Challenge Testing to Determine Growth of Listeria monocytogenes on Fresh Enoki Mushrooms at 4 °C and 10 °C Storage Temperatures
Bibliographic record
Abstract
Recent listeriosis outbreaks and recalls related to high prevalence and counts of Listeria monocytogenes in enoki mushrooms imported from South Korea and China represent a current food safety concern. Unlike domestically produced mushrooms, imported products are often packaged without free air exchange and are associated with a longer shelf life. The present study used challenge tests to investigate the potential for harvested enoki mushrooms stored under refrigeration to support the growth of L. monocytogenes, to better inform food safety regulators of the risk associated with low levels of L. monocytogenes on enoki mushrooms ready for retail. Counts of L. monocytogenes rose significantly on enoki mushroom portions from 30 to 1,000 CFU/g within 4 days at 10 °C (n = 202) and 9 days at 4 °C (n = 138). Curve fitting into the Baranyi growth model indicated a 100-fold increase in 3.7 days (10 °C) and 8.8 days (4 °C). Additional factors examined in the study included the effect of the presence of residual mushroom growth substrate and Listeria innocua as enoki background microbiota. L. innocua was associated with significantly (p < 0.001) lower maximum levels of L. monocytogenes during challenge tests at 10 °C. High prevalence of L. innocua was observed on imported enoki (15 of 18 lots) and is of concern as this species shares environmental niches with L. monocytogenes and thus a risk factor; monitoring for it should be promoted. L. monocytogenes growth on enokis was accelerated when residual enoki growth substrate was present, with a significant (p < 0.05) impact on L. monocytogenes levels by Day 2 at 10 °C and Day 3 at 4 °C, which prompts consideration for removing substrate before packaging. Finally, small-scale sampling suggests a lack of consistency in baseline contamination of L. monocytogenes among individual packages of the same lot, of interest with regards to sampling approaches for imported enoki mushrooms prior to retail.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".