Thesis (Ph. D.)--University of Hong Kong, 1975.

Thesis (doctoral)--Rijks-Universiteit te Utrecht, 1932. / Bibliography: p. 112-116.

Thesis (Ph.D.)--University of Hong Kong, 1975. / Also available in print.

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

Graduation date: 1949

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

Made available in DSpace on 2015-04-17T14:49:27Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1652130 bytes, checksum: c211617d969984519d85dc26c1432c15 (MD5) Previous issue date: 2012-12-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Sun-dried beef is a largely consumed, appreciated product in Brazil. However, there are few scientific studies regarding its tenderness. Tenderness is a relevant issue because consumers usually refer to it as the main quality attribute for meat. Studies on sun-dried beef tenderness in samples sold in the market of João Pessoa, followed by the assessment of the natural maturation effects on the tenderness of laboratory processed sun-dried beef were carried out in order to learn and improve this product quality. The efficiency of both milk and whey as potential tenderizing agents for sun-dried beef was also tested. Therefore, an instrumental analysis, shear force (SF), sensory analysis (QDA), sarcomere length (SL), and collagen quantification were also used as indicators. The research on the meats sold in João Pessoa has identified large variations. City divided into regions (R1, R2 and R3) were called acquired samples A1, A2 and A3, respectively. Sun-dried beef from region 3 was considered very soft by tasters, achieving 6.7 points; the maximum SF was 2.70 kgf and the highest SL was 1.89 μm. Furthermore, samples 1 and 2 showed almost equal values for tenderness (SF and QDA), except for SL, which have indicated sample 2 as the less tender. Concerning the laboratory processed meats, the raw materials were tested in maturation intervals of 7,14, and 21 days at 0°C before processing. According to the tested indicators, maturation has positively influenced tenderness in every sun-dried beef sample. QDA, SF, and myofibrillar fragmentation index (MFI) showed concordant data, suggesting that the sample matured for seven days was the softest. On the other hand, probably due to the small quantity of connective tissue in the meat cut used in processing, collagen quantification was not suitable as evaluation tool for assessing sun-dried beef tenderness. Immersing meat for 24 and 48 hours at 4 °C in milk and whey before processing helped testing both substances as potential tenderizer agents for sun-dried beef. It was verified that the applied treatments have failed to alter the processed meat composition, as it was also proved that dairy enzymes did not change the tenderness of these products. What probably occurs is the enhanced flavor generated by the use of milk in the meat processing, which provides greater acceptance by consumers. Thus, it is suggested that maturation as raw-material treatment for sun-dried beef processing provides tenderness, improves its quality and provides an increase in the added value of this typically Brazilian product. / A carne-de-sol é um produto de largo consumo e apreciação no Brasil, entretanto, são poucos os estudos científicos relativos à sua maciez. O interesse nesse assunto refere-se ao fato de que a maciez é o principal atributo de qualidade relativo às carnes referido pelo consumidor. Com o objetivo de conhecer e melhorar a qualidade desse produto pesquisou-se a maciez das carnes-de-sol comercializadas no comércio de João Pessoa e em seguida, verificou-se o efeito da maturação natural na maciez de carnes-de-sol processadas em laboratório. Também foi testada a eficácia do leite e do soro de leite como agentes amaciadores da carne-de-sol, sendo utilizados como indicadores a força de cisalhamento (FC), a análise sensorial através da análise descritiva quantitativa (ADQ), o comprimento do sarcômero (CS) e a quantificação do colágeno. Na pesquisa das carnes comercializadas em João Pessoa foram identificadas grandes variações. Da cidade dividida em regiões (R1, R2 e R3) foram adquiridas amostras denominadas A1, A2 e A3, respectivamente. A carne-de-sol da região 3 foi considerada muito macia pelos provadores, com pontuação de 6,7; apresentou FC máxima de 2,70 kgf e maior CS com 1,89 μm. Paralelamente, as amostras 1 e 2 apresentaram valores de maciez muito próximos (FC e ADQ) exceto pelo CS que indicou a amostra 2 como menos macia. Quando as carnes-de-sol foram processadas em laboratório, testou-se 7, 14 e 21 dias de maturação a 0 ºC das matérias-primas previamente ao processamento. Segundo os indicadores testados, a maturação influenciou positivamente na maciez de todas as carnes-de-sol. Através da ADQ, da FC e do IFM verificou-se que a amostra maturada por sete dias foi a mais macia. Já a quantificação de colágeno não se apresentou como um eficaz instrumento avaliativo de maciez em carnes-de-sol provavelmente devido ao corte cárneo utilizado para o processamento conter baixas quantidades de tecido conjuntivo. No estudo do leite e do soro de leite como prováveis agentes amaciantes foram testados a imersão da carne por 24 e 48 horas a 4 °C previamente ao processamento em carne-de-sol. Foi verificado que os tratamentos aplicados não alteraram a composição das carnes processadas, assim como ficou constatado que as enzimas lácteas não modificaram a maciez dos produtos. O que provavelmente ocorre é o fato de que o leite atua como um agente melhorador do sabor da carne, o que é percebido e apreciado pelo consumidor. Diante do exposto, pode-se concluir que maturar a carne por sete dias previamente à elaboração da carne-de-sol ocasiona uma melhoria na qualidade do produto e assim, proporciona um incremento no valor agregado desse alimento tradicional brasileiro.

