Control of Salmonella enterica serovar Typhimurium and Listeria monocytogenes on lettuce and radish sprouts by combined treatments with thymol, acetic acid, and ultrasound

Abstract

Lettuce or radish sprouts carrying Salmonella enterica serovar Typhimurium or Listeria monocytogenes were treated individually or in combination with thymol, acetic acid (AA), and/or ultrasound (US) at 23 ± 2 °C for 10 min. Approximately 0.17–1.71, 0.47–3.19, or 0.85–3.91 log-reductions against S. Typhimurium and L. monocytogenes were observed when submerged in 312.5 ppm (=minimal inhibitory concentration; MIC) thymol, 1% AA or MIC thymol + 1% AA at 23 ± 2 °C for 10 min. When treated simultaneously with MIC thymol +0.5% AA dipping at 23 ± 2 °C for 10 min, S. Typhimurium decreased by ≥ 5.00 log CFU/g on radish sprouts stored at 4 °C within 48 h and remained undetectable during 7 days of storage at 4 °C. In particular, dipping in 1/2*MIC thymol +0.5% AA together with 40 kHz US reduced S. Typhimurium and L. monocytogenes by 1.88–3.06 log CFU/g on radish sprouts, which had acceptable sensory properties. The highest lethal activity for killing S. Typhimurium and L. monocytogenes was achieved, ranging from 1.31 to 2.42 log CFU/g on lettuce or 2.02 to ≥4.48 log CFU/g on radish sprouts after combined treatments with MIC thymol +1% AA + 40 kHz US simultaneously at 23 ± 2 °C for 10 min. © 2022 Elsevier Ltd