Listeria monocytogenes GROWTH INHIBITION IN INOCULATED FRESH PANELA CHEESE BY THE ADDITION OF Rhoeo discolor AQUEOUS EXTRACTS COMBINED WITH POTASSIUM SORBATE

Natural resources have been exploited in the search for new bioactive compounds. Rhoeo discolor is a plant commonly employed in traditional folk medicine throughout Latin America. The antimicrobial effect of extracts derived from this plant, have proven effective against a variety of microorganisms. The inhibitory effect against Listeria monocytogenes growth of two aqueous extracts obtained from dry Rhoeo discolor leaves at 25 degrees C and 90 degrees C and containing 3200, 1600, 800, 400, 200, 100, 50, 25, 12.5, 6.3, 3.1 or 1.6 solids/mL was evaluated.. These extracts were then combined with 50, 25, 12.5, 6.3, 3.1 and 1.6 mg/kg of potassium sorbate. The extracts that showed better inhibitory effect by the reduction of two full logarithmic growth cycles were those containing 800 or 400 mu g/rnL of R. discolor extract and 6.3, 3.1 or 1.6 mg/kg of potassium sorbate, these were tested in inoculated Panela cheese and where later evaluated in terms of L. monocytogenes growth inhibition. Acceptance analyses were performed to determine alteration in the organoleptic properties in control and experimental (non-inoculated) cheese. Results revealed that the additions of R discolor extracts and potassium sorbate in these concentrations did not affect organoleptic properties. Experimental cheese samples were in occasions ranked better than the control cheese regarding organoleptic parameters.