1a. Objectives (from AD-416):
To develop techniques to improve food safety and quality of fresh and fresh-cut produce using ultra-sound and other emerging technologies; to investigate the effect of various new sanitizers on pathogen reduction and shelf-life extension of fresh-cut fruits and vegetables; and to gain a greater understanding of how fresh-cut processing conditions affect plant metabolism, microbial growth, and their interactions.
1b. Approach (from AD-416):
ARS will acquire the basic knowledge of the factors influencing pathogen transference during lettuce harvesting. The Cooperator will provide the expertise in equipment design and disinfection. Advanced molecular and microbiological techniques will be applied to quantify pathogen concentrations spanning a range of realistic contaminant loads and field conditions; creative engineering approaches will be utilized to optimize coring knife design and develop enhanced sanitation practices.
3. Progress Report:
The rough welding joints on currently used in-field lettuce coring knives provide sites conducive to bacterial attachment and resistant to cell removal during sanitation treatments. Two new coring devices designed to mitigate pathogen attachment were fabricated and evaluated. The coring rings of the knives were dip inoculated with soil slurry containing 106 E. coli cells and treated with chlorinated water with and without ultrasonication for 30, 60, and 120 s. The two modified coring knives harbored significantly fewer E. coli cells and allowed for more effective sanitizer treatment than did the currently used commercial model. Ultrasound treatment reduced the E. coli O157:H7 counts on the prototype coring knives to below the detection limit of 1.10 log per cm² at both the coring ring blade and welding joint within 30 s in 1 ppm of chlorinated water. The redesigned coring knives and a combined ultrasound plus chlorine sanitation treatment may provide practical options for minimizing the microbial safety hazards of lettuce processed by core-in-field operations.