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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Stanovení vybraných kovů v ovocných kompotech / Determination of selected metals in fruit compotes

Hauerlandová, Petra January 2012 (has links)
This diploma thesis deals with the determination of some metals in fruit compotes packed in cans. There is described the production of fruit compotes and metal packaging legislation relating to the studied issues, the possibility of contamination of food packaging components, packaging corrosion, metal migration from packaging and techniques used for the analysis of metals in the food industry. Concentrations of metals in 14 different fruit compotes from a commercial network in the Czech Republic were determined by ICP-MS technique in the experimental part. Concentrations of metals were detected only in the juice of stewed fruit, because the juice is in direct contact with the surface of packaging, and metals are transferred first into it. The measured values were compared with the maximum permissible levels of metals in fruit compote determined by European legislation. In some cases there were found higher concentrations of tin, but other metals did not exceed the allowable amounts. Concentrations of metals in the compote varied depending on the kind of compote, which could be due to a different chemical composition of compotes depending on the origin of food and process of the fruit production, or a different cans coating material.
2

Human health implications of exposure to xenoestrogens from food

Thomson, Barbara Mary January 2005 (has links)
This thesis aims to assess the human health impact of exposure to estrogenic compounds from the diet. A multi-disciplinary approach is taken to address various aspects of this issue. An introduction to xenoestrogens, including international research priorities, wildlife and human health effects, mechanisms of action, structure activity relationships and additivity of estrogenic effects is provided as background information. An assessment of exposure to a range of naturally occurring and synthetic estrogenic compounds found in food is derived in Chapter 2. The assessment combines new and existing data on food concentration, food consumption and serum levels for each xenoestrogen. Exposure is combined with relative estrogenic potency data from published bioassasy data to estimate risk relative to normal circulating levels of estradiol. Assuming additivity of xenoestrogens, for an average New Zealand male and for post-menopausal women, xenoestrogens in the diet contribute an additional 12-90% of estrogenicity above normal circulating levels. For a pre-menopausal female, the contribution from the diet represents in the order of an additional 2%. The level of exposure determined in this thesis would seem to be of pharmacological relevance, especially for men with low levels of estrogen and for post-menopausal women. Bisphenol A (BPA) is an important monomer used in the manufacture of epoxy resins for internal food can linings. A survey of the BPA content of a range of 80 canned foods available to the New Zealand consumer was undertaken and the results used in the exposure and risk assessments. BPA was detected in all foods analysed except soft drinks, at concentrations ranging from <10-29 µg/kg, except for individual samples of tuna, corned beef and coconut cream that were 109, 98 and 191 µg/kg respectively. None, of over 4000 individual exposure scenarios, exceeded the temporary Tolerable Daily Intake (TDI) of 10 µg/kg body weight per day set by the Scientific Committee on Food in 2002. Intestinal microflora influence the bioavailability of the naturally occurring xenoestrogens genistein and daidzein that contribute significantly to total estrogenicity from the diet. The degradation of genistein and daidzein by the faecal microfloral of 5 human subjects was variable and unpredictable between individuals and within an individual. These findings have important implications for the promotion and prescription of soy foods and supplements for disease prevention and health benefits. The "yeast assay" is one of a number of methods available to measure estrogenicity. This assay was established and validated. In utero exposure to estrogenic compounds at critical periods of sexual differentiation and endocrine development may imprint for health effects observed later in life. Placental transfer of estrogenicity, from 17β-estradiol was studied using the human placental perfusion model and the yeast assay. The placenta provides a protective barrier to the transfer of estrogenicity. Experiments with genistein showed that 5-15% placental transfer occurred, suggesting that in utero exposure might be in the order of 10% of maternal exposure. The thesis concludes with consideration of a genomic approach to substantiate, or refute, the mechanistic link between exposure to xenoestrogens and claimed human health effect. Such an approach offers exciting opportunity to clarify the mode of action of the synthetic versus the naturally occurring xenoestrogens, to confirm or dispute additivity of effect that is an important premise of the exposure assessment, to identify key genes involved in the many possible health effects and thence risk to the individual from dietary exposure to xenoestrogens.
3

Caractérisation et écologie microbienne de lignes de production de conserves / Characterization and microbial ecology of canned food process lines

