Antimicrobial activities of the juice were shown against foodborne pathogens including Listeria monocytogenes, Salmonella Typhimurium and E.coli O157:H7.
The researchers said that in the presence of 10% blackberry juice, growths of all pathogens were inhibited (P < 0.05).
Growth was measured in broth (Luria–Bertani for E. coli O157:H7 and S. Typhimurium and brain heart infusion for L. monocytogenes), skim and whole milk supplemented with 10% blackberry juice.
The growth of L. monocytogenes, S.Typhimurium and E. coli O157:H7 were inhibited by 2–4 logs CFU/mL in broth and 1–2 logs CFU/mL in milk.
Growth of the pathogens was inhibited after 24 hours incubation in liquid bacterial culture media with blackberry juice.
Bacterial growth was analyzed by comparing viable cell counts between the treatment and control at 0, 24, 48 and 72 hours. Growth in broth or milk without the juice was used as the control.
Phenolic compounds benefit
Biswas et al said the findings could be due to phenolic components of the berry.
Studies have shown that blueberry juice can inhibit the growth of foodborne bacterial pathogens but, unlike blackberry juice, it does not affect the growth of probiotic bacteria.
Growth of E. coli O157:H7, S. Typhimurium and L. monocytogenes were reduced by 1.65, 3.34 and 2.40 logs CFU/mL, respectively as compared with the growth in broth alone.
The effects of 10% blackberry juice in broth remained throughout the 72 hour period with E. coli O157:H7 in broth inhibited the growth by 1.65, 2.61 and 3.35 logs CFU/mL at 24, 48 and 72 hours.
Results of Salmonella and L. monocytogenes had similar trends indicating the role of blackberry juice in the reduction of growth of E. coli O157:H7, S.Typhimurium and L. monocytogenes in broth were significant and time dependent.
Effects of blackberry juice on Lactobacillus strains showed it promoted the growth of the beneficial bacteria.
Growth of Lactobacillus strains were stimulated (1–4 logs CFU/mL) by blackberry juice in milk and 1–2.5 logs CFU/mL in Man–Rogosa–Sharpe (MRS) broth.
The effects of blackberry juice on the growth of Lactobacillus strains (L. casei, L. plantarum, and L. rhamnosus) showed different results depending on the species.
For L. plantarum and L. casei, 10% supplemented blackberry juice in MRS broth promoted the growth significantly only at 48 hours.
Growth of L. plantarum was stimulated (2.74–4.20 logs CFU/mL) by blackberry juice in skim and whole milk at all the time points.
Source: Food Control
Online ahead of print DOI: 10.1016/j.foodcont.2013.08.042
“Effects of blackberry juice on growth inhibition of foodborne pathogens and growth promotion of Lactobacillus”
Authors: Hongshun Yang, Daniel Hewes, Serajus Salaheen, Cassandra Federman, Debabrata Biswas