Inactivation of Salmonella enterica serovar Typhimurium and quality maintenance of cherry tomatoes treated with gaseous essential oils

The antimicrobial activity of the essential oils (EOs) from cinnamon bark, oregano, mustard and of their major components cinnamaldehyde, carvacrol, and allyl isothiocyanate (AIT) were evaluated as a gaseous treatment to reduce Salmonella enterica serovar Typhimurium in vitro and on tomatoes. In diffusion tests, mustard EO and AIT showed the greatest inhibition of Salmonella, followed by cinnamon EO and cinnamaldehyde, while oregano and carvacrol showed the least inhibition. SEM images of S. Typhimurium on tomatoes suggest that the EOs and their major components damaged the bacterial cell wall and membrane, and the damage was more obvious after post-treatment storage at 10°C for 4 and 7 days. Salmonella on inoculated tomatoes was reduced by more than 5 log CFU/g by mustard EO and AIT, by 4.56 and 3.79 log CFU/g following cinnamon EO and cinnamaldehyde treatments, respectively, and 1.54 and 3.37 log CFU/g after oregano EO and carvacrol treatments, respectively. Mustard EO and AIT induced discoloration, softening, and loss of the vitamin C and lycopene during 21 days of storage at 10°C, while treatment with cinnamon EO and cinnamaldehyde did not result in significant changes in tomato quality. Tomatoes treated with oregano EO had better quality compared with non-treated samples after storage. Therefore, treatment with cinnamon and oregano EO and their major components appeared to be feasible for inactivation of Salmonella on tomatoes and maintaining quality.