Effect of polyphenol content on the antimicrobial activity of natural extracts from agro-industrial by-products

The main objective of the present study was to investigate the effect of the conditions of extraction by Accelerated Solvent Extraction (ASE) technology on the bioactive antimicrobial activity of extracts from by-products of cauliflower, broccoli, orange, and mandarin. The antimicrobial activity of extracts, with concentrated phenol content, was evaluated against four of the most important foodborne pathogens: Salmonella enterica serovar Typhimurium, Escherichia coli O157:H7, Bacillus cereus, and Listeria monocytogenes. The largest phenol content (1252.12 +/- 38.29 mu g gallic acid/mL) was recovered from cauliflower extract. Cauliflower and mandarin extracts were effective against both Gram-positive and Gram-negative bacteria, showing the highest inhibition zones, 16 1 mm and 17 +/- 0.4 mm respectively, against 105 cfu/mL S. Typhimurium. The antimicrobial effectiveness of the extracts was influenced by the ASE extraction conditions, initial contamination level, and microbial strain.