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  5. Quality Assessment of Corn Silage

Silage is a high-moisture fodder which is fed to cattle, livestock, and other ruminant animals. It is formed by partially fermenting forage plants such as wheat or corn in a silo. Fermented crops have high palatability and nutritional value, but during fermentation process, silage bacteria produce volatile fatty acids, which include lactic acid in large amounts that often gives fermented crops a sour note. Sometimes moisture allows for the possible growth of molds and toxic substances produced by fungi and mold, such as aflatoxins and Fusarium moniliform (moldy corn disease); both being potentially fatal if ingested. Molds and fungus produce odors also containing microbial volatile organic compounds (MVOC), which are perceived by humans as musty smells and could be harmful.

Three most common molds associated with silages include Penicillium roqueforti, Aspergillus fumigatus, and Monascus ruber. Some molds even lead to the development of dangerous mycotoxins that make silage unfit for livestock consumption and could even be lethal to animal health. Some of such molds proliferate when the crop is in growing stage, while others propagate during storage.

Storage molds originate from soil-borne spores that are brought into the silo with all forages. They need oxygen from air to sporulate and commence growing in silages. Mostly storage mold blooms when pH is greater than 4.5, a result of yeast activity that could arise at low pH in the presence of oxygen, causing pH to rise above 4.5. Therefore, grain samples before and after fermentation should be tested to determine potential health risks of the mycotoxins. Field molds occur only in cereal grain crops, like corn and wheat, therefore in corn, Gibberella, Aspergillus, and Fusarium ear rots are accountable for producing a range of mycotoxins, including vomitoxin, zearalenone, T-2, fumonisin, and aflatoxin.

As any amount of mold in corn kernels or wheat berry is considered damaged, detection of such rotten kernels should be detected soon. Electronic Sensor Technology’s Portable zNose® is a useful tool for assessing the quality of aromatic food products such as corn and wheat silage. It helps in detecting the damaged moldy grain kernels by quantifying the musty odor. To speculate the efficiency of zNose®, sour, musty and good corn samples were evaluated.

The chromatogram results of testing all type of corn samples displayed the profound quantification and clear difference among all the samples:

  • The lactic acid peak in the sour samples was clearly visible.

  • The distinctive compound peaks of musty corn were different from other samples and were not present to any large extent in other samples.

  • The relatively odor free chromatograms of both good corn samples are in stark contrast as well.

The relatively odor free chromatograms of both good corn samples give only small images as their odor concentration is low. Whereas, the lactic acid peak of sour samples and the distinctive compound peaks of moldy corn are easily recognizable, indicating high concentrations. Therefore zNose® unlike other electronic noses is unique with substantial features and capacity. It is portable, accurate and speedy in rendering testing results with precision.


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