Vegetable farmers are looking for practical ways to address food safety risks. This interest stems in part from passage of the Food Safety Modernization Act (FSMA), increased demand on the part of produce buyers for growers to follow Good Agricultural Practices (GAPS), and a growing awareness that food safety is a key consumer concern. Reducing levels of bacteria in vegetable wash water is one way to reduce food safety risks, specifically the risk of cross-contamination whereby one contaminated item leads to the spread of a pathogen to other items being washed in the same water. Leafy greens in particular warrant concern about cross contamination because large volumes of these crops are often washed in the same water, the crops are low-growing and often exposed to splashing soil which can contain pathogens, and they are typically consumed raw.
An on-farm research study evaluated the effect of multiple rinses, and use of an organically-approved sanitizer, on the level of generic E. coli in leafy greens wash water on Vermont farms. Water samples were collected weekly or biweekly from 3 farms in 2012 and 4 farms in 2013. These were analyzed by the Vermont Dept. of Health Laboratory. The results demonstrated that the highest labeled rate of sanitizer in the first wash was most effective in reducing E. coli levels (99.8% reduction). Triple washing without sanitizer was also very effective (96.9% reduction). Double washing or using a half-rate of sanitizer reduced E. coli but were not as effective.
Farmers were informed about the research findings results via presentations, extension newsletters and individual consultations (100 farms). A fact sheet was developed and a YouTube video was produced to encourage growers to improve their washing systems by using multiple rinses and/or an approved water sanitizer. Growers were recruited to take their own water samples to test leafy greens wash water during summer of the 2014 season. Pre-paid test kits from the Vermont Dept. of Health were provided for this purpose to 55 farms.
Forty-three farms submitted a total of 80 pairs of wash water samples which represented the first and final rinses from their leafy greens wash system. These were tested by for generic E. coli level. Thirty-four of these farms also completed surveys that estimated an aggregate of 447,000 pounds of leafy greens were washed, with a market value of over $2 million. Multiple rinses reduced the E. coli levels in wash water across all farms and wash system types. Several farms had very high E. coli levels in their first rinse, which were only reduced to zero after sanitizer treatment regardless of the number of rinses used. This suggests that the addition of sanitizer is a grower’s best method of reducing cross contamination in rinse water.