Open Access Repository

Kinetic and physiological responses of Listeria monocytogenes to novel non-thermal inactivation treatments and their application to minimally processed seafood


Downloads per month over past year

Bittencourt, Claudio da Rocha (2009) Kinetic and physiological responses of Listeria monocytogenes to novel non-thermal inactivation treatments and their application to minimally processed seafood. PhD thesis, University of Tasmania.

[img] PDF (Whole thesis)
whole_Bittencou...pdf | Request a copy
Full text restricted
Available under University of Tasmania Standard License.


Listeria monocyto genes is a facultative anaerobic pathogen found in soil and water,
on vegetation, food contact surfaces and in raw food materials including seafood. It
grows at refrigeration temperatures and up to 14% sodium chloride making it almost
impossible to control in fresh or minimally-processed seafood under aerobic or
anaerobic storage conditions.
This thesis considers strategies to control growth of this bacterium on seafood using
both established and novel non-thermal technologies and seeks to elucidate
physiological mechanisms underlying one of the approaches, namely high pressure
Chapter 1 reviews the microbiology of seafood including normal microbiota, spoilage
processes, pathogen ecology and occurrence and non-thermal processes that are
currently used or have the potential to be utilized by the seafood industry. It serves as
reference material for the following chapters. Chapter 2 describes an empirical assessment of several preservatives proposed as antilisterial
agents. In collaboration with a local Atlantic salmon smokehouse, three
commercially available antimicrobial preparations were applied directly to salmon
fillets prior to smoking with the intent to stop Listeria monocyto genes growth on
vacuum packed cold smoked salmon (CSS). The challenge trial extended over 40
days at 4°C and 10°C. Microbial and sensorial analyses were conducted in parallel.
Results showed that two of the three treatments evaluated presented listeriostactic
activity. The remaining compound appeared not to penetrate in the salmon flesh and
challenge the Listeria monocyto genes introduced to the inner flesh after slicing. From
the sensorial point of view one of the successful Listeria monocyto genes growth
inhibitors performed slightly better than the other but significantly better than the untreated CSS, making it a good candidate to control the growth of this pathogen in
this commodity.
A search for novel, cold-active, anti-listerial bacteriocins is the focus of Chapter 3.
Specifically, 1600 Actinobacterial isolates from Antarctic or Sub-Antartcic regions
were screened against five different Listeria monocyto genes strains for their capacity
to produce cold active antimicrobials. Several promising isolates were identified and
their active products partially characterized. The investigation demonstrated that
Antarctic or Sub-Antarctic soils harbour potentially valuable antimicrobial producers
with specific capacity to target single pathogen species and their potential to food
safety and industry. Future bio-prospecting research for antimicrobials against
pathogens of human concern should include species from other extreme environments
as well.
Chapter 4 and 5 describe studies concerning physiological responses of Listeria
monocyto genes to high pressure processing (HPP). Chapter 4 explores whether the
cell membrane is an important mediator of the effects of HPP and reports studies of
changes in the fatty acid composition of the membrane in response to HPP. The
results suggested that under pressure, irrespective of the growth phase, Listeria
monocyto genes tries to adapt by changing the abundance of iso branched-chain fatty
acid of its cell membrane. This fatty acid adaptive response is different from that
caused by cold, pH and heat stresses. In Chapter 5 microarray technology is used to
assess changes in gene expression under the same experimental conditions showing
that HPP seems to invoke a cell maintenance state but strongly suppresses genes
associated with catabolism and virulence.
Chapter 6 synthesises the results of the work undertaken, attempts to determine the
applicability of the novel non-thermal technologies (applied alone or as part of a multi hurdle approach) to increase the safety of minimally processed seafood products
against listeriosis and identifies future research needs.

Item Type: Thesis (PhD)
Copyright Holders: The Author
Copyright Information:

Copyright 2009 the Author – The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

No access or viewing until July 2011. Available for use in the Library and copying in accordance with the Copyright Act 1968, as amended. Thesis (PhD)--University of Tasmania, 2009. Includes bibliographical references

Date Deposited: 25 Nov 2014 00:57
Last Modified: 11 Mar 2016 05:53
Item Statistics: View statistics for this item

Actions (login required)

Item Control Page Item Control Page