Chau Wing-sze. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 238-262). / Abstracts in English and Chinese. / Abstract (in English) --- p.i / Abstract (in Chinese) --- p.iv / Acknowledgement --- p.vi / Contents --- p.ix / List of Figures --- p.xv / List of Tables --- p.xvi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Introduction of samples --- p.2 / Chapter 1.3 --- Flavor of Chinese salted-dried fish --- p.4 / Chapter 1.4 --- Objectives of the study --- p.5 / Chapter 2. --- Literature review --- p.7 / Chapter 2.1 --- Introduction --- p.7 / Chapter 2.2 --- Volatile compounds in fresh fish --- p.8 / Chapter 2.2.1 --- Groups of volatile compounds --- p.9 / Chapter 2.2.2 --- Variation in fresh fish flavor --- p.12 / Chapter 2.2.2.1 --- Intrinsic factor --- p.12 / Chapter 2.2.2.2 --- Environmental factors --- p.15 / Chapter 2.2.2.3 --- Post harvest conditions --- p.16 / Chapter 2.3 --- Fish preservation --- p.17 / Chapter 2.3.1 --- Preservation methods --- p.18 / Chapter 2.3.1.1 --- Drying --- p.19 / Chapter 2.3.1.2 --- Salting --- p.19 / Chapter 2.3.1.3 --- Fermentation --- p.21 / Chapter 2.3.2 --- Theory of drying and salting --- p.21 / Chapter 2.3.3 --- Different protocols in the world --- p.23 / Chapter 2.3.3.1 --- European methods --- p.24 / Chapter 2.3.3.2 --- Southeast Asian methods --- p.25 / Chapter 2.3.3.3 --- Thai methods --- p.27 / Chapter 2.3.3.4 --- Chinese method --- p.28 / Chapter 2.3.3.5 --- Local method --- p.29 / Chapter 2.3.4 --- Consumption procedures --- p.31 / Chapter 2.3.5 --- Advantages of drying besides preservation --- p.31 / Chapter 2.3.5.1 --- Convenience in transportation --- p.32 / Chapter 2.3.5.2 --- Flavorization --- p.32 / Chapter 2.3.5.3 --- Nutritional values --- p.33 / Chapter 2.4 --- Flavor of salted-dried fish --- p.34 / Chapter 2.4.1 --- Taste of salted-dried fish --- p.35 / Chapter 2.4.2 --- Aroma of salted-dried fish --- p.35 / Chapter 2.4.3 --- Flavor of Chinese salted-dried fish --- p.37 / Chapter 2.4.4 --- Parameters affect the flavor and quality of salted-dried fish --- p.38 / Chapter 2.4.4.1 --- Freshness --- p.38 / Chapter 2.4.4.2 --- Temperature --- p.39 / Chapter 2.4.4.3 --- Post harvest freezing and thawing --- p.40 / Chapter 2.4.4.4 --- Gutting --- p.42 / Chapter 2.4.4.5 --- Salt quality --- p.43 / Chapter 2.5 --- Biological deterioration in salted fish --- p.46 / Chapter 2.6 --- Salted-dried fish in Hong Kong --- p.47 / Chapter 3. --- Materials and methods --- p.55 / Chapter 3.1 --- Materials --- p.55 / Chapter 3.1.1 --- Abbreviation of names of samples --- p.55 / Chapter 3.1.2 --- Handling of samples --- p.56 / Chapter 3.2 --- Method --- p.58 / Chapter 3.2.1 --- Modified Simultaneous steam distillation-solvent extraction (SDE)-Steaming --- p.58 / Chapter 3.2.2 --- Concentration --- p.59 / Chapter 3.2.3 --- Gas chromatography-mass spectrometry (GC-MS) --- p.59 / Chapter 3.2.4 --- Compound identification --- p.60 / Chapter 3.2.5 --- Quantification of compounds --- p.60 / Chapter 3.2.6 --- Moisture analysis --- p.62 / Chapter 3.2.7 --- Texture analysis --- p.62 / Chapter 3.2.8 --- Statistical analysis --- p.63 / Chapter 3.2.9 --- OAV calculation --- p.64 / Chapter 4. --- Results and Discussion --- p.66 / Chapter 4.1 --- Threadfin --- p.66 / Chapter 4.1.1 --- Overall description of volatile compounds in salted-dried threadfin --- p.66 / Chapter 4.1.2 --- Characteristic compounds in delayed (D) groups of samples --- p.68 / Chapter 4.1.3 --- Characteristic compounds in regular (R) groups of samples --- p.70 / Chapter 4.1.4 --- Common compounds found in the eight groups of samples --- p.71 / Chapter 4.1.5 --- Comparison of common compounds among individual groups of salted-dried fish --- p.78 / Chapter 4.1.5.1 --- Comparison between delayed and regular salting methods --- p.78 / Chapter 4.1.5.2 --- Comparison between locations of purchase --- p.80 / Chapter 4.1.5.3 --- Comparison between samples from different years (2000 and 2001) --- p.81 / Chapter 4.1.6 --- Exclusive compounds found in delayed salted (D) or regular salted (R) fish --- p.83 / Chapter 4.1.7 --- Conclusion of threadfin --- p.84 / Chapter 4.2 --- White herring --- p.85 / Chapter 4.2.1 --- Overall description of volatile compounds in salted-dried white herring --- p.85 / Chapter 4.2.2 --- Characteristic compounds in delayed (D) groups of samples --- p.87 / Chapter 4.2.3 --- Characteristic compounds in regular (R) groups of samples --- p.88 / Chapter 4.2.4 --- Common compounds found in the eight groups of samples --- p.89 / Chapter 4.2.5 --- Comparison of common compounds among individual groups --- p.94 / Chapter 4.2.5.1 --- Comparison between delayed and regular salting methods --- p.94 / Chapter 4.2.5.2 --- Comparison between locations of purchase --- p.96 / Chapter 4.2.5.3 --- Comparison between samples from different years --- p.97 / Chapter 4.2.6 --- Conclusion of white herring --- p.98 / Chapter 4.3 --- Pawak croaker --- p.100 / Chapter 4.3.1 --- Overall description of volatile compounds in salted-dried pawak croaker --- p.100 / Chapter 4.3.2 --- Characteristic compounds in delayed (D) groups of samples --- p.102 / Chapter 4.3.3 --- Characteristic compounds in regular (R) groups of samples --- p.105 / Chapter 4.3.4 --- Common compounds found in the eight groups of samples --- p.106 / Chapter 4.3.5 --- Comparison of common compounds among individual groups of salted-dried fish --- p.111 / Chapter 4.3.5.1 --- Comparison between delayed and regular salting methods --- p.111 / Chapter 4.3.5.2 --- Comparison between locations of purchase --- p.114 / Chapter 4.3.5.3 --- Comparison between two batches of samples from different years --- p.115 / Chapter 4.3.5.4 --- Characteristic compounds of pawak croaker --- p.117 / Chapter 4.3.6 --- Conclusion of pawak croaker --- p.118 / Chapter 4.4 --- Overall comparison of compounds of the three species --- p.120 / Chapter 4.4.1 --- Introduction --- p.120 / Chapter 4.4.2 --- Comparison of three species of fishes --- p.121 / Chapter 4.4.2.1 --- Delayed- and regular- smell contributors --- p.122 / Chapter 4.4.3 --- The difference among the groups of fishes --- p.123 / Chapter 4.4.3.1 --- Effect of different body compositions of fishes --- p.124 / Chapter 4.4.3.1.1 --- Lipid originated volatile aldehydes --- p.125 / Chapter 4.4.4 --- Common compounds detected in all three species of salted-dried fishes --- p.126 / Chapter 4.4.4.1 --- Compounds with high calculated aroma values (OAV) --- p.127 / Chapter 4.4.4.2 --- Compounds with low calculated aroma values (OAV) --- p.130 / Chapter 4.4.5 --- Effect of treatment methods --- p.132 / Chapter 4.4.6 --- Effect of locations of collection of samples on the composition --- p.134 / Chapter 4.4.7 --- Effect of time of collection of samples on the composition --- p.135 / Chapter 4.4.8 --- Characteristic compounds found only in one species --- p.135 / Chapter 4.4.8.1 --- Characteristic compounds of threadfin --- p.136 / Chapter 4.4.8.2 --- Characteristic compounds of white herring --- p.136 / Chapter 4.4.8.3 --- Characteristic