Effects of blackberry juice on growth inhibition of foodborne pathogens and growth promotion of Lactobacillus

Berries such as blueberry, blackberry and raspberry possess several biological activities including antimicrobial and nutritional effects. In this study, the antimicrobial activities of blackberry (Rubus fruticosus) juice against foodborne pathogens including Listeria monocytogenes, Salmonella Typhimurium and Escherichia coli O157:H7 were investigated. Inhibition of growth of these foodborne pathogens was measured in broth (Luria–Bertani broth for E. coli O157:H7 and S. Typhimurium, and brain heart infusion broth for L. monocytogenes), skim milk and whole milk supplemented with 10% blackberry juice at different time points (0, 24, 48 and 72 h). The effects of blackberry juice on the growth of Lactobacillus casei, Lactobacillus plantarum and Lactobacillus rhamnosus were also investigated in Man–Rogosa–Sharpe (MRS) broth and skim and whole milk supplemented with blackberry juice. The growth of L. monocytogenes, S. Typhimurium and E. coli O157:H7 were significantly inhibited by blackberry juice by 1–3 logs in both milk and broth. We also observed that the growths of Lactobacillus strains were significantly stimulated (1–4 logs CFU/mL) by blackberry juice in both milk and MRS broth. These data clearly demonstrate that diluted blackberry juice can be used as a preservative in food processing and a preventive in foodborne infections as a natural antimicrobial.