Science Snippets!

Extrusion-cooking is often used to process raw grain/meal into an array of different products. In the extrusion process, meal is exposed to high temperatures, high pressure, and shearing forces. Mycotoxins are known potent toxins and can be detrimental to human and animal health. The level of mycotoxin contamination in cereal grain and other crops depends on infection rate and the local environment.

Cazzaniga et al. (2001), based in Argentina, performed an intertesting study on vomitoxin (DON) and Aflatoxin B1 (AFB1) content in red corn (maize) meal and extrusion cooking variables. The authors spiked corn meal samples with 50.0 ppb (parts per billion) AFB1, or 5.0 ppm (parts per million) DON. Cazzaniga et al. (2001) then exposed the corn meal to two different temperatures: 150 or 180°C, and two different moisture contents: 15 or 30%. Before the cooking process the authors added 1.0% sodium metabisulphite to half of the samples, while the other half did not receive the sodium additive. Cazzaniga et al. (2001) measured reduction in DON and AFB1 (by HPLC), output (grams per minute), mechanical energy consumption, and water solubility of the extruded samples, among others.

A 95 to 99% reduction in DON was achieved by extrusion cooking the corn meal, regardless of temperature, moisture, or sodium metabisulphite additive. The sodium metabisulphite additive increased the DON reduction to 99% at both 150 or 180°C, and 15 or 30% moisture content. Thus a 5.0 ppm DON contamination was reduced to 0.25 ppm in this study's corn meal samples.

Only a maximum of 25% reduction in AFB1 was observed. Again, the sodium metabisulphite additive resulted in the 25% reduction of AFB1 regardless of temperature or moisture content. However, without the sodium additive, only a temperature of 180°C and 30% moisture resulted in a 25% reduction of AFB1. The authors propose more severe extrusion settings to reduceAFB1. Interestingly, the sodium metabisulphite additive also resulted in a higher extrusion output (gram per min.), and the additive reduced the consumption of the mechanical energy.

Taken together, AFB1 seems a lot more resistant to extrustion cooking than DON. Adding 1.0% sodium metabisulphite seems a good way to reduce extrusion cooking temperatures to obtain maximum reduction in DON and AFB1. The sodium metabisulphite additive also seemed to affect the extrusion output and mechanical energy consumption.

Reference:

Cazzainga, D., J.C. Basílico, R.J. González, R.L. Torres, and D.M. de Greef. 2001. Mycotoxins inactivation by extrusion cooking of corn flour. Letters in Applied Microbiology. 33:114-147.