Clove and Thyme Essential Oils: From Molecular Docking to Food Application─A Study of Their Preservative Properties in Buttermilk

This study investigates clove (CEO) and thyme (TEO) essential oils as natural preservatives, focusing on their composition, antimicrobial and antioxidant properties, and application in buttermilk. In the first part, GC-MS analysis identified eugenol (73.45%) and thymol (27.53%) as the major bioactive compounds in CEO and TEO, respectively. Antioxidant activity assays revealed strong performance for CEO, with EC₅₀ values of 0.058 mg/mL for H₂O₂ scavenging and 0.063 mg/mL for DPPH, significantly outperforming TEO (EC₅₀ values of 0.102 and 0.106 mg/mL, respectively). In vitro antibacterial assays demonstrated CEO's superior efficacy, achieving minimum inhibitory concentrations (MICs) as low as 25 mg/L against Gram-positive bacteria and 50 mg/L against Gram-negative bacteria, while TEO exhibited MICs ranging from 50 to 100 mg/L. Molecular docking highlighted selective binding of eugenol (-6.5 kcal/mol) and thymol (-5.9 kcal/mol) to bacterial enzymes, underpinning their selective antimicrobial mechanisms. In the second part, buttermilk was fortified with CEO and TEO, and sensory analysis revealed that TEO significantly enhanced aroma and taste, achieving a mean score of 7.93 for taste at 100 μg/mL, while CEO exhibited a more neutral sensory impact with a mean score of 6.14 at the same concentration. Additionally, CEO and TEO supplementation promoted LAB growth, sustaining beneficial microbial populations over a 5-day storage period and preserving microbiological quality comparable to untreated samples. These findings highlight CEO and TEO as effective natural preservatives for functional food systems, combining selective antimicrobial, antioxidant, and sensory benefits.