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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 changes of proteins 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: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 11, 2013
Publication Date: May 14, 2013
Repository URL: http://handle.nal.usda.gov/10113/58187
Citation: Simsek, S., Ohm, J., Lu, H., Rugg, M., Berzonsky, W., Alamri, M., Mergoum, M. 2013. Effect of pre-harvest sprouting on physicochemical changes of proteins in wheat. Journal of the Science of Food and Agriculture. 94:205-212.

Interpretive Summary: Very humid conditions before harvest can cause sprouting of the wheat kernel, which is termed pre-harvest sprouting (PHS). The aim of this study was to examine the variation in proteins and free asparagine concentration in PHS damaged (sprouted) hard red and white spring wheat genotypes. Protein content of sprouted wheat samples was lower than that of non-sprouted samples; however, their differences were not related to sprouting levels of wheat genotypes. PHS greatly affected composition of proteins in wheat samples. Polymeric proteins in sodium dodecyl sulfate buffer unextractable proteins (UNP) are known to have positive relationships with flour dough characteristics. The PHS damage elevated the degradation of polymeric proteins of UNP in wheat samples. Free asparagine is known to be one of the primary components involved in formation of carcinogenic acrylamide during baking. PHS damage increased free asparagine content together with protein degradation in wheat samples. Hard spring wheat genotypes that had higher susceptibility to PHS tend to exhibit a larger degree of degradation of UNP and higher free asparagine concentration in sprouted wheat samples.

Technical Abstract: High moisture before harvest can cause sprouting of the wheat kernel, which is termed as pre-harvest sprouting (PHS). The aim of this study was to examine the variation in physicochemical properties of proteins and free asparagine concentration in PHS damaged (sprouted) hard red and white spring wheat genotypes. Protein contents of sprouted wheat samples were lower than that of non-sprouted samples; however, their differences were not significantly (P>0.05) correlated with sprouting score. Sodium dodecyl sulfate buffer extractable proteins and unextractable proteins (UNP) were analyzed by high performance size exclusion chromatography. PHS damage elevated endo-protease activity and consequently, increased the degradation of polymeric proteins of UNP. Genotypes that had greater tolerance to sprouting showed less degradation of proteins. Free asparagine is known to be a precursor for formation of carcinogenic acrylamide during high heat treatment. Free asparagine content had significant correlations (P<0.01) with sprouting score, endo-protease activity and protein degradation. Genotypes with higher endo-protease activity tend to exhibit larger degree of degradation of UNP and higher free asparagine concentration in sprouted wheat samples.

Last Modified: 8/30/2014
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