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

Simsek, Senay, Ohm, Jae-Bom, Lu, Haiyan, Rugg, Mory, Berzonsky, William, Alamri, Mohammed S., Mergoum, Mohamed
Journal of the science of food and agriculture 2013 v.94 pp. 205
acrylamides, asparagine, carcinogens, correlation, degradation, enzyme activity, free amino acids, genotype, heat treatment, physicochemical properties, proteinases, proteins, seeds, size exclusion chromatography, sodium dodecyl sulfate, spring wheat, sprouting
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, endoprotease activity and protein degradation. Genotypes with higher endoprotease activity tend to exhibit a larger degree of degradation of UNP and higher free asparagine concentration in sprouted wheat samples.