311 |
Pb-Pb Isotopic and X-ray Tomographic Constraints on the Origin of ChondrulesCharles, Christopher 02 August 2013 (has links)
207Pb*/206Pb* chronometry was used to obtain the ages of Ca,Al-rich inclusions (CAIs) and chondrules found in ancient meteorites. Assuming a 238U/235U=137.88, Pb/Pb ages of chondrules in NWA801 (a CR2 meteorite) are 4564.6±1.0 Ma, chondrules in Mokoia (a CV3 chondrite) are 4564.2±1.1Ma, and CAIs in Mokoia are 4567.9±5.4 Ma. The Pb/Pb age of NWA801 chondrules is concordant with 26Al/26Mg ages of CR chondrules. However if a 238U/235U < 137.88 is used, the age for NWA801 chondrules becomes younger by ~1Ma and discordant with 26Al/26Mg ages of CR chondrules. This suggests either a discrepancy with the U compositions or the initial Mg isotopic compositions of NWA801 chondrules. The shapes of NWA801 chondrules, and blebs of FeNi metal in the meteorite matrix, were further studied by 3D X-ray micro-computed tomography (CT). Most chondrules (92%) were ‘armoured’ with one discontinuous layer of FeNi metal. Two layers of FeNi metal (one on the exterior and one concentric through the interior separated by silicate) were rare <8%. Chondrules and matrix blebs occur as oblates, prolate, spheres and triaxial spheroids. It is proposed that the shapes were made free-floating in the nebula likely by flash-melting precursors into molten droplets that were vibrating as harmonic oscillators that ‘froze-in’ their shapes during cooling. Parent-body metamorphism and shock are not likely processes affecting the matrix-bleb and chondrule shapes. Chondrules with ≥2 FeNi metal layers were likely formed by mergers and not by successive deposition and annealing of metal in multiple flash-melting events. Attempts to obtain 207Pb*/206Pb* ages from chondrules and CAIs by thermal extraction (TE)- TIMS were unsuccessful. However LA-ICP-MS was shown to be useful for rapidly determining Pb isotopic trends in meteorites and unknown objects. In particular, it was shown that 137La (T1/2=60ky) should be detectable in recently fallen meteorites using LaF−4 to suppress the 137Ba
isobar during tandem accelerator mass spectrometry combined with a novel instrumental technique for isobar separation.
|
312 |
Pb-Pb Isotopic and X-ray Tomographic Constraints on the Origin of ChondrulesCharles, Christopher 02 August 2013 (has links)
207Pb*/206Pb* chronometry was used to obtain the ages of Ca,Al-rich inclusions (CAIs) and chondrules found in ancient meteorites. Assuming a 238U/235U=137.88, Pb/Pb ages of chondrules in NWA801 (a CR2 meteorite) are 4564.6±1.0 Ma, chondrules in Mokoia (a CV3 chondrite) are 4564.2±1.1Ma, and CAIs in Mokoia are 4567.9±5.4 Ma. The Pb/Pb age of NWA801 chondrules is concordant with 26Al/26Mg ages of CR chondrules. However if a 238U/235U < 137.88 is used, the age for NWA801 chondrules becomes younger by ~1Ma and discordant with 26Al/26Mg ages of CR chondrules. This suggests either a discrepancy with the U compositions or the initial Mg isotopic compositions of NWA801 chondrules. The shapes of NWA801 chondrules, and blebs of FeNi metal in the meteorite matrix, were further studied by 3D X-ray micro-computed tomography (CT). Most chondrules (92%) were ‘armoured’ with one discontinuous layer of FeNi metal. Two layers of FeNi metal (one on the exterior and one concentric through the interior separated by silicate) were rare <8%. Chondrules and matrix blebs occur as oblates, prolate, spheres and triaxial spheroids. It is proposed that the shapes were made free-floating in the nebula likely by flash-melting precursors into molten droplets that were vibrating as harmonic oscillators that ‘froze-in’ their shapes during cooling. Parent-body metamorphism and shock are not likely processes affecting the matrix-bleb and chondrule shapes. Chondrules with ≥2 FeNi metal layers were likely formed by mergers and not by successive deposition and annealing of metal in multiple flash-melting events. Attempts to obtain 207Pb*/206Pb* ages from chondrules and CAIs by thermal extraction (TE)- TIMS were unsuccessful. However LA-ICP-MS was shown to be useful for rapidly determining Pb isotopic trends in meteorites and unknown objects. In particular, it was shown that 137La (T1/2=60ky) should be detectable in recently fallen meteorites using LaF−4 to suppress the 137Ba
isobar during tandem accelerator mass spectrometry combined with a novel instrumental technique for isobar separation.
