1a. Objectives (from AD-416):
The overall goals of the project are to establish the degree of efficacy of chlorine dioxide (ClO2) gaseous application in disinfecting fresh leafy greens and cherry tomatoes, to establish the point of dose-dependent injury to fresh quality and shelf-life so that such injury can be avoided, to evaluate the integration of post-harvest strategies of product sanitizing and exposure to an antimicrobial through packaging to assure the microbial safety of fresh produce, and to further improve, extend and transfer treatment application methods to end-users so that adoption of a commercially feasible process becomes possible.
1b. Approach (from AD-416):
1. Identify ClO2 gas treatment conditions that can inactivate human pathogens on fresh-cut leafy vegetables and cherry tomatoes without causing treatment-induced quality defects. 2. To determine a specific package design that ensures and maximizes effective gases distribution inside the package even in hard to reach areas. 3. Determine the efficacy of the packaging system in inactivating foodborne pathogens and prolonging the shelf life of lettuce, spinach and cherry tomatoes. 4. Evaluate a pilot scale treatment, using ERRC BSL-2 pilot processing facility, to demonstrate technical and economical feasibility.
3. Progress Report:
The impact of package design on antimicrobial efficacy of chlorine dioxide (ClO2) gas for fresh-cut lettuce was carried out. Commercially available bags were modified to create gas reservoirs (GR) allowing gas release from one side of the bag, from both sides, or in the center (1-GR, 2-GR, or mid-GR, respectively). ClO2 was generated in the GR gas at either 4 or 8 mg ClO2 per kg lettuce per day. Escherichia coli O157:H7-inoculated fresh-cut lettuce was packed in the bags and stored at 4 C for up to 7 d. Increasing ClO2 gas dose resulted in greater log10 CFU/g reductions of E coli O157:H7. Significantly greater (p < 0.05) log10 CFU/g reductions of E coli O157:H7 were observed in lettuce samples taken from locations adjacent to the GR. The performance of 2-GR bags indicated that the same degree of antimicrobial effect could be achieved with the lower ClO2 dose. Pilot scale ClO2 gas treatment of whole green tomatoes was conducted at the ERRC – BL-2 pilot plant facility.