Relationships between falling number, a-Amylase activity, milling, and sponge cake quality of soft white wheat

Authors: Kiszonas, Alecia; Engle, Douglas; Pierantoni Arroyo, Leonardo; Morris, Craig

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2018
Publication Date: 5/9/2018
Publication URL: https://handle.nal.usda.gov/10113/6472240
Citation: Kiszonas, A., Engle, D.A., Pierantoni Arroyo, L.A., Morris, C.F. 2018. Relationships between falling number, a-amylase activity, milling, and sponge cake quality of soft white wheat. Cereal Chemistry. 95:373-385.
DOI: https://doi.org/10.1002/cche.10041

Interpretive Summary: The Perten-Hagberg Falling Number method was developed to measure the activity of a amylase in wheat and other cereal flours, meals, and malts. Of note, at the time, a certain level of a-amylase was considered highly beneficial to bread baking (and still is). Of further note, the most widely accepted means of measuring a-amylase activity at that time was the method of Sandstedt et al. (1939) (American Assoc. Cereal Chemists 1957), which expressed a-amylase activity in what were referred to as ‘SKB’ units. The Falling Number method of Perten (1964) was quickly adopted as a means of assessing the degree of sprout damage: Sweden 1964, Ireland 1965, and the U.S. 1967 (flour) (Perten 1967). Sprouted wheat exported from the U.S. Pacific Northwest in 1968 prompted a visit of U.S. experts with Japanese millers and bakers, and constituted a step bringing about understanding of the role the FN test might play in determining alpha-amylase activity as an index of sprout damage in grain for export. The Falling Number method has become firmly entrenched in the U.S. export wheat industry, with contract specifications for Soft White and Western White Wheat generally set at a minimum of 300 s. In 2016, wheat harvested in the U.S. Pacific Northwest experienced sporadic but at times severe low Falling Numbers. Growers routinely received discounts for grain with Falling Numbers below 300 s, which drove renewed interest in the Falling Number test itself and overwhelmed official inspection and testing laboratories with requests for testing. Since many of these low Falling Number occurrences were not associated with rain events typical of pre-harvest sprouting, the present studies were initiated to explore the relationship between Falling Number, a-amylase activity, milling and end-product quality, focusing on soft white wheat.

Technical Abstract: Falling Number of wheat is an important quality predictor and carries with it significant economic impact. Lower Falling Numbers are associated with higher a-amylase activity and poorer soft wheat end-use quality, especially sponge cake. In the present study two sample sets were examined, the first was comprised of grower samples that had been officially inspected, the second set was made up of pure varieties from common locations. Falling Number was generally moderately well correlated with a-amylase activity (r ˜ 0.6 to 0.7); the relationship was not improved by using Liquefaction Number or log transforming a-amylase activity. Stirring Number, an alternative to Falling Number, was less well correlated with a-amylase (r = 0.3 to 0.6). Milling reduced a-amylase activity in break and straight-grade flours compared to grain, but did not eliminate a-amylase activity. Sugar snap cookie diameter was unrelated to Falling Number or a amylase activity. Japanese sponge cake quality, on the other hand, was variably associated with Falling Number and a amylase activity. Among the grower samples, the expected trend was observed: lower Falling Number was correlated with higher a amylase activity, and smaller, harder cakes with poorer texture. In contrast, among the set of pure varieties, no such relationship was observed. It seemed that likely the inherent genetic differences in cake quality of specific varieties out-weighed the effects of a amylase (and similarly relationships with Falling Number). Storing grain one year had some slight positive effect of reducing a amylase activity. In conclusion, field samples of soft white wheat showed the general inverse relationship between Falling Number and a amylase activity. However, the relationship was not strong enough to consider Falling Number a highly robust predictor of a amylase activity or of sponge cake quality. The results of this study illustrate the complex relationship among Falling Number, a amylase, milling and sponge cake quality.