|
313 |
Dynamics of residual non-aqueous phase liquids in porous media subject to freeze-thawSingh, Kamaljit, Engineering & Information Technology, Australian Defence Force Academy, UNSW January 2009 (has links)
This project concerns the effect of freeze-thaw cycles on the pore-scale structure of nonaqueous phase liquid (NAPL) contaminants in water-saturated porous media. This problem is of critical importance to the entrapment of such contaminants in cold temperate, polar and high altitude regions, and has not been examined in the literature to date. This research work is conducted in three stages: (i) two-dimensional nondestructive visualisation of residual light non-aqueous phase liquid (LNAPL), and dense non-aqueous phase liquid (DNAPL), in porous media subject to successive freeze-thaw cycles; (ii) three-dimensional experiments on LNAPL in porous media subject to freeze-thaw, with quantification of phase volumes by X-ray micro-computed tomography (micro-CT); and (iii) the explanation of results by several pore scale mathematical and conceptual models. The two-dimensional cell experiments (using a monolayer of 0.5 mm diameter glass beads held between two glass sheets), and three-dimensional X-ray micro-CT experiments reveal a substantial mobilisation and rupture of ganglia during successive freeze-thaw cycles; this includes the detachment of smaller ganglia from larger ganglia and the mobilisation of NAPL in the direction of freezing front. The experiments also reveal significant shedding of numerous single/sub-singlet ganglia along narrow pore corridors, their entrapment in growing polycrystalline ice, and the coalescence of such small ganglia during thawing to form larger singlets. These changes were more predominant where the freezing commenced. The results of the experimental studies were interpreted by developing several mathematical and conceptual models, including freezing-induced pressure model, Darcy's law model, multipore ganglia model (rupture coefficient) and ice-snap off model.
|
314 |
Characterisation of surface traits of Helicobacter pylori and their role in the infectious process /Petersson, Christoffer January 2003 (has links) (PDF)
Diss. Linköping : Univ., 2003.
|
315 |
Etudes comparatives de différents processus de séchage de fraise par air chaud, lyophilisation et autovaporisation instantanée : application à la préservation des contenus biologiques / Comparatives studies of different drying process of strawberry hot air drying freeze-drying and swell-drying : application on the biological compounds preservationAlonzo Macias, Maritza 14 May 2013 (has links)
La présente étude concerne l’évaluation de l’impact du séchage par air chaud (HAD), lyophilisation (FD) et « swell drying » (SD), procédé couplant le séchage par air chaud avec le procédé de Détente Instantanée Contrôlée (DIC), sur les fraises (Fragaria var. Camarosa). Il s’agit de comparer et de contraster les performances des procédés et la qualité du produit fini séché en termes des cinétiques de séchage et de réhydratation, de contenus en molécules bioactives et activité antioxydante, et des paramètres caractéristiques de texture comme croquant et croustillant. Les résultats obtenus ont montré que le procédé de SD comparé aux procédés classiques de séchage et de lyophilisation, réduit d’une façon importante le temps de séchage ainsi que les coûts d’opération. D’autre part, SD conserve la qualité nutritionnelle des fraises en gardant leur contenu en composants bioactifs et en augmentant leur disponibilité. De plus, une corrélation importante entre la capacité antioxydante et le contenu total d’anthocyanes a été établie. D’autre part, les fraises séchées par SD ont montré une très intéressante macro et micro-structure. Les produits ont présenté une haute expansion et une croustillance significative due au phénomène de micro-alvéolation par décompression instantanée par DIC. D’ailleurs, il a été possible de mesurer les caractéristiques instrumentales de croustillance/croquance des échantillons finaux séchés. Grâce à la possibilité de modifier, contrôler et optimiser les paramètres opératoires du procédé DIC, il a été possible d’obtenir un produit du type « snack » croustillant avec une très haute valeur nutritionnelle. / The aim of this study was to evaluate the effect of hot air drying (HAD), freeze-drying (FD) and swell drying (SD), which is a coupling of hot air drying to instant controlled pressure drop, (DIC) on the strawberry (Fragaria var. Camarosa) to compare and to contrast its quality in terms of drying and rehydration kinetics, bioactive compounds and its antioxidant activity, and texture parameters as crunchy and crispy features. The obtained results shown that SD method helped to reduce the drying time leading to a low-cost processing compared with classical hot air drying and freezedrying. SD globally preserved the strawberry’s nutritional value and bioactive compounds, increasing their availability. Moreover, a strong correlation between antioxidant activity and total anthocyanin content was established in SD strawberries. On the other hand, the swell-dried strawberries showed an interesting macro and micro-structure. They presented a high expansion ratios and significant crispness provoked by the micro-alveolation phenomenon induced as consequence of the instant decompression process in the DIC treatment. Moreover, it was possible to instrumentaly measure the crispy/crunchy features of the final dried samples. By assessing such crispy and healthy contents of fruit “snacking”, it was possible to modify, control, and optimize DIC operating parameters. And, it can be designed according to the industrial or consumer needs.