Alimentos submetidos a processos tecnológicos que requerem altas temperaturas apresentam um grande potencial para a produção de óxidos de colesterol (OsC). Inúmeras evidências indicaram que os óxidos de colesterol são potencialmente citotóxicos, aterogênicos, mutagênicos e carcinogênicos. Em pescados, a oxidação do colesterol está favorecida pela presença de ácidos graxos poliinsaturados e altos níveis de colesterol. O camarão salgado-seco é particularmente suscetível à formação de óxidos de colesterol devido a sua composição lipídica, ao seu processamento e as condições de estocagem. O objetivo deste trabalho foi determinar a ocorrência de produtos da oxidação do colesterol e analisar o perfil lipídico em camarão salgado-seco. Analisou-se cinqüenta amostras de camarão salgado-seco por cromatografia líquida de alta eficiência (HPLC), através da qual foram determinados os teores de óxidos de colesterol. O colesterol e os óxidos de colesterol (7ß-OH, 7?-OH, 7-Ceto e 25-OH) foram analisados simultaneamente. O perfil de ácidos graxos foi determinado por cromatografia gasosa e para a avaliação da oxidação lipídica foi empregado o teste de TBARS. Os resultados indicaram que as amostras examinadas continham: 7ß-OH (34,63-72,56 µg/g), 7?-OH (5,02-12,12 µg/g), 7-Ceto (7,44-32,68 µg/g) e 25-OH (2,37-22,88 µg/g), sendo o 7ß-OH o óxido predominante. A quantidade de (OsC) nas amostras analisadas variou consideravelmente (4,52 a 77,30 µg/g). Quanto ao teor de colesterol total e a concentração média de TBARS, os resultados variaram de 73,88 a 247,69 mg/100g e 0,023 a 1,30 mgMA/Kg respectivamente. O perfil de ácidos graxos encontrado foi de 27,48 % saturados, 43,90% monoiinsaturados e 28,61% poliinsaturados. Este estudo indicou que as amostras estavam oxidadas, tanto pela presença de produtos da oxidação do colesterol como pelos valores de TBARS. Tal oxidação foi, provavelmente, iniciada no processamento e em condições inadequadas de armazenamento. Os resultados reforçaram a importância da reavaliação dos procedimentos que envolvem o manuseio de pescados, particularmente do camarão salgado-seco, desde a captura até a determinação do tempo de prateleira, no sentido de minimizar as reações oxidativas. / Foods submitted to technological processes that require high temperature present a great potential for production of cholesterol oxides (COPs). Several evidences have indicated that COPs are potentially cytotoxic, atherogenic, mutagenic, and carcinogenic. In sea food, the cholesterol oxidation is favored by the presence of unsaturated fatty acids and high cholesterol levels. The salted-dried shrimp is particularly susceptible to the formation of COPs due to its lipidic composition, the processing and storage conditions. The objective of this work was to determine the occurrence of cholesterol oxidation products and to analyze the lipidic profile in salted-dried shrimp. Fifty samples of salted-dried shrimp were evaluated, and the cholesterol oxides were quantified by high-performance liquid chromatography (HPLC). Cholesterol and COPs (7ß-hydroxycholesterol, 7?- hydroxycholesterol, 7-Ketocholesterol and 25- hydroxycholesterol) were simultaneously analyzed. The fatty acids profile was determined by gas chromatography, and for the evaluation of lipidic oxidation the TBARS method was used. The results indicated that the samples contained: 7ß-OH (34.63-72,56 µg/g), 7?-OH (5.02-12.12µg/g), 7-Keto (7.44-32.68 µg/g) and 25-OH (2.37-22.88 µg/g). These data indicated that 7?-OH was the predominant product. The amount of COPs in the samples varied considerably, ranging from 4.52 to 77.30 µg/g. Regarding to the total cholesterol content and the average concentration of TBARS, the results varied from 73.88 to 247.69 mg/100g, and 0.023 to 1.30 mgMA/Kg, respectively. The fatty acids profile was: 27.48% saturated, 43.90% monounsaturated and 28.61% polyunsaturated. This study indicated that the samples were oxidized, by the presence of COPs and the values of TBARS as well. Such oxidation was probably initiated under inadequate conditions of processing and storage. These results reinforced the need of revaluation of the fishing handling procedures, particularly the salted-dried shrimp, including all the stages - from the capture to the de shelf-life determination, in order to minimize the oxidative reactions.

