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Wheat Falling Number. What Is It?
Grain elevators paying close attention to falling numbers!
We are getting reports of discounting or rejection of wheat grain because of a low falling number test. The Falling Number (FN) Test for wheat is an indication of preharvest sprouting that has occurred. With the heavy rain during the end of grain fill and just after physiological maturity, this apparently caused an increase in this problem. Often the sprout damage may not be visible, yet the falling number is reduced. Normally our soft red wheat has some resistance against sprouting so this is often not a major problem for us. Our varieties do vary in their resistance to pre harvest sprouting. Virginia Tech has developed a nice factsheet on the issue.
The germination process causes an increase in alpha amylase, an enzyme that breaks down starch. The longer the grain sprouts, the greater the amount of alpha amylase is formed. This enzyme is a problem, because it reduces the quality of flour, and products made from the flour. It can cause sticky dough, and affect loaf volume and shelf life. In pasta, sprouting can reduce shelf life, increase cooking loss, and result in softer cooked pasta.
The falling number (FN) test gives an indication of the amount of sprout damage that has occurred in a wheat sample. It measures the effect of the enzyme on wheat quality. The test calculates the amount of time it takes for a plunger to fall to the bottom of a glass tube that is filled with a heated paste of wheat meal and water. The time taken for the plunger to fall is known as the falling number, and is reported in seconds. High quality wheat makes a very thick paste. The greater the sprout damage, the less sticky the paste, and will result in a much lower FN.
So, what is an acceptable falling number? According to the USDA Wheat Quality Lab, if the FN is greater than 300, there is no sprout damage. If the FN is 200 to 300, there is some sprouting. If the FN is less than 200, severe sprout damage is present. In some cases, good quality wheat can be blended to bring the FN up to a required level. If the quality required for milling cannot be improved by blending, it will have to be utilized for other uses (most likely feed wheat), often resulting in a substantial price deduction.
Pre harvest sprouting can also affect seed germination. If you were planning to replant the seed for cover crop or grain production, this would be a good year to consider a germination test. PDA maintains a seed testing laboratory that can provide this service.