Control of Salmonella enterica and Listeria monocytogenes in hummus using allyl isothiocyanate

Abstract

Hummus (chickpea dip) is a ready-to-eat product which has been implicated in several foodborne outbreaks and food recalls. This study aimed to screen the antimicrobial activity of allyl isothiocyanate (AITC) against 5 strains of each of Salmonella enterica and Listeria monocytogenes using a disc diffusion method. Additionally, the antimicrobial activity of 0.1–1.5% (v/w) AITC against both pathogens and aerobic bacteria in hummus was also investigated. The inhibition zones of AITC were 8.5–15 and 7.0–8.5 mm against the S. enterica and L. monocytogenes strains, respectively, at 37 °C. S. enterica numbers were reduced by >6 log10 CFU/g in hummus containing ≥0.5% AITC by 3 days at both 4 and 10 °C. While 0.1–0.25% AITC reduced S. enterica by 2.5–5.1 log10 CFU/g at 4 °C or by 4.7–6.0 log10 CFU/g at 10 °C by 10 days. Similarly, L. monocytogenes numbers decreased by >6 log10 CFU/g in hummus with ≥0.5% or ≥1.0% AITC at 4 or 10 °C, respectively, by 3 days. Further, 0.25% AITC significantly reduced L. monocytogenes in hummus by 2.7 and 4.3 log10 CFU/g at 4 and 10 °C, respectively. Moreover, 0.1% AITC reduced L. monocytogenes by 1.8 log10 CFU/g in hummus at 10 °C and inhibited the growth at 4 °C for up to 10 days. The aerobic bacterial count also significantly decreased in un-inoculated hummus treated with 1.0–1.5% AITC at both 4 and 10 °C, while a concentration of 0.25–0.5% AITC inhibited their growth at 4 °C. AITC can be used to reduce the risk of salmonellosis or listeriosis in hummus and extend its shelf-life.