Evaluation of a standard reference material for falling number

Authors: Delwiche, Stephen - Steve; Rausch, Steven - Steve; Vinyard, Bryan

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2020
Publication Date: 1/20/2020
Citation: Delwiche, S.R., Rausch, S.R., Vinyard, B.T. 2020. Evaluation of a standard reference material for falling number. Cereal Chemistry. https://doi.org/10.1002/cche.10259.
DOI: https://doi.org/10.1002/cche.10259

Interpretive Summary: Falling number (FN) is a decades-old method performed worldwide that assesses wheat for its quality in making bread, noodles, cakes, and other products. Low values signify poor quality, while higher ones, usually desired, indicate a dormancy in the enzymes that break down starch into smaller molecules. The method is a common specification in sales contracts and, in some countries, a component in official grading operations. Because of the heavy reliance of FN in commerce, a means to verify the stability of the method is desired. Herein a study is described that searched for the 'best' material to use as a standard, with best defined as having high precision and long shelf life. Four native starches were tested. Corn starch was deemed best, showing week-to-week variation of less than 2 percent. The recommendations offered in this work will benefit official inspection agencies and wheat commerce in general by instilling confidence that the instruments and operations used to perform FN are accurate and precise.

Technical Abstract: Falling number (FN), a longstanding procedure that indirectly measures alpha-amylase activity, is routinely used in official inspection operations and commerce to describe the starch integrity of wheat lots. Because price may be moderated by FN, good precision of this procedure is essential. A study was enacted to search for and characterize a reference material that can be used to monitor FN instruments in a network. Four native starches were selected: corn, potato, rice, and wheat. Weekly measurements were made over three months using two FN instruments. Pure native corn starch was the most suitable of the four starches for use as a standard reference material for FN, with repeatability precision producing a coefficient of variation (CV) of 1.4-1.7%. The non-cereal starch, potato, had the poorest precision (CV = 6.1-6.9%). All starches were stable, showing no time effect over the evaluation period. Because of increased reliance on FN as a grading criterion or pricing threshold, added pressure is placed on regulatory bodies to assure the industry of the integrity of system. This work establishes precision limits for time monitoring of FN instruments.