Purpose: Modifications in coring tool designs were evaluated for reduced cross-contamination of iceberg lettuce heads.
Methods: The original tool had a straight bottom edge core knife attached with welding. Modifications were done to the welding, coring knife and length. Design D2L2 (Design, Length) was similar to original design but did not have a welded edge. Design D3L1 had an angled edge bottom while D1L2 had a short front straight bottom edge. The blade length of original tool and modified designs- D1L2, D2L2, D3L1 were 7.5, 10.5, 10.5 and 7.5 cm, respectively. All tools were surface contaminated with Escherichia coli K12 and then used to core 100 lettuce heads consecutively. The cored regions were scraped from all 100 heads and tested for E. coli after enrichment. All tool designs were dipped in bioluminescent Salmonella Newport contaminated- water, water with lettuce extract, and tryptic soy broth (TSB) for 2 min and imaged using EMCCD camera to observe bacterial attachment.
Results: Absence of welding from original tool design resulted in the highest reduction in E. coli transfer. Original tool and welding free D2L2 resulted in 91±9% and 44±11.9% E. coli positive lettuce heads, respectively. Elimination of the welded region resulted in a progressive decrease of E. coli on cored lettuces. Lettuces 80-100 cored with original tool and D2L2 were 86.7% and 26.7% positive for E. coli, respectively (P<0.05). Incorporation of a short front straight edge resulted in 65.6±5.6% (D1L2) of cored lettuce heads being positive for E. coli. Biophotonic imaging indicated that immersion in water containing lettuce extract and TSB caused increased attachment of Salmonella to tool surface compared to water.
Significance: Modified coring tool designs can help reduce cross-contamination of cored iceberg lettuce heads. Biophotonic imaging can be used to visualize bacteria attached on produce surfaces.