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

BACKGROUND High moisture 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 physicochemical properties of proteins in PHS‐damaged (sprouted) hard red and white spring wheat genotypes. Specifically, protein content, enzyme activity and degradation of proteins were evaluated in sound and PHS‐damaged wheat. RESULTS 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 (SDS) buffer extractable proteins (EXP) and unextractable proteins (UNP) were analyzed by high‐performance size exclusion chromatography. PHS damage elevated endoprotease activity and consequently increased the degradation of polymeric UNP 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 (P < 0.01) with sprouting score, endoprotease activity and protein degradation. CONCLUSIONS Genotypes with higher endoprotease activity tend to exhibit a larger degree of degradation of UNP and higher free asparagine concentration in sprouted wheat samples. © 2013 Society of Chemical Industry