HIGH-SPEED OPTICAL SORTING OF SOFT WHEAT FOR REDUCTION OF DEOXYNIVALENOL

Authors: Delwiche, Stephen - Steve; Pearson, Thomas; Brabec, Daniel - Dan

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2005
Publication Date: 11/1/2005
Citation: Delwiche, S.R., Pearson, T.C., Brabec,, D.L. 2005. High-speed optical sorting of soft wheat for reduction of deoxynivalenol. Plant Disease Journal. 89(11):1214-1219.

Interpretive Summary: Fusarium head blight (FHB) is a fungal disease that affects cereal grains such as wheat, barley, corn, oats, and rye. FHB is becoming increasingly more prevalent throughout the northern hemisphere, while, at the same time, countries are becoming more restrictive on the allowance of FHB-contaminated grain in food and feed. In addition to reducing harvest yield and diminishing the quality of breads from wheat and beer from barley malt, FHB poses a greater problem in that this fungus produces a metabolite known as deoxynivalenol, also called vomitoxin or DON. This mycotoxin can cause sickness in humans and non-ruminant animals. Because of this health risk, nearly 100 countries have placed or are planning to place regulatory or advisory limits on DON concentration in raw and processed wheat formulations. For example, in the United States, the Food and Drug Administration has established voluntary advisory limits for DON that the domestic food and feed industries follow. Currently, this level stands at 1 part per million (ppm) for finished wheat products for human consumption. Should such limits become more stringent by action of the U.S. Government changing from an advisory to a regulatory condition for DON (as it does with other mycotoxins, such as aflatoxin), farmers, traders, and processors will face the potential of having no means to market wheat that possesses elevated levels of DON. Therefore, a study was undertaken to examine to potential of high-speed optical sorting for removal of FHB-contaminated kernels. More than 40 samples of soft red winter and soft white wheat, each approximately 5 kg, were obtained from commercial mills in the eastern United States. The sorter, which uses detectors and interference filters, one in the visible region (675 nm) and the other in the near-infrared region (1480 nm), consists of a series of parallel inclined channels. Each channel conveys a stream of single-file kernels that are observed by the detectors upon exiting each channel, whereupon air jets are used to divert the damaged kernels. Detector wavelengths and threshold signals were chosen to heighten the separation of normal and Fusarium-contaminated kernels. Results indicate that DON concentration were reduced by approximately one half on average, with further reduction arising from the resorting of accepted material. Representing the first reported work to the authors knowledge on the application of high-speed optical sorting of Fusarium-infected wheat, this study is intended to benefit the wheat trade and processing industries who will be faced with increasing pressure to maintain safe and low levels of DON in cereals and their products.

Technical Abstract: Fusarium head blight (FHB) is a fungal disease that affects small cereal grains, such as wheat and barley, and is becoming more prevalent throughout much of the World's temperate climates. The disease poses a health risk to humans and livestock because of the associated production of the mycotoxin, deoxynivalenol (DON or vomitoxin). A study was undertaken to examine the efficiency of high-speed, optical sorting of intact wheat kernels for reduction of DON concentration. Soft red winter (n = 32) and soft white (n = 3) wheat samples, known to have elevated levels of FHB, were obtained from commercial mills throughout the eastern United States. An additional 7 samples of wheat from the discard piles of in-mill cleaners were also studied. Fusarium-damaged wheat, cleaned of non-kernels and foreign material (~4.5 kg/sample, DON range = 0.6-20 mg/kg), was fed into a commercial high-speed bichromatic sorter operating at a throughput of 0.33 kg/(channel-min) and a kernel rejection rate of 10%. A wavelength filter pair combination of 675 and 1480 nm was selected for sorting, based on prior research. Visual measurements of the proportion of Fusarium-damaged kernels were collected on incoming and sorted (separate analyses of accepted and rejected seed), as were measurements of DON concentration. Results indicated that the fraction of DON contaminant level in the sorted wheat to that in the unsorted wheat ranged from 18 to 112 percent, with an average of 51 percent. Nine of the 35 regular samples and all 7 of the discard pile samples underwent a second sort, with 5 from this second set undergoing a third sort. Multiple sorting was effective in producing wheat whose DON concentration was between 16 and 69 percent of its original, unsorted value.