The aim of this research was to evaluate the antimicrobial activity of rosemary and buffered vinegar formulations on bacteria Pseudomonas and Shewanella, and to evaluate the impact of the formulations on shelf-life extension of common carp (Cyprinus carpio) fillets. Minimal inhibitory concentrations (MIC) were determined with broth microdilution method. MIC values were determined in broth and in food model for bacterial strains Pseudomonas fragi, Pseudomonas psychrophila, Shewanella putrefaciens and Shewanella xiamenensis. Determined MIC values ranged from 0,39 mg/mL to 6,25 mg/mL. The most efficient antimicrobial activity was with concentrations 1,56 mg/mL and 3,13 mg/mL, therefore, in further analyses, carp fillets were treated with formulations in these concentrations. The antimicrobial activity of the formulations on fillets was determined quantitatively by the standard plate count method. The growth of mesophilic and psychotrophic aerobic bacteria, bacteria of the genus Pseudomonas and H2S-producing bacteria was observed. Although the lowest MIC values were determined for the rosemary extract, the best antimicrobial activity, when applied to the fillet, was determined for buffered vinegar and for combination of rosemary extract and buffered vinegar, both in concentration 3,13 mg/mL. The results of experimental work confirm that rosemary extracts and buffered vinegar inhibit the growth of bacteria Pseudomonas and Shewanella. We also confirmed that by using these extracts we can reduce the microbial population of common carp fillets.
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