Antioxidant activity, microbial viability, and sensory attributes of traditional-yogurt enriched with silymarin

Silymarin, derived from Silybum marianum (milk thistle) seeds, is known for its anti-oxidative properties. The study examines how various concentrations of silymarin (0, 25, 50, and 100 mg/L) affect anti-oxidative activity, phenolic content, pH, viscosity, sensory qualities, and Lactobacillus delbrueckii (L. delbrueckii) viability in yogurt stored for 7, 14, and 21 days at 4 °C, aiming to understand its impact on yogurt quality and health-promoting properties. Antioxidant activity and L. delbrueckii viability of fortified yogurt were increased (58.26 mg GAE/g and 17.45%) with increasing the concentration of silymarin while decreasing pH, viscosity, and sensory scores. A T3 (100 mg silymarin/L) exhibited decreasing viscosity from 7.06 ± 0.79 to 6.27 ± 0.13 Pa·s on Days 1–21, while T0 (control) had higher viscosity from 11.36 ± 0.63 to 9.48 ± 0.16 Pa·s. Microbial counts decreased from 4.7–7.14 to 7.6–12.3 log CFU/g by Days 1–21, with predominant Streptococcus thermophilus (S. thermophiles) and Lactobacillus bulgaricus (L. bulgaricus), the absence of coliforms, and minimal mold and yeast growth. Initially, T1 was preferred due to its superior flavor, texture, and overall acceptability scores. Controlled silymarin addition improves yogurt's antioxidant activity and bacterial viability without compromising sensory attributes, making it a promising functional food.