André, Stéphane 16 June 2015 (has links)
Si les flores contaminantes représentent la plupart du temps, dans les conserves, un risque industriel aujourd'hui maitrisé, la flore d'altération, de par sa résistance importante à la température, continue à constituer une cause de pertes économiques majeures. Pourtant cette dernière restait cependant peu caractérisée. En s'appuyant sur les travaux réalisés ces dernières années au sein de l'unité de microbiologie EMaiRIT'S du CTCPA (unité d'Expertise dans la Maitrise du Risque Industriel en Thermorésistants Sporulés du Centre Technique de la Conservation des Produits Agricoles), les principaux objectifs de cette thèse ont été (i) d'identifier et caractériser, en vue de sa maitrise ultérieure, la flore d'altération sporulante (ii) d'identifier l'origine de ces flores dans les conserveries et enfin (iii) de déterminer des moyens de maitrise.Pour cela, un état des lieux des bactéries sporulées d'altération des conserves a été effectué avec la collaboration de 122 conserveries sur plus de 10 ans en France. Cette caractérisation des espèces altérantes a permis l'élaboration d'un outil de biologie moléculaire (SporeTraQTM) afin d'identifier rapidement ces germes ou de pouvoir les détecter au sein d'une population complexe. En parallèle, l'amélioration de la connaissance de la thermorésistance de ces espèces, principale caractéristique de la flore sporulante, a été menée. A ce paramètre, il a été associé une relation avec la chimio résistance des spores. Identifiée, nous avons cherché à localiser cette flore d'altération au sein des usines à l'aide de plusieurs campagnes de prélèvements sur différents légumes. Au final, la flore spécifique du procédé de fabrication des conserves a été identifiée, caractérisée et localisée en vue d'améliorer la maitrise du risque microbien soit par une maitrise des contaminations et/ou un nettoyage plus performant (localisation au niveau d'étapes unitaires, efficacité de molécules sporicides) soir par un barème optimisé (en relation avec la thermorésistance). De plus, ce travail a été conduit au sein d'une approche bénéfice/risque représentant le futur de l'évolution des procédés agro-alimentaires associant amélioration de la qualité nutritionnelle et maintien de la maitrise sanitaire. Cette thèse s'appuie sur 5 publications de rang A. / Microbial contaminants of safety concern represent most of time, in canned food, an industrial risk which is well mastered. However, the spoilage flora, due to its high heat resistance, is responsible for major economic losses. Nevertheless, these bacteria remained poorly characterized. Based on the works realized during last 10 years within the EMaiRIT'S unit of microbiology of the CTCPA (expertise unit of the French Technical Center of the Preservation of Food, focused on Management of Industrial Risk liked to Heat Resistant Spores), the main objective of this thesis were: i) to identify and to characterize, with the aim of its later control, the spoilage spore forming bacteria florae ii) to identify the origin of these florae in canning factories and finally iii) to determine ways of control.For that purpose, a current inventory of spore forming bacteria in spoiled canned food was made with the cooperation of 122 canning factories over more than 10 years in France. This characterization of the spoilage species allowed the elaboration of a molecular biology tool (SporeTraQTM) for quick identification of these germs or their detection within a complex population. In parallel, the improvement of the knowledge about the heat resistance of these species, main characteristic of the spores, was led. In addition, the chemical resistance of spores was investigated. When identified, we tried to localize these spores on canning factories lines, with several sampling plans, on various vegetables. At the end, the specific spore forming bacteria related to the industrial canning process was identified, characterized and localized, allowing to improve the microbial risk control either by a more efficient cleaning, and through optimized process schedules. Furthermore, this work was driven within a benefic / risk approach representing the future of the food-processing evolution with improvement of the nutritional quality and the preservation of the sanitary control.This thesis leans on 5 publications of rank A.
4

Human health implications of exposure to xenoestrogens from food

Thomson, Barbara Mary January 2005 (has links)
This thesis aims to assess the human health impact of exposure to estrogenic compounds from the diet. A multi-disciplinary approach is taken to address various aspects of this issue. An introduction to xenoestrogens, including international research priorities, wildlife and human health effects, mechanisms of action, structure activity relationships and additivity of estrogenic effects is provided as background information. An assessment of exposure to a range of naturally occurring and synthetic estrogenic compounds found in food is derived in Chapter 2. The assessment combines new and existing data on food concentration, food consumption and serum levels for each xenoestrogen. Exposure is combined with relative estrogenic potency data from published bioassasy data to estimate risk relative to normal circulating levels of estradiol. Assuming additivity of xenoestrogens, for an average New Zealand male and for post-menopausal women, xenoestrogens in the diet contribute an additional 12-90% of estrogenicity above normal circulating levels. For a pre-menopausal female, the contribution from the diet represents in the order of an additional 2%. The level of exposure determined in this thesis would seem to be of pharmacological relevance, especially for men with low levels of estrogen and for post-menopausal women. Bisphenol A (BPA) is an important monomer used in the manufacture of epoxy resins for internal food can linings. A survey of the BPA content of a range of 80 canned foods available to the New Zealand consumer was undertaken and the results used in the exposure and risk assessments. BPA was detected in all foods analysed except soft drinks, at concentrations ranging from <10-29 µg/kg, except for individual samples of tuna, corned beef and coconut cream that were 109, 98 and 191 µg/kg respectively. None, of over 4000 individual exposure scenarios, exceeded the temporary Tolerable Daily Intake (TDI) of 10 µg/kg body weight per day set by the Scientific Committee on Food in 2002. Intestinal microflora influence the bioavailability of the naturally occurring xenoestrogens genistein and daidzein that contribute significantly to total estrogenicity from the diet. The degradation of genistein and daidzein by the faecal microfloral of 5 human subjects was variable and unpredictable between individuals and within an individual. These findings have important implications for the promotion and prescription of soy foods and supplements for disease prevention and health benefits. The "yeast assay" is one of a number of methods available to measure estrogenicity. This assay was established and validated. In utero exposure to estrogenic compounds at critical periods of sexual differentiation and endocrine development may imprint for health effects observed later in life. Placental transfer of estrogenicity, from 17β-estradiol was studied using the human placental perfusion model and the yeast assay. The placenta provides a protective barrier to the transfer of estrogenicity. Experiments with genistein showed that 5-15% placental transfer occurred, suggesting that in utero exposure might be in the order of 10% of maternal exposure. The thesis concludes with consideration of a genomic approach to substantiate, or refute, the mechanistic link between exposure to xenoestrogens and claimed human health effect. Such an approach offers exciting opportunity to clarify the mode of action of the synthetic versus the naturally occurring xenoestrogens, to confirm or dispute additivity of effect that is an important premise of the exposure assessment, to identify key genes involved in the many possible health effects and thence risk to the individual from dietary exposure to xenoestrogens.
5

