Leafy Greens: Risk Reduction and Industry-related Interventions

Introduction: Raw leafy-greens are a power packed, nutritious food; however, there have been multiple foodborne disease outbreaks associated over the past years.

Purpose: The goal of this study was to design practical methods and improve sanitation protocols to reduce the levels of pathogenic contamination on fresh produce in restaurant kitchens.

Methods: Lettuce was purchased from local grocery stores and inoculated with a pathogenic cocktail composed of Listeria monocytogenes (LM), Salmonella Typhimurium (ST) and Escherichia coli O157:H7 (EC). Romaine lettuce (100 g) was added to 50 ml of 10⁸CFU/ml inoculum cocktail in a sterile beaker. The lettuce was dried for one hour in a biosafety cabinet, followed by the analysis of the 30 s, 2 min, and 5 min water-wash submersion controls. Intervention analyses were conducted as follows: USDA certified organic vegetable wash submersions (30 s/2 min/5 min), and 1:1 acid to oil dressing (including acetic, citric acid, and olive oil; 30 s/2 min). Methods for isolation and enumeration were in accordance with the Bacteriological Analytical Manual. Samples were aseptically stomached with 0.1% peptone buffer for 120 s, serially diluted, and plated on EMB (ST and EC enumeration) or PALCAM agar (LM) enumeration.

Results: Samples exposed to the oil and acid dressing for 30 s showed a reduction in ST and EC counts to below the detectable limits (5.6-log CFU/g reduction) and a 2.4-log CFU/g reduction in LM. Samples submerged in the USDA certified organic vegetable wash for 30 s showed a reduction in ST and EC counts by 1.4 log CFU/g and LM by 0.8 log CFU/g.

Significance: The use of practical, inexpensive protocols for leafy green sanitation could enhance food safety practices within the restaurant industry, especially while catering to immunocompromised individuals. It is, also, especially crucial to design and disseminate educational materials focused on science-based interventions to stakeholders.