compounds of pawak croaker --- p.138 / Chapter 4.5 --- Texture --- p.139 / Chapter 4.5.1 --- Introduction --- p.139 / Chapter 4.5.2 --- Results and Discussion --- p.141 / Chapter 4.5.2.1 --- Comparison between regular and delayed salted-dried fishes --- p.141 / Chapter 4.5.2.1.1 --- Effects of enzymatic reaction --- p.141 / Chapter 4.5.2.1.2 --- Effects of fermentation --- p.142 / Chapter 4.5.2.1.3 --- Frozen period before regular salting --- p.143 / Chapter 4.5.2.2 --- Comparison between raw and steamed salted-dried fishes --- p.145 / Chapter 4.5.2.3 --- Moisture content of salted-dried fishes --- p.146 / Chapter 4.5.3 --- Conclusion --- p.147 / Chapter 5. --- Conclusion and Significance --- p.233 / Chapter 5.1 --- General conclusion --- p.233 / Chapter 5.2 --- Significance of the study --- p.235 / References --- p.238 / Appendix I --- p.263 / Appendix II --- p.264

No description available.

First grade and second grade Nampla, commercially produced Thai fish sauces, were analyzed for their chemical and microbiological composition. First grade commercially produced Nampla contained higher amounts of total nitrogen, formol nitrogen, free and total amino acids compared to second grade sauce. Most of the essential amino acids were present in both grades of sauces. Low microbial counts of halotolerant microorganisms were observed in both sauces. The use of trypsin and chymotrypsin to accelerate the rate of fish sauce fermentation produced from herring, one of the underutilized fish species in Quebec, was investigated. Results showed that supplementation with trypsin and chymotrypsin increased significantly the rate of proteolysis, the amounts of total nitrogen, formol nitrogen and free amino acids in the final fish sauces (p 0.05). (Abstract shortened by UMI).

No description available.

No description available.

Yeung Chi-wang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 128-144). / Abstracts in English and Chinese. / Abstract (in English) --- p.i / Abstract (in Chinese) --- p.iv / Acknowledgement --- p.vi / Contents --- p.vii / List of Figures --- p.xi / List of Tables --- p.xiii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Literature review --- p.3 / Chapter 2.1 --- Nutritional facts of fish --- p.3 / Chapter 2.2 --- Aroma of fish --- p.5 / Chapter 2.2.1 --- Carbonyls and alcohols --- p.6 / Chapter 2.2.2 --- Sulphur-containing compounds --- p.7 / Chapter 2.2.3 --- Bromophenols --- p.9 / Chapter 2.2.4 --- Hydrocarbons --- p.9 / Chapter 2.2.5 --- Off flavor in fish --- p.9 / Chapter 2.2.6 --- Autoxidation of fish meat --- p.10 / Chapter 2.2.7 --- (Z)-4-heptenal in cooked and stored fish --- p.10 / Chapter 2.2.8 --- Volatile acids --- p.11 / Chapter 2.3 --- Salted-dried fish in Hong Kong --- p.11 / Chapter 2.3.1 --- Salted-dried fish used in this study --- p.13 / Chapter 2.3.2 --- Salting methods of the salted-dried fish used in this study --- p.14 / Chapter 2.3.3 --- Salting method used in Tai O --- p.15 / Chapter 2.4 --- Aroma analysis --- p.19 / Chapter 2.4.1 --- Extraction methods --- p.19 / Chapter 2.4.1.1 --- Steam distillation methods --- p.20 / Chapter 2.4.1.2 --- Solvent extraction methods --- p.22 / Chapter 2.4.1.3 --- Headspace methods --- p.22 / Chapter 2.4.2 --- Screening of important aroma contributing volatile compounds --- p.23 / Chapter 2.5 --- Overview --- p.26 / Chapter Chapter 3 --- Method Development --- p.28 / Chapter 3.1 --- Introduction --- p.28 / Chapter 3.2 --- Methodology --- p.29 / Chapter 3.2.1 --- Reproducibility of