Os objetivos deste trabalho foram determinar o tipo de corte, a temperatura de armazenamento e os materiais de embalagem que proporcionam melhor manutenção da qualidade de melão minimamente processado. No primeiro experimento foram testados dois tipos de corte (cubo e fatia) e três temperaturas de armazenamento (3º, 6º e 9ºC). No segundo experimento os melões minimamente processados em cubos foram acondicionados em diversos materiais de embalagem e armazenados à 3ºC. Os materiais de embalagem foram: AFG: filme poliolefínico com antifog da DuPont 15mm; HP: filme poliolefínico da DuPont 15mm; PD-900: filme poliolefínico da Cryovac 58mm; PEBD: filme de polietileno de baixa densidade 87mm; PP: filme de polipropileno 52mm; BB-200: filme multicamada da Cryovac 65mm e PET: embalagem rígida de polietileno tereftalato. No terceiro experimento foi testado a injeção da mistura gasosa (5% O2 + 20% CO2 + 75% N2) em 3 diferentes materiais de embalagem: BB-200: filme multicamada da Cryovac 65mm; PBC: filme poliolefínico Probag Conservax 64mm e PP: filme de polipropileno 52mm e o armazenamento foi realizado à 3ºC. Melões acondicionados em embalagem com perfurações foram utilizados como controle. Todos os materiais de embalagem utilizados neste trabalho tiveram sua taxa de permeabilidade ao O2 e CO2 determinadas. No primeiro experimento foram determinadas as características físico-químicas e sensoriais a cada 3 dias por um período de 9 dias. No segundo experimento foi realizado um monitoramento da composição gasosa do espaço livre das embalagens durante 8 dias e no 9º dia avaliou-se as características físico-químicas e sensoriais. No terceiro experimento determinou-se as características físico-químicas, sensoriais, microbiológicas e a composição gasosa do espaço livre das embalagens a cada 3 dias durante 12 dias. Os tipos de corte estudados não influenciaram a qualidade do melão. O armazenamento à 3ºC apresentou maior eficiência na manutenção da firmeza e das características sensoriais. Os filmes AFG e HP apresentaram alta taxa de permeabilidade ao O2 e CO2 e praticamente não possibilitaram a modificação da atmosfera. Os filmes PD-900, PEBD, PP e BB-200 apresentaram as menores taxas de permeabilidade aos gases, porém a modificação da atmosfera do interior destes filmes foi pequena. A embalagem rígida, apesar de alta taxa de permeabilidade aos gases, promoveu maior modificação da atmosfera, provavelmente devido à menor relação área de permeação da embalagem/massa de melão, porém o equilíbrio dos gases nesta embalagem só ocorreu após o 6º dia. Em todos os filmes as características físico-químicas foram mantidas, enquanto as características sensoriais foram mantidas apenas nos melões em embalagem de PET. A injeção de 5% de O2 + 20% CO2 + 75% N2 nos filmes BB-200, PP e PBC teve pouca influência nas características sensoriais e físico-química dos melões. Verificou-se que a injeção da mistura gasosa (independente da embalagem) controlou o crescimento de microorganismos e que os melões do controle apresentaram alta contagem de bactérias mesófilas a partir do 9º dia. / The objective of this work was to determine the cut type, storage temperature and packaging materials for better quality maintenance in minimally processed melons. In the first experiment two cut types (cube and slice) and three storage temperatures (3, 6 and 9ºC) were evaluated. In the second experiment minimally processed melon in cubes were wrapped in several packaging materials with passive modified atmosphere and stored at 3ºC. The packaging materials were: AFG: DuPont polyolephinic antifog film 15mm; HP: DuPont polyolephinic film 15 mm, PD-900: Cryovac polyolephinic film 58 mm, PEBD: low density polyethylene film 87 mm, PP: polypropylene film 52 mm; BB-200: Cryovac multlayer film 65mm and PET: rigid polyethylene terephthalate tray. In the third experiment the melons were wrapped in several packaging materials with active modified atmosphere (5% O2 + 20% CO2 + 75% N2) and stored at 3ºC. The packaging materials were: BB-200: Cryovac multlayer film 65mm; PBC: Probag Conservax polyolephinic film 64mm and PP: polypropylene film 52 mm. Melons wrapped in packaging with perforations were used as control. The gas permeability of each film was determined. In the first experiment physical-chemical and sensorial characteristics were determined each 3 days during 9 days. In the second experiment gases composition analyses were monitoring during 8 days and in the 9 th day physical-chemical and sensorial characteristics were determined. In the third experiment physical-chemical, sensorial and microbiological characteristics and the gas composition were evaluated each 3 days during 12 days. Cut types did not influence the melon quality. The storage at 3ºC had higher efficiency maintaining firmness and sensorial characteristics. Films AFG and HP had high rate permeability to O2 and CO2 and practically did not allow atmosphere modification. Films PD-900, PEBD, PP and