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United States Department of Agriculture

Agricultural Research Service

Research Project: Enhancement of Hard Spring Wheat, Durum, and Oat Quality

Location: Cereal Crops Research

Title: Effect of pre-harvest sprouting on physicochemical properties of starch in wheat

Authors
item Simsek, Senay -
item Ohm, Jae-Bom
item Lu, Haiyan -
item Rugg, Mory -
item Berzonsky, William -
item Alamri, Mohammed -
item Mergoum, Mohamed -

Submitted to: Foods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 26, 2014
Publication Date: April 2, 2014
Repository URL: http://handle.nal.usda.gov/10113/58656
Citation: Simsek, S., Ohm, J.-B., Lu, H., Rugg, M., Berzonsky, W., Alamri, M.S., Mergoum, M. 2014. Effect of pre-harvest sprouting on physicochemical properties of starch in wheat. Foods. 3:194-207.

Interpretive Summary: Pre-harvest sprouting (PHS) in wheat (Triticum aestivum L.) refers to sprouting of mature wheat kernels due to untimely rains before harvest. The objective of this study was to provide fundamental information on the degradation of starch in kernels due to PHS of hard red spring (HRS) and hard white spring (HWS) wheat. Nonsprouted and sprouted HRS and HWS wheat samples were compared to investigate changes in starch associated with PHS. Levels of alpha-amylase, which primarily acts to decompose starch molecules, were higher for sprouted wheat samples than non-sprouted wheat samples. High alpha-amylase activity in the sprouted samples resulted in the partial degradation of starch and greatly reduced flour hot paste viscosity for the sprouted samples as determined by a Rapid Visco Analyzer. The degradation of starch granules in kernels by PHS was also visually observed by scanning electron microscopy (SEM). The SEM images showed that starch granules in sprouted samples were partially hydrolyzed. Size of starch molecules was analyzed by high performance size exclusion chromatography (HPSEC). The HPSEC profiles indicated that the starch from sprouted samples had relatively lower molecular weight than that of non-sprouted samples. PHS changed the physicochemical properties of starch, which is expected to significantly impact the quality of end-use products prepared from sprouted samples.

Technical Abstract: Pre-harvest sprouting (PHS) in wheat (Triticum aestivum L.) occurs when physiologically mature kernels begin germinating in the spike, often because harvest coincides with untimely rain. The objective of this study was to provide fundamental information on the physicochemical changes of starch due to PHS in hard red spring (HRS) and hard white spring (HWS) wheat. Nonsprouted and sprouted HRS and HWS wheat samples were used to investigate changes in starch chemistry. The mean values of a-amylase activity of non-sprouted and sprouted wheat samples were 0.12 CU/g and 2.00 CU/g, respectively. High a-amylase activity in the sprouted samples resulted in the partial degradation of starch. The sprouted samples exhibited very low peak viscosity and final viscosity compared to nonsprouted wheat samples, as determined by a Rapid Visco Analyzer. Scanning electron microscopy images showed that starch granules in sprouted samples were partially hydrolyzed. Based on high performance size exclusion chromatography profiles, the starch from sprouted samples had relatively lower molecular weight than that of non-sprouted samples. PHS changed the physicochemical properties of starch, which is expected to significantly impact the quality of end-use products prepared from sprouted samples.

Last Modified: 9/22/2014
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