COMPARATIVE SUBCHRONIC TOXICITY STUDIES OF NIXTAMALIZED AND WATER-EXTRACTEDFUSARIUM MONILIFORME CULTURE MATERIAL

Authors: Voss, Kenneth; Bacon, Charles; Meredith, Filmore; Norred, William

Submitted to: Food and Chemical Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Corn is often contaminated by the mold Fusarium moniliforme which produces toxins called fumonisins. Fumonisins cause diseases of farm and laboratory animals and there is evidence suggesting they cause human cancer. To make masa flour, the main ingredient of tortillas, ground corn is nixtamalized. During this process, fumonisins are converted to hydrolyzed fumonisins. Using a fumonisin B1 producing isolate of F. moniliforme, we experimentally made moldy corn and then fed diets containing equal amounts of a)unprocessed moldy corn (CM diet); b)nixtamalized moldy corn (NX diet); c)water-extracted moldy corn (WE diet); or d)uncontaminated corn (control diet) to rats. Fumonisin B1 content of the CM and WE diets was 71 ppm and 8 ppm, respectively. The NX diet contained 58 ppm hydrolyzed fumonisin B1, but no detectable fumonisin B1. Kidney disease of the type caused by fumonisin B1 was found in all rats given the CM, WE, or NX diets. Liver disease consistent with fumonisin B1 exposure was found in CM fed rats and to a lesser extent in the NX fed rats, but not in rats fed the WE diet. The findings indicate that nixtamalization did not appreciably alter the toxic effects of the moldy corn; that hydrolyzed fumonisins cause the same liver and kidney diseases as fumonisins; and that water extraction, but removing most of the fumonisin B1, was more effective than nixtamalization for detoxifying the moldy corn.

Technical Abstract: Fumonisins are mycotoxins produced by Fusarium moniliforme and other Fusarium species which grow on corn. They cause species-specific toxicoses and are suspected to cause human esophageal cancer. The effect of nixtamalization, the process by which masa flour is produced by alkaline hydrolysis of corn, on the organ-specific toxicity of a F. moniliforme culture material (CM) containing fumonisin B1 (FB1) was studied and the effectiveness of nixtamalization and water extraction for detoxifying CM compared. Male rats (n=10/group) were fed equivalent weights (5% CM in the diet) of nixtamalized CM (NX) providing 58 ppm hydrolyzed FB1 (HFB1) and no FB1, water-extracted CM (WE) providing 8 ppm FB1, or CM providing 71 ppm FB1 for four weeks. A control group (SC) was fed a diet containing sound seed corn which had no detectable FB1. NX was hepatotoxic and hephrotoxic. Serum chemical and histopathological effects were qualitatively indistinguishable from those induced by the CM, although liver lesions in the NX group were noticeably less severe. In contrast, hepatic lesions were not found in WE fed rats. Kidney lesions found in the WE group were similar in severity to those in rats fed NX or CM. Thus, the organ-specific effects of nixtamalized CM containing hydrolyzed F1 were similar to those of the FB1-containing CM and nixtamalization was not as effective as water extraction for detoxification of fumonisin-containing corn.