Storage conditions affecting increase in falling number of soft red winter wheat grain

Authors: Ji, Taehyun; Baik, Byung-Kee

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2015
Publication Date: 5/1/2016
Publication URL: http://handle.nal.usda.gov/10113/5488154
Citation: Ji, T., Baik, B.-K. 2016. Storage conditions affecting increase in falling number of soft red winter wheat grain. Cereal Chemistry. 93:263-267.

Interpretive Summary: Prolonged rainfall at harvest time along with accompanying cool temperatures, which are common in the eastern region of the U.S.A., induce the sprouting of wheat grain in the field before harvest and a corresponding increase in alpha-amylase activity, considerably decreasing grain quality and marketability. Falling number (FN) of wheat grain is an indicator of the degree of sprouting. Wheat grain of FN less than 300 is considered sprout-damaged, and thus is subjected to a price reduction and may even be rejected by grain traders and millers depending on the severity of sprouting damage. In our previous study on the effects of storage time on wheat grain quality, we observed a significant increase in FN of wheat grain during storage for 21 weeks. The elucidation of storage conditions to ensure a maximum increase in FN would be helpful for mitigating the price penalty imposed on sprout-damaged wheat grain, and also processing and product quality problems. Wheat grain samples of varying FN from several cultivars obtained by malting, by incubating wheat stalks, or directly from the field harvest were used to determine the effects of cultivar, storage temperature, grain moisture content and initial FN on changes in FN and alpha-amylase activity. Falling number of wheat grain increased significantly during storage regardless of variety, grain moisture content, initial FN and storage temperature. The magnitude of FN increase during storage was different among wheat varieties and storage temperatures, but the effects of FN before storage and grain moisture content were not consistent. The increase in FN of wheat grain during storage was much greater at 35'C than at 5'C. Changes in alpha-amylase activity of wheat grain during storage and the effects of storage conditions on those changes were either not significant or not consistent among cultivars and methods used to obtain wheat grain of varying FN. Nevertheless, a negative relationship was observed between alpha-amylase activity and FN of wheat grain. The increases in FN of wheat grain during storage could be maximized with increased storage temperature.

Technical Abstract: Falling number (FN) of wheat grain, a measure of preharvest sprouting, tends to increase during storage; however, grain and storage conditions that impact FN changes are poorly understood. Wheat grain samples of varying FN from several cultivars were obtained by malting, by incubating wheat stalks, or directly from the field, and used to determine the effects of cultivar, storage temperature, grain moisture content and initial FN on changes in FN and alpha-amylase activity. Changes in FN of malted grain during storage were significantly affected by temperature, but the effect of grain moisture content in the range of 10-13% was not evident. The FN of malted grain increased when stored at 5, 23 and 35°C for 20 weeks by averages of 9.4, 24.1 and 34.4, respectively. Storage temperature significantly influenced the increase in FN of grain obtained from incubated stalks when stored for 8 weeks, whereas the effects of initial FN were different between cultivars. Wheat grain obtained directly from the field also exhibited significant increases in FN during 8 week storage at 5, 23 and 35°C with average increases of 10.0, 27.1 and 38.5, respectively. The impact of alpha-amylase activity on the increase in FN during storage was evident only for field-harvested grain of varying FN. Alpha-amylase activity exhibited a negative logarithmic relationship (r = -0.94) with FN in field-harvested grain. The magnitude of the changes in alpha-amylase activity varied by cultivar.