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Published on: August 9, 2011
Contamination of Zophobas morio Larvae Rearing Substrate with Listeria monocytogenes: A Preliminary Study
Filippo Fratini1,2, Luca Ciurli1, Mario Forzan1
1Department of Veterinary Sciences, University of Pisa, Viale delle Piagge 2, 56124 Pisa, Italy.
Abstract:
The interest in edible insects is continuously increasing due to their environmental, nutritional, and productive features. The aim of this study was to evaluate the effects and survival of Listeria monocytogenes in Zophobas morio rearing, using two different bacterial loads (2 and 6 log CFU/g). We also considered the effect of washing, fasting, and cooking treatments on the larvae. During the experimental trial, no mortality was observed among the larvae. The L. monocytogenes loads decreased over time, and it was below the detection limit for crates inoculated with 2 log CFU/g, while the substrate inoculated with 6 log CFU/g reached loads of 4.26 (without larvae) and 2.83 log CFU/g (with larvae). Due to the absence of L. monocytogenes in the larvae on day seven, it was not possible to assess the fasting treatment or the washing and the cooking. However, when looking at the total microbial count, significant effects were revealed for all treatments. The unfasted larvae showed no effect of washing, while the total microbial counts decreased after washing in the fasted larvae. This proves that fasting is a good treatment in terms of hygiene assurance for the consumer.
Insights
Edible insect farming shows promise, but Listeria monocytogenes survival in Zophobas morio larvae requires careful management. Fasting larvae significantly improved hygiene by reducing total microbial counts before processing.
Area of Science:
- Food Science
- Microbiology
- Entomology
Background:
- Edible insects are gaining traction for their sustainability and nutritional value.
- Ensuring the microbiological safety of edible insects is crucial for consumer confidence.
- Zophobas morio larvae are a potential source of protein, necessitating safety assessments.
Purpose of the Study:
- To investigate the survival and behavior of Listeria monocytogenes in Zophobas morio larvae.
- To evaluate the efficacy of washing, fasting, and cooking treatments on reducing bacterial loads.
- To assess the impact of different initial bacterial concentrations on larval contamination.
Main Methods:
- Zophobas morio larvae were reared and inoculated with Listeria monocytogenes at two concentrations (2 and 6 log CFU/g).
- Larvae underwent treatments including washing, fasting, and cooking.
- Listeria monocytogenes loads and total microbial counts were monitored over time.
Main Results:
- Listeria monocytogenes loads decreased over the experimental period, falling below detection limits at lower inoculums.
- Higher initial bacterial loads resulted in detectable L. monocytogenes in the substrate, but significantly reduced in the presence of larvae.
- While L. monocytogenes survival was limited, fasting significantly reduced total microbial counts, enhancing hygiene.
- Washing was effective on fasted larvae, but not on unfasted larvae, highlighting the importance of pre-treatment.
Conclusions:
- Fasting is an effective pre-treatment for Zophobas morio larvae to improve hygiene and reduce microbial load.
- Further research is needed to optimize processing methods for edible insect safety.
- Edible insect production requires stringent safety protocols to mitigate microbial risks.