La production industrielle des silicones génère des effluents aqueux contenant des siloxanes et polysiloxanes, chargés en sels à divers stades de la filière. Dans une perspective de développement durable et pour tenir compte des préoccupations grandissantes autour de l'impact environnemental des rejets industriels, des procédés d'épuration sont recherchés. L'objectif de cette étude est d'évaluer les performances de deux procédés, nanofiltration et oxydation biologique, pour le traitement des effluents aqueux polysiloxaniques. Des expériences de nanofiltration frontale ont été réalisées. Les essais préliminaires avec des solutions synthétiques, mélange d'eau et des siloxanes, ont montré une rétention quasi-totale des siloxanes dans tous les cas testés. Des expériences ont ensuite été menées avec des effluents représentatifs des effluents usines de différentes compositions pour évaluer la robustesse du procédé. Nous avons montré que la nanofiltration réduit efficacement la charge organique globale de l'effluent et réduit significativement la concentration en siloxane. La dilution provoque une diminution de l'abattement du COT et de la rétention des siloxanes mais la qualité du perméat est améliorée. L'augmentation de la salinité réduit la qualité du filtrat. Des essais de micro et ultrafiltration des mêmes effluents ont montré que seule la NF permet d'atteindre un niveau de rétention important des siloxanes. Des essais de nanofiltration tangentielle ont ensuite été réalisés afin de préparer une étude plus complète nécessaire en vue d'une éventuelle l'industrialisation du procédé. La biodégradabilité des siloxanes a été explorée par la méthode Oxitop. Aucune activité biologique provoquée par les siloxanes n'a été enregistrée lors de tests Oxitop réalisés avec des boues activées de stations d'épuration, mais aucun effets toxique ou inhibiteur n'ont été observés non plus. Un bioréacteur à membrane pilote a été alimenté pendant 5 mois au laboratoire avec une solution contenant des siloxanes pour tenter d'acclimater les boues activées aux siloxanes. Les tests Oxitop effectués avec des boues issues du pilote n'ont pas mis en évidence d'acclimatation des micro-organismes aux siloxanes. / Industrial production of silicones generates liquid streams containing siloxanes with high salinity. In a perspective of sustainable development and to consider the growing concern about the environmental impact of industrial residues, we are looking for treatment processes to remove siloxanes in wastewater. This study aims to evaluate the performance of two processes for the treatment of effluents containing siloxanes: nanofiltration and biological oxidation, Frontal nanofiltration experiments were carried out. Firstly, experiments with synthetic solutions (mix of water and siloxanes) have shown almost total siloxane retention in all conditions investigated. Then, experiments were performed with effluents of different compositions representative of industrial ones in order to evaluate the process robustness. It was concluded that nanofiltration is efficient to reduce the total organic content of the effluent and significantly reduces siloxanes concentration. Dilution of the effluent causes a decrease in TOC reduction and siloxanes retention, but the permeate quality is improved. Increasing salinity reduces the filtrate quality. Micro and ultrafiltration of identical effluents confirmed that only NF can reach a high level of siloxane retention. Tangential nanofiltration experiences were performed in order to prepare a more complete study which is necessary to anticipate industrialization of the process. Siloxanes biodegradability was explored by Oxitop method. No biological activity induced by siloxanes was recorded in Oxitop tests with activated sludge from wastewater treatment plant, but no toxic or inhibitory effects were observed. A pilot membrane bioreactor was fed in the laboratory for 6 months with a solution containing siloxanes to try to acclimate activated sludge to siloxane. Oxitop tests performed with sludge taken from the pilot did not show acclimation of microorganisms to siloxanes.