injection mode --- p.29 / Chapter 3.2.2 --- Optimization of the sample preparation procedure --- p.29 / Chapter 3.2.3 --- Gas chromatography-mass spectrometry coupled with cooled injection system (GC-MS-CIS) --- p.30 / Chapter 3.3 --- Results and discussion --- p.31 / Chapter 3.3.1 --- Reproducibility of the cooled injection system --- p.31 / Chapter 3.3.2 --- Efficiency of different injection modes --- p.33 / Chapter 3.3.3 --- Optimal equilibrium Time --- p.33 / Chapter 3.3.4 --- Conclusion --- p.37 / Chapter Chapter 4 --- Volatile compounds in the headspace of salted-dried fish --- p.38 / Chapter 4.1 --- Introduction --- p.38 / Chapter 4.2 --- Materials and Methods --- p.39 / Chapter 4.2.1 --- Sample preparation --- p.39 / Chapter 4.2.2 --- Headspace analysis and gas chromatography-mass spectrometry (GC-MS) --- p.42 / Chapter 4.2.3 --- "Identification, quantification and odor activity values (OAV) of compounds" --- p.43 / Chapter 4.2.4 --- Statistical analysis --- p.44 / Chapter 4.3 --- Results and discussion --- p.45 / Chapter 4.3.1 --- Headspace profiles of three salted-dried fishes in Hong Kong --- p.45 / Chapter 4.3.1.1 --- Aldehydes and alcohols --- p.63 / Chapter 4.3.1.2 --- Hydrocarbons and ketones --- p.66 / Chapter 4.3.1.3 --- Nitrogen- (N-)containing and sulfur- (S-)containing compounds --- p.68 / Chapter 4.3.1.4 --- "Esters, furans and pyrazines" --- p.72 / Chapter 4.3.1.5 --- "Acids, pyrroles and pyridine" --- p.73 / Chapter 4.3.1.6 --- Important aroma contributing compounds in salted-dried fish --- p.74 / Chapter 4.3.2 --- Influence of steaming on the salted-dried fish headspace --- p.75 / Chapter 4.3.3 --- Difference in the headspace of salted-dried fish purchased between the first and second year --- p.76 / Chapter 4.3.4 --- Influence of salting methods on the salted-dried fish aroma --- p.76 / Chapter 4.3.5 --- Difference between salted-dried fish purchased at Sai Wan and Tai O --- p.78 / Chapter 4.3.6 --- Difference between salted-dried fish produced from difference fish species --- p.78 / Chapter 4.4 --- Conclusion --- p.79 / Chapter Chapter 5 --- Aroma active compounds in salted-dried fish --- p.81 / Chapter 5.1 --- Introduction --- p.81 / Chapter 5.2 --- Materials and Methods --- p.82 / Chapter 5.2.1 --- Sample preparation --- p.82 / Chapter 5.2.2 --- Gas chromatography static headspace analysis and olfactometry GC-SHA-O and aroma extract dilution analysis (AEDA) --- p.84 / Chapter 5.2.3 --- Compound identification --- p.85 / Chapter 5.2.4 --- Calculation of flavor dilution (FD) factor --- p.85 / Chapter 5.3 --- Results and discussion --- p.86 / Chapter 5.3.1 --- Aroma active compounds in salted-dried fish --- p.86 / Chapter 5.3.1.1 --- Strong and Potent aromas --- p.87 / Chapter 5.3.1.2 --- Roasted aromatic aromas --- p.94 / Chapter 5.3.1.3 --- Floral aromas --- p.95 / Chapter 5.3.1.4 --- Vegetative aromas --- p.96 / Chapter 5.3.1.5 --- Penetrating aromas --- p.97 / Chapter 5.3.1.6 --- Common aromas --- p.98 / Chapter 5.3.2 --- Characteristic of aroma active compounds between steamed and non-steamed salted-dried fish --- p.99 / Chapter 5.3.3 --- Differences in aroma active compounds between regular and delayed salted-dried fish --- p.100 / Chapter 5.3.4 --- Characteristic aroma of different species of salted-dried fish --- p.105 / Chapter 5.3.5 --- Characteristic aroma of salted-dried fish purchased at Sai Wan and Tai O --- p.108 / Chapter 5.3.6 --- Characteristic aroma of salted-dried fish purchased in 2001 and 2002 --- p.108 / Chapter 