Resistant starch and hydrothermal treatment of cornmeal: Factors in aflatoxins and fumonisin B1 reduction and bioaccessibility

Abstract

The objective of the present study was to evaluate the effect of a hydrothermal treatment on the residual levels of aflatoxins (G2, G1, B2, B1) and fumonisin B1 in cornmeal, and to investigate the chemical constituents of cornmeal that could affect potential reductions during in vitro digestion. For this purpose, cornmeal (fine and coarse) were spiked with mycotoxins, and then subjected to hydrothermal treatment. Mycotoxin quantification was determined before and after the treatments; while in vitro mycotoxins bioaccessibility was evaluated after the hydrothermal treatments. Treated samples were also characterized based on their macro components and resistant starch. The hydrothermal treatment of mycotoxin-spiked coarse cornmeal resulted in 36–52% reduction of the aflatoxin and 39% of fumonisin B1 levels; while fine cornmeal showed reductions of 0–41% aflatoxin and 59% fumonisin B1 levels. The reduction of the aflatoxins G2, B2 and B1 was significantly correlated (p < 0.1) with the concentration of the starch. Reductions of the fumonisin B1 levels were significantly correlated (p < 0.05) with concentration of resistant starch and reducing sugars. In the fine cornmeal, 63% of the aflatoxins (G2, B2 and B1) and 27% of the fumonisin B1 were free for absorption in the small intestine; while the remaining fractions (37% aflatoxins and 73% fumonisin B1) were degraded or bound to some component of the matrix. In coarse cornmeal the percentage of bioaccessibility was higher (91% aflatoxins and 35% fumonisin B1) than observed with the fine cornmeal. The non-bioaccessible fumonisin B1 fraction that remained bound to the matrix, possibly was associated to the non-digestible starch, since the reduction of this mycotoxin showed a high correlation with the concentration of resistant starch in the matrix.