Effect of soapwort extract on physical and sensory properties of sponge cakes and rheological properties of sponge cake batters

Soapwort extract yields relatively stable, soap-like foam in aqueous solution because of its saponin content. The objective of this study was to utilise the advantage of the high foam forming capacity of soapwort extract in the production of sponge cakes. Egg white proteins were partially replaced with soapwort extract in the sponge cake formulation. The effects of soapwort extract addition on the rheological and physical properties of cake batters and on the physical and sensory properties of sponge cakes were determined. Replacing egg white proteins with soapwort extract, up to 75% by weight, did not have any significant influence on the specific gravity of batters (p > 0.05). Addition of soapwort extract into the cake mixture did not influence the flow behaviour indices (n) of cake batters nor the consistency indices (K) of cake batters. In general, replacing egg white proteins with soapwort extracts (up to 75% by weight) did not alter physical properties of sponge cakes. Replacing egg white proteins with soapwort extract had no unfavourable influence on the sensory properties of sponge cakes. Indeed, sponge cakes formulated with soapwort extract (by replacing egg white proteins by 50% and 75% on weight basis) received significantly higher chewiness scores than did control cakes (p < 0.05). This study showed that egg white proteins could be partially replaced with soapwort extract in the formulation of sponge cakes.