5.4 --- Conclusion --- p.108 / Chapter Chapter 6 --- Important volatile compounds in salted-dried fish --- p.112 / Chapter 6.1 --- Comparison between OAV and SHA-O --- p.112 / Chapter 6.2 --- Overall conclusion --- p.114 / Chapter 6.2.1 --- Effects of steaming on salted-dried fish aroma --- p.114 / Chapter 6.2.2 --- Effects of salting methods on salted-dried fish aroma --- p.117 / Chapter 6.2.3 --- Characteristics aroma of salted-dried fish prepared from different fish species --- p.120 / Chapter 6.2.4 --- Characteristics aroma of salted-dried fish purchased from different locations --- p.120 / Chapter 6.2.5 --- Characteristics aroma of salted-dried fish purchased from different periods --- p.125 / References --- p.128 / Appendix --- p.145

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Thesis (MScFoodSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: The preservation of various fresh fish products is achieved by either smoking, salting, canning, freezing or fermenting a highly perishable raw product. Since many of these facilities are not readily available, the use of fermentation as a means of preserving the product has been extensively practiced. However, the fermentation of fish is a time consuming practise and only by accelerating the process would it be possible to ensure the production of a more cost effective and readily available safe end-product. The quality of the fermented fish product is partially determined by the fermentation conditions and the metabolic activity of the microbes present. The rapid identification of the microbes present during the fermentation would enable the selection of possible starters to ensure an accelerated production of high quality fermented fish products. This study was thus undertaken to develop identification fingerprints for bacteria isolated from fermented fish products. A 1300 bp fragment of the 16S rRNA genes of each of the bacteria previously isolated was successfully amplified using the PCR technique. The isolates included strains of the genera Bacillus, Staphylococcus, Sphingomonas, Kocuria, Brevibacillus, Cryseomonas, Vibrio, Stenotrophomonas and Agrobacterium. The data obtained can, therefore, be used in the identification of these microbes isolated from other similar fermented fish products. The fingerprints could also be used to assist in determining the dominant microbial populations responsible for the characteristic qualitative changes occurring in the fish product during fermentation. The microbial composition of a fermenting fish product partially determines the quality of the end-product, therefore, the use of selected bacterial starters could result in the accelerated production of a microbial safe fermented fish product. A further objective of this study was to accelerate the production of a fermented fish product by inoculating macerated trout with either selected lactic acid bacteria (LAB) or with selected bacteria with high proteolytic activity over a 30 day fermentation period. The LAB included a combination of Lactobacillus plantarum, Lactococcus diacetylactis and Pediococcus cerevisiae strains, whereas the bacteria with high proteolytic activity included strains of Kocuria varians, Bacillus subtilis, two strains of B. amyloliquefaciens and a combination of these bacterial species. The quality of the fermented product was determined using changes in product pH, titratable acidity (%TA) and free amino nitrogen (FAN) formation as efficiency parameters. The data obtained during the