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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. |
