Decontamination of Listeria monocytogenes in king oyster mushrooms (Pleurotus eryngii) by combined treatments with organic acids, nisin, and ultrasound

This study was conducted to evaluate the effectiveness of 1-3% organic acids alone or in combination with 0.1% nisin and/or 40 kHz ultrasound (US) on the reduction of Listeria monocytogenes in king oyster mushrooms stored at 25 degrees C. While L. monocytogenes in king oyster mushrooms was reduced by 3.01 log CFU g(-1) after dipping in 3% malic acid (MA) at 25 degrees C for 30 min, the application of 40 kHz US and 0.1% nisin resulted in 0.30 and 2.25 logreductions, respectively. When L. monocytogenes in mushrooms was subjected to a combined treatment with 3% MA, 0.1% nisin, and 40 kHz US at 25 degrees C for 20-30 min, this bacterium dropped to <1.48 log CFU g(-1), leading to a significant collapse in the cytoplasm with formation of intracellular ruptures and breakage of cell membranes. Synergistic effect of MA-nisin dipping incorporated with US was observed in a food model.

Automated summary

The study showed that dipping king oyster mushrooms in 3% malic acid, combined with 40 kHz ultrasound and 0.1% nisin, effectively reduced Listeria monocytogenes. Further reduction was observed when all three treatments were combined, leading to significant collapse in bacterial cells.