Purpose: The objective was to investigate the efficacy of wash water containing plant antimicrobials against Salmonella Newport on organic romaine and iceberg lettuces and baby spinach during reuse.
Methods: Three types of organic leafy greens- romaine lettuce, iceberg lettuce or baby spinach samples were immersed into 200 ml of 106 CFU/ml Salmonella Newport culture for 2 min, and dried in a biohood for 30 min. Plant extracts (olive or apple extract) and essential oils (oregano or cinnamon oil) washes were prepared at 3% and 0.3% concentrations, respectively. Produce samples were immersed into wash water for 2 min, and stored in stomacher bags at 4°C. The wash water was reused 5 times to treat five batches of leafy green samples one after another. Produce samples were taken at day 0, 1, and 3 to enumerate Salmonella Newport survivors. Wash water samples were also taken after each wash to enumerate Salmonella population. Phosphate buffered saline was used as a control.
Results: For olive and apple extract treatments, the Salmonella log reductions were 0.5-2.0, 0.5-2.6 and 0.8-2.7 at day 0, 1 and 3, respectively. The 5-time reuse of 3% olive and apple extracts did not reduce their antimicrobial effects. Oregano and cinnamon oil treatments caused 1.5-3.4, 1.4-3.4 and 0.8-3.4 log reductions at day 0, 1 and 3, respectively. There were no Salmonella survivors detected in olive extract, oregano, and cinnamon oil wash waters after each wash.
Significance: The results demonstrated that wash water with plant antimicrobials can be recycled to reduce the costs for produce industry.