P3-114 Efficacy of a Citric Acid-based Organic Sanitizer against Salmonella enterica and Escherichia coli K-12 on Organic Leafy Greens during Wash Water Recycling

Tuesday, July 28, 2015
Hall B (Oregon Convention Center)
Libin Zhu, University of Arizona, Tucson, AZ
Rita Mild, Rose State College, Midwest City, OK
Sadhana Ravishankar, University of Arizona, Tucson, AZ
Introduction: Post-harvest treatment with sanitizers is an effective way to reduce pathogenic and background microorganisms on organic leafy greens.

Purpose: The objective of this study was to investigate the efficacy of a citric acid-based organic sanitizer (organic ChicowashTM) against Salmonella enterica serovar Newport on organic leafy greens in laboratory scale and surrogate Escherichia coli K-12 on iceberg lettuce in a large scale with recycling of wash water.

Methods: In the laboratory scale test, ten grams of organic iceberg or romaine lettuce, baby or mature spinach samples were inoculated with Salmonella Newport and treated with 200 ml of 1:20 Chicowash for 1 or 2 min.  In the large scale test, seven kilograms of organic iceberg lettuce were inoculated with E. coli K-12, treated with 75 liters of 1:20 Chicowash for 2 min, and 4 additional batches of lettuce samples (7 kilograms each) were washed consecutively. Samples were stored at 4°C and enumerated for surviving Salmonella or E. coli K-12 at day 0, 1 and 3. De-ionized water and tap water were used as controls for laboratory and large scale tests, respectively.

Results: In the laboratory scale test on 4 leafy green types, Chicowash caused 0.1 - 1.3 and 0 - 1.2-log reduction in Salmonella population at day 0 for 1 and 2 min treatments, respectively; at day 1,  reductions of 1.6 - 2.7 and 1.4 - 2.1 logs were observed for 1 and 2 min treatments, respectively. The greatest reductions were seen at day 3; 2.1 - 2.5 and 2.3 - 2.9 logs for 1 and 2 min treatments, respectively. In the large scale test, Chicowash showed similar reductions in E. coli K-12 population on iceberg lettuce after each wash; 1.6 - 1.9, 2.3 - 2.6, and 2.9 - 3.5 logs for day 0, 1 and 3, respectively. The reduction was storage time dependent.

Significance: The results could provide the organic produce industry with more options to select alternate natural sanitizers for post-harvest treatments.