Use of MRI for the characterization of the bread process

The prohibition of invasive, continuous measurements on dough and bread partially limited the full comprehension of the underlying mechanisms of the different steps in the bread-making process. After mixing, the positioning of thermocouples for assessing heat transfer in dough is absolutely not precise as dough is highly deformable. During proving, invasive measurements may provoke dough collapse. During baking and post chilling, the fragility of the porous structure and the presence of water vapour in large proportion will induce bias when sampling. Continuous, often non invasive, methods have been developed and tested during the last decade; they applied to freezing (Lee et al., 2002), proving (van Duynhoven et al., 2003; Takano et al., 2002; Whitworth et al., 1999) and baking (Thorvaldsson et al., 1999). Nevertheless, in most works using MRI (magnetic resonance imaging) the relation between the MRI signal and the studied parameter (ice or gas fraction, water content etc.) was not clearly established and only the raw signal was exploited. The objective of the present paper is to present quantitative MRI methods recently developed and through selected case studies, to illustrate the performances of such tool for assessing heat and mass transfer, and food structure changes taking place during different steps of bread-making.