The food spoilage potential of the genus Chryseobacterium is the ability of a
pure culture of this genus to produce the metabolites that are associated with
the spoilage of a particular food product. A careful combination of microbial,
sensory and chemical analyses are required to determine the food spoilage
potential of the genus Chryseobacterium. The role and significance of the
genus Chryseobacterium in food and their proven and potential significance
as food spoilage bacteria have not been studied in equal detail as the
taxonomy and nomenclature of this genus and this has been the main reason
for the present research project. It was regarded as necessary to obtain a
better understanding of the characteristics of these organisms pertaining to
their food spoilage potential. The purpose of this work would be to add to the
knowledge on this genus and in the process inform the food scientist of the
practical implications of food contamination by this group of microorganisms.
The ability to utilise carbon sources by Chryseobacterium species tested in this study does not directly reflect the probability of food spoilage defects, but
the BIOLOG system can be used as an effective screening method for
identifying the carbon sources that could be investigated further for their
potential to produce food spoilage defects. Phenotypic tests on
Chryseobacterium species can be used as an alternative method to
investigate the hydrolysis of food components and the production of
metabolites, which could result in potential food spoilage defects such as
putrefaction and alkalinisation, which are usually associated with disagreeable
odours. Some Chryseobacterium species had the ability to decarboxylate
some of the precursors of biogenic amines at different temperatures and in
the presence of different sodium chloride concentrations. This results in the
formation of biogenic amines which could cause amine poisoning and these
organisms should consequently be regarded as significant spoilage
organisms in food products. In this study it was observed that Chryseobacterium species were able to
grow at 4°C, at a pH of 5 to 10 and at sodium chloride concentrations of 1 to
3%. It is known that Chryseobacterium species have the potential to spoil
milk. For these reasons a decrease in temperature (below 4°C ), in pH (below
5) and an increase in sodium chloride concentration (above 4%) will inhibit the
growth of this genus and have a preservative effect in products with these
characteristics. Optimum growth was observed at 25°C, and it could be
expected that spoilage defects in food products, kept at this temperature
would develop most rapidly. The genus Chryseobacterium has the potential
ability to produce spoilage defects due to proteolytic and lipolytic activity.
Such activity could result in off-flavours and off-odours. Similarly the
production of phospholipase C could enhance lipolysis and rancidity defects.
Chryseobacterium species were able to produce volatile compounds in milk.
The primary alcohols produced were not likely to contribute to flavour, while
the carboxylic acids can be responsible for the production of a variety of
flavours (e.g. fruity). Sensory evaluation on inoculated milk samples resulted
in the identification of odour descriptors, such as âputridâ and âsmelly feetâ.
It is therefore advantageous to use a technique such as gas chromatography
to identify volatile compounds produced by the genus Chryseobacterium.
This will help in evaluating the spoilage potential of this genus in a product
such as milk more accurately. The role and significance as well as the
potential food spoilage defects of Chryseobacterium species should be
investigated in more detail in more practical scenarios.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-01262007-135247 |
| Date | 26 January 2007 |
| Creators | Mielmann, Annchen |
| Contributors | Prof PJ Jooste, Dr CJ Hugo |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-01262007-135247/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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