Near infrared spectroscopy was used to monitor wheat flour and water dough mixing. The present study had for objective to identify mechanisms involved in the near infrared spectrum modifications induced by mixing. The N-IR signals were recorded by Fourier transform N-IR spectrometer (between 1000 nm and 2500 nm), using an external probe. The mathematical treatment of raw and second derivative spectrums was made by principal component analyses (PCA). PCA analyses were restricted to 3 principal components because their scores convey 87 to 99% of the total information bound to the spectrum variations. The physicochemical dough changes during mixing were evaluated by measurements of water interaction rates by a centrifugation method, protein insolubility levels by SE-HPLC, dough consistency by invasive probe, and dough extensional properties. The PCA analysis of raw N-IR spectrum describes the contribution of physical mechanisms (dough granular state and surface aspect). The PCA analysis of derived spectrum gives a physicochemical description (water interactions and the proteins insolubility) of dough mixing of the various vectors. The mixing time associated to the minimal values of the factorial coordinates of raw or derived spectrums on the first principal component is similar to the time necessary to reach maximal values of the dough consistency and minimum content of glutenin macro-polymers. The N-IR description of different flour dough mixing demonstrated the ability of the N-IR spectral methodto monitor the process.
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