The antibacterial effect of Ziziphora clinopodioides essential oil and nisin against Salmonella typhimurium and Staphylococcus aureus in doogh, a yoghurt-based Iranian drink

Doogh is the most popular and commonly consumed yoghurt-based Iranian drink. The aim of this study was to investigate the antibacterial effects of Ziziphora clinopodioides essential oil (ZEO) at 0.10 and 0.20% concentrations, nisin at 250 and 500 IU mL^-1, and their combination against Salmonella typhimurium and Staphylococcus aureus in doogh during storage at 4 ˚C for 9 days. Nine batches were studied as follows: control: no ZEO or nisin added, A: 0.10% ZEO, B: 0.20% ZEO, C: 250 IU mL^-1 nisin, D: 500 IU mL^-1 nisin, E: 0.10% ZEO + 250 IU mL^-1 nisin, F: 0.10% ZEO + 500 IU mL-1 nisin, G: 0.20% ZEO + 250 IU mL^-1 nisin and H: 0.20% ZEO + 500 IU mL^-1 nisin. Based on gas-chromatography and mass spectrometry, carvacrol (65.22%), thymol (19.51%), p-cymene (4.86%) and ɣ-terpinene (4.63%) were the major components of ZEO. The populations of S. typhimurium and S. aureus in samples treated with all concentrations of the ZEO and nisin were kept below 1 log CFU mL^-1 on day 5 of storage, while the count of S. typhimurium and S. aureus was found as 2.72 ± 0.02 and 2.21 ± 0.00 log CFU mL^-1 on day 5 for untreated samples, respectively. The ZEO separately and in combination with nisin, was very effective against these two common food-borne pathogens. The ZEO alone and in combination with nisin could be considered as a potential strong antimicrobial agent that can be used for the growth inhibition of aforementioned bacteria in food products especially doogh.