Effect of cinnamic acid and its derivatives on structure of gluten proteins – A study on model dough with application of FT-Raman spectroscopy

Fourier transform Raman spectroscopy was applied to study interactions between gluten proteins and five phenolic acids during mixing of the model dough. Phenolic acids: cinnamic, p-coumaric, caffeic, ferulic and chlorogenic acids were chosen and added in the amount of 0.05%, 0.1% and 0.2%. These compounds differ in the type of functional groups present at the phenolic aromatic ring, and hence antioxidant activity. Farinographic results show a change in the dough behaviour in the presence of phenolic acids which can be regarded as a dough breakdown. This phenomenon occurs the fastest for caffeic acid, and the slowest for p-coumaric acid that are characterized by the highest and lowest antioxidant activity, respectively. The structural changes observed in gluten proteins also depend on the antioxidant activity of phenolic acids. The largest changes were observed in conformation of disulphide bridges, content of free SH groups and tryptophan environment as a result of caffeic and chlorogenic acids addition. The present results indicate that the studied phenolic acids may incorporate into gluten network or may be closed in hydrophobic pockets without formation of any chemical bonds.