fermentation of the macerated trout showed that the selected starters did not have a significant effect on the pH decrease in the product over a 30 day fermentation period. The LAB strains did not have a significant effect on the %TA of the fermenting fish product, yet the presence of these bacteria appeared to limit the FAN production in the product. The bacteria with high proteolytic activity resulted in slightly enhanced %TA values and a higher FAN content in the fermented product. It was also determined that the LAB and Kocuria varians, in contrast to the Bacillus spp. inoculums, did not survive the fermentation conditions well, possibly due to the low pH environment. The presence of the starter bacteria in the fermenting fish mixture at the end of the fermentation was also successfully determined with the use of the PCR-RFLP technique. The fermented fish product, obtained at the end of the fermentation period, had a good aroma and compared favourably to similar commercially available fermented fish products. The use of different microbial starters could in future enable the production of a diverse range of high quality products, which could be produced and marketed locally. / AFRIKAANSE OPSOMMING: Die preservering van ‘n verskeidenheid vars vis produkte word bereik deur die hoogs bederfbare produk te rook, te sout, te blik, te vries of te fermenteer. Aangesien baie van hierdie fasiliteite nie geredelik beskikbaar is nie, is die gebruik van fermentasie as ‘n preserverings metode al ekstensief beoefen. Die fermentasie van vis is egter 'n tydsame proses en slegs deur die versnelling van die proses sal dit moontlik wees om die produksie van ‘n meer koste effektiewe en geredelike beskikbare veilige eindproduk te verseker. Die kwaliteit van die gefermenteerde vis produk word gedeeltelik bepaal deur die fermentasie kondisies en die metaboliese aktiwiteit van die mikrobes teenwoordig. Die vinnige identifikasie van die mikrobes teenwoordig gedurende die fermentasie sal die seleksie van moontlike suursels om die versnelde produksie van hoë kwaliteit gefermenteerde vis produkte moontlik maak. Hierdie studie is dus onderneem om identifikasie vingerafdrukke vir bakteriee wat gei'soleer is van gefermenteerde vis produkte moontlik te maak. ‘n 1300 bp fragment van die 16S rRNA gene van elkeen van die bakteriee wat voorheen gei'soleer is, is suksesvol geamplifiseer deur die PCR tegniek. Die isolate sluit in stamme van die genera Bacillus, Staphylococcus, Sphingomonas, Kocuria, Brevibacillus, Cryseomonas, Vibrio, Stenotrophomonas en Agrobacterium. Die data kan dus gebruik word in die identifikasie van hierdie mikrobes as dit gei'soleer word van ander gefermenteerde vis produkte. Die vingerafdrukke kan ook gebruik word om die dominante mikrobiese populasies wat verantwoordelik is vir die kenmerklike kwalitatiewe veranderinge wat plaasvind in die vis produk gedurende die fermentasie, te identifiseer. Die mikrobiese samestelling van ‘n fermenterende vis produk bepaal gedeeltelik die kwaliteit van die eindproduk, daarom kan die gebruik van geselekteerde bakteriese suursels die versnelde produksie van ‘n mikrobies veilige gefermenteerde vis produk teweeg bring. ‘n Verdere doel van hierdie studie was om die produksie van ‘n gefermenteerde vis produk te versnel deur fyngemaakte forel met of geselekteerde melksuurbakteriee of met geselekteerde bakteriee met hoë proteolitiese aktiwiteit te inokuleer oor ‘n 30 dag fermentasie periode. Die melksuurbakteriee het ingesluit ‘n kombinasie van