Effect of enrichment with spice extracts on yoghurt quality: Optimizing the extraction process and sensory properties

Abstract This study investigated the potential of yoghurt enrichment with spice extracts. Firstly, optimal ultrasound (US)-assisted extraction conditions for thyme, cinnamon, and ginger samples were determined according to Taguchi L 9 (3 3 ) design including variables such as solute content (1–5%), US temperature (25–55 °C) and US time (5–15 min). The effect of spice extracts incorporated into yoghurt formulations at three levels (0.5%, 1%, 1.5%) on pH, titratable acidity, syneresis, color), total phenolic content (TPC), antioxidant activity (AA), and sensory properties were evaluated. The results revealed statistically significant differences ( p < 0.05) between the yoghurt with spice extract and the control concerning the analyzed parameters. However, a significant enhancement in bioactive properties was observed with an increase in enrichment ratio. Unfortunately, this increase in fortification resulted in a notable decline in sensory acceptability of the yoghurt samples. Specifically, the yoghurt fortified with 0.5% thyme extract had lower values of syneresis, pH and color difference and higher values of acidity, TPC and AA than that of plain yoghurt. Moreover, this sample had the highest overall acceptability score in entropy-based MOORA optimization of sensory scores. The present study demonstrates that the techno-functional and functional characteristics, as well as sensory properties of yoghurt, can be enhanced through the enrichment of spice extract. Graphical abstract