Do tyrosine crosslinks contribute to the formation of the gluten network in common wheat (Triticum aestivum L.) dough?

The relationships between flour proteins, the rheological properties of bread dough, and the formation of crosslinks between tyrosine residues during dough formation was investigated in 28 wheat varieties commonly cultivated in Spain. The glutenins were the most influential components for strength (W) and the ratio tenacity/extensibility (P/L), especially the high molecular weight (HMW) glutenins and, in particular, the type x form. HMW glutenins are rich in tyrosine, and these amino acids may be involved in the formation of covalent interactions, putatively involving tyrosyl–tyrosyl crosslinks, in the gluten network. Reverse phase high performance liquid chromatography was used to determine the quantity of dityrosine and isodityrosine derivatives produced under different treatments during gluten formation. Correlations were found between the quantity of gluten present in the flour and the quantity of dityrosines formed, as well as between these modified amino acids and the total quantity of HMW glutenins and type x HMW glutenin subunits. The addition of potassium bromate to the hydrated flour stimulated the formation of tyrosine crosslinks increasing the appearance of tyrosine derivatives. Quantitatively, crosslinking between tyrosine residues appears to be small and of little importance in the structure of the gluten network compared to the disulfide bonds that form between cysteine residues.