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Poster: Biology & Disease Mgmt: Postharvest Pathology & Mycotoxins


Rapid detection of preexisting internal Leuconostoc spp. spoilage populations in fresh-cut carrots during storage
K. BRITT (1), T. Suslow (1) (1) UC Davis, U.S.A.

During an extended period of abnormally short quality retention in mixed component packaged salads, due primarily to rapid decay, a root-cause investigation was undertaken. From an initial investigative assessment, this study focused on identification of the primary underlying microbiological cause and suggested the need for a rapid detection screening of raw material. Analysis of several lots of unprocessed product, approx. 6 cm abrasively peeled carrot plugs, revealed the accumulation of an aqueous slime in the shipping bag void space and around the extremely softened plug surfaces. This premature diagnostic sign of lactic acid bacteria (LAB) spoilage, specifically Leuconostoc spp., developed in cold storage (2.5°C) after two weeks. Efforts were undertaken to determine whether the Leuconostoc was internalized in raw material or primarily environmental contamination with a proliferating reservoir of LAB in the primary processing and packaging environment. Polymerase chain reaction (PCR) primers specific for the amplification of a sequenced region of the Leuconostoc 16S ribosomal RNA gene confirmed the taxonomic identity. Total initial LAB and Leuconostoc bacterial populations isolated from symptomatic carrots ranged from log?? 7.5–8.5 and log?? 3.5–4.0 CFU/g carrot tissue weight respectively, and increased log?? 2 CFU/g log?? and 3.5 CFU/g respectively in population density on asymptomatic and symptomatic raw carrot material during two week refrigerated storage.