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Description of Chemical Changes Implied During Bread Dough Mixing by FT-ATR Mid-Infrared Spectroscopy

¹UMR 1208 Ingénierie des Agropolymères et Technologies Emergentes, CIRAD, INRA, Montpellier SupAgro, Université Montpellier 2, F-34000 Montpellier. ²Corresponding author. Phone: 33 (0)4 99 61 28 60. Fax: 33 (0)4 99 61 30 76. E-mail: cuq@supagro.inra.fr

The aim of the present study was to investigate the ability of mid-infrared (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. The MIR spectra collections recorded during mixing were analyzed after standard normal variate using principal component analysis (PCA) and after second-derivative treatment. The 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) allows three 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. The variation during bread dough mixing time of the different amide III bands identified after the second-derivative show that α-helical, β-turn, and β-sheet structures increase while random coil structure decreases, suggesting that the gluten structure is becoming a more ordered structure. The MIR mixing time identified as being the maximum scores value on the PC1 scores plots was associated with the time at which the dough apparent torque begin to collapse, suggesting that the MIR spectroscopy could monitor bread dough development.