Physical aspects of the improvement of dough by fat

Abstract

Shortening containing a fraction which is solid at dough temperatures is an essential ingredient in rapid breadmaking processes, but optional in long fermentation processes. Hypotheses concerning the action of fat are reviewed, and it is concluded that physical mechanisms, rather than those involving lipid oxidation, account for the increased loaf volume on the addition of shortening to the dough. Recent work using ‘model’ fats has shown that increased loaf volume results when sufficient of the solid component remains ‘free’ in the dough, and work with stored flour confirmed the importance of the free lipid fraction. A study of carbon dioxide release from doughs during baking showed that fat increases gas retention in the initial stage of rapid expansion. It is suggested that the solid components of the fat facilitate the production of orientated structures in dough, which can persist even when the temperature exceeds the melting point of the fat, and that these structures favour gas retention in the earliest stages of baking.