Lactobacillus plantarum, Lactococcus diacetylactis en Pediococcus cerevisiae, terwyl die bakterieë met hoë proteolitiese aktiwiteit stamme van Kocuria varians, Bacillus subtilis, twee stamme van Bacillus amyloliquefaciens en ‘n kombinasie van hierdie bakteriese stamme ingesluit het. Die kwaliteit van die gefermenteerde produk is bepaal deur die veranderinge in die pH, titreerbare suur (%TS) en vrye amino stikstof (VAS) vorming van die produk as effektiwiteits parameters te gebruik. Die data wat verkry is gedurende die fermentasie van die fyngemaakte forel het gedui daarop dat die geselekteerde suursels nie ‘n merkwaardige effek op die afname in pH in die produk oor ‘n 30 dag fermentasie periode het nie. Die melksuurbakteriee het nie ‘n merkwaardige effek op die %TS van die gefermenteerde vis produk gehad nie, terwyl dit geblyk het dat die teenwoordigheid van hierdie bakterieë die produksie van VAS in die produk belemmer het. Die bakteriee met hoe proteolitiese aktiwiteit het ‘n effense verhoogde %TS en ‘n hoër VAS inhoud in die gefermenteerde produk veroorsaak. Dit is ook bepaal dat die melksuurbakteriee en Kocuria varians, in teenstelling met die Bacillus spp. inokulums, nie die fermentasie kondisies goed oorleef het nie, moontlik as gevolg van die lae pH omgewing. Die teenwoordigheid van die suursel bakteriee in die fermenterende vis mengsel aan die einde van die fermentasie is ook suksesvol bepaal met die PKR-RFLP tegniek. Die gefermenteerde vis produk, verkry aan die einde van die fermentasie periode, het ‘n goeie aroma gehad en het goed vergelyk met soortgelyke kommersieel beskikbare gefermenteerde vis produkte. Die gebruik van verskillende mikrobiese suursels kan in die toekoms die produksie van ‘n diverse reeks hoë kwaliteit produkte wat plaaslik geproduseer en bemark kan word moontlik maak.

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.

Ma Wing-chi, Joyce. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 131-148). / Abstracts in English and Chinese. / Abstract (in English) --- p.i / Abstract (in Chinese) --- p.iv / Acknowledgement --- p.vi / Contents --- p.viii / Abbreviation --- p.xii / List of Tables --- p.xiii / List of Figures --- p.xv / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Literature review --- p.5 / Chapter 2.1 --- Fisheries in Hong Kong --- p.5 / Chapter 2.2 --- Flavor of seafood --- p.6 / Chapter 2.2.1 --- Lipid-derived volatile aroma compounds --- p.7 / Chapter 2.2.2 --- "Alcohols, aldehydes and ketones" --- p.8 / Chapter 2.2.3 --- Enzymatic conversion of sulfur- and nitrogen-containing precursors --- p.9 / Chapter 2.2.4 --- Thermally generated compounds --- p.9 / Chapter 2.2.5 --- Bromophenols --- p.10 / Chapter 2.2.5.1 --- General properties of bromophenols --- p.11 / Chapter 2.2.5.2 --- Threshold of bromophenols --- p.14 / Chapter 2.2.5.3 --- Toxicity of bromophenols --- p.17 / Chapter 2.2.5.4 --- Previous studies about bromophenols --- p.19 / Chapter 2.2.5.5 --- Bromophenols in aquacultured seafood --- p.20 / Chapter 2.2.5.6 --- Possible dietary sources of bromophenols --- p.20 / Chapter 2.2.5.7 --- Possibility of increasing bromophenol content in aquacultured fish --- p.23 / Chapter 2.3 --- Criteria for selecting experimental fish model --- p.24 / Chapter 3. --- Distribution of Bromophenols in selected Hong Kong seafoods --- p.27 / Chapter 3.1 --- Introduction --- p.27 / Chapter 3.2 --- Materials and methods --- p.28 / Chapter 3.2.1 --- Sample collection and preparation --- p.28 / Chapter 3.2.2 --- Simultaneous