Effect of baking and frying on the in vivo toxicity to rats of cornmeal containing fumonisins

Effects of different extrusion conditions on the chemical and toxicological fate of fumonisin B1 in maize: a short review

Fumonisin B1 (FB1) is a common mycotoxin found in maize and maize-based food products. Although FB1 is relatively heat stable and survives most thermal processes, extrusion cooking has been shown to be effective at reducing levels of the toxin in contaminated maize. This review summarises studies on the chemical and toxicological fate of FB1 in maize extruded under different conditions. Overall, these studies indicate that stability of FB1 depends on the extrusion conditions, e.g. temperature and screw speed, and that the presence of reducing sugars augment apparent loss of the toxin. The chemical fate of FB1 was investigated by measuring FB1, hydrolysed FB1, and N-substituted FB1 compounds with a mass balance approach while the relative toxicity was determined by rat feeding trials. FB1 in contaminated grits was reduced by 21-37% and 77-87% in the absence and presence of 10% (w/w) glucose, respectively, during single-screw extrusion. Greater reductions of 64-72% and 89-94% were achieved by twin-screw extrusion. Mass balance analysis showed that most of the FB1 in grits extruded without glucose was recovered as FB1, whereas the FB1-glucose reaction product, N-(deoxy-D-fructos-1-yl)-fumonisin B1 was the prevalent form after extrusion with glucose. 23 to 38% of FB1 in extruded grits with and without added glucose was bound to component(s) of the maize grits. Only 37-46% of FB1 present in unextruded grits could be recovered as one of the fumonisin species (hydrolysed FB1, N-substituted FB1 compounds) or as matrix-bound forms in extruded grits. Reduced FB1 concentrations in extruded grits and the even lower concentrations in grits extruded with glucose resulted in a dose-dependent reduction of toxicity as shown by the less severe apoptotic lesions and sphingolipid effects that were found in the kidneys of rats. In summary, extrusion processing, especially with glucose supplementation, is potentially useful to reduce FB1 concentrations and toxicity of contaminated maize.

Reduced toxicity of fumonisin B1 in corn grits by single-screw extrusion

Corn grits spiked with 30 microg/g fumonisin B1 and two batches of grits fermented with Fusarium verticillioides (batch 1 contained 33 microg/g, and batch 2 contained 48 microg/g fumonisin B1), which were extruded by a single-screw extruder with and without glucose (10%, dry weight basis) supplementation were fed to rats. Control groups were fed uncontaminated grits. Extrusion with glucose more effectively reduced fumonisin B1 concentrations of the grits (75 to 85%) than did extrusion alone (10 to 28%). With one exception, the fumonisin B1-spiked and fermented extrusion products caused moderately severe kidney lesions and reduced kidney weights, effects typically found in fumonisin-exposed rats. Lesions in rats fed the least contaminated grits (batch 1) after extrusion with 10% glucose were, however, significantly less severe and not accompanied by kidney weight changes. Therefore, extrusion with glucose supplementation is potentially useful for safely reducing the toxicity of fumonisins in corn-based products and studies to determine the optimal conditions for its use are warranted.

Reduction of fumonisin B1 in corn grits by single-screw extrusion

This study was designed to determine the efficacy of extrusion in reducing fumonisin B1 in corn flaking grits in the presence and absence of glucose. In addition, degradation products of fumonisin B1 during extrusion were identified and quantitated with a mass balance approach. Uncontaminated clean corn grits, grits spiked with 30 microg/g fumonisin B1, and grits fermented with Fusarium verticillioides M-2552 (40-50 microg/g fumonisin B1) were extruded in the presence and absence of glucose (10%, w/w) using a single-screw extruder. Extrusion decreased fumonisin B1 by 21-37%, whereas the same process with added glucose further decreased fumonisin B1 by 77-87%. LC-fluorescence and LC-MS showed that most fumonisin in the extruded samples without added glucose was the fumonisin B1 form, whereas the main degradation product in grits extruded with glucose was N-(deoxy- d-fructos-1-yl)fumonisin B1. The formation of hydrolyzed fumonisin B1 was not significant during extrusion. Results suggest that extrusion in the presence of glucose may reduce fumonisin B1 in corn grits significantly.

Toxic Effects of Fumonisin in Mouse Liver Are Independent of the Peroxisome Proliferator-Activated Receptor α

Fumonisin mycotoxins occur worldwide in corn and corn-based foods. Fumonisin B1 (FB1) is a rodent liver carcinogen and suspected human carcinogen. It inhibits ceramide synthase and increases tissue sphinganine (Sa) and sphingosine (So) concentrations. Events linking disruption of sphingolipid metabolism and fumonisin toxicity are not fully understood; however, Sa and So were shown to bind mouse recombinant peroxisome proliferator-activated receptor alpha (PPARalpha) in vitro. To investigate the role of PPARalpha in fumonisin hepatotoxicity in vivo, wild-type (WT) and PPARalpha-null mice were fed control diets or diets containing 300 ppm FB1, Fusarium verticillioides culture material (CM) providing 300 ppm FB1, or 500 ppm of the peroxisome proliferator WY-14,643 (WY) for 1 week. WY-fed WT mice exhibited hepatomegaly, an effect not found in WY-fed PPARalpha-null mice, and WY did not change liver sphingoid base concentrations in either strain. Hepatotoxicity found in FB1- and CM-fed WT and PPARalpha-null mice was similar, qualitatively different from that found in WY-treated animals, and characterized by increased Sa concentration, apoptosis, and cell proliferation. Transcript profiling using oligonucleotide arrays showed that CM and FB1 elicited similar expression patterns of genes involved in cell proliferation, signal transduction, and glutathione metabolism that were different from that altered by WY. Real-time RT-PCR analysis of gene expression demonstrated PPARalpha-dependence of lipid metabolism gene expression in WY-treated mice, whereas PPARalpha-independent alterations of genes in lipid metabolism, and other categories, were found in CM- and FB1-fed mice. Together, these findings demonstrate that FB1- and CM-induced hepatotoxicity in mice does not require PPARalpha.

Effects of thermal food processing on the chemical structure and toxicity of fumonisin mycotoxins

Fumonisins are Fusarium mycotoxins that occur in corn and corn-based foods. They are toxic to animals and at least one analogue, fumonisin B1, is carcinogenic to rodents. Their effect on human health is unclear, however, fumonisins are considered to be risk factors for cancer and possibly neural tube defects in some heavily exposed populations. It is therefore important to minimize exposures in these populations. Cleaning corn to remove damaged or moldy kernels reduces fumonisins in foods while milling increases their concentration in some and reduces their concentration in other products. Fumonisins are water-soluble and nixtamalization (cooking in alkaline water) lowers the fumonisin content of food products if the cooking liquid is discarded. Baking, frying, and extrusion cooking of corn at high temperatures ( > or = 190 degrees C) also reduces fumonisin concentrations in foods, with the amount of reduction achieved depending on cooking time, temperature, recipe, and other factors. However, the chemical fate of fumonisins in baked, fried, and extruded foods is not well understood and it is not known if the reduced concentrations result from thermal decomposition of fumonisins or from their binding to proteins, sugars or other compounds in food matrices. These possibilities might or might not be beneficial depending upon the bioavailability and inherent toxicity of decomposition products or the degree to which bound fumonisins are released in the gastrointestinal tract. In this review the affects of cooking and processing on the concentration and chemical structure of fumonisins as well as the toxicological consequences of known and likely fumonisin reaction products are discussed.