Doogh is one of the most popular fermented dairy drinks in the Middle East, but the risk of yeasts growth has always prompted manufacturers to use chemical preservatives. This study aimed to explore the usage of essential oil of Zataria multiflora Boiss L. (ZEO) and ZEO nanoemulsion (ZEON) as the natural preservative in Doogh, a fermented dairy product, due to its antioxidant and antimicrobial properties. Based on the Gas chromatographymass spectrometry analysis, the main components of ZEO were carvacrol (56.64 %), α-pinene (23.20 %), thymol (10.01 %), O-cymene (2.87 %) and γ-terpinene (1.30 %). The average droplet size and polydispersity index of ZEON were 107.5 nm and 0.226, respectively. The antioxidant activity (IC50) of ZEO and ZEON was 40 and 15 (μg/mL), respectively. The results of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests for ZEO and ZEON (mg/mL) against foodborne bacteria showed that Escherichia coli ATCC 25,922 was the most resistant bacteria (MICZEO = 48, MBCZEO = 96; MICZEON=15.86, MBCZEON = 31.72), while Staphylococcus aureus ATCC 29,213 and Bacillus cereus ATCC 11,778 were the most sensitive bacteria (MICZEO = 3, MBCZEO = 6; MICZEON = 0.99, MBCZEON = 3.96). Adding ZEO and ZEON at a concentration of 1/4 MIC to the Doogh significantly (p < 0.01) reduced the growth of coliforms, S. aureus, and fungi compared to the control and improved the oxidative stability of the Doogh up to 60 days and had no significant effects on its pH, titratable acidity, dry weight, and fat content. The results confirmed that the addition of ZEON as a natural preservative in Doogh increased oxidative stability, improved sensory properties, and increased its shelf life up to 60 days of storage. The study of this topic can provide initial approaches for the use of nanoemulsions to promote natural food preservation strategies.
