Effect of soy protein isolate concentration and whipping time on physicochemical and functional properties of strawberry powder

The objective of this work was to study the effect of soy protein isolate concentration (0.5-9%) and whipping time (1-8 min) on foam characteristics, physicochemical and functional properties of hot air foam-mat-dried strawberry powder. An optimization of foaming conditions was performed by response surface methodology to maintain the studied responses within acceptable limits. The foam was prepared using different concentrations of soy protein isolate solution (32%) and dried at 50 degrees C in a thin layer (4 mm as a thickness). The concentration of soy protein was the predominant parameter affecting foam density, expansion, and stability, and physicochemical and functional properties of strawberry powder. Total phenolic content, total flavonoid content, antioxidant activity, water holding capacity, and oil holding capacity increased by about 26, 47, 166, 21, and 48%, respectively, with an increase in the concentration of soy protein isolate, compared to the control sample. Contrary, the whipping time showed a contradicted effect on all studied responses except the foam expansion and oil holding capacity.