NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
September 21, 2000
Rains that occurred before the spring wheat and durum harvest was complete in northern North Dakota resulted in weathered and sprout damaged grain, and subsequent market discounts.
According to Michael Peel, extension agronomist at North Dakota State University, an obvious quality problem from sprouting is reduced test weight. The germination process, activated in mature grain that is too wet to harvest, reduces nutrients in the grain, primarily a loss of starch.
Sprouting also reduces total protein, although at first glance it may appear that sprouted grain is higher in protein. This is biologically impossible, Peel says. For example, a sample of undamaged wheat weighing 60 pounds per bushel and containing 12.3 percent protein would have 7.5 pounds of protein per bushel. Following sprouting the protein test might be 13.1 percent, but the test weight is reduced to 55 pounds per bushel. A bushel of grain now contains only 7.3 pounds of protein.
Sprouting activates enzymes in the wheat kernel, which causes serious quality problems for processors. Compounding the problem, says Peel, is that sprout damage can affect the inside composition of the grain kernel even though the exterior of the kernel seems sound. The falling number test is used to detect this sprout damage.
The falling number is a measure of the time required for a plunger to fall through a slurry made from flour and water. The time in seconds is the unit of measurement. The higher the enzymatic activity, the less time is required to break down the starch. Therefore, the lower the falling number, the greater the sprout damage.
Generally speaking, he says, falling numbers above 300 indicate no sprout damage, numbers between 200 and 300 indicate some sprouting, and falling numbers below 200 indicate severe damage.
"There are subtle indicators to look for when sprouting is suspected but not visible," says Peel. "Weathered kernels, of course, is the first clue. Also, weather conditions that lead to sprouting also favor development of fungi that cause black point. Wheat with a weathered appearance and black point is likely to also have sprout damage."
Sprouting counts as damaged kernels when wheat is graded. U.S. No. 1 grade wheat can have up to 2 percent damaged kernels while No. 2 wheat can have 2.1 to 4 percent damaged kernels, No.3 can have 4.1 to 7 percent, No. 4 wheat can have 7.1 to 10 percent, and No. 5 wheat can have 10.1 to 15 percent damaged kernels.
Sprouting will not increase in storage, but wheat put in storage at high moisture levels will have severe mold problems, Peel says.
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Source: Michael Peel, (701) 231-8307
Editor: Gary Moran, (701) 231-7865