Résumé
The aim of this study was to investigate the ability of mid-IR (MIR) spectroscopy to identify physicochemical changes in the French bread dough mixing process. An ATR FT-MIR spectrometer at 4000-800 cm-1 was used. MIR spectra collections recorded during mixing were analysed using principal component analysis (PCA) and second-derivative treatment. Results were interpreted in terms of chemical changes involved in dough development and more particularly in terms of secondary structural protein changes (amide III). The loading spectrum associated with principal component 1 (PC1) allowed 3 MIR wave number regions of variations (3500-3000, 1700-1200, and 1200-800 cm-1) to be identified. The loading spectrum associated with PC1 describes an increase in the relative protein band intensities and a decrease in relative water and starch band intensities. Variation during bread dough mixing time of the different amide III bands identified after the second-derivative shows that alpha-helical, beta-turn, and beta-sheet structures increase while random coil structure decreases, suggesting that the gluten structure is becoming a more ordered structure. MIR mixing time identified as being the max. scores value on the PC1 scores plots was associated with the time at which the dough apparent torque begins to collapse, suggesting that the MIR spectroscopy could monitor bread dough development