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United States Department of Agriculture

Agricultural Research Service

Research Project: Innovative Technologies and Process Optimization for Food Safety Risk Reduction Associated with Fresh and Fresh-Cut Leafy Green Vegetables

Location: Environmental Microbial and Food Safety Laboratory

2012 Annual Report


1a.Objectives (from AD-416):
1. Inactivation of pathogens and prevention of cross-contamination through optimization of produce wash system design and operation; 2. Development of innovative washing processes and technologies; and 3. Prevention of pathogen proliferation in supply chain.


1b.Approach (from AD-416):
This project takes a system-based and trans-disciplinary approach to address food safety issues of leafy green vegetables. The project involves research in the fields of mechanical engineering, microbiology, post-harvest technology, and food processing. "Speciality Crop Research Initiative."


3.Progress Report:

Intensive studies were conducted to evaluate the effect of free chlorine concentrations and contact times on the inactivation of various types of human pathogens in wash water containing organic residues typically encountered in industrial produce washing systems. Results showed that increased tomato or lettuce juice extract concentration in wash water was significantly associated with increased water turbidity, chemical oxygen demand, and decreased residual free chlorine. The reduced water quality conditions significantly affected pathogen survival. Residual chlorine concentration and contact time were critical factors in determining the pathogen disinfection efficacy of chlorine solution in produce wash water. Pathogen cells exposed to chlorine for sufficient contact time experienced extensive damage to cytoplasmic membranes as confirmed by microscopy. A new, state-of-the-art electrolyzed water generator was provided to USDA-ARS-BARC by Trustwater Corp. as an in-kind support to our research. This equipment electrolyzes a saturated salt solution to generate two solutions:.
1)Ecasol, a neutralized (pH 6.8) solution of pure hypochlorous acid (~1000 ppm free chlorine) and.
2)Aversol, a solution of pure sodium hydroxide (pH 13.6). We are in the early stages of conducting side-by-side comparisons of Ecasol and the commonly used sanitizer (sodium hypochlorite) at the same free chlorine levels to compare their effects on pathogen reduction and the prevention of cross-contamination during the leafy green washing process. Preliminary results have indicated that Ecasol solutions are equally as effective in simulated wash-water containing various organic loads, and with the value added benefit of on-site generation, minimized toxic byproducts and virtual elimination of corrosive effects associated with sodium hypochlorite solutions.


Last Modified: 12/22/2014
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