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The effect of refrigeration on growth of pathogens as a preventive measure within the HACCP system during processing of finfish

By  Hákon Jóhannesson

A thesis submitted in partial fulfillment of the requirements of the degree B.S. Honours in the Department of Food Science, University of Iceland

Supervisors: Dr. Róbert Hlöđversson and Dr. Kristberg Kristbergsson

Kópavogur, June 1999

The following  is the abstract drawn out of the thesis:



Raw fish is considered an excellent substrate for supporting growth of many bacterial pathogens known to cause food poisoning in man. There are many necessary processing steps that follow after the catch of the fish to make it suitable for the consumer. If pathogens are able to reach the flesh of the fish during processing they can grow there if they are left uncontrolled. Refrigeration of the fish in the fishing vessel and during storage at the processor is a normal procedure to preserve the freshness of the catch. The catch is usually surrounded by ice and stored at refrigeration temperatures until processing.

The aim of this study was to determine the effect of refrigeration during storage and processing as a preventive measure on growth of pathogens. The main parts were measuring the time-temperature profile of finfish as it went through two fish processors of different sizes in Iceland by following its course through the main processing steps. Also to gather information on potential pathogens by reviewing the literature and research data. By using these findings it was possible to perform a Hazard Analysis of the process. A hazard analysis has to be performed when a processor develops a food safety system called Hazard Analysis Critical Control Point system (HACCP system). The aim of this was threefold. First to draw a clear flow chart with time-temperature values. Secondly to suggest potential bacterial hazards, from the review, that may be introduced or increased at each step. Finally to conclude, based on findings of the study, whether these potential hazards are reasonably likely to occur. In order to get a different perspective an alternative evaluation was done by comparing the observed process temperature to the minimum growth temperature of the potential pathogens.

The main findings from this study were fourfold: Potential seafood related pathogens originate from two main sources from where they gain access to the fish; the ones indigenous to the ocean itself, the natural environment of the fish. Bacterial pathogens that harbour and originate in humans, animals and the soil can also find access to the fish during storage and processing. From the review these added up to twelve bacterial pathogens. These pathogens are virulent to humans, causing foodborne disease after ingestion if consumed in foods in which the organism has reached unsafe levels, sometimes resulting in toxin production. Secondly it was found when measuring temperature from the first processing step to the last one that it rose significantly in all cases. Thirdly, based on the hazard analysis it was concluded that under the given average conditions observed at the bigger processor, there was not a reason to conclude that the potential pathogens would grow there to such a number to cause food safety problems during processing. The fish is normally heated thoroughly during food preparation and almost all of the pathogens or their toxins are heat sensitive. It was finally concluded that most of the pathogens observed can grow over the temperature range that was measured during processing.

These results should be a concern for the industry. This is especially true if pathogens are present in the raw material and conditions are not good enough. This may happen during storage or handling if cross-contamiation occurs or hygiene is not good enough combined with time-temperature abuse. This will allow more time for pathogens to grow at higher temperature and also the possibility of certain strains from two of these bacterial pathogens to produce heat tolerant toxins which will not be inactivated during normal food preparation.

© 1999 Hákon Jóhannesson.