Understanding Wheat Quality Tests
By Sally Sologuk and Brian Sorenson, Northern Crops Institute
Gone are the days when a farmer could just load his grain into a wagon and simply sell it at market. Today's grain marketing involves scientific tests and tools that prove the wheat's quality. Each year, Northern Crops Institute in Fargo, N.D., teaches processors, producers, elevator managers, and industry personnel how to better use and understand these tests.
“Protein and moisture are key quality tests for both grade and marketing price of wheat,” according to Brian Sorenson, Technical Director at Northern Crops Institute, Fargo, N.D. “Farmers are most familiar with these tests since almost all HRS wheat is purchased on protein content.”
Falling number is a test more recently introduced into country elevators. It gives an indication of the amount of sprout damage that has occurred within a wheat sample. Generally, a falling number value of 350 seconds or longer indicates low enzyme activity and very sound wheat. As the amount of enzyme activity increases, the falling number decreases. Values below 200 seconds indicate high levels of enzyme activity.
Why is this important? Sprouting can affect food made from wheat in many ways. It can reduce mixing strength, cause sticky dough, and affect loaf volume and shelf life. In pasta, sprouting can reduce shelf life, increase cooking loss, and produce softer cooked pasta.
“Often, the falling number test causes frustration and confusion,” says Sorenson. “The level and impact of sprout damage is not fully realized until it is processed into bread or pasta. The falling number test does not directly measure amylase enzyme activity, but measures changes in the physical properties of the starch portion of the wheat kernel caused by these enzymes during the test.”
Falling number tests can be run in remote locations like elevators or testing facilities and replicated anywhere in the world. This is important to importers who need to verify the quality of their purchases. Many buyers from export markets have written minimum tolerances of 300 to 350 seconds into their purchase contracts. In the past several years, grain buyers have discounted wheat for falling number values below 300 seconds.
Other tests run on wheat at the elevator are:
Protein is a very important factor in HRS wheat since premiums or discounts are applied based on the protein content of the wheat. Most of our markets, both domestically and internationally, are purchasing HRS wheat with a target protein content of 14-15%. High protein HRS wheat is used for making high gluten bread flour and for blending with lower protein wheat to improve its baking quality and performance. Protein is very important for durum, also, because a minimum 13.5% protein is needed to produce premium pasta with 12.5% protein.
Vitreous kernel count (Dark, Hard, and Vitreous or DHV) is a test performed on both HRS and durum wheat that indicates kernel hardness. Many buyers feel that high levels of DHV in HRS wheat will give them improved levels of bread making performance. In durum wheat, high levels of HVAC (hard vitreous amber color) produce a higher milling extraction of semolina and less flour production. Many of the domestic and international durum millers will specify HAD (hard amber durum) requiring 75% HVAC. Some may even purchase 85-90% HVAC as choice milling durum.
Test weight is important because it gives an indication of the milling yield. A low test weight tells a miller that he will get a lower production of usable flour or semolina. Wheat that is plump and has a high test weight is very valuable to the miller because it provides a high flour and semolina extraction.
For more information about the falling number test, see: http://www.ag.ndsu.nodak.edu/aginfo/smgrains/fallnum.htm
How to conduct a
Falling Number Test:
Step 1 : NCI Food Technologist prepares a sample for the falling number test. Whole ground wheat or flour and water is added to the test tubes and shaken to form a slurry.
Step 2 : Stirring rods are inserted into the test tubes, which are placed in the boiling water bath (212 F) in the falling number apparatus. They are automatically stirred for 60 seconds, causing the starch-water slurry to thicken due to starch swelling or “gelatinization.” When starch granules become gelatinized, they are increasingly susceptible to degradation by amylase enzymes, which increases the rate of thinning in the slurry.
Step 3: After mixing and heating, the stirrers are released at the top of 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 by amylase enzymes. A falling number value of 300 seconds or longer indicates low enzyme activity and very sound wheat.