Bdellovibrionaceae (BD) are unique, predatory, endoparasitic, Gram-negative bacteria. As the world's smallest living hunter they prey on other Gram-negative bacteria giving them potential as biological control agents. Prior to this study, however, there were no reports of BD in New Zealand. The overall aim of this research was to isolate BD from New Zealand sources, characterise them and investigate their potential role as a biological control agent. The history, characteristics, life cycle and mechanism of predation of this organism are reviewed and the possibility of the industrial applications of BD, are discussed. In this study, a halophilic species of BD was isolated from fourteen coastal sea water sites around New Zealand. Thirteen isolates were characterised using proven characterisation techniques including general, microscopic and molecular techniques. It was found that the isolates were taxonomically identical or very closely related to each other and belong to the genus Bacteriovorax. The predation pattern of BD isolates was examined against a group of Gram negative bacteria in solid and liquid media. The predation patterns and efficiencies of the different BD isolates were similar, which confirms that the BD isolates are closely related, are selective in their predation, and prey on some Gram-negative bacteria but not all. The rapid loss of culture viability of BD is well known, but no studies have been reported to date on the survival of pure cultures of BD at different temperatures. The survival rate of BD in dense suspensions at different temperatures without host bacteria was investigated and it was observed that pure BD cultures can be stored with minimal reduction in numbers at temperatures ranging from 4°C to 20°C. However, significant reductions in numbers were observed at -1 8"C, 30°C and 37°C after 13 to 16 days. The effects of the 13 New Zealand BD isolates on the growth of a population of Photobacterium phosphoreum were examined to select the best isolate for in vitro application. All of the isolates tested had considerable reduction effect against P. phosphoreum. Some isolates were more effective than others, despite their taxonomic similarity to each other. The isolate OT2 was selected for further studies based on these results. The in vitro efficacy of BD was assessed against late exponential cultures of a seafood spoilage bacterium, P. phosphoreum, originally isolated from Cod fillets from Denmark. Loglo reductions of P. phosphoreum and some other Gram-negative bacteria ranged from 4.5 to 4.8 after 9 h of incubation at 25OC. BD was effective in reducing the numbers of P. phosphoreum at pH 5.5 to 8.5 and salinity 0.9 to 4.5% (wlv). A significant interaction was observed between the prey and predator concentrations and nutrient concentration. Prey concentrations were observed to be the most vital factor in predation and the most favourable predation conditions were at a prey concentration of -8 loglo colony forming units (CFU)/mL, together with a predator concentration of 3 - 7 loglo plaque forming units (PFU)/mL and a prey : predator ratio of >5.0. The thresholds of the prey and predator concentrations for predation were observed to be 3.7 loglo CFUImL and 3.9 loglo PFUImL, respectively. The trials carried out in this study focused on the efficiency of BD on a pure culture of one organism, P. phosphoreum and not on mixed cultures of Gramnegative spoilage bacteria, the normal condition observed in saltwater fish. There has been very little research in this field and the results of these trials suggest further investigation into the effect of BD on mixed cultures of Gram-negative spoilage organisms is warranted. Since only one isolate of BD (OT2) was examined against only one spoilage bacterium (P. phosphoreum) in liquid medium, the evidence of these findings must be restricted to these particular conditions. Future studies, using a range of BD isolates against a mixture of spoilage and pathogenic organisms in solid medium are warranted. The biopreservation capability of BD in extending the shelf life of king salmon was evaluated. A significant effect was observed at 20°C but not at 10°C. At 20°C the shelf life was extended through extension of the lag phase of growth of the prey bacteria and a reduction in total numbers attained. Sensory evaluation of the salmon product being tested confirmed that the shelf life was extended. However, at 10°C there was no reduction in prey organisms, which suggested that the strain of BD used is ineffective at refrigeration temperatures.

Thesis (M.S.)--University of North Carolina Wilmington, 2008 / Title from PDF title page (viewed May 26, 2009) Includes bibliographical references (p. 31-33)

Thesis (Ph. D.)--Columbia University, 1917. / Vita. "Scomber scombrus, was chosen as an ideal fish for an investigation of this sort."--P. 6. Bibliography: p. 22-24.

Thesis (Ph. D.)--University of Florida, 1981. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 173-175).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 70-82). Also available on the World Wide Web.

