Particle size distribution of soy flour affecting the quality of enriched gluten-free cakes

- Coarsest soy flours increased the viscosity of gluten-free layer and sponge batters.
- Soy flour incorporation produced a lower sponge cake specific volume.
- Particle size influence was more pronounced on sponge cakes.
- Finest soy flours produced sponge cakes with higher specific volume.
- Soy flour addition delayed layer and sponge cakes staling during storage.

In this study, soy flour of three particle sizes (<132, 132-156 and >156 μm) were used to substitute 15% and 30% of starch in layer and sponge cakes formulations. Batter microstructure, density and viscosity, and cake specific volume, texture and colour were evaluated. Results showed that soy flour incorporation in layer cakes decreased batter density as its particle size increased and also increased batter viscosity. However, batter prepared with intermediate flour particle size led to the lowest viscosity while the coarse fraction presented the highest viscosity. In sponge cakes, soy flour incorporation increased batter density. At 30%, the fraction with the larger particle size had the lower density. Batter viscosity was only affected in the case of 30% soy flour substitution, being significantly decreased with the use of the fine fraction. Enrichment of layer cakes did not affect their specific volumes but a flattened shape was obtained. Soy flour incorporation decreased layer cakes hardness. In contrast, its incorporation reduced the sponge cake specific volume as the addition percentage and the particle size increased. Soy flour incorporation prevented cakes from staling during storage.