Non-destructive imaging of bread and cake structure during baking.

ABSTRACT Many aspects of bread and cake structure develop during proof and baking. However, it has hitherto been difficult to study these processes directly due to the delicate nature of the products and the hostile environment of the oven. The non-destructive methods of X-ray computed tomography (CT) and magnetic resonance imaging (MRI) were used to study changes in product structure during proof and baking. For proof, doughs were placed in a scanner in a humidified box. For baking, a dedicated oven was constructed, consisting of an insulated glass chamber located within the scanner, heated by air conveyed from a remote, thermostatically controlled heater. The methods have also been used to study cooling of products after baking, and thawing of frozen products. Scans were made at intervals of time during processing, enabling dynamic processes to be studied. The effects of flour properties, recipe and process variations were studied. Processes observed in bread included inward progression of dough expansion and setting, oven spring, formation and breaking of the crust, and compression and collapse of peripheral structures. For cakes, processes included convection in low viscosity batters, evidence of a foam to sponge conversion towards the end of baking, and formation of elongated tunnel holes in muffins. CT provided a clear visualisation of changes in bubble structure and MRI was better suited to study of thawing processes.