Effectiveness of Acidic Electrolyzed Water in Reducing Microbial Load on Lettuce Produced in a High Tunnel

High tunnel extends the production season for vegetables. Collection of rain water provides an alternative source of irrigation water during the growing season. However, rainwater is prone to contamination by animal feces and environmental dusts and debris. Preliminary studies showed that the collected rain water was high in bacteria incluing E. Coli. This lead to high microbial load on the vegetables produced. The objective of this study was to determine the effects of acidic electrolyzed water on microbial load of black seed lettuce produced under this condition. Black seed lettuce was grown in a high tunnel. They were irrigated with rainwater collected in black plastic tanks and tranferred with a solar powered pump. Lettuce leaves were harvested manually and transported to the lab in a cooler for analysis. The leaves (100 g) were cut into one centimeter length and mixed well before samples of 10 g each were taken. The samples were treated with no rinsing, rinsing with tap water or acidic electrolyzed water.  For the rinsing treatment, black seed lettuce were rinsed with 500 ml of tap water or 500 ml acidic electrolyzed water in a plastic container placed on a shaker at 20 rpm for 5 minutes. The leaves were mixed with 90 ml of Peptone water, homogenized in a stomacher for 2 minutes before the solution was inoculated onto petrifilm plates for total aerobic count after proper dilution.  The total aerobic bacteria counts were 2425, 1485 or 25 CFU/g for lettuce with no rinse, rinsed with tap water or acidic electrolyzed water, respectively. Rinsing with tap water reduced the microbial load by 40%, whereas rinsing with acidic electrolyzed water reduced the micorbial load of lettuce leaves by 99%. These results indicate that acidic electrolyzed water can be an effective decontaminating treatment for vegetables irrigated with rainwater during production.