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Thesis: Equipment hygiene and risk assessment measures as tools in the prevention of Listeria monocytogenes contamination in food processes
18.01.2008
Kaarina Aarnisalo, Research Scientist from VTT presents her doctoral thesis “Equipment hygiene and risk assessment measures as tools in the prevention of Listeria monocytogenes contamination in food processes” on 25 January 2008 at the Helsinki University of Technology.
A problematic pathogen occurring in food processing is Listeria
monocytogenes. Its efficient control at the processing plant level
requires good equipment hygiene, including functioning good manufacturing and
hygiene practices used by all employees, effective means of decontamination
and rapid detection of contamination sources, as well as hazard analysis
systems supported by risk assessment procedures.
The thesis
of Kaarina Aarnisalo focuses on deficiencies and improvements in these
equipment hygiene and risk assessment practices with the aim of elucidating
and developing the most efficient practices against L. monocytogenes.
The
hygienically most problematic types of equipment in the Finnish food industry
were identified as the packaging machines, conveyers, dispensers, slicing
machines and cooling machines. The main reason for the equipment being
considered as problematic was poor hygienic design. Equipment designers must
focus their performance on more suitable equipment design. Clear deficiencies
were also found in hygiene performance of the maintenance personnel in food
processing plants. The results of these studies also indicate that L.
monocytogenes may be transferred through maintenance work. Training of
maintenance personnel with reference to hygienic practices must be increased.
The results of the thesis showed that lubricants used in food processing
equipment may act as contamination vehicles of L. monocytogenes.
An
investigation of the efficiency of eight commonly used commercial
disinfectants against L. monocytogenes strains at +5°C was performed.
The tested agents were generally efficient at the recommended concentrations
and effect times, with only a few exceptions.
Risk assessment
practices were developed by investigating and modelling recontamination of a
product and by a plant-level quantitative risk assessment. Recontamination was
modelled by investigating transfer of L. monocytogenes from slicing
blade to slices of cold-salted salmon. As a concluding example, a practical
approach to quantitative risk assessment at the plant level of L.
monocytogenes in heated marinated broiler legs is presented. This approach
helps food processors in illustrating the risks caused by the products for
consumers.
PHOTO:
Sampling from a slicing machine.
Further information:
VTT, Kaarina Aarnisalo, Research Scientist, tel. +358 20 722 7126