The periodic 15 s change of direction was also introduced to further increase the agitation during the wash process to ultimately aid in microbial cell detachment from surfaces and increase the ability of NEO water penetrate the leaf surfaces.
The combination of reducing the pH to 6.5, increasing washing speed to 100 rpm and manually changing wash direction helped improve the reductions observed on both pathogens. For S. Typhimurium DT 104 (5.15 log CFU/g reductions), the aim of achieving a 5-log reduction was attained but the same was not observed for E. coli O157:H7.
Although a 5-log reduction for E. coli O157:H7 on iceberg lettuce was not achieved, these two treatments achieved significantly more reductions (3.94 and 4.07 vs 2.4 and 3.2 log CFU/g) than the NEO water with a pH of 7.5 described in Afari et al. (2015), suggesting improved efficacy of the washing process.