This study investigated the antimicrobial activity of malic acid (MA), grapefruit seed extract (GSE), and combined (MA+GSE) treatment against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on fresh-cut lettuce. The antimicrobial effects of 1% MA and 0.5% GSE alone and in combination (1% MA+0.5% GSE) were tested on artificially inoculated lettuce during storage at 5°C for 14 days. The maximum reductions of E. coli O157:H7, S. Typhimurium, and L. monocytogenes were 4.96, 4.80, and 3.95 log CFU/g observed with MA+GSE during storage for 14 days, respectively. MA+GSE showed the greatest reduction against in E. coli O157:H7 and L. monocytogenes. These results indicate that the combined treatment was more effective than MA and GSE alone treatment. Therefore, it suggests that MA + GSE could be used as an effective intervention method for improving microbiological safety of fresh-cut lettuce.
Keywords: foodborne pathogens; grapefruit seed extract; lettuce; malic acid; reduction.