The recent rains and subsequent delays in harvest have many of you worried about sprout damage in their wheat and barley. Sprout damaged wheat and barley pose a real problem for the industry and because of these problems local elevators will steeply discount sprouted grain. Brian Sorenson, Technical Director at the Northern Crops Institute in Fargo describes in some detail below what happens when sprout damage occurs and what effect that has on milling and baking quality. In addition he provides some detail about the falling number test, which is routinely done to check for sprout damage.

A question I have received in recent days is whether you can blend away grain with sprout damage and thus low falling numbers with grain that is sound and has high falling numbers. The general recommendation is that is probably not the best idea. The reasons for not blending are the following:

• The ratio of sprouted grain versus sound grain is not easily determined. You cannot take two lots of grain with falling numbers of 200 and 400 seconds and  expect an average falling number of 300 if you would blend the grain lots 50/50. In the article below, Brian Sorenson also explains in some detail what effect a few sprouted kernels can have in an otherwise sound grain sample.

• The miller and bakers still will have problems with product quality that will adversely affect their bottom line, which in return will harm our region's reputation is a provider of sound, high quality grain as a whole.

Sprout Damage In Cereal Grains and the Falling Number Assay
Brian Sorenson, Technical Director, Northern Crops Institute - Fargo, ND

Sprouting in grain can occur once the kernel has reached maturity; therefore, when mature wheat is subjected to proper moisture levels, temperature and time, it begins to sprout. The physiological changes needed to produce a new plant require energy and nutrients, which is why the wheat kernel produces enzymes to breakdown starch (amylases), oil (lipases) and protein (proteases). This process is exploited in the production of barley malt, which is an enzyme and nutrient "package" vital to the brewing of beer. When moisture levels in the wheat decrease prior to threshing, the sprouting process stops, and if it stops before there are visible signs of sprouted kernels it is called incipient sprouting.

The impact of sprouting on foods produced from wheat depends on the amount of enzymes present and breakdown of the kernel. Sprouting lowers test weight and flour yield, lowering the grade and value to the miller. The impact on baking quality is observed by lower absorption (water added in baking, which reduces bread yield), reduced mixing strength and tolerance, and sticky dough. It can also affect loaf volume, crust strength and crumb texture, whereas a wet and gummy crumb causes problems with slicing and shelf life. The effects on durum are lower test weight, reduced semolina yield and color. In the processing of semolina and pasta, sprouting increases semolina speck counts, reduces shelf life of dried pasta (due to checking or cracking), increases cooking loss, and produces softer cooked pasta.

Much of the frustration and confusion centers on the falling number test used to detect sprouting. The level and impact of sprout damage is not fully realized until it is processed into bread or pasta. It was for this reason that the falling number test was developed. Falling number does not directly measure amylase enzyme activity, but measures changes in the physical properties of the starch portion of the wheat kernel.

When wheat is ground into flour and mixed with water it forms a slurry. Upon heating, the viscosity of the slurry increases due to cooking or "gelatinization" of the starch. This is the basis for preparing gravy. The falling number test begins with the mixing of ground wheat and water in test tubes to form the slurry. The tubes are placed in a boiling water bath (212^oF) and automatically stirred for 60 seconds, causing the starch-water slurry to thicken due to starch gelatinization. After mixing, the stirrers are released at the top of the slurry and begin to fall. When starch granules swell (become gelatinized), they are increasingly susceptible to degradation by amylase enzymes, which increases the rate of thinning in the slurry. The falling number apparatus records the time for the stirrer to fall through the slurry. The rate at which the stirrer falls is directly related to the amount of starch degradation.

There are no standards for falling number, as it is not an official grading factor in FGIS grain inspection and grading process. Generally speaking, a high falling number value (FN > 350 seconds) indicates low enzyme activity and sound wheat. As the amount of enzyme activity increases, the falling number decreases. In the past several years, grain buyers have discounted heavily for falling number values below 300 seconds. Values below 200 seconds indicate high levels of enzyme activity. Falling number values are also important overseas, as many of the export markets have written minimum tolerances of 300 to 350 seconds into their purchase contracts.

When correctly run, the falling number test is fairly repeatable; however, contamination of the sample from a multitude of sources, including the grinder used to make the test flour, can decrease the falling number value. Tests conducted at the Department of Cereal and Food Sciences at NDSU on durum illustrate how contamination can affect the test results. Two visibly sprouted wheat kernels added to 200 grams of sound wheat (.03%) reduced the falling number (FN) by 100 seconds. In another test, sprouted durum flour (FN = 66 seconds) was added at a level of only 1.6% to a sound sample, lowering FN by 34 seconds.

Flushing the grinder by grinding a certain amount of wheat can affect subsequent samples. This was observed in a test in which a sprouted sample (FN = 66 seconds) was followed by a grinder flush of 300 grams of sound wheat. Enough flour was in the system to reduce the falling number from 344 to 325 seconds. Values of 19 and 34 seconds seem small, unless the wheat to be tested is 10 seconds above a discount threshold level. If a small sample of undamaged wheat is ground immediately following a sample with severe sprout damage, without adequate flushing or cleaning of the grinder, substantial contamination is possible.

Proper cleanout of the grinder is time consuming, but may be necessary after grinding a sample with a low falling number. Effective grinder cleaning requires removing the grinding head cover and sample collector to remove flour reside using a brush, compressed air or a vacuum cleaner. Remember, taking precautions to minimize contamination can greatly improve the accuracy of the falling number test, which is important for all parties involved.