PRESERVATION, ENHANCEMENT, AND MEASUREMENT OF GRAIN QUALITY AND MARKETABILITY
Location: Engineering and Wind Erosion Research Unit
Title: Detection of lesser grain borer larvae in internally infested kernels of brown rice and wheat using an electrically conductive roller mill
Submitted to: Cereal Foods World
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2012
Publication Date: March 16, 2012
Citation: Brabec, D.L., Pearson, T.C., Flinn, P.W. 2012. Detection of lesser grain borer larvae in internally infested kernels of brown rice and wheat using an electrically conductive roller mill. Cereal Foods World. http://dx.doi.org/10.1094/CPLEX-2012-0316-01R.
Interpretive Summary: A small mill was designed to facilitate detection of rice and wheat kernels infested by hidden stored grain insects. These insects bore into kernels as tiny larvae and live their entire pre-adult life inside the kernels, with no visible indication that they are there. When they reach adulthood, they emerge from the kernel and can lay thousands more eggs which can lead to loss of grain and poor quality. Given that the immature insects are hidden inside the kernels, there is no good method to detect infested kernels. The modified mill was shown to have high accuracy in detecting infested kernels. This will allow better monitoring for these pests and allow better quality control of incoming and outgoing product, leading to better overall grain quality.
Modifications were made to a small laboratory mill to enable the detection of rice kernels infested by immature, hidden stored-grain insects. The mill, which was originally designed for wheat, monitors the electrical conductance through the grain and detects kernels that are infested with live insects based on abrupt changes in the electrical conductance as the insects are crushed between the mill rolls. The mill was adapted to detect rice infested by immature lesser grain borers by altering the gearing and reducing the gap between the two mill rolls to produce shear between the rolls. The samples of infested long-grain brown rice and hard red winter wheat were tested in both the modified and original mills. The detection rates for rice kernels infested with large, medium and small larvae of the lesser grain borer were 97%, 83%, and 42%, respectively, in the modified mill and 61%, 22%, and 4%, respectively, in the original mill. Similar detection rates were observed in medium-grain and short-grain brown rice in the modified mill. Improved detection rates when using the modified mill were also observed in infested hard red winter wheat. The detection rates in hard red winter wheat kernels infested by large, medium, and small larvae were 98%, 94%, and 78%, respectively, with the modified mill and 78%, 67%, and 38%, respectively, with the original mill. Additional time was required to process a sample with the modified mill than with the original mill. For rice, a 500g sample could be processed in approximately 150 seconds, making the instrument useful for quality control checks of incoming or outgoing product or for monitoring grain in storage to determine whether fumigations are necessary.However, for wheat, kernels often bridged in the modified mill so the benefit from increased accuracy may not outweigh the feeding issues.