Alimentos submetidos a processos tecnológicos que requerem altas temperaturas apresentam um grande potencial para a produção de óxidos de colesterol (OsC). Inúmeras evidências indicaram que os óxidos de colesterol são potencialmente citotóxicos, aterogênicos, mutagênicos e carcinogênicos. Em pescados, a oxidação do colesterol está favorecida pela presença de ácidos graxos poliinsaturados e altos níveis de colesterol. O camarão salgado-seco é particularmente suscetível à formação de óxidos de colesterol devido a sua composição lipídica, ao seu processamento e as condições de estocagem. O objetivo deste trabalho foi determinar a ocorrência de produtos da oxidação do colesterol e analisar o perfil lipídico em camarão salgado-seco. Analisou-se cinqüenta amostras de camarão salgado-seco por cromatografia líquida de alta eficiência (HPLC), através da qual foram determinados os teores de óxidos de colesterol. O colesterol e os óxidos de colesterol (7ß-OH, 7?-OH, 7-Ceto e 25-OH) foram analisados simultaneamente. O perfil de ácidos graxos foi determinado por cromatografia gasosa e para a avaliação da oxidação lipídica foi empregado o teste de TBARS. Os resultados indicaram que as amostras examinadas continham: 7ß-OH (34,63-72,56 µg/g), 7?-OH (5,02-12,12 µg/g), 7-Ceto (7,44-32,68 µg/g) e 25-OH (2,37-22,88 µg/g), sendo o 7ß-OH o óxido predominante. A quantidade de (OsC) nas amostras analisadas variou consideravelmente (4,52 a 77,30 µg/g). Quanto ao teor de colesterol total e a concentração média de TBARS, os resultados variaram de 73,88 a 247,69 mg/100g e 0,023 a 1,30 mgMA/Kg respectivamente. O perfil de ácidos graxos encontrado foi de 27,48 % saturados, 43,90% monoiinsaturados e 28,61% poliinsaturados. Este estudo indicou que as amostras estavam oxidadas, tanto pela presença de produtos da oxidação do colesterol como pelos valores de TBARS. Tal oxidação foi, provavelmente, iniciada no processamento e em condições inadequadas de armazenamento. Os resultados reforçaram a importância da reavaliação dos procedimentos que envolvem o manuseio de pescados, particularmente do camarão salgado-seco, desde a captura até a determinação do tempo de prateleira, no sentido de minimizar as reações oxidativas. / Foods submitted to technological processes that require high temperature present a great potential for production of cholesterol oxides (COPs). Several evidences have indicated that COPs are potentially cytotoxic, atherogenic, mutagenic, and carcinogenic. In sea food, the cholesterol oxidation is favored by the presence of unsaturated fatty acids and high cholesterol levels. The salted-dried shrimp is particularly susceptible to the formation of COPs due to its lipidic composition, the processing and storage conditions. The objective of this work was to determine the occurrence of cholesterol oxidation products and to analyze the lipidic profile in salted-dried shrimp. Fifty samples of salted-dried shrimp were evaluated, and the cholesterol oxides were quantified by high-performance liquid chromatography (HPLC). Cholesterol and COPs (7ß-hydroxycholesterol, 7?- hydroxycholesterol, 7-Ketocholesterol and 25- hydroxycholesterol) were simultaneously analyzed. The fatty acids profile was determined by gas chromatography, and for the evaluation of lipidic oxidation the TBARS method was used. The results indicated that the samples contained: 7ß-OH (34.63-72,56 µg/g), 7?-OH (5.02-12.12µg/g), 7-Keto (7.44-32.68 µg/g) and 25-OH (2.37-22.88 µg/g). These data indicated that 7?-OH was the predominant product. The amount of COPs in the samples varied considerably, ranging from 4.52 to 77.30 µg/g. Regarding to the total cholesterol content and the average concentration of TBARS, the results varied from 73.88 to 247.69 mg/100g, and 0.023 to 1.30 mgMA/Kg, respectively. The fatty acids profile was: 27.48% saturated, 43.90% monounsaturated and 28.61% polyunsaturated. This study indicated that the samples were oxidized, by the presence of COPs and the values of TBARS as well. Such oxidation was probably initiated under inadequate conditions of processing and storage. These results reinforced the need of revaluation of the fishing handling procedures, particularly the salted-dried shrimp, including all the stages - from the capture to the de shelf-life determination, in order to minimize the oxidative reactions.