BB-200 had the smallest rate permeability to gases, even when the modification of the interior atmosphere of these films was small. The rigid packaging despite high permeability rate to the gases, promoted large atmosphere modification, probably due to the smallest relationship permeation area of the packaging: melon mass, but gases balance happened only after the 6 th day. The physical-chemical characteristics were maintained in all films, while the sensorial characteristics were maintained only the PET packing. Modified atmosphere by injection of 5% of O2 + 20% CO2 + 75% N2 showed low influence in the physical-chemical and sensorial characteristics. It was found that the gaseous mixture (independent of the packaging) restricted the microorganisms growth while control showed high mesophilics bacteria count after the 9 th day.

O mel de abelhas é um produto biológico muito complexo, cuja composição varia notavelmente em função da flora visitada pelas abelhas e das condições climáticas e edáficas da região onde foi produzido. Este trabalho teve como objetivos confrontar os resultados das análises físico-químicas entre as amostras de méis produzidos em diferentes localidades do Brasil por Apis mellifera e por Meliponíneos e investigar se o mel produzido por essas abelhas nas suas diferentes regiões de origem apresenta níveis toleráveis de contaminantes inorgânicos. Para tanto, foram avaliadas 56 amostras de méis de A. mellifera e 56 amostras de méis de Meliponíneos dos Estados da Bahia, Minas Gerais, Mato Grosso do Sul, Paraíba, Piauí, Paraná, Santa Catarina e São Paulo, em relação aos seguintes parâmetros: umidade, atividade de água, viscosidade, pH, acidez livre, índice de formol, açúcares redutores, sacarose aparente, teor de cinzas, cor, condutividade elétrica, hidroximetilfurfural, atividade diastásica e metais (Hg+2, Zn+2, Cd+2, Pb+2 e Cu+2). Foi utilizada a técnica de Voltametria de Redissolução Anódica de Pulso Diferencial (DPASV) para quantificar os metais, e métodos convencionais e próprios para mel nas demais análises. Os resultados mostraram que a legislação atual, referente ao mel de A. mellifera, não é adequada para os parâmetros açúcares redutores, umidade e atividade diastásica de algumas espécies de Meliponíneos. Pôdese concluir que as espécies A. mellifera, Tetragonisca angustula, Melipona quadrifasciata, M. scutellaris, M. mandacaia, M. fasciculata, M. subnitida produzem méis com características físico-químicas diferentes e próprias de cada uma delas. Para todas as espécies avaliadas, os níveis de contaminantes inorgânicos encontrados nos méis foram toleráveis à saúde humana. Os méis produzidos por A. mellifera apresentaram variações nas características físico-químicas: atividade de água, viscosidade, acidez livre, índice de formol, açúcares redutores, condutividade elétrica, hidroximetilfurfural, atividade diastásica e o mineral zinco, em função dos diferentes locais onde foram produzidos. / The honeybee is a very complex biological product, whose composition varies markedly depending on the plant visited by the bees and the weather and soil conditions in the region where it was produced. This study aimed to compare the results of physicochemical analysis between the samples of honey produced in different locations in Brazil by Apis mellifera and Meliponid and to investigate whether honey produced by these bees, in different regions of origin, has tolerable levels of inorganic contaminants. To this end, we evaluated 56 samples of honey from A. mellifera and 56 samples of honey from Meliponid from the states of Bahia, Minas Gerais, Mato Grosso do Sul, Paraíba, Piauí, Paraná, Santa Catarina and São Paulo, for the following parameters: moisture content, water activity, viscosity, pH, free acidity, formol index, reducing sugars, apparent sucrose, ash content, color, electrical conductivity, hydroxymethylfurfural, diastase activity and metals (Hg+2, Zn+2, Cd+2, Pb+2 and Cu+2). Differential Pulse Anodic Stripping Voltammetry (DPASV) technique was used to quantify the metals, and, to the other analysis, conventional and suitable methods for honey were used. The results showed that the current legislation, referring to the honey of A. mellifera, is not appropriate for the parameters reducing sugars, moisture content and diastase activity of some species of Meliponid. It was concluded that the species A. mellifera, Tetragonisca angustula, Melipona quadrifasciata, M. scutellaris, M. mandacaia, M. fasciculata, M. subnitida produce honeys with different and specific physico-chemical characteristics. For all species studied, levels of inorganic contaminants found in honey were tolerable to human health. The honey produced by A. mellifera showed variations in physicochemical water activity, viscosity, free acidity, formol index, reducing sugars, electrical conductivity, hydroxymethylfurfural, diastase activity and the mineral zinc, depending on the different locations where they were produced.

