Functionality of Puroindoline in Breadmaking

Summary

The formation and stabilization of protein films at air-water interfaces represents a crucial event in breadmaking. Two basic and cystine-rich lipid-binding proteins, puroindoline-a and puroindoline-b, have recently been isolated from wheat flour (Blochet et al, 1993; Gautier et al, 1994). Puroindolines are of interest for their good foaming properties and their capacity to prevent destabilization of protein foams by lipids (Wilde et al, 1993; Dubreil et ai, 1996). It has been suggested that puroindolines, in association with wheat polar lipids, could play a major role in the formation and expansion of gas cells in bread dough and therefore in the structure and texture of bread crumb (Marion and Clark, 1996). In the present study, puroindoline-a was found to be the major protein at the air/water interfaces of dough liquor foam, in close relation with its affinities for wheat lipids. When this lipid-binding protein was added to wheat flours prepared from puroindoline-free cultivars, a homogeneous fine crumb was obtained with the three flours used, whereas the rheologic properties of flour interfered greatly with the effect of puroindoline on bread volumes.