Food spoilage characteristics of Chryseobacterium species

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Date
2006-05
Authors
Mielmann, Annchen
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Publisher
University of the Free State
Abstract
English: 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 “putrid” and “smelly feet”. 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.
Afrikaans: Die genus Chryseobacterium se voedselbederf potensiaal is die vermoë van ´n rein kultuur (van hierdie genus) om die metaboliete te produseer wat geassosieer is met die bederf van ‘n spesifieke voedselproduk. ‘n Sorgvuldige kombinasie van mikrobiese, sensoriese en chemiese analises word vereis om die voedselbederf potensiaal van die genus Chryseobacterium te bepaal. Die rol en betekenis van die genus Chryseobacterium, asook hul bewese en potensiële betekenis as voedselbederf bakterieë, is nie so breedvoerig bestudeer soos die taksonomie en nomenklatuur van hierdie genus nie. Die hoofdoel van hierdie studie was dus om die potensiële voedselbederf eienskappe van die genus Chryseobacterium te bepaal. Dit was as nodig beskou om ‘n beter begrip van hulle eienskappe en voedselbederf potensiaal te verkry, asook om die voedselwetenskaplike oor die praktiese implikasies van voedsel kontaminasie deur hierdie groep organismes in te lig en om die kennis op hierdie aspekte van lede van die Chryseobacterium genus te verbreed. Die vermoë van Chryseobacterium spesies om koolstofbronne te gebruik, soos getoets in hierdie studie, weergee nie direk die waarskynlikheid van voedselbederf defekte nie, maar die BIOLOG sisteem kan as ‘n effektiewe siftingsmetode gebruik word om die koolstofbronne te identifiseer wat verder bestudeer kan word vir hulle pote nsiaal om voedselbederf defekte te produseer. Fenotipiese toetse op Chryseobacterium spesies kan as ‘n alternatiewe metode gebruik word om die hidrolise van voedselkomponente en die produksie van metaboliete te ondersoek wat potensiële voedselbederf gebreke soos verroting en alkalinisasie tot gevolg kan hê. Hierdie gebreke word gewoonlik met onaangename reuke geassosieer. Sommige Chryseobacterium spesies het die vermoë om sommige van die voorlopers van biogeniese amines te dekarboksileer by verskillende temperature en in die teenwoordigheid van verskillende natrium chloried konsentrasies. Dit het die vorming van biogeniese amiene, wat amien vergiftiging kan veroorsaak, tot gevolg. Hierdie organismes moet gevolglik as betekenisvolle bederf organismes in voedselprodukte beskou word. Chryseobacterium spesies was in staat om by 4°C, by ‘n pH van 5 tot 10 en by ‘n natrium chloried konsentrasie van 1 to 3% te groei. Dit is bekend dat Chryseobacterium spesies die potensiaal het om melk te kan bederf. Daarom sal ‘n afname in temperatuur (onder 4°C), in pH (onder 5) en ‘n toename in natrium chloried konsentrasie (bo 4%) die groei van hierdie genus inhibeer en het ‘n preserverende werking in produkte met hierdie eienskappe. Optimum groei het by 25°C plaasgevind en dit kan verwag word dat bederf defekte vinnig sal ontwikkel in voedselprodukte wat by hierdie temperatuur gehou word. Die genus Chryseobacterium het die potensiaal om bederf defekte te veroorsaak as gevolg van proteolitiese en lipolitiese aktiwiteit. Sulke aktiwiteite kan afgeure en –reuke tot gevolg hê, terwyl die produksie van fosfolipase C lipolise en galsterigheid kan veroorsaak. Chryseobacterium spesies was in staat om vlugtige komponente in melk te produseer. Die geproduseerde primêre alkohole het waarskynlik nie bygedra tot geure nie, terwyl die karboksielsure verantwoordelik kan wees vir die produksie van verskillende geure (bv. vrugtig). Sensoriese evaluering op geïnokuleerde melkmonsters het die identifikasie van reukbeskrywers soos “vrot” en “stink voete” tot gevolg gehad. Dit is dus voordelig om ‘n tegniek soos gas chromatografie te gebruik om vlugtige komponente te identifiseer wat deur die genus Chryseobacterium geproduseer word en om die bederf potensiaal van hierdie genus in ‘n produk soos melk meer akkuraat te evalueer. Die rol en betekenis asook die potensiële voedselbederf defekte van Chryseobacterium spesies moet in meer besonderheid in meer praktiese scenarios bestudeer word.
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Keywords
Food spoilage, Food -- Microbiology, Food contamination, Spoilage, Potential, Defects, Off-flavours, Off-odours, Chryseobacterium, Dissertation (M.Sc. (Microbial, Biochemical and Food Biotechnology))--University of the Free State, 2006
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