Listeria monocytogenes in fish farming and processing: Academic dissertation

Hanna Miettinen

Research output: ThesisDissertation

38 Citations (Scopus)

Abstract

Contamination of fish products with Listeria monocytogenes, a bacterium causing listeriosis, presents a risk to consumer health. To better control this, the present study investigated the prevalence and sources of L. monocytogenes in different stages of fish production chain as well as the effects of a pasteurisation method on rainbow trout roe products. Farmed rainbow trout from different fish farms were found to contain L. monocytogenes at an average rate of 9%. L. monocytogenes prevalence varied greatly among fish farms from 0 to 75%. The bacterium occurred almost exclusively in the gills (96%) and only sporadically in the skin and viscera. Special effort should be focused on the isolation and removal of rainbow trout gills before L. monocytogenes contamination spreads further. The main L. monocytogenes contamination sources in the studied fish farm were the brook and river waters, as well as other runoff waters from environment. Rainy weather conditions were found to increase the probability of finding L. monocytogenes in the fish farm environment. The fish farm did not spread L. monocytogenes contamination, but suffered contamination from environmental sources. L. monocytogenes appeared on cleaned surfaces of one-third of the 23 studied fish processing factories, at least sporadically. The presence of Listeria spp. on the factory surfaces was indicative of increased possibility of occurrence in the fish products. Contamination of different ready-to-eat fish products with L. monocytogenes varied from 0 to 20%. The pulsed-field gel electrophoresis typing of L. monocytogenes isolates, from 15 fish factories, showed that the same pulsotypes of L. monocytogenes, isolated form fish products, occurred also in raw fish and fish production environments. Thus, raw fish materials and production environment are sources of L. monocytogenes contamination that both need to be properly controlled. Presence of L. monocytogenes in different Finnish fish species roe products in retail markets varied between 2 to 8%. Recovery of L. monocytogenes was significantly higher in fresh-bought roe products (18%) than in frozen or frozen-thawed (1%) roe products. Pasteurisation of rainbow trout roe, at 62 °C or at 65 °C for 10 minutes, eliminated inoculated 8 log units of L. monocytogenes. The quality of pasteurised vacuum packaged rainbow trout roe was found to be consistently good, in terms of microbial as well as sensory quality, for up to six months stored at 3 °C.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • University of Helsinki
Supervisors/Advisors
  • Korkeala, Hannu, Supervisor, External person
  • Wirtanen, Gun, Supervisor, External person
  • Raaska, Laura, Supervisor, External person
Thesis sponsors
Award date11 Nov 2006
Place of PublicationHelsinki
Publisher
Print ISBNs952-92-1078-7
Electronic ISBNs952-10-3440-8
Publication statusPublished - 2006
MoE publication typeG5 Doctoral dissertation (article)

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fish processing
fish culture
Listeria monocytogenes
fish farms
fish products
Oncorhynchus mykiss
factories
raw fish
fish production
pasteurization
gills
retail marketing
listeriosis
bacteria
animal organs
Listeria

Cite this

Miettinen, H. (2006). Listeria monocytogenes in fish farming and processing: Academic dissertation. Helsinki: University of Helsinki.
Miettinen, Hanna. / Listeria monocytogenes in fish farming and processing : Academic dissertation. Helsinki : University of Helsinki, 2006. 77 p.
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title = "Listeria monocytogenes in fish farming and processing: Academic dissertation",
abstract = "Contamination of fish products with Listeria monocytogenes, a bacterium causing listeriosis, presents a risk to consumer health. To better control this, the present study investigated the prevalence and sources of L. monocytogenes in different stages of fish production chain as well as the effects of a pasteurisation method on rainbow trout roe products. Farmed rainbow trout from different fish farms were found to contain L. monocytogenes at an average rate of 9{\%}. L. monocytogenes prevalence varied greatly among fish farms from 0 to 75{\%}. The bacterium occurred almost exclusively in the gills (96{\%}) and only sporadically in the skin and viscera. Special effort should be focused on the isolation and removal of rainbow trout gills before L. monocytogenes contamination spreads further. The main L. monocytogenes contamination sources in the studied fish farm were the brook and river waters, as well as other runoff waters from environment. Rainy weather conditions were found to increase the probability of finding L. monocytogenes in the fish farm environment. The fish farm did not spread L. monocytogenes contamination, but suffered contamination from environmental sources. L. monocytogenes appeared on cleaned surfaces of one-third of the 23 studied fish processing factories, at least sporadically. The presence of Listeria spp. on the factory surfaces was indicative of increased possibility of occurrence in the fish products. Contamination of different ready-to-eat fish products with L. monocytogenes varied from 0 to 20{\%}. The pulsed-field gel electrophoresis typing of L. monocytogenes isolates, from 15 fish factories, showed that the same pulsotypes of L. monocytogenes, isolated form fish products, occurred also in raw fish and fish production environments. Thus, raw fish materials and production environment are sources of L. monocytogenes contamination that both need to be properly controlled. Presence of L. monocytogenes in different Finnish fish species roe products in retail markets varied between 2 to 8{\%}. Recovery of L. monocytogenes was significantly higher in fresh-bought roe products (18{\%}) than in frozen or frozen-thawed (1{\%}) roe products. Pasteurisation of rainbow trout roe, at 62 °C or at 65 °C for 10 minutes, eliminated inoculated 8 log units of L. monocytogenes. The quality of pasteurised vacuum packaged rainbow trout roe was found to be consistently good, in terms of microbial as well as sensory quality, for up to six months stored at 3 °C.",
author = "Hanna Miettinen",
note = "NT Food solutions",
year = "2006",
language = "English",
isbn = "952-92-1078-7",
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Miettinen, H 2006, 'Listeria monocytogenes in fish farming and processing: Academic dissertation', Doctor Degree, University of Helsinki, Helsinki.

