Antimicrobial effect of UV-C treated fresh-cut broccoli against Listeria monocytogenes
The aim of this study was to investigate the effect of different doses of UV-C light as a postharvest treatment to control the attachment and subsequent growth of Listeria monocytogenes on fresh-cut broccoli. Growth of the bacteria was studied under in vitro and in vivo conditions. UV-C treated (0, 2.6 and 5.2 kJ m-2) broccoli branchlets were inoculated with L. monocytogenes at various times (0, 6, and 24 h) after treatment and tested for bacterial growth up to 8 days. Broccoli extracts obtained through fractionation and partitioning between different solvents (n-hexane, 10% methanol, n-butanol, and aqueous) were tested in vitro against the growth of L monocytogenes. Broccoli extracts from all doses of UV-C irradiation significantly reduced the growth of L. monocytogenes when inoculated 24 h post treatment while only the extract from higher UV-C dose was effective in reducing growth in samples inoculated 6 h after the treatment. The most potent extracts were aqueous and butanol which restricted the growth of L. monocytogenes in samples treated with 5.2 kJ m-2 and extracted 24 h after the treatment. Phytochemical analysis of the same samples using LC-MS confirmed that UV-C treatment induced particular chemical compounds that may restrain microbial growth. These findings confirm that UV-C treatment is effective in stimulating the synthesis of phytochemical compounds that may inhibit the growth of L. monocytogenes in fresh-cut broccoli. Therefore, this treatment could be used as a hurdle technology to reduce the risk of post-harvest contamination and to ensure microbial safety of fresh produce.
Gamage, G.R., Heyes, J.A., Palmer, J.S. and Wargent, J. (2016). Antimicrobial effect of UV-C treated fresh-cut broccoli against Listeria monocytogenes. Acta Hortic. 1120, 187-192
secondary metabolites, postharvest, human pathogen