Made available in DSpace on 2016-04-28T14:58:57Z (GMT). No. of bitstreams: 1 2006-Nilber Kenup Hernandes.pdf: 2004617 bytes, checksum: 031cfe61d7bb727196791c4404d4e145 (MD5) Previous issue date: 2006-12-12 / This study was aimed at investigating the effects of low-dose gamma irradiation on shelf-life extension and phytosanitary safety of minimally processed red beet with basis on physicochemical; microbiological; chemical and sensory analyses. The samples (Beta vulgaris ssp. vulgaris L.), Early Wonder cultivar, were cultivated in the experimental area of the Horticulture Sector of the Departamento de Fitotecnia of the Instituto de Agronomia, Universidade Federal Rural do Rio de Janeiro, Serop?dica, RJ, as part of two experiments performed during the second semester of 2005. In each experiment, 1200 plants (40 per linear meter of terrain) were sowed. Physicochemical analyses (fresh mass; length; average diameter and total soluble solids) of the edible part of the red beets (their tuberous roots) were periodically carried out in order to assess the most appropriate time for harvest by monitoring the development of the plants. Those times were found to be 104 and 73 days after transplanting, respectively. The harvested edible part of the roots were minimally processed and separated in two groups: (1) gamma irradiated (with doses of 0.5; 1.0 and 1.5 kGy) and (2) non-irradiated (control). All samples were stored at 8 ?C. Microbiological analyses were performed during the storage period (22 and 21 days, for experiments 1 and 2, respectively) in order to evaluate the phytosanitary quality of the samples (Salmonella sp.; coliforms and total count of mesophilic aerobic and lactic acid bacteria). The samples irradiated with 1.0 and 1.5 kGy were found to remain appropriate for consumption for 21 days, as compared to only 7 days for the control. Monitoring of chemical composition was also performed and included the determination of saccharose; glucose; fructose and vitamins B1 and B2. No difference was found between the concentrations of those vitamins in irradiated and control samples at the end of the storage period, whereas significant changes in sugar contents were detected independently of the dose. In addition, physicochemical analyses investigated the evolution of pH; total acidity; total soluble solids and ascorbic acid throughout storage. Samples from experiment 2 were also subjected to sensory analyses for overall appearance and aroma at 4 different post-irradiation times. The results indicated that the samples irradiated with 1.0 and 1.5 kGy remained good for consumption for 20 days. Therefore it can be concluded that the application of those doses extended the shelf life of the samples without harming their nutritional and sensory quality. Finally, the results indicate that the dose of 1.0 kGy is the most appropriate for the conservation of red beet among those tested. / O objetivo deste estudo foi avaliar, por meio de an?lises microbiol?gicas; qu?micas; f?sicoqu?micas e sensoriais, os efeitos de baixas doses de radia??o gama na extens?o da vida ?til e na garantia da seguran?a microbiol?gica da beterraba vermelha (Beta vulgaris ssp. vulgaris L.), cultivar Early Wonder minimamente processada. Dois experimentos foram realizados, em condi??es de campo, em ?rea experimental do Setor de Horticultura do Departamento de Fitotecnia do Instituto de Agronomia da UFRRJ, Serop?dica, RJ, no segundo semestre de 2005. Em cada experimento, foram transplantadas 1200 mudas (40 por metro linear de canteiro). Foram realizados ensaios f?sico-qu?micos (massa fresca; comprimento; di?metro m?dio e teor de s?lidos sol?veis totais) da parte comest?vel (por??o tuberosa) da beterraba, para avalia??o do est?gio de desenvolvimento das plantas, visando ? determina??o do ponto ideal de colheita. As beterrabas dos experimentos 1 e 2 foram colhidas 104 e 73 dias ap?s o seu transplante, respectivamente. As partes tuberosas foram minimamente processadas