Purpose: This study aimed to investigate the survival of Salmonella enterica (SE), Listeria monocytogenes (LM), and O157:H7 and non-O157 Shiga toxin-producing Escherichia coli (STEC) on 10 types of fresh-cut produce often available in food pantries.
Methods: Fresh-cut produce items: apple, cantaloupe, carrot, cucumber, celery, onion, pepper, radish, strawberry, and tomato, were gleaned or purchased from local retailers. For each produce/pathogen trial, seven 25-g aliquots of produce were inoculated with a single-pathogen cocktail of SE (5 strains), LM (5 strains), or O157 and non-O157 STEC (11 strains) (0.025 ml inoculum) to 3-log CFU pathogen/g. Samples were stored at 10°C for up to 5 days with periodic sampling and spread-plating on appropriate agar for pathogens or native flora. Triplicate trials were conducted for each pathogen/produce combination. Log surviving cells (CFU/g) was plotted versus incubation time.
Results: There were five survival patterns: 1) Cantaloupe, celery, cucumber: no change in pathogen, native microflora increased 2 to 3 log CFU/g; 2) Carrot, pepper, radish: decrease in pathogen by 1 log CFU/g; native microflora increased by 1 to 2 log CFU/g; 3) Tomato: decrease in pathogen survival; native microflora increased by 1-log CFU/g; 4) Apple, strawberry: no change in viability of SE or STEC; no survival of LM; 5) Onions: decrease of 1-log CFU/g for pathogens, decrease in native flora counts. Levels of native microflora varied from 3 to 7 log CFU/g at time 0.
Significance: Fresh-cut produce items did not support or enhance the growth of pathogens. These results are counter to research which has shown the rapid growth of pathogens on produce items such as cantaloupe, and suggest that native microflora may play an important role in the safety of fresh produce.