In this study, a number of experiments were undertaken to investigate possible methods for effective improvement of the texture and flavour of canned late-run chum salmon. These included removal of the skin and bones from the fish, processing of the boneless-skinless steaks in retort pouches, brine treatment using two washes with an 8% salt solution for one hour each time, and a precanning treatment in which the boneless-skinless steaks were soaked in a solution of 10% tripolyphosphate and 2% brine for two minutes. Only fish of advanced sexual maturity were used. The canned salmon was steam processed at 120°C for 65 minutes in an FMC laboratory retort. This was based on a known commercial process for 307 x 115 cans. Heat penetration studies were carried out to design the process schedules for the pouched samples. It was found that the pouched product required 48% less thermal processing time than the canned product to achieve similar lethality. Sensory results showed that the removal of the skin and bones did not produce any significant improvement in the flavour and acceptability of the fish. There was no significant difference between the polyphosphate/brine samples and the untreated (control) samples for all attributes tested. The brine treatment also did not improve the texture of the samples. However, there was less detection of late-run flavour in the brine treated samples when compared to the control. Comments offered by panelists described these samples as having a salty/briny flavour. Pouched samples had a firmer, drier and more fibrous texture than the canned product. They also scored better in terms of late-run flavour. Acceptance of the fish however was only moderate. As a consequence, although this study demonstrated an improvement in the texture and flavour of the pouched late-run chum in comparison to the canned product, it was concluded that a more acceptable pouched product could probably be obtained by using late-run salmon of less advanced sexual maturity. Results of linear regression analysis showed that significant relationships were obtained between sensory firmness, fibrousness and chewiness and instrumental hardness, maximum slope and chewiness. However, none of the sensory parameters were well predicted by the instrumental results. / Land and Food Systems, Faculty of / Graduate

No description available.

The purpose of this research was to determine the feasibility of pasteurizing crabmeat in retort pouches compared to cans. Retort pouches and cans were packed with various amounts of crabmeat, pasteurized to an internal temperature of 185°F (85°C) for 1 min, and subsequently cooled. The criteria for evaluation were total processing time, process lethality (F value), microbiological stability and sensory evaluation. Pasteurizing crabmeat in retort pouches resulted in total processing times that were significantly less (P ≥ 0.05) than cans. Also, pasteurizing to targeted F values provided a more rapid and efficient way to achieve equivalent processes. Thus, equivalent can processes were given to pouches in significantly less (P ≥ 0.05) time. Microbial loads were reduced by greater than 99% in both pouches and 65 cans following pasteurization to a target F value (F⁶⁵₁₈₅ = 24). This reduction was maintained during 6 months storage at 36°F (2.2°C). Sensory evaluations conducted over a 6 month period indicated no real preference for crabmeat packaged in retort pouches or cans. However, crabmeat packed in pouches was significantly better (P ≥ 0.05) on some weeks. Hedonic scores indicated meat in both types of containers were acceptable for the duration of the study. It was concluded that packaging and pasteurizing crabmeat in retort pouches is an acceptable, if not superior, method of pasteurization. / Master of Science

Thesis (D. Tech. Environmental health) -- Central University of technology, Free State, 2011 / Apart from being the primary food source of many cultures around the world, fish contains notable amounts of essential fatty acids that are required by the human body, thus making fish a vital part of the human diet. In South Africa Cape hake is a well-known and highly consumed local fish species, which is transported from coastal areas countrywide where the fresh fish are displayed on ice in various retail stores. Fish is known to be highly susceptible to spoilage and, as a result, the maintenance of the cold-chain in related products is of particular importance. Additionally, recent trends showing a decline in natural fish resources have instigated growing concerns about the sustainability and optimal utilisation of fish as a food source. Against this backdrop, this study aimed at determining the influence of storage parameters on selected triglycerides and their possible metabolic pathways. Also applying prediction modelling of fatty acids and volatiles as instruments to assess exposure of Cape hake fillets to excessive microbial contamination and, in effect, be indicative of the environmental parameters (for example temperature) that may influence such contamination. Randomly selected juvenile hakes were filleted and stored under various simulated retail storage conditions, under either controlled or uncontrolled environmental conditions. For each hake filleted, one fillet was inoculated with an increased load of autochthonous microbiota, and the corresponding fillet was kept at similar temperature conditions. All fillets were monitored over a ten day period, during which fatty acid and volatile samples were collected and analysed. From the resulting triglycerides a selection of fatty acids were profiled and their possible metabolic pathways investigated. Fish maturity, the distribution of the fatty acids and the implication thereof in the nutritional value were also assessed. Conventional chemometric methods utilising mathematical expressions were subsequently utilised in order to predict contamination and whether the cold chain was sustained, while an artificial neural network (ANNs) were designed to predict excessive microbial contamination in the fillets. The results showed that the nutritional value of fish differs notably with its maturity and size. Mathematical equations were furthermore found to be effective assessment instruments to indicate the percentage differences in storage temperature, as well as consequent microbial influences. Thus, this approach may introduce mathematical prediction modelling as a promising mechanism to assess Cape hake spoilage. An artificial neural network (ANN) was successfully designed, that succeeded in distinguishing between Cape hake fillets displayed and stored on ice that have been exposed to excessive contamination and those that have not been exposed. In the latter case, the selected variable was a fatty acid, hexadecanoic acid, used as biochemical indicator. This modulating approach may provide a platform for future shelf-life studies on related muscle tissue. Ultimately, the study endeavoured to add to the body of knowledge regarding the biochemical and microbiological changes related to Cape hake storage, the prediction thereof via contemporary methods and contributing to the safety and effective utilization of this unique and declining South African nutritional resource.