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 ۰.۱۰ and ۰.۲۰% concentrations, nisin at ۲۵۰ and ۵۰۰ IU mL-۱, and their combination against Salmonella typhimurium and Staphylococcusaureus in doogh during storage at ۴ ˚C for ۹ days. Nine batches were studied as follows: control: no ZEO or nisin added, A: ۰.۱۰% ZEO, B: ۰.۲۰% ZEO, C: ۲۵۰ IU mL-۱ nisin, D: ۵۰۰ IU mL-۱ nisin, E: ۰.۱۰% ZEO + ۲۵۰ IU mL-۱ nisin, F: ۰.۱۰% ZEO + ۵۰۰ IU mL-۱ nisin, G: ۰.۲۰% ZEO + ۲۵۰ IU mL-۱ nisin and H: ۰.۲۰% ZEO + ۵۰۰ IU mL-۱ nisin. Based on gas-chromatography and mass spectrometry, carvacrol (۶۵.۲۲%), thymol (۱۹.۵۱%), p-cymene (۴.۸۶%) and ɣ-terpinene (۴.۶۳%) 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 ۱ log CFU mL-۱ on day ۵ of storage, while the count of S. typhimurium and S.aureus was found as ۲.۷۲ ± ۰.۰۲ and ۲.۲۱ ± ۰.۰۰ log CFU mL-۱ on day ۵ 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.

Keywords:

Doogh , nisin , Salmonella typhimurium , Staphylococcus aureus , Ziziphora clinopodioides