e separadas em 2 grupos de amostras: controle (n?o irradiadas) e irradiadas (0,5; 1,0 e 1,5 kGy), sendo que todas foram armazenadas a 8 ?C. Avalia??es realizadas ao longo do per?odo de armazenamento (22 e 21 dias, nos experimentos 1 e 2, respectivamente) permitiram monitorar a: qualidade microbiol?gica (Salmonella sp.; coliformes; contagem total de bact?rias aer?bias mes?filas e contagem de bact?rias l?ticas); a composi??o qu?mica (determina??o dos teores de: sacarose; glicose e frutose e vitaminas B1 e B2) e as propriedades f?sico-qu?micas (pH; acidez total titul?vel; teor de s?lidos sol?veis totais e teor de ?cido asc?rbico). As amostras do experimento 2 foram tamb?m submetidas a an?lises sensoriais (apar?ncia e aroma) em quatro ocasi?es ap?s a irradia??o. Os resultados das an?lises microbiol?gicas indicaram que somente as amostras irradiadas com 1,0 e 1,5 kGy mantiveram-se pr?prias para o consumo por 21 dias, enquanto que as n?o irradiadas apresentaram vida ?til inferior a 7 dias. Ao fim do per?odo de avalia??o, n?o foi observada diferen?a entre os teores das vitaminas B1 e B2 das amostras irradiadas em rela??o ?s de controle. Os teores dos a??cares, por outro lado, sofreram altera??es significativas ao longo do tempo, independentemente das doses aplicadas. Em contraste, n?o foram constatadas altera??es indesej?veis nas propriedades f?sico-qu?micas ocasionadas pela irradia??o. Os resultados das an?lises sensoriais indicaram que as amostras irradiadas com doses de 1,0 e 1,5 kGy mantiveram-se dentro dos padr?es de aceitabilidade por 20 dias. Consistentemente, verificou-se que a aplica??o dessas doses foi eficaz para estender a vida ?til, sem prejudicar a qualidade nutricional ou sensorial das amostras. Finalmente, conclui-se que a dose de 1,0 kGy mostrou-se como a mais apropriada, dentre aquelas estudadas, para a irradia??o de beterraba vermelha minimamente processada.

Made available in DSpace on 2016-04-28T20:12:47Z (GMT). No. of bitstreams: 1 2006-Fabio Sampaio Vianna Ramos Filho.pdf: 1341377 bytes, checksum: 3765a981914fbb9e6f21fb33b9857a02 (MD5) Previous issue date: 2006-08-28 / This dissertation involves a study on the bovine meat chain based on data collecting of the last years leading to an analysis about its functioning and a general view on its dynamics. The behavior of the bovine meat consumer market both worldwide and in Brazil tends to follow a new demand pattern. The initial premise is about the new demand patterns focusing on the issues of food quality and food security. From this premise it is believed that the organic food market presents a growth due to the new demands for quality food consumption. The aim of this dissertation is to study the process of building new production and consumption networks of bovine meat, following the hypothesis that recent transformations in the meat market are triggered by a consumption demand based on strict regulations and criteria of quality and food security. The development of organic cattle is based on control protocols as the certification for organic food and of other legal and control tools demanded by the meat market. It is presupposed that the organic meat production meets the requirements on demand patterns indicated by the market. The question on food security and quality is discussed in this dissertation and a new debate is opened on the complexity influence of the chain dynamics on consumption demand. This dissertation uses the principles of the New Economic Sociology to build a theoretical discussion on the dynamics of the meat chain and the consumption demand. Based on contemporary authors, the convention theory and the socio-technical theories are used to analytically explore the relationship and the behavior of the agents involved. We try to understand the tendency of the new forms of chain organization through an analysis on social and economic relations among the agents of the different involved segments. The new forms are represented by networks