Estudio de pre-factibilidad para la instalación de una planta productora de mango (Mangifera indica) en almíbar para el mercado de Lima Metropolitana

Cárdenas-Palomino, Gabby-Alexandra, Ortiz-Caja, José-Enrique January 2016 (has links)
El presente estudio tiene como objetivo determinar la pre-factibilidad de la instalación de una planta procesadora de conservas de mango en almíbar a partir de la evaluación de la viabilidad de mercado, tecnológica, económica y financiera. Para la elaboración de conservas se utilizará como materia prima principal el mango nacional de gran calidad y reconocimiento. Esta investigación resulta relevante debido a que en los últimos años el precio de las conservas se ha ido incrementando debido a la creciente demanda existente por estos productos. Otro aspecto importante para la relevancia de esta investigación es que se le dará valor agregado al mango peruano. / Trabajo de investigación
6

Estudo da interação produto embalagem em folha-de-flandres aplicada a polpa de cupuaçu (Theobroma grandiflorum) / Study of product tinplate package interaction applied on cupuaçu pulp (Theobroma grandiflorum)

Felipe, Augusta Maria Paulain Ferreira 12 January 2008 (has links)
Orientador: Celia Marina de Alvarenga Freire / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-12T11:33:25Z (GMT). No. of bitstreams: 1 Felipe_AugustaMariaPaulainFerreira_D.pdf: 5466222 bytes, checksum: 02a424089af5fbce85c2746574716881 (MD5) Previous issue date: 2008 / Resumo: As características das latas em folha-de-flandres utilizadas no acondicionamento da polpa de cupuaçu foram estudadas com o objetivo de avaliar a interação produto/embalagem uma vez que, este fruto apresenta elevada acidez e por sua produção ser expressiva na Amazônia torna-se necessário a avaliação dos fatores que possam indicar a adequação deste tipo de embalagem à polpa. A lata em folha-de-flandres apresenta vantagens de uso tais como baixo peso, hermeticidade, boa resistência mecânica, praticidade, conveniência de transporte e utilização pelo consumidor. No entanto, a ocorrência de interações entre o material da lata e o produto pode causar perda de qualidade e perda de propriedades físicas e mecânicas da lata. A técnica de Espectroscopia de Impedância Eletroquímica foi aplicada para verificar os aspectos da interação embalagem e produto durante o período de estocagem de 300 dias a temperatura de 32º C. Foram analisadas as características físicas das embalagens, assim como os teores de ferro e estanho dissolvidos, propriedades físico-químicas microbiológicas e sensoriais no produto. Os resultados mostraram que a associação da técnica de espectroscopia de impedância eletroquímica, espectrometria de emissão atômica microscopia de varredura e as demais utilizadas, proporcionaram um entendimento quanto ao desempenho do verniz utilizado, sugerindo que, a aplicação do verniz na região de solda do corpo das embalagens constituiu-se em um fator determinante para a perda das características protetivas do revestimento. / Abstract: The characteristics of the tinplate cans used in the packaging of cupuaçu pulp, were studied aiming the evaluation of the interaction product/packaging, provided that this fruit has high acidity and its has a massive production in the Amazon region, it becomes necessary the evaluation of the factors that may indicate the adequacy of this type of packaging to the pulp. The tinplate can has advantages in usage such as low weight, hermeticism, high mechanical strength, practicality, and transport and customer-usage conveniences. However, the occurrence of interactions between the product and the can material may cause quality loss of the product, besides physical and mechanical properties loss of the can. The technique of electrochemistry impedance spectroscopy was applied to verify aspects of the interaction between the package and product during a 300-day storage period at a temperature of 32o C. Physical characteristics of the cans, levels of dissolved iron and tin, besides physical, chemical, microbiological, and sensory properties of the product were analyzed. The results showed that the combination of the electrochemical impedance spectroscopy technique, atomic emission spectrometry, scanning microscopy and other used provided an understanding on the performance of the varnish used, suggesting that its application on the welding region of the packaging is a determinant factor to the loss of protective features of the coating. / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

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