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Effects of Falling Number Sample Weight on Prediction of α-Amylase Activity

¹Research food technologist, United States Department of Agriculture, Agricultural Research Service, Soft Wheat Quality Laboratory, Ohio Agricultural Research & Development Center, Ohio State University, Wooster, OH 44691. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.

Reports vary on the effects of falling number (FN) sample weight on test precision, reproducibility, and predictability of α-amylase activity. Straight grade flours of 200 samples (25 cultivars × 2 locations × 2 N₂ levels × 2 repetitions) were assayed for α-amylase activity and FN. Location significantly affected α-amylase activity and FN values. The coefficients of variation (CV) for the FN tests were 5.75, 2.12, 1.93, 1.72, 4.27, and 14.47%, when assayed with sample weights of 7, 6, 5.5, 5, 4.5, and 4 g, respectively. The FN test with the greatest reproducibility between sample replicates (lowest LSD and highest ratio of range/LSD) was also produced using the 5-g sample weight. By reducing FN sample weight from 7 to 5 g, FN values that averaged 350 sec, considered essentially sound, averaged 215 sec, thus shortening the FN test time by an average of 2 min and 15 sec when assaying sound wheat flour. The results suggest a review of the 7-g stipulation of AACC Approved Method 56-81B for FN in favor of reduced sample weight.