Effect of pre‐harvest sprouting on physicochemical changes of proteins in wheat

<jats:title>Abstract</jats:title><jats:sec><jats:title>BACKGROUND</jats:title><jats:p><jats:bold>High moisture before harvest can cause sprouting of the wheat kernel, which is termed pre‐harvest sprouting (<jats:styled-content style="fixed-case">PHS</jats:styled-content>). The aim of this study was to examine the variation in physicochemical properties of proteins in <jats:styled-content style="fixed-case">PHS</jats:styled-content>‐damaged (sprouted) hard red and white spring wheat genotypes. Specifically, protein content, enzyme activity and degradation of proteins were evaluated in sound and <jats:styled-content style="fixed-case">PHS</jats:styled-content>‐damaged wheat</jats:bold>.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p><jats:bold>Protein contents of sprouted wheat samples were lower than that of non‐sprouted samples; however, their differences were not significantly (<jats:italic>P</jats:italic> > 0.05) correlated with sprouting score. Sodium dodecyl sulfate (SDS) buffer extractable proteins (EXP) and unextractable proteins (<jats:styled-content style="fixed-case">UNP</jats:styled-content>) were analyzed by high‐performance size exclusion chromatography. <jats:styled-content style="fixed-case">PHS</jats:styled-content> damage elevated endoprotease activity and consequently increased the degradation of polymeric <jats:styled-content style="fixed-case">UNP</jats:styled-content> and free asparagine concentration in wheat samples. Free asparagine is known to be a precursor for formation of carcinogenic acrylamide during high heat treatment, such as baking bread. Free asparagine content had significant correlations (<jats:italic>P</jats:italic> < 0.01) with sprouting score, endoprotease activity and protein degradation</jats:bold>.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p><jats:bold>Genotypes with higher endoprotease activity tend to exhibit a larger degree of degradation of <jats:styled-content style="fixed-case">UNP</jats:styled-content> and higher free asparagine concentration in sprouted wheat samples. © 2013 Society of Chemical Industry</jats:bold></jats:p></jats:sec>