Development and optimization of a mixed beverage made of whey and water-soluble soybean extract flavored with chocolate using a simplex-centroid design

This study aimed to combine the nutritional advantages of whey and soybean by developing a type of chocolate beverage with water-soluble soybean extract dissolved in whey. Different concentrations of thickeners (carrageenan, pectin and starch – maximum level of 500 mg.100 mL^-1) were tested by a simplex-centroid design. Several physicochemical, rheological, and sensory properties of the beverages were measured and a multi-response optimization was conducted aiming to obtain a whey and soybean beverage with increased overall sensory impression and maximum purchase intention. Beverages presented mean protein levels higher than 3.1 g.100 mL^-1, a low content of lipids (< 2 g.100 mL^-1) and total soluble solids ≥20 g.100 mL^-1. Response surface methodology was applied and the proposed for overall impression and purchase intention presented R²=0.891 and R²=0.966, respectively. The desirability index (d-value=0.92) showed that the best formulation should contain 46% carrageenan and 54% pectin in the formulation. The formulation manufactured with this combination of thickeners was tested and the overall impression was 7.11±1.09 (over a 9-point hedonic scale) and the purchase intention was 4.0±1.3 (over a 5-point hedonic scale), thus showing that the proposed models were predictive.