Optimization of an organic yogurt based on sensorial, nutritional, and functional perspectives

The effects of purple grape juice (PGJ), grape skin flour (GSF), and oligofructose (OLI) on proximate composition, total phenolic content (TPC), antioxidant activity (AA), sensory, physicochemical, and textural properties of yogurts were analyzed using response surface methodology. Multiple regression models were proposed and results showed that PGJ increased the viscosity, AA, and TPC, while GSF increased the ash and total fiber contents of yogurts. GSF and OLI increased the hardness and consistency. A simultaneous optimization was performed to maximize TPC, ash and fibers contents, and sensory acceptance: a yogurt containing 1.7% GSF and 8.0% PGJ had a high fiber (5.60 ± 0.13%) and ash (0.76 ± 0.02%) contents, TPC (28.32 ± 2.10 mg GAE/100 g), AA toward DPPH (57.85 ± 1.36 mg AAE/100 g), and total reducing capacity (28.86 ± 5.19 mg QE/100 g). The optimized yogurt had 79% acceptability index, indicating the use of PGJ and GSF is a feasible alternative to increase the functional properties of yogurts.