Abstract
A measurement system was designed to study changes in the volume, pressure, and viscosity of dough leavened by baking powder during model baking. Analysis of the volume changes demonstrated two baking stages, i.e. dough expansion and crumb shrinking. Through the analysis of pressure and viscosity extremes, the expansion stage was divided into five phases: stress relaxation (R) characterised by a mild pressure decline; gluten matrix softening (S), during which the decrease in viscosity is accompanied by a gradual pressure rise contributing to substantial dough expansion (by ∼54 %); starch gelatinisation and protein aggregation (G) characterised by rapidly increasing viscosity; gas bubble opening (O) reflecting a rapid pressure reduction; and boiling of water in dough (B), which ends at initiation of crumb shrinking. The study showed that enrichment of the dough with carob fibre increased the contribution of phases S and O to dough expansion at the cost of phase G. A similar contribution of the expansion phases was reported for the Bombona cultivar, which exhibits the highest gluten content. In contrast, the Finezja and Katoda cultivars, which have a lower gluten level, were characterised by an approximately two-fold higher impact of phase G on the increase in dough expansion. The results indicated that the developed method for identification of baking expansion phases of leavened dough can be useful in baking characteristics of raw materials and bakery additives.
Highlights
A baking temperature induces a variety of physical and chemical processes that transform viscous-liquid dough into bakery product with solid and cellular-structured crumb (Mondal and Datta 2008)
The most readily observable symptom of these processes is dough expansion accompanied by externally invisible changes in its cellular structure
In addition to the amount of the gas accumulated in the bubbles, the increase in its pressure induced by the rising temperature enhances gas bubble expansion
Summary
A baking temperature induces a variety of physical and chemical processes that transform viscous-liquid dough into bakery product with solid and cellular-structured crumb (Mondal and Datta 2008). The temperature rise increases CO2 saturation, forcing its diffusion from the liquid to gaseous phase of dough. In addition to the amount of the gas accumulated in the bubbles, the increase in its pressure induced by the rising temperature enhances gas bubble expansion. At the end of baking when the dough temperature in the peripheral zone reaches the water boiling point, the produced water vapour pressure is an additional force maintaining the further dough expansion process until the end of the thermosetting of the crumb cellular structure (Wang and Sun 1999). The loaf volume begins to decrease (Rouillé et al 2010; Sommier et al 2005; Wagner et al 2007)
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