Short communication: Antibacterial and antibiofilm effect of natural substances and their mixtures over Listeria monocytogenes, Staphylococcus aureus and Escherichia coli

Natural antimicrobial agents used as food additives and agents for active food packaging development are a promising way to reduce food-associated microbial risks. We compared the antibacterial and antibiofilm effect of seven natural-origin additives suitable for active food packaging (calcium lactate, citric acid, curcumin, erythorbic acid, garlic extract, hop extract, nisin) against Listeria monocytogenes, Staphylococcus aureus, and Escherichia coli. Minimal inhibitory concentration (MIC) and MIC for biofilm formation (MICBF) were determined. All the tested substances provided a significant antibacterial effect (p <= 0.05); among the tested bacteria, E. coli was the most resistant strain to all substances (p <= 0.05). Citric acid (MIC and MICBF 0.25-0.5 wt%), garlic extract (MIC and MICBF 2.0-4.0 wt%), and erythorbic acid (MIC 3.0-5.0 wt%; MICBF 2.0-5.0 wt%) were evaluated as the most effective ones. Further, mixtures of garlic extract and i) calcium lactate, ii) curcumin, iii) erythorbic acid, iv) hop extract, v) nisin provided synergy and higher bacterial suppression than the substances alone, even for E. coli (p <= 0.05). Thus, this strategy of combining two food additives could prolong the product shelf-life when incorporated, for example, into functionalized food packaging (nano)materials.

Automated summary

The study compared the antibacterial and antibiofilm effects of seven natural-origin additives, with citric acid, garlic extract, and erythorbic acid being identified as the most effective. Furthermore, mixtures of garlic extract with other additives showed synergy in bacterial suppression, even against E. coli.