PNW Falling Numbers
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About

When wheat grain is sold, the Hagberg-Perten Falling Number test is performed to detect starch degradation. Grain with a falling number below 300 seconds is purchased at a discount because starch degradation leads to poor end-use quality. For example, low falling numbers lead to sticky noodles, cakes that fall, and bread that doesn't rise.

In recent years, low falling numbers have led to substantial losses for farmers in the Pacific Northwest. Low falling numbers resulted mainly from preharvest sprouting due to rain falling on mature grain in the field in 2011, 2013, and 2016. However, low falling numbers have also occurred without rain. This can happen as a consequence of large temperature fluctuations during late grain filling. This phenomenon is called late maturity alpha-amylase or LMA. During these years, different wheat varieties exhibited different tendencies towards low falling numbers in response to rain or temperature changes.

The purpose of this website is to share some falling numbers data. This website was initiated in 2013 in response to a request from the Washington Grain Commission to make publicly available falling numbers data for varieties from the 2013 and 2014 Washington State University Cereal Variety Trials. This effort has continued, and so far there is data from the 2013, 2014, 2015 and 2016 Washington State University Cereal Variety Trials. To see the data on this website click here.

Some observations

It is possible to form hypotheses as to the causes of low falling numbers in the WSU Cereal Variety Trials in recent years. Our hypotheses were formed by comparing weather data from AgWeatherNet and other sources to the time when the wheat was likely susceptible to LMA and sprouting based on the average heading date and harvest date of each location. Our views are as follows.

2013. Preharvest sprouting occurred in Colton, Fairfield, Mayview, Pullman, Reardan, St. John, and Lamont for winter wheat, and in Endicott, Fairfield, and St. John for spring wheat. Potential LMA events occurred in Mayview, Moses Lake, and Walla Walla.

2014. Preharvest sprouting occurred in Almira, Anatone, and Fairfield. Potential LMA events occurred in Bickleton, Connell, Moses Lake, and Ritzville.

2015. Preharvest sprouting occurred in Pullman. It is difficult to determine the cause of low FN at the remaining locations. The Phadebas(R) Amylase Test revealed that some samples with FNs below 300 sec did not show alpha-amylase enzyme levels consistent with induction by preharvest sprouting or LMA. We speculate that some of the low FN in 2015 may have been due to the fact that kernels were shriveled as a result of heat stress and thus had low starch content. Thus, 2015 data must be interpreted with caution as it may not reflect preharvest sprouting or LMA susceptibility.

The falling number test

The Hagberg-Perten Falling Number (FN) test is used to measure damage to the starchy endosperm as a consequence of amylase enzyme action. This method is based on the fact that a slurry of wheat flour in water will gelatinize upon boiling – just like making gravy. Starch chains cleaved by alpha-amylase fail to gelatinize well. The more alpha-amylase in the sample, the faster the stirrer falls, the lower the falling number. Bakers prefer a falling number above 300. While bakers can add alpha-amylase to their dough if the falling number is high, they cannot remove alpha-amylase once it is there. Also, bakers like to have a consistent product. Keep in mind that a small increase in alpha-amylase content has a big effect on falling numbers and quality – so it is unwise to mix sprouted grain with sound because it will just compromise the quality of the sound grain. For example, mixing equal amounts of grain with a falling number of 100 and a falling number of 400, will result in grain with a falling number much lower than 250. This video from Perten Instruments demonstrates the falling number method.

Additional information

This August 2016 Washington State University Extension article, entitled "Managing the Risk of Low Falling Numbers in Wheat", answers frequently asked questions about falling numbers in wheat production. Some additional information can be found in the Wheat Life article Preventing those falling number blues from 2013, and the Wheat Life article Falling numbers: research strategies to stay out of the red from 2014, by Camille M. Steber, Arron H. Carter and Michael Pumphrey.

Funding

Washington Grain Commission projects 7599 and 7336 provided funding for falling numbers testing of the entire WSU Cereal Variety Trials in 2013 and 2014. Washington Grain Commission project 5389 and the USDA-ARS provided funding for falling numbers testing of a portion of the 2015 variety trial. Falling number data for 2016 are being funded in part by USDA-ARS and the Washington Grain Commission project 5389. It should be noted that the main goal of projects 7599 and 5389 is to select for genetic material with robust falling numbers within the spring and winter wheat breeding programs. Thus, many breeding and mapping lines are being tested for falling numbers, LMA, and preharvest sprouting susceptibility. These data do not appear on this website.

People

The principal investigators of the Washington Grain Commission funded projects are Camille M. Steber (USDA-ARS), Michael O. Pumphrey (WSU), and Arron H. Carter (WSU). Major collaborators include Ryan Higgenbotham (WSU Cereal Variety Trial), Kimberly Garland Campbell (USDA-ARS), Craig Morris (USDA-ARS), and Douglas Engle (USDA-ARS). The technician obtaining the falling numbers data were Tracy Harris (USDA-ARS), Xavian Thompson (WSU, project 7336) and Allie Druffel (WSU). They were assisted by Rehana Parveen (WSU), Robert DeMacon (WSU), Carissa Corrigan (WSU undergraduate student), Kristofor Ludvigson (WSU undergraduate student), and Rylee Suhadolnik (WSU undergraduate student). WSU graduate students working on other aspects of the project have included Shantel Martinez, Keiko Tuttle, and Stephanie Sjoberg. Camille M. Steber maintains this website.