groups were fed diets amended with unprocessed corn (UC) or nixtamalized corn (NUC). Both nixtamalization and the sham nixtamalization procedure reduced FB1. As a result, FB1 concentration was reduced from 9.1 ppm in the CM diet to 2.1 ppm in the NCM diet and 1.2 ppm in the SCM diet. Improved reduction was achieved when corn was present during nixtamalization (NCMC diet = 0.5 ppm FB1). In contrast, the corn had no effect on reductions achieved during the sham process (SCMC diet = 1.0 ppm). Moderate lesions and widespread apoptosis were found in the kidneys from rats fed the CM. Less severe, subtle lesions with fewer apoptotic cells were found in the group given the NCM. The presence of corn during nixtamalization further reduced toxicity as lesions indicative of fumonisin exposure were not found in the rats fed NCMC or in rats fed SCM, SCMC, UC or NUC. Sa and Sa 1-phosphate findings showed a similar pattern. The concentration of Sa plus Sa 1-phosphate decreased in the groups as follows: CM (600 – 800 nmol/g) > NCM (400-600 nmol/g) > SCM and SCMC (30-90 nmol/g). Lowest concentrations (< 8 nmol/g) were found in the NCM, UC and NUC groups. Together, these results provide evidence that interactions between FB1 and matrix constituents of corn take place during nixtamalization and that these interactions are beneficial, leading to reduced toxicity of the cooked product.