Posted 20 October 2008. PMN Crop News.
Preharvest Sprouting and Mold Appering in 2008 Barley Crop
Quality factors, such as preharvest sprouting (PHS) and mold, have appeared in the 2008 barley crop
North Dakota State University. www.ndsu.nodak.edu
Fargo, North Dakota (October 2, 2008)--According to the National Agricultural Statistics Service, the 2008 barley harvest is almost 92 percent complete nationwide. In early September, some protein and plump quality issues appeared. Since then, other quality factors, such as preharvest sprouting (PHS) and mold, have appeared in the 2008 crop. Both can render a barley crop unacceptable for malting and can cause problems for maltsters and brewers.
“IBMS scientists and collaborators are continually researching for methods to identify PHS damage and to produce resistant varieties,” says Paul Schwarz, North Dakota State University Institute of Barley and Malt Sciences director.
“PHS or pregermination, referred to as germination of kernels on the plant before harvest, typically occurs when rainy or wet weather conditions delay harvest in the field,” says Richard Horsley, NDSU barley breeder. “Plants with low seed dormancy generally are more susceptible to PHS. These phenomena of PHS and dormancy have been extensively studied worldwide in several cereal crops, including barley, bread wheat and durum wheat. Barley with PHS is an ever-present concern in the malting barley industry because it can lead to reduced grain yield, grain quality and malting quality. Thus, PHS imposes serious technological and economic impacts on growers, maltsters and brewers.”
Low dormancy, combined with the wet, cool summer weather conditions, has led to serious PHS problems in the upper Midwest in recent years. The occurrence of barley PHS in 2002 in Minnesota and North Dakota was the most serious since the regional barley crop quality survey was initiated in 1977.
A barley plant having kernels with rootlets or even leaves growing out of it obviously is sprouted. A more difficult problem to spot may be partially sprouted barley. Another term used in the malting industry to describe germinating barley with just the tips of the rootlets (radicle) emerging from the kernel is “chitted.” Barley with incipient sprouting or chitting initially may regerminate. However, the germination percentage may drop to unacceptable levels (less than 95 percent) during storage. The buyer determines the allowable amount of sprouted kernels.
“However, research done outside of NDSU has shown that the amount of sprouted kernels should not exceed 2 percent to 3 percent in malting barley to avoid large losses in germination during storage,” Horsley says. “Other problems due to PHS that can arise during the malting process include nonuniform germination, increased water sensitivity and higher mold growth. Use of malt made from barley with PHS may result in low wort (the liquid used to make beer) yields during brewing. Grain not acceptable for malting because of PHS usually is used for animal feed.”
Dormancy usually is determined by a germination test of manually threshed kernels, while several techniques are available for determining the extent of PHS. To determine the range of PHS damage, one of two types of methods is used. One is a visual score of grain germination. The other is an enzyme-related -amylase, measurement, including direct and indirect measurement of the enzyme which is produced during germination.
In the U.S., visual examination for sprouted grain is the official method approved by the U.S. Department of Agriculture’s Grain Inspection, Packers and Stockyards Administration. A limitation of this method is that it is subjective and cannot detect the extent of sprout damage in some instances.
Another test for sprout damage is the pearling test. It is used a great deal in the U.S. by the malting industry. This test relies on a visual examination of the kernels following pearling to remove a portion of the husk.
A widely used group of methods used by malting barley procurers is to determine PHS based on the measurement of the enzyme alpha-amylase. In sound or unsprouted barley, the enzyme alpha-amylase is not found because it is produced during germination. The two most commonly used methods for detecting the presence of alpha-amylase are measurement of falling number (FN) on the falling number apparatus and stirring number (SN) on the rapid visco-analyzer.
Both methods indirectly measure alpha-amylase activity by the evaluation of starch pasting properties. The FN method is used more in the wheat industry and the SN method is used more in the malting barley industry in the U.S. Both methods have been approved by the American Society of Brewing Chemists (ASBC) as standard methods for assessment of barley PHS damage.
“Because PHS was severe and widespread in 2002, it became obvious that a standardization of methods would be helpful,” says Scott Heisel, American Malting Barley Association (AMBA) vice president and technical director. “At the time, the industry measured PHS using a pearling method, while the Federal Grain Inspection Service (FGIS) measured sprout damage by a visual method without pearling. Generally, the FGIS method underestimated sprouting compared with the industry method. This created a problem with crop insurance. Producers with coverage for sprout damage had barley that was rejected by the industry (using a pearling method) but insurers only recognized the FGIS method as official. In many cases, producers could not collect because the official method underestimated sprouting.”
Because of these problems, the AMBA began to organize collaboratives with the barley industry, FGIS and NDSU late in 2002 and early 2003. These were organized to satisfy the new testing method requirements of both the FGIS and ASBC. FGIS accepted a method called “injured by sprout” in December 2003. ASBC accepted the "sprout damage by pearling” method at the annual ASBC meeting in 2004. The outcome for growers was that the injured-by-sprout FGIS method officially was recognized by crop insurance providers (Risk Management Agency) beginning with the 2008 crop at levels above 1 percent.
Rongshuang Lin, a former doctorial student in Horsley’s barley breeding/genetics project, developed a screening test to identify barley varieties that may be susceptible to PHS as part of her dissertation research. This test involves the harvesting of barley spikes at harvest maturity, placing them in the freezer so they do not begin the process of losing dormancy, hand threshing the heads and germinating the seeds in Petri dishes. Using this technique, Horsley and Lin were able to determine that varieties, such as Robust or Tradition, with moderate dormancy and resistance to PHS may have germination ranging between 20 percent and 35 percent. Nondormant varieties, such as Stander and Legacy, that are susceptible to PHS may have germination ranging between 60 percent and 90 percent.
Horsley’s project continues using this test to determine potential susceptibility to PHS in experimental barley lines in the NDSU barley-breeding program and to screen dormancy levels in breeding lines from seven barley-breeding programs in the U.S. This work is being funded by the USDA’s Cooperative State Research, Education, and Extension Service Barley Cooperative Agricultural Project.
Another problem seen by some producers in certain areas this year is mold in the harvested crop. For a long time, brewers have avoided barley that is visibly moldy because of problems that can be encountered in brewing.