Antilisterial activity of <em>Cymbopogon citratus</em> on crabsticks

• Main Authors: Prateebha Ramroop, Hudaa Neetoo
• Format: Article
• Language: English
• Published: AIMS Press 2018-02-01
• Series: AIMS Microbiology
• Subjects: lemon grass; <em>Listeria monocytogenes</em>; <em>Listeria innocua</em>; surimi; sensory; pH
• Online Access: http://www.aimspress.com/microbiology/article/1820/fulltext.html

<em>Listeria monocytogenes</em> is a gram positive, psychrotrophic, facultative anaerobic bacterium and it is the etiological agent of listeriosis, a severe foodborne disease of major public health concern. There is a rising concern about the cross-contamination of surimi-based products with <em>L. monocytogenes</em> during handling and storage. Lemon grass (<em>Cymbopogon citratus</em>) is known to exhibit strong antimicrobial activity against bacteria due to the presence of citral. The objectives of this research were: (i) to develop a water-based extraction procedure for the antimicrobial component(s) in lemon grass and (ii) to evaluate the antimicrobial effect of a concentrated water-based extract and commercial essential oil (EO) of lemon grass against <em>L. innocua</em> (ATCC 33090), a surrogate strain of <em>L. monocytogenes</em>, <em>in vitro</em> and on crabsticks. Briefly, antilisterial activity of concentrated extract and commercial EO of lemon grass was tested using the agar well diffusion technique. Crabsticks were subsequently inoculated with <em>L. innocua</em> to a final density of ca. 4 log cfu/g and then coated with 500 ml of either concentrated extract or 0.5% commercial EO and stored at 4 °C for up to 15 days. Samples were then subjected to microbiological analysis every 5 days to enumerate counts of <em>Listeria</em>.<em></em> Following the agar well diffusion assay, inhibition zones with mean diameters of 18.3 and 21.0 mm were obtained with the concentrated extract and commercial EO respectively. The population of <em>L. innocua</em> in WBE-coated (4.2 log cfu/g) and 0.5% EO-coated (2.7 log cfu/g) samples were significantly lower (<em>P</em> &lt; 0.05) after 15 days than their untreated control counterpart (5.2 log cfu/g). Lemon grass extract and essential oil have the potential to control growth of <em>L. monocytogenes</em> in seafood surimi products with minimal adverse effect on the organoleptic characteristics of the product and thus can possibly be used as a natural food preservative.