Antibacterial Effect of Malic Acid Against Listeria monocytogenes, Salmonella enteritidis and Escherichia coli in Mango, Pineapple and Papaya Juices

Consumption of un-pasteurized fruit juices has increased in recent years due to their freshness and other attractive characters. Contamination of those by pathogenic microorganisms is considered as one of the major problems. Organic acid treatments, such as malic acid treatment, are used to control these contaminations. Aim of this study was to evaluate the antimicrobial activity of malic acid against Listeria monocytogenes, Salmonella enteritidis and Escherichia coli in Mango, Pineapple and papaya juices. Minimal Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) of malic acid against those bacteria were evaluated for all tested fruit juices which were stored at 5, 20 and 35°C. Antibacterial effect of malic acid was observed against all tested bacteria under all tested conditions. The antibacterial activity was depended upon the type of bacteria, type of fruit juice and storage conditions. Antibacterial effect was higher in high temperature storage than low temperature storage. High concentration of malic acid was needed for Papaya juice compared to other fruit juices to reduce microbial population by a same amount. E. coli was found to be more resistant to antimicrobial activity of malic acid compared to the other two bacteria. According to the results of this study, E. coli can be recommended as a test bacterium in testing organic acids to be used as food preservatives. Further, these tests should be carried out in refrigerated temperature to find out more effective organic acids, as the lowest antibacterial activity of malic acid was observed at 5°C in this study.