Berries—such as blueberry, blackberry, and raspberry—possess several biological activities including antimicrobial and nutritional effects. A study published in Food Control shows that blackberry juice may be used as a preservative in food processing and a preventive in foodborne infections as a natural antimicrobial.
The researchers investigated the antimicrobial activities of blackberry (Rubus fruticosus) juice against foodborne pathogens including Listeria monocytogenes, Salmonella Typhimurium, and Escherichia coli O157:H7. They measured the inhibition of growth of these foodborne pathogens 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 hrs). 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 researchers found that 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. They also observed that the growths of Lactobacillus strains—good bacteria—were significantly stimulated (1–4 logs CFU/mL) by blackberry juice in both milk and MRS broth.