The transfer rate of Salmonella Typhimurium from contaminated parsley to other consecutively chopped batches via cutting boards under different food handling scenarios

- Transfer rate was strongly and negatively correlated with contamination levels.
- Transfer rate persisted in a diminishing trend across consecutively chopped parsley.
- Transmission of bacterial cells was reduced via washed cutting boards.
- Cross-contamination risk was recorded via cutting board held for 24 h at 30 °C.

In many Mediterranean and Middle Eastern countries, leafy green parsley is typically eaten raw and prepared by fine chopping several batches. This study aimed to quantify the transfer rate of S. Typhimurium (Tr) across all chopped batches in scenarios that resemble normally occurring operations in restaurants and home kitchens. Fresh parsley leaves were inoculated at concentrations of 6 and 3 log CFU/g and chopped on a polyethylene cutting board (CB). Uninoculated parsleys were sequentially chopped in individual batches on the same cutting surface, 1) instantly (CB Instant), 2) after washing in water and holding at 30 °C 24 h (CBWW), 3) after washing in soapy water, sponge scrubbing and holding at 30 °C 24 h (CB SW). Using the high inoculum levels, the mean Tr was 0.012 ± 0.04, 0.014 ± 0.02 and 0.010 ± 0.008, via CB Instant, WW and SW, respectively. Comparatively, the Tr mean values were significantly higher with the low inoculum levels, 0.60 ± 0.65 and 0.64 ± 0.46, via CB Instant and CB WW respectively, and transmissions of S. Typhimurium significantly decreased across consecutively chopped batches on both washed CBs (P < 0.05). These results demonstrated continuous transfer of Salmonella cells, from contaminated parsley to cutting boards and subsequently re-contaminating up to 6 batches of parsley chopped consecutively on the same surface. A greater cross-contamination rate was recorded during the initial phases of chopping and remained at 24 h at 30 °C. Vigilant cleaning and sanitation procedures on cutting surfaces should be a fundamental requirement after use with fresh produce, particularly if there is a likelihood of insufficient food safety measures at harvest and post-harvest stages.

The population size of S. Typhimurium on successively chopped batches of parsley after initial chopping of artificially contaminated samples.A decreasing trend in the recovery of S. Typhimurium, particularly with high inoculum levels on source, along the three successive batches of un-inoculated parsley chopped subsequent to initially chopped 100 g parsley inoculated, a) instantly on same cutting board (CB Instant), b) after water wash of same cutting board and holding for 24 h at 30 °C (CB WW), c) after soap and water wash combined with soft sponge rubbing and holding for 24 h at 30 °C (CB SW). The latter scenario was not tested with low inoculum levels.*Initially chopped inoculated parsley (log CFU/g).L = low inoculum; H = High inoculum.136