Alternative Falling Number Measurement Tested by Wheat Marketing Center – May Benefit U.S. Farmers, Global Customers

An alternative way of measuring falling numbers that would benefit U.S. wheat farmers and customers around the world who rely on U.S. crop quality earned positive reviews during product testing late last year at the Wheat Marketing Center (WMC), Portland, Ore.

Meanwhile, there is renewed hope for a “rapid” system that will allow farmers to test falling numbers in the field – as they harvest their wheat.

Washington State University leading the way

In January, during the U.S. Wheat Associates (USW) Winter Board of Directors meeting, WMC Technical Director Dr. Jayne Bock provided an update on her team’s participation in the project. Bock credited Washington State University (WSU) for developing the system, which is described as “faster and more accurate” than the decades-old falling number test currently being used.

U.S. wheat farmers also played a role in the product testing – WMC used samples of soft white (SW), hard red winter (HRW), hard red spring (HRS) and hard white (HW) wheat.

Amber Hauvermale, a research assistant professor in Washington State University’s (WSU) Department of Crop and Soil Sciences, led a team that was behind the project.

“Amber and the WSU team were the drivers of this project, and they worked hard to develop the test and the technology itself,” Bock said. “The Wheat Marketing Center became involved when WSU and its commercial partner, EnviroLogix, had developed a prototype and needed to perform beta testing on the new equipment and the method. We had wheat samples coming through our lab during the 2024 harvest, and we regularly test for falling number. So we agreed to test the WSU test.”

Importance of measuring falling numbers

In general, the falling number is a factor that helps define the quality of wheat for buyers. It also affects the price farmers receive. A low falling number, resulting from high alpha-amylase levels in the sample, significantly lowers the price paid to growers.

The current method, called the Hagberg-Perten Falling Numbers Test, originated about 70 years ago. It requires mixing a wheat meal sample with water, then putting that mixture on an instrument that heats water to the boiling point. A falling number is the time that it takes for a plunger to fall through a test tube of the wheat meal “gravy.”

In the wheat industry, prices can be discounted when falling numbers go below 300 seconds. According to one estimate, low falling numbers cost the grain industry millions of dollars each year.

The new method of measurement aims to be more accurate.

“The grain industry needs accessible tools that are deployable across diverse testing environments (farms, elevators, labs) to quickly identify low falling numbers in a time frame that allows for effective quality management,” Hauvermale said. “The immediate goal with the new rapid test is to preserve grain quality at harvest every year. Additionally, we hope this test will help wheat breeders select for improved wheat varieties with fewer falling number problems. We are encouraged by the performance of the new rapid test in the first year of pilot studies and have received positive industry and grower feedback about its potential usefulness.”

Grain science and practicality

One of the big issues with the Hagberg-Perten Falling Number Test has been that it is based on an indirect measure of enzyme activity – starch viscosity – and that viscosity varies with altitude

and pressure. As a result, testing varies in different places, Bock explained.

“One of the issues with the falling number instrument can be sensitivity to testing elevation, so just like baking a cake, you have to follow different baking instructions at different elevations,” she added. “It’s kind of the same thing with the falling number test in that you have to apply a correction, and while it’s gotten better with the transition from elevation correction to barometric pressure correction, it’s still something that you have to apply every single time you run the test.”

Another issue with the current method is that it can capture more than just enzyme activity.

“We assume that when we have a low falling number it’s due to preharvest sprouting. We make that universal assumption,” Bock said. “But there are other reasons there might be a low falling number. Maybe there was some kind of weather event that affected starch, and those don’t necessarily imply that the wheat is not suitable for baking. And so the main challenge is there are other causes of low falling number that don’t necessarily reflect what the baking potential is of the wheat being tested.”

A different way of measuring

The WSU project is based on a direct measurement.

“Basically they have created a test that directly measures the alpha amylase using little test strips, and it provides correlated number values,” Bock said. “The number test is based on gelatinizing the starch and seeing what kind of viscosity you get. If that viscosity is low, you get an exceptionally low falling number. What this new test is doing is directly measuring the presence of that alpha amylase. It does not rely on the cause of viscosity. There are many things that can affect starch viscosity.”

Bock and WMC received a prototype device at their office in Portland right before the 2024 harvest and trained on how to run the test. As wheat samples came in, WMC staff ran the traditional falling number test – and then ran the new alternative test.

Promising results, discoveries

“We had those tests side by side to see how they compared to one another,” Bock said.
“At the end of harvest, we shared our results with the Washington State team and the EnviroLogix team. The agreement was quite good. What we found was that, depending on the class of wheat, protein content can influence how well the results correlate. Again, the falling number is based on viscosity and protein will influence that viscosity. So, we are finding that there is a little bit of a correction factor that needs to be applied for protein content. We were also able to identify samples where the old test measured a low falling number, and the alternative test identified it as good, sound wheat.”

The samples were pulled, and it was discovered there was a weather event, a freeze, which happened sometime in the spring.

“We don’t know how, but the freeze influenced the starch in a way that gave us a low falling number,” Bock said. “The alternative falling test correctly identified that there was no amylase present and when we baked using those same samples, we got nice cake performance. We could see that the baking quality was not impacted. It was an example where the new alternative test correctly classified those samples, whereas the traditional test did not.”

Good reviews from testing

Overall, Bock described the new test as “a bit more sensitive and more accurate in correctly classifying samples relative to the falling number.”

Still, she expects there will be more testing and more possibilities for the new test, even as EnviroLogix moved forward and made test kits commercially available starting in January.

“They obviously have greatest confidence with soft white wheat right now, but they’re expanding their data set to include more hard wheats, and soft red winter (SRW) wheat,” she said. “As time goes on and they have more samples to work with, I expect we’ll continue beta testing to make sure correlations are set up properly for all hard and soft wheat classes, and eventually durum.”

Allowing farmers to test could become a reality.

“My understanding is that moving forward they will be looking to develop a faster version of the test, one that eventually will allow growers to be able to use out in the field,” Bock said. “I know that is one of the goals and they are working toward it.”