Effects of supplementation with algerian Nigella sativa bioactive compounds on quality of yogurt

Abstract

The characteristics of Algerian Nigella sativa (Ns) seeds were investigated after extraction with three aqueous ethanol concentrations (40, 60 and 80%) at three seed concentrations (2.5, 5 and 7.5%) referred as T, F and S, respectively. Aqueous ethanol extraction (40%) at 2.5 and 5% Ns seed concentration [T40% and F40%] had the highest total phenolic and total flavonoid contents. Higher seed (7.5%) and aqueous ethanol concentrations (60 and 80%) extracts [S60% and S80%] exhibited the maximum antioxidant activity. T80% and S40% extract exerted high antimicrobial activity against Escherichia coli and Staphylococcus aureus, respectively. Four stirred yogurts formulated with 0, 0.5, 1 and 2% of S60% extract were evaluated for physicochemical and sensory properties; two of these formulated yogurts were further investigated for stability under refrigerated storage (4 °C for 21 days). Yogurt formulated with 0.5% of S60% extract exhibited the highest antioxidant activity, high titratable acidity, low pH and increasing syneresis during storage. However, the control yogurt had higher syneresis than the fortified yogurt (60 vs 46% at 21 days storage).