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

- Purple grape skin flour, oligofructose, and juice were used to manufacture an organic yogurt.
- Response surface methodology was used to model compositional, sensory, and functional data.
- The optimized yogurt formulation had 5.6 g/100 g fibers and high total phenolic content.
- Yogurt formulations had excellent sensory acceptance.
- Purple grape skin flour and juice may be used to enhance nutritional quality of yogurts.

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.