Natural Preservation of Yogurt Using Origanum vulgare and Thymus vulgaris Essential Oils: Microbial, Physicochemical, and Sensory Assessment

The demand for natural preservatives in food systems has increased interest in plant‐derived essential oils (EOs), particularly Origanum vulgare (OEO) and Thymus vulgaris (TEO), due to their antimicrobial properties. This preliminary study evaluated their antifungal activity and their effectiveness in preserving Lebanese yogurt. Both EOs exhibited strong antifungal activity against Aspergillus niger and Kluyveromyces marxianus , with OEO showing higher potency ( M I C = 0.00076 % )[ v / v ]ompared with TEO (MIC = 0.80 % [ v / v ]). In yogurt applications, EO‐treated samples demonstrated delayed microbial spoilage compared with controls. In opened samples, Y&M growth appeared on Day 8 in controls but was delayed to Day 22 in EO‐treated samples. In sealed samples, untreated yogurt exceeded acceptable microbial limits by Day 30, whereas EO‐treated samples maintained microbiological stability under refrigerated storage conditions up to Day 150. Titratable acidity increased from 0.80% to 1.50% by Day 8 in controls, whereas EO‐treated samples reached only 1.40% by Day 150, indicating delayed acidification. Sensory evaluation confirmed maintained acceptability throughout the extended storage period. These findings demonstrate that OEO and TEO effectively inhibit fungal growth and delay spoilage in yogurt, supporting their potential application as natural antimicrobial preservatives in dairy systems.