September/
October 1998
Effects of sampling size, method limited in barley DON study
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Prairie Grains is the
official publication of
the Minnesota
Association of
Wheat Growers,
North Dakota Grain
Growers Association,
South Dakota Wheat,
Inc., and the
Minnesota Barley
Growers Association.
Three primary conclusions were drawn from the study:
1) Increasing sample size does not appear to significantly decrease variability of test results.
2) Sample selection method does not appear to cause generally greater variability among DON measurements.
3) No single factor was identified that will significantly reduce variability of DON measurement in an easy and cost effective manner.
"The study results disproved myths related to DON testing of barley," says John Mittleider, executive administrator of the North Dakota Barley Council. "We now have thorough scientific evidence that sample collection method and the testing of larger samples have limited effect on the variability of test results. Much of the variability appears to be associated directly with the technology."
Lance Gaebe, Executive Director of the North Dakota Grain Growers Association, says he feels that today's technology is not adequate to meet the needs of the marketplace. "Buyers and sellers alike demand technology which yields highly repeatable results, unfortunately, those demands cannot be achieved with today's technology," he says.
According to the final report, the variability among individual test results is related to the concentration of DON in the lot. Using official inspection, observed test results between 0.1 to 1.1 parts per million would not be unreasonable for a lot containing 0.6 ppm DON. For a lot with 4.0 ppm, a reasonable range for test results may be 3.0 to 5.0 ppm. Since measurement appears to be the source of variability, one of the few alternatives to significantly improve the consistency of test results is to make multiple independent measurements on a lot and average the results. Unfortunately, that will double or triple the cost of the test, currently about $25-$30 per test, says Gaebe.
There are three primary sources of variability in measurement from analytical tests, according to GIPSA: 1) the sample, 2) sample preparation, and 3) the analytical method. "Results of the study show conclusively that little variability was associated with the sample," says Mittleider. "Since dividing, grinding, mixing and dissemination of
the samples was conducted by the same agency, variation resulting from sample preparation should be minimal. One would surmise the majority of variation in test results is a reflection of the analytical methods used in the study."
The GIPSA-approved test kits Neogen Veratox and Romer FluoroQuant, in addition to gas chromatography and HPLC, were utilized to test for DON levels. No single detection method appeared to provide more repeatable test results.
Over 2,400 tests were conducted on nearly 500 barley samples ranging from 0.5 to 5.0 ppm DON. The study was supported by the NDBC and GIPSA. Other cooperators included the Grand Forks Grain Inspection Department, North Dakota Grain Growers Association, North Dakota Grain Dealers Association, North Dakota State University, Neogen Corporation and Romer Labs. n