Purpose: The effectiveness of sanitation methods and microbial prevalence on apples were evaluated to assess potential risks.
Methods: Listeria spp. samples were collected from cold storage rooms and outdoor areas; a comparison of sanitation practices was performed. Samples were analyzed and compared using several methods for generic Listeria, and in some cases, Listeria monocytogenes. For examination during storage, apples with and without direct surface water contact were harvested, held under refrigerated atmosphere (RA) storage (n=200) or controlled atmosphere (CA) storage with ozone (n=218) and without ozone (n=198) treatment and tested for total coliforms, generic E. coli, Listeria spp., Listeria monocytogenes, E. coli O157:H7, and Salmonella spp.
Results: Before cleaning, generic Listeria was detected in storage rooms. Only aggressive cleaning vastly reduced observation of Listeria spp. in all areas examined, including damaged floors and floor bumpers. Generic Listeria were observed on forklifts, cleaning equipment and outdoor traffic areas. Examination of methods showed variability among methods, however 6 of 9 areas examined (equipment, non-line equipment, line support, drain, drencher parts, and cold room floors) were confirmed positive by qPCR or IMS followed by qPCR. Apples directly contacted by surface irrigation water had a higher presence of generic E. coli (12.3%; 19/155) compared to controls (3.3%; 6/181). Presence of total coliform and generic E. coli decreased during storage; ozone treatment may have reduced microbial levels during CA storage.
Significance: Microbial contamination can enter packinghouses on fruit or through routes of contamination associated with vehicles, cleaning equipment and worker foot traffic. Emphasis on cleaning and sanitizing in production areas is necessary to prevent Listeria contamination.