Project summary: Baking and crusting
Dr Dan Jefferson at Heriot Watt University’s Mathematics Department has been investigating the physical processes leading to the formation of crusts on bread, with collaborators RHM Technology. An improved understanding of the factors leading to crust characteristics will allow manufacturers to produce new products tailored to specific market sectors.

Any model of crust formation must involve the setting and bursting of gas bubbles in the dough during baking, and the collapse of the burst bubbles as the inner dough expands. These processes lead to an increase in density of the bread at the outer surface.

The factors affecting the crust formation include the physical characteristics of the oven and of the dough and of the baked bread. The project consisted of two main strands. The first was the development of a phenomenological model for heat conduction and bubble fracture to obtain numerical predictions of crust density, width and mass. The dough was assumed to set at a particular temperature and the bubbles were assumed to fracture at a slightly higher temperature. The second strand involved the development of a model from more basic physical principles, using asymptotic methods to predict water and heat transport, and then combine these with models for fracture and setting to determine density variation across the loaf.

In implementing his phenomenological model, Jefferson worked with Prof. Kevin Parrott at Greenwich University to develop a program that has a rapid run time while still delivering accurate results.

The model developed allows the user to investigate the effects of changing these parameters and understanding the resulting effect rapidly, without the need to determine the effect experimentally in each case. Therefore experiments can be used in a more efficient way in the development of new products and the solution of operational problems.

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