Kinetics of crust formation during conventional French bread baking

64 breads were baked in a deck oven under conventional French baking conditions. Their hearth and surface temperatures were measured at various baking times using thermocouples and Infra-red thermometer; their moisture content was determined after sampling of the external layer, termed the “crust”, and by weighing breads. In addition, an image analysis method, based on saturation and colors, allowed determination of a mask of crust and the kinetics of its mean thickness. Associated with hydrothermal kinetics, it showed that the development of crust was achieved at a final local temperature of 160 °C and moisture of 5% for an average final thickness of 1.7 mm. DSC analysis of crust samples also underlined the significance of non gelatinized starch in the crust. This result was interpreted by representing the hydrothermal history of crust in a starch melting diagram. ► During French baking, bread crust temperature reaches 160 °C and final moisture 5%. ► Average thickness, defined by image analysis or moisture content, is about 1.7 mm. ► Crust hydrothermal pathway explains the content of non gelatinized starch.