The main objective of this study was to determine the effect of fruit ripeness and drying method on the oxidative stability and micro-component content of avocado oil extracted with supercritical carbon dioxide (SC-CO2). A secondary objective was to determine the effect of fruit ripeness, method of fruit drying and extraction method on the extractability of avocado oil with hexane and SC-CO2. For the oil extractability study, unripe and ripe avocado fruit pieces were either freeze-dried or oven-dried (80oC) and extracted with hexane or SC-CO2. For both extraction methods, oil yield was higher from ripe fruit than from unripe fruit. Scanning electron microscopy (SEM) indicated structural degradation during ripening, making the oil more available for extraction in ripe fruit. Oil from freeze-dried samples was in most cases more extractable than from oven-dried samples possibly through formation of rigid structures due to starch gelatinisation and dehydration and protein crosslinking around the oil cells during oven drying. Oil yield was higher with hexane than with SC-CO2 extraction because hexane is less selective, permeates the whole plant material and leads to a more complete extraction, while SC-CO2 may create paths of least resistance in the plant material where it moves preferentially, thus leading to a less complete extraction. For oxidative stability studies and micro-component characterisation, oil extractions were performed on an industrial scale SC-CO2. extractor. For all treatments (unripe freeze-dried, ripe freeze-dried, unripe oven-dried, ripe oven-dried), oil was divided into four fractions and analysed for fatty acid profile, peroxide value (PV), anisidine value (AV), free fatty acids (FFA), oxidative stability index (OSI), colour, tocopherol, sterol, chlorophyll, carotenoid and total unsaponifiable content. Oil from ripe, freeze-dried avocado had relatively lower levels of chlorophyll, carotenoids and tocopherols, than oil samples from the other treatments. This may be due to relatively higher lipoxygenase levels in ripe fruit which may bring about higher oxidative breakdown of these components. Also, the activity of lipoxygenase may be preserved under the lower temperature conditions of freeze-drying, but inactivated at high temperature during oven-drying. Intensity of blue and red on the Lovibond colour scale of all oil samples as well as chlorophyll and carotenoid content increased with progressive extraction. These pigments are presumably extracted in the latter stages of extraction because they are located in chloroplasts, chromoplasts and idioblast cells with thicker membranes than the parenchyma cells where triglycerides are located. Levels of total sterols, total tocopherols and their isomers did not show any specific trends with progressive extraction, which could be related to their location in cell membranes where they would be extracted concurrently with the triglycerides. Levels of total unsaponifiables were mostly higher in the first than the latter fractions. This could be due to the early elution of non-polar waxes which are highly soluble in SC-CO2 and highly available due to their location on the surface of the avocado skin. The fatty acid profile of the avocado oil was not influenced by the degree of ripeness or drying method and therefore did not affect the OSI. Oleic acid increased while linoleic acid decreased with progressive extraction. Compared to the changes observed in levels of some of the micro-components, the changes in fatty acid levels with progressive extraction were relatively small and the fatty acid profile alone could not explain the OSI of the oil. Oil from oven-dried avocado had lower PVs but higher AVs than oil from freeze-dried fruit indicating more advanced oxidative deterioration in oil from oven-dried samples than from freeze-dried samples. FFA levels were higher in oil from ripe, freeze-dried fruit. Levels of hydrolytic enzymes increase during fruit ripening and are preserved during freeze-drying while they are inactivated during oven-drying. FFA levels decreased with progressive extraction. Free fatty acids are very soluble in the SC-CO2 and due to their location on the surface of the plant material, they could be extracted early in the extraction. Oil from oven-dried fruit had relatively higher OSI compared to the other treatments. The OSI of all samples increased with progressive extraction. There was a significant negative correlation between FFA and OSI for both drying methods. AV correlated positively with OSI for oil from oven-dried fruit and negatively for oil from freeze-dried fruit. AV contributed the most to the prediction of OSI in oven-dried fruit, while FFA contributed the most in freeze-dried fruit. It was suggested that the high OSI of oil from oven-dried fruit, despite its high AV, may be due to the presence of compounds with high antioxidant activity in the oil formed through the high temperatures of the oven-drying process. Therefore, using multiple regression techniques, predictive models were developed to determine the effect of the micro-components on the oxidative stability of the oil. The OSI correlated positively with chlorophyll (0.83) and carotenoids (0.80). The models indicated that chlorophyll and carotenoids were the most important variables in predicting the oxidative stability of avocado oil extracted with SC-CO2. This might be due to the antioxidant effect of carotenoids and the possible formation of pheophytin and pyropheophytin, thermal breakdown products of chlorophyll, which exert antioxidant effects in oil. / Thesis (PhD (Food Science))--University of Pretoria, 2008. / Food Science / unrestricted

