As the Number Falls, Alternatives Advanced to the Hagberg-Perten Falling Number Method: a Review

Authors: HU, YANG - Washington State University; SJOBERG, STEPHANIE - Washington State University; CHEN, JAMES - Washington State University; HAUVERMALE, AMBER - Washington State University; Morris, Craig; Delwiche, Stephen - Steve; Cannon, Ashley; Steber, Camille; ZHANG, ZHIWU - Washington State University

Submitted to: Comprehensive Reviews in Food Science and Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2022
Publication Date: 4/11/2022
Citation: Hu, Y., Sjoberg, S.M., Chen, J., Hauvermale, A.L., Morris, C.F., Delwiche, S.R., Cannon, A., Steber, C.M., Zhang, Z. 2022. As the Number Falls, Alternatives Advanced to the Hagberg-Perten Falling Number Method: a Review. Comprehensive Reviews in Food Science and Food Safety. 21(3):2105-2117. https://doi.org/10.1111/1541-4337.12959.
DOI: https://doi.org/10.1111/1541-4337.12959

Interpretive Summary: Starch degradation, a primary cause of poor end-use quality in wheat, is mediated by alpha-amylase enzymes. The Falling Number (FN) method is the industry's standard method of assessing starch degradation in wheat. However, the FN test is time-consuming and produces variable results. In addition, the presence of alpha-amylase can lead to huge economic losses for growers, millers, and bakers. Farmers receive severe discounts for grain with an FN below 300 sec because bakers find that low FN/high alpha-amylase is associated with high risk of poor end-product quality. This review describes four alternative tests that have the potential to replace the FN test and increase profits for the wheat industry.

Technical Abstract: This review examines the application, limitations of, and potential alternatives to the Hagberg-Perten falling number (FN) method used in the global wheat industry to detect the risk of poor end-product quality. By viscometry, the FN test indirectly detects the presence of the alpha-amylase, the primary enzyme that digests starch. Wheat is used to make a wide variety of products including bread, cakes, cookies, and noodles. Unfortunately, wheat product quality can be severely degraded by preharvest sprouting (PHS), germination on the mother plant due to moist or rainy weather before harvest. Alpha-amylase is produced in grain due to PHS and a second phenomenon called late maturity alpha-amylase (LMA), which is induced by temperature fluctuations during the grain filling stage of development. PHS has a stronger negative impact on quality than LMA, possibly due to expression of additional hydrolytic enzymes. Wheat grain with low falling number/high alpha-amylase results in annual losses in the U.S. alone of ~ $1 billion to farmers, traders, millers, and bakers. Unfortunately, a large amount of sound wheat can be ruined if mixed with a small amount of sprouted wheat. Although blending of PHS- or LMA-damaged wheat with sound wheat may be used as a means of moving affected grain through the marketplace, care must be taken to avoid grain lots from falling below contract specifications for FN. The FN method is successfully employed to detect alpha-amylase after harvest. However, point of receival limitations of the method include sampling variability, labor-intensiveness, and destructive nature of the test, and an inability to differentiate between LMA and PHS. Alternatives to the FN method include the rapid-visco analyser (a dynamic viscometer), enzyme assays, immunoassays, near-infrared spectroscopy, and hyperspectral imaging (HSI). Fast and robust alternatives to FN could be used to preserve the value of wheat grain or flour by avoiding inadvertent mixing of high and low FN lots at every stage of the grain operations from harvest, through transport, storage, milling, and end-product.