and alliances built around targets which are meant to take care of the consuming market in a direct way using a differentiated product and a mark that adds economic, social and environmental values. The results show that in order to analyze the potential market, it is necessary to analytically explore the consumption dynamics. The theoretical basis used in this dissertation is not enough to deepen the analysis on the issues of consumption dynamics. The new ways of organization of the organic food chain uses a principle from the theory of conventions which defines the rules starting from the relationship between the actors and that this collective process contributes to the construction of new technological and quality patterns. The dissertation concludes that it is necessary to deepen the studies and analyses of the new organic food networks and alliances by introducing theoretical principles that may help the understanding of this new initiative on the light of the sociology of consumption. / A disserta??o aborda a cadeia da carne bovina por meio de um levantamento de dados dos ?ltimos anos, permitindo uma an?lise sobre seu funcionamento e uma vis?o geral sobre a sua din?mica. O comportamento do mercado consumidor de carne bovina no mundo e no Brasil indica tend?ncias para um novo padr?o de demanda. A premissa inicial ? sobre os novos padr?es de demanda com enfoque na quest?o da qualidade e da seguran?a do alimento. A partir desta premissa, parte-se do pressuposto de que o mercado de alimentos org?nicos apresenta um crescimento movido as novas demandas de consumo por alimentos de qualidade. O objetivo da disserta??o ? estudar o processo da constru??o de novas redes de produ??o e de consumo de carne bovina, com a hip?tese de que as recentes transforma??es do mercado de carnes s?o movidas por uma demanda de consumo, baseada em r?gidas normas e crit?rios de qualidade e seguran?a alimentar. O desenvolvimento da pecu?ria org?nica ? pautado em protocolos de controle como a certifica??o dos alimentos org?nicos e dos demais instrumentos legais e de controle exigidos nos mercados de carnes. A priori, a produ??o de carne org?nica atende ?s exig?ncias sobre os padr?es da demanda apontados pelo mercado. A quest?o da qualidade e da seguran?a do alimento ? discutida na disserta??o e abre-se um debate sobre a influ?ncia da complexidade na din?mica da cadeia sobre a demanda de consumo. A disserta??o busca nos princ?pios da Nova Sociologia Econ?mica uma base para a discuss?o te?rica sobre a din?mica da cadeia da carne e a demanda de consumo. A teoria das conven??es e a teoria s?cio-t?cnicas, por meio dos autores contempor?neos, s?o recorridas para explorar analiticamente as rela??es e os comportamentos dos agentes envolvidos. Procura-se entender a tend?ncia das novas formas de organiza??o da cadeia por meio de uma an?lise sobre as rela??es sociais e econ?micas entre os agentes dos diversos segmentos envolvidos. As novas formas s?o representadas por redes e alian?as constru?das em torno de objetivos voltados a atender o mercado consumidor de forma direta, com um produto diferenciado e uma marca que agregue valores econ?micos, sociais e ambientais. Os resultados demonstram, que para realizar uma an?lise do potencial de mercado ? necess?rio explorar de forma anal?tica a din?mica de consumo. As bases te?ricas consideradas na disserta??o n?o s?o suficientes para aprofundar a an?lise nas quest?es da din?mica de consumo. As novas formas de organiza??o na cadeia da carne org?nica buscam na teoria das conven??es, um embasamento de que as regras s?o definidas a partir do relacionamento entre os atores e que este processo coletivo contribui para a constru??o de novos padr?es tecnol?gicos e de qualidade. A disserta??o conclui que ? necess?rio aprofundar os estudos e an?lises das novas redes e alian?as de carne org?nica, introduzindo bases te?ricas que colaborem para o entendimento sobre estas novas iniciativas no enfoque da sociologia do consumo.

