Inhibitory effects of cinnamon and thyme essential oils against Salmonella spp. in hummus (chickpea dip)

Abstract

The antimicrobial activity of different essential oils was screened against five Salmonella serotypes using disk diffusion. Cinnamon (Cinnamomum zeylanicum) and thyme (Thymus vulgaris) essential oils exhibited the highest activity with inhibition zones of 22.5–38.5 mm in diameter. These oils were also investigated for their ability to control Salmonella and mesophilic aerobic bacteria (MAB) in hummus stored at 4 or 10°C. Salmonella cells were not detected in hummus with 0.5%–1.0% cinnamon essential oil by 7 or 1 d, respectively, at both 4 and 10°C. Cinnamon oil at 0.5%–1.5% reduced the MAB in hummus by 1.3–4.6 log CFU/g at 4 or 10°C. However, addition of 0.5%–1.5% thyme essential oil to hummus reduced Salmonella by 1.0–2.9 log CFU/g, at 4°C by 10 d. Thyme oil also inhibited growth of MAB in hummus and the count remained constant until the end of storage at 4°C, but at 10°C, thyme oil was less inhibitory. Practical applications Consumption of hummus has been linked to several salmonellosis outbreaks. Addition of cinnamon and thyme essential oils at concentrations of 0.5% may improve the safety and extend the shelf-life of hummus with acceptable organoleptic properties.