Impact of compositionally diverse cereal flour water extracts on the gas cell size distribution and extensional rheology of model gluten-starch doughs

The role of water-extractable (WE) cereal flour constituents, and particularly WE proteins, in determining bread dough gas cell stability and bread specific volume (SV) remains ill-understood. We investigated the impact of compositionally diverse cereal flour aqueous extracts on bread SV, dough extensional rheology, and dough gas cell size distribution. To this end, aqueous extracts from wheat, rye, and defatted oat flours were either used as such, or their composition was modified by dialyzing out (i) low molecular mass constituents or (ii) both low molecular mass constituents and enzymatically hydrolyzed carbohydrates. These modifications generated wheat, rye, and oat extracts with increasing protein purities. Incorporating wheat or rye extracts in model gluten-starch (GS) doughs increased bread SV by 12-18%, regardless of modification, suggesting that not WE carbohydrates but probably proteins drive this effect. Dough extensional rheology and gas cell size distribution data could not explain these bread SV increases. It is hypothesized that wheat/rye WE proteins stabilize gas cells in dough by adsorbing at their interfaces. Incorporating oat extracts in GS dough led to a 50% decrease in bread SV. This was associated with oat extract-containing doughs having a lower strain hardening index, a lower gas cell number density, and a more heterogeneous gas cell size distribution. That similar effects were observed irrespective of the modification type suggests that oat WE proteins may be responsible for the adverse impact on dough and bread properties. Future efforts will focus on investigating direct gas cell stabilization effects by WE cereal flour constituents.