This thesis addresses the problem healthcare facilities are having in maintaining proper food temperatures while transporting meals to patients after food has left the kitchen area. Induction heat has been a known method for generating heat for many years. The commercial food industry currently uses this technology, which is beginning to appear in the residential sector as well because of developments made by manufacturers. This study focuses on the top commercial brand models of induction heaters and the supporting materials currently used to create heat sources to maintain food temperatures in hospitals and long term care facilities. The research in this thesis includes data recorded from 6,000 total induction cycles from the 3 leading induction heating models. The focus of the research was to gather data concerning the models’ reliability to consistently create the intended inducement of radio frequency waves as well as deliver consistent temperature reactions from the recorded induction cycles. There were 18,000 temperature data points recorded during different time intervals for each of the induction cycles for the entire study. The results indicate the current technology not only is reliable in creating inductions fields but also in delivering consistent temperatures in the supporting materials being heated. Induction has been used historically as a fast heating process to treat large metal products and requires no direct contact to create or transfer heat to a surface (Rudnev et al., 2003). The speed and consistent application of heat transfer that has been derived by modern manufacturing induction practices makes it a logical use of existing technology to be applied in maintaining temperatures of food in the healthcare market. However, the focus for commercial equipment manufacturers has been to market products that can consistently maintain desired food temperatures, particularly in the healthcare industry. Traditionally, heating foods was accomplished by physically applying heat to areas where food is stored, in order to reach a certain temperature, and then working to deliver that food to the patient in a timely manner or before it cooled to temperatures that would be deemed too cold for consumption. If the food was too cold, before it was served to the patient, then it was typically micro waved in order to reheat the food. However, reheating food in the microwave is not only detrimental, but it also degrades food quality, texture, and visual presentation (Harvard Health, 2015). As a result, the effort demanded to deliver all foods to all patients, while the food is still at an ideal temperature, has resulted in an increased cost of labor. This is because healthcare facilities have had to hire additional workers to meet the demands placed on the nutrition department related to safe temperatures and speed of food delivery (Aladdin, 2013).

<p>Hampshire crosses of different genotype and sex were used to investigate the effects of rearing system, feed and handling on sensory quality, consumer preference and cooking loss. A selected and trained panel carried out descriptive tests. Two preference tests were carrieout by, in each case, 200 consumers.</p><p> The genotype had a major effect on sensory quality in all four studies irrespective of rearing system, feed and sex. In three of the four studies pork from RN¯ carriers scored higher for juicines, tenderness, acidulous taste and meat taste intensity. </p><p> Sex showed contradictory effects on sensory quality, while rearing system and feed had minor effects on sensory properties of pork. </p><p> Hams (<i>M. biceps femoris</i>) from pigs reared outdoors scored lower for juiciness and acidulous taste than hams from pigs reared indoors. Loins from pigs organically reared (KRAV) scored lower for juiciness and higher for crumbliness than ones from pigs conventionallreared.</p><p> Loins (<i>M. longissimus dorsi</i>) aged four days from conventionally fed pigs were juicier than ones from silage-fed pigs. When loins were aged eight days there was no difference in juicines while acidulous taste became weaker and tenderness and meat taste intensity increased.</p><p> In the case of loins stored frozen one year, those from silage-fed pigs scored higher for acidulous taste and off-flavour than those from conventionally fed pigs.</p><p>Cooking, thawing and total loss data showed minor and contradictory differences between genotypes, sexes, rearing systems and feeding regimes. </p><p> Organically and conventionally produced loins were equally liked and loins from RN¯ carrier pigs were preferred to loins from non-carriers.</p>

The factors that determine the efficiency of energy transfer in aquatic food webs have been investigated for many decades. The plant-animal interface is the most variable and least predictable of all levels in the food web. In order to study determinants of food quality in a large lake and to test the recently proposed central importance of the long-chained eicosapentaenoic acid (EPA) at the pelagic producer-grazer interface, we tested the importance of polyunsaturated fatty acids (PUFAs) at the pelagic producerconsumer interface by correlating sestonic food parameters with somatic growth rates of a clone of Daphnia galeata. Daphnia growth rates were obtained from standardized laboratory experiments spanning one season with Daphnia feeding on natural seston from Lake Constance, a large pre-alpine lake. Somatic growth rates were fitted to sestonic parameters by using a saturation function. A moderate amount of variation was explained when the model included the elemental parameters carbon (r2 = 0.6) and nitrogen (r2 = 