steam distillation-solvent extraction (SDE) --- p.30 / Chapter 3.2.3 --- Gas chromatography / mass spectrometry (GC/MS) --- p.30 / Chapter 3.2.4 --- Compound identification and quantification --- p.31 / Chapter 3.2.5 --- Recoveries --- p.33 / Chapter 3.2.6 --- Moisture determination --- p.34 / Chapter 3.2.7 --- Statistical analysis --- p.34 / Chapter 3.3 --- Results and discussion --- p.34 / Chapter 3.3.1 --- Distribution of bromophenols in seafoods --- p.34 / Chapter 3.3.1.1 --- Bromophenols in marine fishes --- p.49 / Chapter 3.3.1.2 --- Bromophenols in mollusks --- p.49 / Chapter 3.3.1.3 --- Bromophenols in crustaceans --- p.50 / Chapter 3.3.2 --- Seasonal variations of TBCs --- p.51 / Chapter 3.3.3 --- Bromophenols in diet contents --- p.52 / Chapter 3.3.4 --- Bromophenol contents of freshwater fish --- p.53 / Chapter 3.3.5 --- Relationship between the living habitats and bromophenol contents --- p.56 / Chapter 3.3.6 --- Bromophenols as flavor compounds in seafoods --- p.58 / Chapter 3.4 --- Conclusion --- p.59 / Chapter 4. --- Distribution of Bromophenols in selected Hong Kong seaweeds --- p.61 / Chapter 4.1 --- Introduction --- p.61 / Chapter 4.2 --- Materials and methods --- p.62 / Chapter 4.2.1 --- Sample collection and preparation --- p.62 / Chapter 4.2.2 --- Simultaneous steam distillation-solvent extraction (SDE) --- p.63 / Chapter 4.2.3 --- Gas chromatography / mass spectrometry (GC/MS) --- p.64 / Chapter 4.2.4 --- Compound identification and quantification --- p.65 / Chapter 4.2.5 --- Recoveries --- p.66 / Chapter 4.2.6 --- Moisture determination --- p.67 / Chapter 4.3 --- Results and discussion --- p.67 / Chapter 4.3.1 --- Distribution of bromophenols in marine algae --- p.67 / Chapter 4.3.2 --- Seasonal variations --- p.76 / Chapter 4.3.3 --- Functions of bromophenols in marine algae --- p.79 / Chapter 4.3.4 --- Marine algae as sources of bromophenols in marine environment --- p.80 / Chapter 4.4 --- Conclusion --- p.81 / Chapter 5. --- Enhancement of bromophenol contents in aquacultured fish by the development of bromophenol-rich fish feeds --- p.83 / Chapter 5.1 --- Introduction --- p.83 / Chapter 5.2 --- Materials and methods --- p.85 / Chapter 5.2.1 --- Preparation of fish feeds --- p.85 / Chapter 5.2.2 --- Storage conditions of fish feeds --- p.88 / Chapter 5.2.3 --- Experimental animals --- p.88 / Chapter 5.2.4 --- Solvent and chemicals --- p.90 / Chapter 5.2.5 --- Extraction and quantification of bromophenols --- p.90 / Chapter 5.2.5.1 --- Simultaneous steam distillation-solvent extraction (SDE) --- p.90 / Chapter 5.2.5.2 --- Gas chromatography / mass spectrometry (GC/MS) --- p.91 / Chapter 5.2.5.3 --- Compound identification and quantification --- p.92 / Chapter 5.2.5.4 --- Recoveries --- p.93 / Chapter 5.2.6 --- Moisture determination --- p.94 / Chapter 5.2.7 --- Statistical analysis --- p.94 / Chapter 5.2.8 --- Sensory test --- p.95 / Chapter 5.3 --- Results and discussion --- p.96 / Chapter 5.3.1 --- Bromophenol contents in wild-harvested and aquacultured fish --- p.96 / Chapter 5.3.2 --- Development of bromophenol-rich fish feed --- p.99 / Chapter 5.3.3 --- Effect of feeding the fish with the fish feed developed --- p.105 / Chapter 5.3.4 --- Sensory evaluation on the flesh of the fish fed with different fish feeds --- p.121 / Chapter 5.3.5 --- Growth of the fish fed with different fish feeds --- p.124 / Chapter 5.4 --- Conclusion --- p.126 / Chapter 6. --- General conclusion and significance of the study --- p.128 / References --- p.131