# Plant Organic Acids as Natural Inhibitors of Foodborne Pathogens
## 4 Discussion
Similar results were presented by the same research group for _Campylobacter jejuni_ obtained from broiler chicken houses. Bacterial growth inhibition occurred at concentrations of acetic acid 0.5-4.1 mg/mL, citric acid 0.26-4.1 mg/mL, and formic acid 0.5-4.1 mg/mL [32]. In another paper, the MIC results demonstrated that acetic acid, citric acid, and tartaric acid inhibited _Salmonella_ Typhimurium at concentrations of 0.312% (3.1 mg/mL), 0.625% (6.3 mg/mL), and 0.312% (3.1 mg/mL) for 10\({}^{3}\); CFU/mL [33]. [PERSON] and [PERSON] [34] reported that the breakpoints of organic acids against the shrimp pathogen _Vibrio hurevyi_ were 0.025-0.05% (0.25-0.5 mg/mL) for formic acid and 0.05-0.1% (0.5-1 mg/mL) for acetic acid, which are lower values than those found in this work. Many data show that higher concentrations than those obtained in this work are required to inhibit foodborne pathogens. In the study by [PERSON] et al. [35], the organic acid with the lowest MIC against _Staphylococcus aureus_, _Enterococcus faecium_, _Bacillus cereus_, _Escherichia coli_, and _Pseudomonas aeruginosa_ was acetic acid (MIC 0.5-2.0 mg/mL). The remaining acids had higher average MIC levels. The activity of ascorbic acid against these bacteria showed the highest MIC, ranging from 4.0 to 16.0 mg/mL. The MIC values for citric acid ranged from 1.0 to 4.0 mg/mL and for succinic acid from 0.8 to 4.0 mg/mL. [PERSON] and [PERSON] [36] demonstrated that the activity of organic acids depends on the pH. The activity against _Listeria monocytogenes_ decreased with increasing pH. For acetic acid, it ranged from 0.5 mM at pH 5.0 to 32 mM at pH 8.0 (30-1920 mg/mL); for citric acid, from 0.5 to 16 mM (96-3072 mg/mL); and for malic acid, from 0.5 to 32 mM (67-4288 mg/mL). [PERSON] and [PERSON] [37] have shown that citric and malic acids at 1% and 2% (10 and 20 mg/mL, respectively) concentrations inhibit the development of _Bacillus subtilis_ biofilm and can destroy mature biofilm. Concentrations of 1% and 2% are several times higher than the MICs obtained in the present work. Similar concentrations were studied in another work [38], where 1%, 2%, and 3% acetic and citric acids reduced the number of _Salmonella_ Enteritidis, _Escherichia coli_, and _Listeria monocytogenes_ in beef meat. However, only the 3% concentrations led to a significant (_p_ < 0.05) reduction in bacteria. In the next paper [39], it was found that acetic acid and citric acid lead to the inactivation of multi-drug-resistant non-typhoidal _Salmonella_ and Shiga-toxin-producing _Escherichia coli_. The authors used acids at a concentration of 4.1 mg/mL, which is higher than the average MICs obtained by us. Unfortunately, the authors did not present MIC results, even though they described this study in their methodology. In studies on sheep and goat meat obtained from freshly slaughtered animals, samples were inoculated with _Staphylococcus aureus_, _Listeria monocytogenes_, _Escherichia coli_, and _Salmonella_ Typhimurium. The meat samples were then washed with a spray containing 2% lactic acid and a combination of 1.5% acetic acid + 1.5% propionic acid. It was shown that the total number of viable microorganisms in the meat was reduced by approximately 0.52 and 1.16 log units, respectively [40]. [PERSON] et al. [41] demonstrated that 1% (10 mg/mL) citric acid leads to the reduction in _Salmonella_ spp., _Staphylococcus_ spp., and thermotolerant coliforms in sheep meat. In studies on the effect of organic acids on _Escherichia coli_ isolated from fresh pork sausage, the highest level required for antibacterial activity was found to be 1.29 M (247 mg/mL) for citric acid and approximately 4 M for acetic acid (240 mg/mL) [42]. In the literature, there is little on the antifungal activity of organic acids, according to PubMed or Scopus databases. In one publication, similar to our studies, much higher concentrations were required to achieve an antifungal effect. _Penicillium_ sp. strains were inhibited by acetic acid at concentrations of 200-800 mM (12,010-48,040 mg/mL) [43].