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Zearalenone (ZEN) is a mycotoxin produced by the fungus Fusarium graminearum. ZEN is found in contaminated barely, maize (corn), and wheat. ZEN can modulate the hormone estrogen and can lead to reproductive dysfunction in livestock. ZEN is a heat-stable compound and is not reduced by heat alone (Ryu et al., 1999).

Ryu et al. (1999) performed a study on the fate of zearalenone in corn grits during extrusion cooking. During extrusion cooking grains are exposed not only to high temperature but also to moisture, high pressure, and shearing forces. Their objective was to determine the effect of extrusion cooking on the stability of ZEN in spiked corn (maize) grits. The authors exposed corn grits to three different moisture contents: 18, 22, or 26%; to three different extrusion barrel temperatures: 120, 140, or 160°C; and to two different screw types: mixing or non-mixing. Corn grits were spiked with ZEN to a concentration of 4.4 µg/g. After the extrusion experiments the corn samples were analyzed for ZEN by HPLC.

The authors found that the ZEN concentration was more reduced at 120 and 140°C than at 160°C. Ruy et al. (1999) found a 74 to 83% ZEN reduction at 120 and 140°C, while only a 66 to 77% reduction at 160°C. The concentration of ZEN was more reduced by using a mixing screw in the extrusion process. The authors believe this to be due to higher shear forces and better uniformity in mixing of the grain (Ryu et al., 1999). However, Ruy et al. (1999) did see a reduction in ZEN in extrusion without a mixing screw. Ruy et al. (1999) did not observe a significant effect of the three moisture levels on the reduction of ZEN. Although they expected a reduction in ZEN at the 26% moisture level due to the higher heat transfer accommodated by moisture. Taken together, Ruy et al. (1999) propose that the high efficacy of extrusion cooking in reducing ZEN is due to high temperature, high pressure and severe shear forces.

Reference:

Ryu, D., M.A. Hanna, and L. B. Bullerman. 1999. Stability of zearalenone during extrusion of corn grits. J. Food Protection. 62:1482-1484.