Submitted to: Multicrop Aflatoxin and Fumonisin Elimination and Fungal Genomics Workshop-The Peanut Foundation
Publication Type: Abstract only
Publication Acceptance Date: 12/2/2003
Publication Date: 3/15/2004
Citation: Voss, K.A., Riley, R.T., Norred, W.P., Bacon, C.W., Meredith, F.I. 2004. The effects of cooking on fumonisins: overview and recent studies. Multicrop Aflatoxin and Fumonisin Elimination and Fungal Genomics Workshop-The Peanut Foundation. October 13-15, 2003, Savannah, Georgia. p. 19. Interpretive Summary: Abstract - no interpretive summary required.
Technical Abstract: Fumonisins are mycotoxins found in corn and corn-based foods. Nixtamalization (cooking in alkaline water) extracts fumonisins from the corn and other cooking methods have been found to variably reduce fumonisin concentrations in foods. However, the extent to which fumonisin-matrix binding or the formation of unknown, but biologically active fumonisin derivatives occurs in cooked products is not known. If novel or matrix-bound fumonisins are present in significant amounts, then routine chemical analysis might underestimate fumonisin concentrations in and toxicity of cooked food products. Bioassay is an approach for investigating the effect of cooking or other chemical/physical treatments on the fate of fumonisins in food matrices that circumvents analytical uncertainty. Corn, masa made from the corn by nixtamalization, and tortilla chips made from the masa were extracted (5 grams each, extracted 3 times with 50 ml acetonitrile/water 1:1), and the extracts combined, dried, and redissolved in 1 ml DMSO. Vero cells were grown to confluence in 1 ml wells and then exposed to the redissolved corn, masa, and tortilla chip extracts (4 microliter/ml medium) for 48 hr. The corn extract inhibited ceramide synthase activity (a fumonisin-specific effect) as shown by a significant increase in the amount of the enzyme's sphingoid base substrate sphinganine (Sa) (mean=132 pmole/well) and the increase in the ratio of sphinganine to sphingosine (Sa/So) in the cells. In contrast, the amount of Sa found in the cells dosed with the masa, baked tortilla chip or fried tortilla chip extracts (mean Sa=14-24 pmole/well) remained low, as did Sa/So (0.17-0.28). Fumonisin B1 concentrations (HPLC analysis of the extracts) of the masa and chips (3.6-6.7 micrograms/g) were likewise reduced 80-90% compared to the corn (32 micrograms/g). In a second experiment, baked cornbread, pan-fried corn cakes, and deep-fried corn fritters were made from cornmeal that had been spiked (5% w/w) with Fusarium verticillioides culture material. The cooked products were then mixed with rodent chow and fed to male rats (n=5) for 2 weeks at high (20% w/w spiked cornmeal equivalents = 1% w/w culture material equivalents) or low (2% spiked cornmeal equivalents) doses. Positive control groups were fed diets containing 20% or 2% w/w of the uncooked spiked cornmeal and a negative control group was fed a diet to which sound corn only was added. Toxic response to the baked cornbread, pan-fried corn cake, deep-fried fritter and positive control diets was similar and characterized by decreased body weight gain (high-dose only), decreased kidney weights, and the apoptotic kidney and liver lesions typically caused by fumonisins in rats. Fumonisin concentrations (fumonisin B1+2) in the high-dose pan-fried corn cake diet (92 ppm) was 30% lower than those of the high-dose baked cornbread (132 ppm), deep-fried fritter (120 ppm) and positive control (131 ppm) diets. Taken together, the results indicate that nixtamalization of corn reduces both the fumonisin concentration and fumonisin-like biological activity of the masa product and that baking and frying had no significant effect on the biological activity of fumonisins in corn-based foods. These experiments also provided no indication that unknown, biologically active fumonisins were formed during cooking.