Listeria monocytogenes in fish farming and processing : Academic dissertation. / Miettinen, Hanna.

Helsinki : University of Helsinki, 2006. 77 p.

Research output: ThesisDissertation

TY - THES

T1 - Listeria monocytogenes in fish farming and processing

T2 - Academic dissertation

AU - Miettinen, Hanna

N1 - NT Food solutions

PY - 2006

Y1 - 2006

N2 - Contamination of fish products with Listeria monocytogenes, a bacterium causing listeriosis, presents a risk to consumer health. To better control this, the present study investigated the prevalence and sources of L. monocytogenes in different stages of fish production chain as well as the effects of a pasteurisation method on rainbow trout roe products. Farmed rainbow trout from different fish farms were found to contain L. monocytogenes at an average rate of 9%. L. monocytogenes prevalence varied greatly among fish farms from 0 to 75%. The bacterium occurred almost exclusively in the gills (96%) and only sporadically in the skin and viscera. Special effort should be focused on the isolation and removal of rainbow trout gills before L. monocytogenes contamination spreads further. The main L. monocytogenes contamination sources in the studied fish farm were the brook and river waters, as well as other runoff waters from environment. Rainy weather conditions were found to increase the probability of finding L. monocytogenes in the fish farm environment. The fish farm did not spread L. monocytogenes contamination, but suffered contamination from environmental sources. L. monocytogenes appeared on cleaned surfaces of one-third of the 23 studied fish processing factories, at least sporadically. The presence of Listeria spp. on the factory surfaces was indicative of increased possibility of occurrence in the fish products. Contamination of different ready-to-eat fish products with L. monocytogenes varied from 0 to 20%. The pulsed-field gel electrophoresis typing of L. monocytogenes isolates, from 15 fish factories, showed that the same pulsotypes of L. monocytogenes, isolated form fish products, occurred also in raw fish and fish production environments. Thus, raw fish materials and production environment are sources of L. monocytogenes contamination that both need to be properly controlled. Presence of L. monocytogenes in different Finnish fish species roe products in retail markets varied between 2 to 8%. Recovery of L. monocytogenes was significantly higher in fresh-bought roe products (18%) than in frozen or frozen-thawed (1%) roe products. Pasteurisation of rainbow trout roe, at 62 °C or at 65 °C for 10 minutes, eliminated inoculated 8 log units of L. monocytogenes. The quality of pasteurised vacuum packaged rainbow trout roe was found to be consistently good, in terms of microbial as well as sensory quality, for up to six months stored at 3 °C.

AB - Contamination of fish products with Listeria monocytogenes, a bacterium causing listeriosis, presents a risk to consumer health. To better control this, the present study investigated the prevalence and sources of L. monocytogenes in different stages of fish production chain as well as the effects of a pasteurisation method on rainbow trout roe products. Farmed rainbow trout from different fish farms were found to contain L. monocytogenes at an average rate of 9%. L. monocytogenes prevalence varied greatly among fish farms from 0 to 75%. The bacterium occurred almost exclusively in the gills (96%) and only sporadically in the skin and viscera. Special effort should be focused on the isolation and removal of rainbow trout gills before L. monocytogenes contamination spreads further. The main L. monocytogenes contamination sources in the studied fish farm were the brook and river waters, as well as other runoff waters from environment. Rainy weather conditions were found to increase the probability of finding L. monocytogenes in the fish farm environment. The fish farm did not spread L. monocytogenes contamination, but suffered contamination from environmental sources. L. monocytogenes appeared on cleaned surfaces of one-third of the 23 studied fish processing factories, at least sporadically. The presence of Listeria spp. on the factory surfaces was indicative of increased possibility of occurrence in the fish products. Contamination of different ready-to-eat fish products with L. monocytogenes varied from 0 to 20%. The pulsed-field gel electrophoresis typing of L. monocytogenes isolates, from 15 fish factories, showed that the same pulsotypes of L. monocytogenes, isolated form fish products, occurred also in raw fish and fish production environments. Thus, raw fish materials and production environment are sources of L. monocytogenes contamination that both need to be properly controlled. Presence of L. monocytogenes in different Finnish fish species roe products in retail markets varied between 2 to 8%. Recovery of L. monocytogenes was significantly higher in fresh-bought roe products (18%) than in frozen or frozen-thawed (1%) roe products. Pasteurisation of rainbow trout roe, at 62 °C or at 65 °C for 10 minutes, eliminated inoculated 8 log units of L. monocytogenes. The quality of pasteurised vacuum packaged rainbow trout roe was found to be consistently good, in terms of microbial as well as sensory quality, for up to six months stored at 3 °C.

M3 - Dissertation

SN - 952-92-1078-7

PB - University of Helsinki

CY - Helsinki

ER -

Miettinen H. Listeria monocytogenes in fish farming and processing: Academic dissertation. Helsinki: University of Helsinki, 2006. 77 p.