Inhibition of Shigella sonnei and Shigella flexneri in Hummus Using Citric Acid and Garlic Extract

Hummus (chickpea dip) is a ready‐to‐eat product that may pose a significant risk to human if pathogens are present. Several organisms including Shigellaspp. have been isolated from hummus. However, studies on the survival and inhibition of Shigellaspp. in food are scarce. This study investigated the growth pattern of Sh. sonneiand Sh. flexneriin hummus at different temperatures (4, 10, and 24 °C). Additionally, the inhibitory activity of different concentrations of citric acid (CA) (0.5%, 1.0%, and 2.0%) and garlic extract (GE) (1.0%, 2.0%, and 3.0%) against Sh. sonneiand Sh. flexneriinoculated into hummus and stored at 4 and 10 °C was investigated. Both Shigellaspp. survived well at 4 °C, while both grew to >7.0 log10after 4 d at 10 °C or 1 d at 24 °C. At 4 °C, CA at 0.5% and 1.0% resulted in a slight reduction in the count (approximately 1.0 log10); a complete elimination of Sh. sonneiwas attained by using 2.0% CA. However, approximately 3.0 log10reduction in Sh. sonneiwas obtained at 10 °C. For Sh. flexneri, CA at 0.5% and 1.0% resulted in a bacteriostatic inhibition. GE at 1.0% and 2.0% resulted in approximately 1.0 to 2.0 log10reduction in Sh. sonneicount at 4 °C, while at 3.0% GE, approximately 4.0 and 3.0 log10reductions were obtained at 4 and 10 °C, respectively. In comparison, the 2.0% and 3.0% GE resulted in a bacteriostatic effect against Sh. flexneriat 4 and 10 °C. This study indicates that Sh. sonneiand Sh. flexnerican survive at 4 °C and can grow well in hummus under mild thermal abuse during storage (10 °C). CA and GE provided a noticeable inhibitory activity against Shigellaspp. and can be used as natural antimicrobial substances to preclude or restrict the growth of Shigellaspp. in hummus.