0.71). A tighter fit was obtained when sestonic phosphorus was incorporated (r2 = 0.86). The nonlinear regression with EPA was relatively weak (r2 = 0.77), whereas the highest degree of variance was explained by three C18-PUFAs. The best (r2 = 0.95), and only significant, correlation of Daphnia's growth was found with the C18-PUFA α-linolenic acid (α-LA; C18:3n-3). This correlation was weakest in late August when C:P values increased to 300, suggesting that mineral and PUFA-limitation of Daphnia's growth changed seasonally. Sestonic phosphorus and some PUFAs showed not only tight correlations with growth, but also with sestonic α-LA content. We computed Monte Carlo simulations to test whether the observed effects of α-LA on growth could be accounted for by EPA, phosphorus, or one of the two C18-PUFAs, stearidonic acid (C18:4n-3) and linoleic acid (C18:2n-6). With >99 % probability, the correlation of growth with α-LA could not be explained by any of these parameters. In order to test for EPA limitation of Daphnia's growth, in parallel with experiments on pure seston, growth was determined on seston supplemented with chemostat-grown, P-limited Stephanodiscus hantzschii, which is rich in EPA. Although supplementation increased the EPA content 80-800x, no significant changes in the nonlinear regression of the growth rates with α-LA were found, indicating that growth of Daphnia on pure seston was not EPA limited. This indicates that the two fatty acids, EPA and α-LA, were not mutually substitutable biochemical resources and points to different physiological functions of these two PUFAs. These results support the PUFA-limitation hypothesis for sestonic C:P < 300 but are contrary to the hypothesis of a general importance of EPA, since no evidence for EPA limitation was found. It is suggested that the resource ratios of EPA and α-LA rather than the absolute concentrations determine which of the two resources is limiting growth.

Lakes are important global ecosystems and many of them are nutrient-poor (unproductive). Especially in northern boreal latitudes, lakes may be heavily subsidized by terrestrial organic material (t-OM) from peat layers in the catchment. Thus, in addition to heterotrophic bacteria and phytoplankton, zooplankton may also use the particulate fraction of peat layer t-OM (t-POM) as a potential food source in those systems. Inputs of t-OM in northern latitudes are anticipated to increase in the future due to increasing precipitation and temperature. As t-OM is a good substrate for bacterial growth and as bacteria can often outcompete phytoplankton for inorganic nutrients, the proportions of heterotrophic bacteria and phytoplankton are expected to change in unproductive lakes. This may have pronounced impacts on zooplankton population dynamics. The aim of my thesis was to investigate how changes in food quality and quantity will affect metazoan zooplankton performance in unproductive lakes. Three laboratory studies assessed the quality of specific food components (phytoplankton, bacteria and peat layer t-POM) and their effects on Daphnia survival, growth and reproduction. Further, a mesocosm study with a full natural plankton community tested the predictions of the Light:Nutrient-Hypothesis in an unproductive clear water lake in situ by adding carbon and inorganic nutrients and changing light availability. I found that pure bacterial (Pseudomonas sp.) or t-POM diets could not sustain Daphnia populations, even though both were readily ingested. Daphnids needed at least 10-20% phytoplankton (Rhodomonas) in the diet to survive and even higher proportions (≥ 50%) were necessary for the production of viable offspring. Further, I showed that the dilution of non-limiting concentrations of Rhodomonas with increasing proportions of Pseudomonas or t-POM led to decreased Daphnia performance. Both Pseudomonas and t-POM lack essential biochemicals (fatty acids and sterols). In contrast, mineral nutrient limitation only occurred on t-POM-dominated diets as evidenced by a labeling experiment that showed Daphnia can incorporate carbon and phosphorus from Rhodomonas and Pseudomonas with similar efficiencies. Thus, peat layer t-POM was a lower quality food than Pseudomonas. This was corroborated by the finding that intermediate additions of Pseudomonas to limiting amounts of Rhodomonas supported increased Daphnia survival, growth and reproduction while t-POM additions had no beneficial effect. My results suggest that high terrestrial stable isotope signals in metazoan zooplankton are most likely derived from t-OM that is channeled tohigher trophic levels via the microbial loop (i.e. heterotrophic bacteria and/or bacterivorous protozoa) but not from direct metazoan feeding on t-POM. Furthermore, bacteria may serve as an important supplement to zooplankton diets when phytoplankton abundance is low. However, a sufficient proportion of high quality phytoplankton is always necessary to fulfil mineral and especially biochemical requirements of zooplankton in unproductive aquatic systems. The results of the mesocosm study showed that the Light:Nutrient-Hypothesis is not applicable to unproductive clear water systems in which the phytoplankton community is dominated by mixotrophs. In the face of the theoretical predictions, low light levels led to decreased zooplankton biomass. This was most likely caused by a shift in the algal community composition towards less edible taxa. Another reason may have been a weakening of the microbial loop. This is in line with the results of the laboratory studies that point out the importance of the microbial food web for zooplankton nutrition in unproductive lakes.

