Location: Microbial and Chemical Food Safety
Project Number: 8072-41420-026-004-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Jan 1, 2024
End Date: Dec 31, 2025
Objective:
“Work-in-progress” ingredients (WIPI) such as shredded carrots and cabbages often as components of final retail products (salads) are stored in large plastic bins for a short time before mixed with other ingredient such as lettuce to form the final consumer products. The objective of the proposed study is to evaluate the survival of Listeria monocytogenes and Salmonella spp. on selected “work-in-progress” ingredients (WIPI) during holding time, and pathogen transference potential onto containers. Specific objectives are to:
1. Evaluate the survival of Salmonella and Listeria on the surface of WIPI during holding time as affected by time, temperature, pre-and post-sanitization, pathogen populations, microbiota and natural antimicrobials.
2. Study the transfer of pathogens from WIPI to holding containers (bins) and reusability of holding containers.
3. Model factors contributing the survival and growth of Salmonella and Listeria on WIPI and transference between pathogens and holding containers.
Approach:
“Work-in-progress” ingredients (WIPI) (carrots, green cabbage, red cabbages, kale, Brussel sprouts, chicory, peas, Romaine lettuce, and baby spinach) inoculated with 2 levels (2 and 6 log CFU/g) of 4-strain cocktails of cold-adapted Listeria monocytogenes and Salmonella spp. will be stored 4, 8 and 12°C for up to 6 days. The WIPI will be washed with 20 ppm chlorine (pH 6.5) and 80 ppm peracetic acid before and after the holding period to study the effects of sanitization. Populations of both non-inured and injured pathogens will be determined every 2 days. Based on earlier studies, it is predicted that pathogen (especially Listeria) populations will decline on shredded carrots and cabbages during holding time, presumably due to the presence of natural antimicrobials and/or competitive microbiota. Therefore, total mesophilic aerobic bacteria, Enterobacteriaceae, lactic acid bacteria, aerobic psychrotrophs, and yeast and mold count will be monitored on the WIPI using appropriate media along with natural antimicrobials on the surface of (and inside) WIPI using liquid chromatographic and spectrophotometric methods. The profile and populations of microbiota and native antimicrobials may be used to predict the survival of pathogens. The potential transfers of pathogens onto holding containers will be determined by placing WIPI with various inoculation levels into WIPI containers followed by tracking pathogens populations on the container surfaces. The contaminated WIPI containers will be re-used to hold WIPI to study the transfer of pathogens from the containers to WIPI. Mathematic models will be performed to predict the growth/survival of pathogens as factors of holding temperature, holding time, level of contamination, sanitization wash, and type of WIPI, as well as relationships among pathogen growth, antimicrobials, and native microbiota. Risk analysis will be performed to estimate the probability of cross-contamination between WIPI and containers. The study will help industry to establish a standardized risk approach for managing WIPI produce components.
