Effect of Nanoemulsification on the Antibacterial and Anti-biofilm Activities of Selected Spice Essential Oils and Their Major Constituents Against Salmonella enterica Typhimurium

In the present study, EOs of commonly used spices i.e. coriander, cumin, fennel, lemongrass and pepper and their major components (linalool, cuminaldehyde, anethole, citral and beta-caryophyllene) were nanoemulsified and investigated for their antibacterial and anti-biofilm activities against Salmonella enterica Typhimurium. The mean droplet size of the nanoemulsion ranged from 16.99 to 165.20 nm for EOs and 22.40 to 223.90 nm for their major compounds. Nanoemulsion of all EOs and their compounds (cuminaldehyde, anethol and citral) were stable for 30 days while phase separation was noticed in linalool and beta-caryophyllene after 5 and 10 days of storage, respectively. Among the investigated samples, citral nanoemulsion showed the highest antibacterial (MIC 0.156%) and anti-biofilm activity (79.9%) and was therefore selected for its application in fresh cut pineapple model. Treatment with citral nanoemulsion on the cut pineapple surface led to 2.57 log CFU/g reduction of the S. enterica Typhimurium population. Scanning electron microscopy revealed reduction of biofilms on the cut pineapple surface upon citral nanoemulsion treatment. Hence, we envisage that citral nanoemulsion can be further explored as natural antibacterial and anti-biofilm agent for food preservation applications.