P1-35 Minimum Effective Concentrations of a New Fresh Produce Wash (First Step+ 10), Compared to Chlorine at Inactivating Foodborne Pathogens in Rinse Water

Monday, August 1, 2016
America's Center - St. Louis
Joshua Gurtler, USDA/ARS, Wyndmoor, PA
Rebecca Bailey, U.S. Department of Agriculture-ARS, Wyndmoor, PA
Xiaoling Dong, NatureSeal, Inc., Lincoln, RI
Stephen Santos, NatureSeal, Inc., Lincoln, RI
Introduction: We previously reported inactivating E. coli O157:H7 (Ec), Salmonella and Listeria monocytogenes (Lm), by a new produce wash, First Step+ 10 (FS+10) at concentrations of 0.5, 0.6, 0.8, 1.0, 1.2, and 1.6%.  Chlorine concentrations in rinse water frequently fall to low levels (e.g., 10-16 ppm), due to inactivation by organics. 

Purpose: Determine the minimal FS+10 concentrations effective at inactivating foodborne pathogens in rinse water, compared to low levels of chlorine.

Methods: An organic interference substance (bovine albumen) was added to multi-strain suspensions of Ec, Salmonella, and Lm, at 0.03% (BSEN 1276 method).  Two additional interference substances (5% fresh-squeezed apple juice (AJ) or 2.5% fresh lettuce juice (LJ)) were also tested.  The three pathogens were challenged with 0.2, 0.3, and 0.4% of FS+10 (for bovine serum, and 0.4 and 0.5% for juices), as well as with 10 and 16 ppm chlorine (citric acid-adjusted to pH 7.0).   

Results: All concentrations of FS+10 (0.2, 0.3, and 0.4%) inactivated >5 logs of all pathogens, with no statistical difference between treatments (P<0.05, Scheffe).  Average log reductions for the three concentrations of FS+10 were Ec (all >5.93), Salmonella (5.14, >5.61, >5.69), and Lm (all >5.7).  FS+10 inactivated statistically greater numbers of all pathogens than 16 ppm chlorine, which was > than that inactivated by 10 ppm chlorine.  Average log reductions for 16 and 10 ppm chlorine were Ec (1.79, 0.64), Salmonella (2.72, 1.20), and Lm (2.77, 1.22).  In the presence of 5% AJ, reductions for 0.5 and 0.4% concentrations of FS+10, respectively, were Ec (6.25, 5.06), Salmonella (>6.78, 6.18), and Lm (>6.69, 2.94).  Log reductions in the presence of 2.5% LJ, were Ec (>6.78, 4.99), Salmonella (>6.87, >6.56), and Lm (6.12, 2.49).

Significance: FS+10 is capable of inactivating pathogens in wash waters with the interference substances tested here, which may assist producers in their food safety hygiene plans.