Use of Fulvic Acid Formulations as Flume-wash Treatments for Reduction of Escherichia coli O157:H7 on Organic Leafy Greens

Escherichia coli O157:H7 is a public health problem worldwide, with leafy greens as a major source of recent outbreaks. Standard organic produce-industry washes have been ineffective in reducing this problem. It is therefore crucial that effective alternatives for washing organic produce be developed. Fulvic acid (FA) is an organic acid reported to have antimicrobial and antifungal properties. The present study evaluated the antimicrobial efficacy of various FA formulations (I, II, III, IV) against E. coli O157:H7 as a flume-wash treatment for organic leafy greens. Organic baby and mature spinach, and romaine and iceberg lettuce, were inoculated with E. coli O157:H7 and washed with FA formulations at 1, 2, and 3% concentrations. Pathogen populations were determined on leafy greens stored at 4˚C over a 3-day period. Treatment with all FA formulations at all three concentrations showed significant reductions (P < 0.05) in E. coli O157:H7 populations compared with the positive control. The most effective treatment was found to be FA-III at 3%, with 2.4 log CFU/g reduction on all leafy greens by day 3. Higher treatment concentrations caused higher reductions in pathogen populations. Fulvic acid could be used as an effective antimicrobial during flume washing and subsequent short-term storage of organic leafy greens.