Structural and Chemical Modifications of Short Dough During Baking

Abstract

Short dough baking was performed in a pilot-scale oven under various conditions allowing macroscopic changes to be studied in relation to physical and biochemical modifications during the baking process. The influence of baking parameters (temperature, humidity and air velocity) on macroscopic and microscopic changes was investigated, together with variations (temperature and moisture content, heating and drying rates) in product variables. The major changes observed during biscuit baking were (i) development of a partially open porous structure associated with reduction in density, (ii) drying, and (iii) surface colouring. Structural changes were due to water vaporisation and gas bubbles produced by the decomposition of the chemical leavening agents used. Expansion stopped because of the depletion of chemical leavening agents and percolation of water vapour at appropriate temperatures. The setting of biscuit structure was not related to thermal aggregation of proteins (which began at 85 °C) or to limited starch granule damage at temperatures below 100 °C. Setting apparently occurred during the cooling period when molten sugars undergo a glass transition. Surface colouring of the biscuit and a subsequent decrease in lightness were correlated with reduced sugar consumption in Maillard reactions.