Improving Produce Safety by Stabilizing Chlorine in Washing Solutions with High Organic Loads

Chlorine solutions are widely used in the fresh and fresh-cut produce industry to reduce microbial populations and prevent pathogen survival and transference during water re-use and re-circulation. However, the copious amount of organic material released from the cut edges of vegetables, and the presence of field soil and debris creates a high demand for free chlorine, reducing the sanitizing potential of wash water just when it is needed most. <P>
Balancing the need for sufficient levels of free chlorine for effective sanitizing with the need to limit formation of hazardous chlorine off-gas during the commercial fresh-cut produce wash operations is a technical challenge. Industry scientists have pioneered development of a novel food-safe (GRAS) chemical product, F86-128, that they found stabilizes chlorine as hypochlorous acid in the presence of high organic loads, thus minimizing the loss of chlorine efficacy in produce wash tanks and flumes. <P>The promising industry research results on F86-128 and hypochlorous acid need to be verified and the effective operational range under various conditions need to be tested by impartial third-party researchers before such products can be introduced to the fresh produce processing industry. <P>This proposal describes several types of studies to be conducted by a USDA-ARS research team to address queries posed by industry, specifically: 1) Evaluate the effect of compound F86-128 on the stability of hypochlorous acid in the presence of high organic load, and determine the influence of organic load, pH, chlorine, and temperature on the effectiveness of F86-128 stabilization of hypochlorous acid; 2) Determine the effect of F86-128 on the pathogen inactivation potential of chlorinated wash water for leafy greens; 3) Determine the effect of F86-128 on the pathogen inactivation potential of chlorinated wash water for other fresh produce including herbs, tomatoes, and cantaloupes; 4) Evaluate the effect of F86-128 on product quality and shelf life, and measure residual levels on finished products.<P> Key features of this proposal include inoculation protocols that simulate realistic field contamination with E. coli O157:H7, Salmonella, and Listeria, use of a pilot-scale fresh-cut facility to simulate commercial wash processes and efficacy evaluated on herbs, tomatoes, and cantaloupes and with biofilms, as well as close consideration of industry concerns and operational limitations. <P>These features will aid development of procedures that are amenable to industrial use, and support rapid, economical adoption of effective sanitization improvements by commercial processors.