Control of Listeria monocytogenes in Refrigerated Ozonated Water

Abstract

ABSTRACT The present work aimed at the effectiveness of ozonated water in the control of Listeria monocytogenes, adopting different combinations of pH, contact time, and storage time under refrigeration. To obtain ozonated water, the dose applied was 21 mg L−1 min−1, for 15 min. Samples of 1.0 L of water were ozonated at the inlet ozone concentration of 21 mg L−1 and a flow rate of 1.0 L min−1. The initial concentrations of ozone dissolved in water were equal to 5.81 mg L−1 at pH 4.0, 5.20 mg L−1, at pH 7.0, and 7.20 mg L−1 at pH 8.2. Samples of ozonated water with different initial pHs were used and stored at 7℃ for up to 24 h. The storage times of the ozonated water under refrigeration were 0, 6, 12, 18, and 24 h. The contact times of L. monocytogenes with ozonated water were 3.0 and 6.0 min. Ozone decomposition kinetics was evaluated. Ozonated water stored at 7℃ proved effective in controlling L. monocytogenes, especially in water pH values of 7.0 and 8.2. The initial pH of the water affects the effectiveness of ozonated water regarding the control of L. monocytogenes. The sharp reduction in ozone concentration was observed in water with pH 4.0, with a half-life of 13 min. For pHs of 7.0 and 8.2, the half-lives were 65 and 45 min, respectively. It is viable to use ozonated water stored at 7℃, for up to 24 h, to inactivate L. monocytogenes, when adopting initial pHs of 7.0 and 8.2, adjusted with sodium bicarbonate.