Holding Fresh-Cut Produce under Refrigeration May Not Prevent Pathogen Growth: Implications for Time-Temperature Control to Reduce Risk

The U.S. Food and Drug Administration Food Code suggests that holding fresh-cut produce at < 5°C will limit growth of pathogenic microorganisms. Here, we determined whether cucumber, onion, pepper, mango, and tomato supported growth of Listeria monocytogenes (LM), Shiga toxin-producing Escherichia coli (STEC), and Salmonella enterica (SALM) at 5, 10, and 22°C. Produce was surface-pasteurized, diced, inoculated with single-pathogen cocktails, and incubated. Survivors were then enumerated with change in population (Δ-log CFU per gram) determined over time. Mango did not support pathogen growth at 5 or 10°C, but SALM and STEC exhibited significant (P < 0.05) growth on mango at 22°C (2.85 and 1.41 Δ-log CFU/g, respectively). At 5°C, significant (P < 0.05) growth was seen on cucumber inoculated with SALM and LM; onion and pepper inoculated with LM; and tomato inoculated with STEC. At 10°C, fresh-cut cucumber, onion, and pepper supported significant (P < 0.05) increases in SALM, STEC, and LM, along with SALM on tomato; Δ-log ranged from 3.37 (onion, LM) to 5.40 CFU/g (pepper, SALM). Growth of pathogens was not significantly different (P < 0.05) at 10 and 22°C for SALM or STEC inoculated onto onion, pepper, cucumber, or tomato. Results suggest that holding fresh-cut produce at or near refrigeration temperatures (5 or 10°C) may not control risk of pathogen growth.