Hampshire crosses of different genotype and sex were used to investigate the effects of rearing system, feed and handling on sensory quality, consumer preference and cooking loss. A selected and trained panel carried out descriptive tests. Two preference tests were carrieout by, in each case, 200 consumers. The genotype had a major effect on sensory quality in all four studies irrespective of rearing system, feed and sex. In three of the four studies pork from RN¯ carriers scored higher for juicines, tenderness, acidulous taste and meat taste intensity. Sex showed contradictory effects on sensory quality, while rearing system and feed had minor effects on sensory properties of pork. Hams (M. biceps femoris) from pigs reared outdoors scored lower for juiciness and acidulous taste than hams from pigs reared indoors. Loins from pigs organically reared (KRAV) scored lower for juiciness and higher for crumbliness than ones from pigs conventionallreared. Loins (M. longissimus dorsi) aged four days from conventionally fed pigs were juicier than ones from silage-fed pigs. When loins were aged eight days there was no difference in juicines while acidulous taste became weaker and tenderness and meat taste intensity increased. In the case of loins stored frozen one year, those from silage-fed pigs scored higher for acidulous taste and off-flavour than those from conventionally fed pigs. Cooking, thawing and total loss data showed minor and contradictory differences between genotypes, sexes, rearing systems and feeding regimes. Organically and conventionally produced loins were equally liked and loins from RN¯ carrier pigs were preferred to loins from non-carriers.

Crustaceans, the most abundant group of organisms that make up zooplankton, form a critical link in the food web between primary-producing phytoplankton and planktivorous fish. Examining this link is essential in order to effectively estimate the amount of energy available to higher trophic levels. The most appropriate currency for tracking energy flow through these food webs is to measure production, or the amount of new biomass generated over a given period of time. Although measurements of primary productivity are routinely made in oceanographic studies, estimates of secondary productivity are rare due to their historical reliance on time-consuming methods. The overall objective of this thesis was to determine the factors influencing temporal variations in community-level crustacean productivity. A simplified lab experiment was used to establish a relationship between diet and chitobiase-based estimates of copepod productivity in response to single versus mixed species phytoplankton diets. In addition, the relationships between primary productivity and chitobiase-based productivity for the entire crustacean zooplankton community were examined over two years in Saanich Inlet, British Columbia, Canada. Lastly, this work determined the abiotic and biotic factors most strongly influencing crustacean productivity in the tropical Guanabara Bay, Rio de Janeiro, Brazil, dominated by the microbial loop. Results from this work show that: (i) copepod populations fed a poor food item take longer to develop through early stages, have lower daily growth rates, and exhibit lower productivity than those fed a good quality food item; (ii) important variations in crustacean productivity are missed when biomass estimates, alone, are used to represent food available to higher trophic levels; (iii) relationships between primary productivity and crustacean productivity can vary interannually and are not necessarily controlled by bottom-up processes; (iv) substantial interannual variations in trophic transfer efficiency (TTE) occur even if average TTE is the same across years; and (v) community-level crustacean productivity in tropical regions dominated by the microbial food loop can be as high as, if not higher than, productivity measured in temperate regions. Ultimately, this work provides insight into how accurate productivity estimates can improve our understanding of zooplankton dynamics in both laboratory and field settings in marine ecosystems worldwide. / Graduate