Evaluation of lemongrass and ginger essential oils to inhibit Listeria monocytogenes in biofilms

Listeria monocytogenes, a foodborne pathogen, is hard to eliminate from food processing environments because it can persist in biofilms. Searching for natural agents that can effectively act against L. monocytogenes biofilms is important to prevent food contamination, especially in the case of ready-to-eat foods. Here, we determine the key components of the lemongrass and ginger essential oils (EOs) and evaluate the activity of each EO against L. monocytogenes biofilms. Biofilms grown on stainless steel and glass coupons were monitored by culture method and confocal laser scanning microscopy (CLSM). These techniques revealed the presence of live and dead cells. Monoterpenes were the main components in the lemongrass EO; monoterpenes and sesquiterpenes were the main constituents of the ginger EO. Although the lemongrass EO affected L. monocytogenes biofilms significantly, none of the tested treatments inhibited the pathogen completely. Therefore, controlling the presence of L. monocytogenes in food processing areas demands preventive measures. Practical application Microbial biofilms constitute a challenge for effective sanitation in the food industry. Synthetic products are commonly used as sanitizers, but consumers have demanded more natural food produced in eco-friendly environments. This scenario has motivated the search for natural antimicrobials that can be applied in food facilities to eliminate microorganisms from biofilms. Plant-derived compounds represent an alternative source of antimicrobials due to their potential acceptance by the consumers and wide availability. This study shows that treatment with lemongrass essential oil significantly affects biofilms formed by the foodborne pathogen Listeria monocytogenes, but the treatment does not eradicate the biofilms. Our results demonstrate that it is possible to identify natural antimicrobials with potential use as alternative sanitizers in the food industry. (AU)