Made available in DSpace on 2016-12-08T16:44:43Z (GMT). No. of bitstreams: 1 PGPV13MA111.pdf: 4178123 bytes, checksum: d68fc297a429c3fa95d6b1a5707ee257 (MD5) Previous issue date: 2013-02-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The pear (Pyrus communis) belongs to the family Rosaceae, is native from asian continent. The cultivation of pear is established in Latin American countries like Argentina and Chile and is in expansion in regions of southern highlands in Brazil. The quantity of fruits produced on Brazilian regions does not meet the demand, being necessary the importation of 90% of pear fruits that are consumed in Brazil. The occurrence of fruit flies (Anastrepha fraterculus) has been a problem on the pear orchards and has caused an increase of the production costs. The aim of this work was to study the infestation of flies related to fruit ripeness of Packham`s and William`s cultivars, in order to characterize the damage resulting from the attack of fruit flies in different stages of fruit maturation and correlate the physical and chemical factors of the fruits with the infestation of fruit flies. Besides, evaluate in laboratory the bioactivity of natural compounds of vegetal and mineral origin in adults of fruit flies. Fruit of Packham`s and William`s cultivars were bagged when they had diameter transversal approximately equal to 20 mm. On the experiment of damage characterization, the fruits were infested by two couples of flies in reproductive age for 48 hours. In laboratory the fruits were individualized in pots with capacity to 750 mL and then were released two couples of fruit flies for 48 hours. Besides, were performed evaluations of chemical (solid soluble and pH) and physical (texture of skin and flesh, color and size) fruit parameters. Field experiments sought to evaluate the occurrence of fruit dropping, galleries and larvae in the fruit endocarp. Laboratory experiments sought to quantify the number of larvae, pupae and adults on the fruits in each stage of maturation. The fruits were immersed in each of the treatments that were: andiroba oil, azadirachtin, kaolin, methidathion and distilled water, and were offered to the fruit flies in tests of free and no-choice. In both test was evaluated the efficiency of the substances and the number of larvae, pupae and adults that remained alive. The fruits of Packham`s cultivar did not suffered early dropping when infested by the fruit fly and enable larval development from 54.9 mm of diameter. The fruits of William`s cultivar suffered early dropping by the fruit fly attack and enable the larval development from 52.8 mm of diameter. The texture of skin and flesh of both cultivars affect the onset of the attack of the fly. Andiroba oil interfered negatively on the oviposition of the fly in laboratory tests with free and no-choice. There was not response of the treatments azadirachtin and kaolin on the oviposition, adult mortality, and number of larvae, pupae and adults found on the fruits / A pereira (Pyrus communis L.) pertence a família Rosaceae, é uma espécie nativa do continente asiático. O cultivo da pereira está estabelecido em países como Argentina e Chile. Nas regiões serranas de Santa Catarina e Rio Grande do Sul o cultivo ainda e pequeno apesar da demanda pela fruta e das condições climáticas favoráveis ao seu cultivo. A quantidade de frutos de pera produzida pelas regiões produtoras brasileiras não atende a demanda, sendo necessária a importação de 90% da fruta que é consumida no território brasileiro. A ocorrência da mosca-dasfrutas (Anastrepha fraterculus) tem sido um problema nos pomares de pereira e tem causado um aumento dos custos de produção. O objetivo desse trabalho foi estudar a infestação de moscas-das-frutas relacionada a maturação dos frutos das cultivares de pera Packham`s e William`s, visando caracterizar os danos decorrente do ataque da moscas-das-frutas em frutos com diferentes estágios de maturação e correlacionar os fatores físico químicos dos frutos com a infestação da mosca-dasfrutas. Além disso, avaliar em laboratório a bioatividade de compostos naturais de origem vegetal e mineral em adultos de moscas-das-frutas. Para os experimentos realizou-se o ensacamento de frutos de pera das cultivares Packham`s e William`s quando os mesmos possuíam diâmetro transversal de aproximadamente 20 mm. No experimento de caracterização de dano a campo, os frutos foram infestados por dois casais de moscas em idade reprodutiva por 48 horas. No laboratório os frutos foram, individualizados em potes com capacidade para 750 mL e em seguida liberados dois casais de moscas por 48 horas. Além disso, também foram realizadas avaliações dos parâmetros químicos (sólidos solúveis totais e pH) e físicos (textura da casca e da polpa, coloração e tamanho) dos frutos. No campo buscou-se avaliar a ocorrência de queda, galerias e larvas no endocarpo dos frutos. No laboratório realizou-se a quantificação de larvas pupas e adultos nos frutos de cada estádio de maturação. Os frutos foram submetidos a imersão em cada um dos tratamentos que foram: óleo de andiroba, Azamax®, caulim, metidationa e água destilada e foram oferecidos a mosca-das-frutas em testes com e sem chance de escolha. Em ambos os testes foi avaliada a eficiência das substâncias utilizadas, além do número de larvas, pupas e adultos sobreviventes. Os frutos de pera da cultivar Packham`s não sofreram queda em razão da infestação da A. fraterculus e possibilitam o desenvolvimento larval a partir de 54,9 mm de diâmetro. Os frutos da cultivar William`s sofreram queda prematura decorrente do ataque da mosca-das-frutas e possibilitam o desenvolvimento larval a partit de 52,8 mm de diâmetro. As texturas da casca e da polpa afetam o início do ataque de A. fraterculus nos frutos de ambas as cultivares de pera. O óleo de andiroba mostrou-se interferir negativamente na oviposicao da mosca das frutas nos testes de laboratório com sem chance de escolha. Não houve resposta dos tratamentos a base de Azamax® e caulim sobre a oviposição, mortalidade de adultos, número de larvas, pupas e adultos encontradas nos frutos

Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-09-16T13:29:16Z No. of bitstreams: 1 TeseRKH.pdf: 7966483 bytes, checksum: 075f420f66971bcdd35c8dbfe1d3c37c (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-16T19:45:53Z (GMT) No. of bitstreams: 1 TeseRKH.pdf: 7966483 bytes, checksum: 075f420f66971bcdd35c8dbfe1d3c37c (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-16T19:45:58Z (GMT) No. of bitstreams: 1 TeseRKH.pdf: 7966483 bytes, checksum: 075f420f66971bcdd35c8dbfe1d3c37c (MD5) / Made available in DSpace on 2016-09-16T19:46:05Z (GMT). No. of bitstreams: 1 TeseRKH.pdf: 7966483 bytes, checksum: 075f420f66971bcdd35c8dbfe1d3c37c (MD5) Previous issue date: 2015-02-26 / Não recebi financiamento / The research proposal was found low cost alternative solution to automatize the classification and selection process to recognize fruit ripeness level using biologic behavior instead of human visual inspection. The goal was to develop low cost and disposable solid state sensor made of office paper with respective equipment for odor monitoring. The concept used to development this sensor was replace the interdigitated electrode with a conductive track using office paper impregnated with an electrolyte that "turns" cellulose fiber in an electrical conductor under gas action. In order to get gas adsorbing surface property for odor monitoring were tested some electrolytes like: Magnesium Chloride, Potassium Iodide, Calcium Hydroxide and others. This configuration replaced the interdigitated electrode per cellulose fiber doped with an electrolyte, it´s the originality of this research. In the fruit ripening process, the major enzymes involved are pectinase to crack the cell walls responsible for the fruits softening, amylase which degrades carbohydrates to simple sugars responsible for the flavor and hydrolase which reduces the amount of chlorophyll responsible for the fruit color change. The reaction that produces ethylene gas (C2H4) is lipids oxidation, the main gas exhaled during the fruits ripening process. The equipment adopted to pick up electrical signal is based on resistance and capacitance measuring that showed reversible electrical signal variation basically due the track geometry and cellulose fiber doping with an electrolyte. Another feature found was the office paper sensor decrease resistivity with fruit odors presence. The sensor manufacturing process is simple, basically consist in printing a mask with a negative image of the track by laser printing and office paper impregnation by an electrolyte. / A proposta da pesquisa foi buscar uma alternativa de baixo custo para automatizar o processo de seleção e classificação do nível de maturação da banana, utilizando-se do reconhecimento de gás exalado no processo de maturação via biológica, em vez da inspeção visual humana. O objeto da pesquisa foi desenvolver um sensor de estado sólido, de baixo custo e descartável, à base de papel sulfite, com o seu respectivo equipamento de monitoramento de odor. O conceito utilizado no desenvolvimento do sensor foi eliminar o eletrodo condutor interdigitado e substitui-lo por uma trilha condutora via dopagem do papel sulfite, impregnando com um eletrólito que “transforma” a fibra de celulose em um condutor elétrico sob a ação de gás. Visando conferir a propriedade de adsorção superficial dos gases no processo de monitoramento de odor, foram testados os seguintes eletrólitos: Cloreto de Magnésio, Iodeto de Potássio, Hidróxido de Cálcio entre outros. Essa configuração de substituir o eletrodo interdigitado por fibra de celulose dopada com um eletrólito traduz a originalidade desta pesquisa. No processo de amadurecimento das frutas, as principais enzimas envolvidas foram: pectinase, que quebra as paredes celulares, responsável pelo amolecimento das frutas; amilase, que degrada carboidratos em açúcares simples, responsável pelo sabor e a hidrolase, que reduz a quantidade de clorofila responsável pela mudança de cor da fruta. A reação que produz o gás etileno (C2H4) é a oxidação de lipídios, principal gás exalado durante o processo de amadurecimento das frutas. O equipamento de captação de sinal elétrico do sensor de estado sólido foi baseado na medição de resistência e capacitância, que apresentou variação de sinal elétrico reversível, basicamente em função da geometria da trilha e da dopagem da fibra de celulose com um eletrólito. Outra característica do sensor de papel sulfite foi a queda da resistividade com a presença de odores da fruta. O processo de fabricação do sensor é simples: consiste basicamente em uma impressão a laser de uma máscara com imagem negativa da trilha e a impregnação do papel sulfite com um eletrólito.