|
316 |
Aplicação do processo de liofilização na obtenção de cajá em pó: avaliação das características físicas, físico-químicas e higroscópicas / Application of freeze-drying to obtain yellow mombin powder: physical, physico-chemical and hygroscopic evaluationsOliveira, Gleison Silva January 2012 (has links)
OLIVEIRA, Gleison Silva. Aplicação do processo de liofilização na obtenção de cajá em pó: avaliação das características físicas, físico-químicas e higroscópicas. 2012. 83 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Tecnologia de Alimentos, Fortaleza-CE, 2012 / Submitted by Nádja Goes (nmoraissoares@gmail.com) on 2016-06-09T12:17:09Z
No. of bitstreams: 1
2012_dis_gsoliveira.pdf: 1196468 bytes, checksum: a8572b9d75384ed2a57b461af4d5a3bf (MD5) / Approved for entry into archive by Nádja Goes (nmoraissoares@gmail.com) on 2016-06-09T12:17:20Z (GMT) No. of bitstreams: 1
2012_dis_gsoliveira.pdf: 1196468 bytes, checksum: a8572b9d75384ed2a57b461af4d5a3bf (MD5) / Made available in DSpace on 2016-06-09T12:17:20Z (GMT). No. of bitstreams: 1
2012_dis_gsoliveira.pdf: 1196468 bytes, checksum: a8572b9d75384ed2a57b461af4d5a3bf (MD5)
Previous issue date: 2012 / The yellow mombin due to its distinctive flavor and pleasant, is a fruit highly appreciated and consumed in various regions of the country. But by presenting a high perishability, it becomes necessary to use processing techniques to extend its availability for consumption throughout the year. Dehydration by freeze-drying has the advantage of an excellent retention of nutritional and sensory characteristics of fresh fruit. To increase retention and to prevent agglomeration of the powder, for example, can be made the use of adjuvants drying such as maltodextrin. In this context, the work aimed at the implementation of the lyophilization process to obtain the pulp of yellow mombin powder, physical characterization and physicochemical pulp and powder yellow mombin, tracking stability during storage and hygroscopic behavior of the tests. With the tests of the experimental design was chosen to test lower humidity, with 17% maltodextrin and 24 hours of freeze drying. The pulp presented characteristics similar to reported by literature, and a concentration of constituents occurred with the pulp dehydration. As for storage, the test control (dried whole) had a useful life of 60 days, unlike the test containing maltodextrin that showed good characteristics throughout the period analyzed. In addition, maltodextrin exerted protective function, preventing further loss of chemical constituents and physical reactions to the product, such as lower rate of increase of hygroscopicity, moisture and water activity. The adsorption isotherms were the characteristics of type III. The mathematical models of BET, GAB and Oswin were the best fit to experimental data of moisture sorption for the full hog plum powder, and powder of hog plum pulp with maltodextrin, the Henderson model was the best fit to experimental points of work. / O cajá, devido ao seu sabor diferenciado e agradável, é um fruto bastante apreciado e consumido em diversas regiões do país. Mas por apresentar uma elevada perecibilidade, torna-se necessário o uso de técnicas de processamento para estender sua disponibilidade para o consumo durante todo o ano. A desidratação por liofilização apresenta como vantagem uma excelente retenção das características nutricionais e sensoriais do fruto “in natura”. Para um aumento desta retenção e evitar aglomerações no pó, por exemplo, pode ser feita a utilização de adjuvantes de secagem como a maltodextrina. Neste contexto, o trabalho teve como objetivo a aplicação do processo de liofilização para obtenção da polpa de cajá em pó, caracterização física e físico-química da polpa e do pó de cajá, acompanhamento da estabilidade durante o armazenamento e comportamento higroscópico dos ensaios. Com a realização dos ensaios do planejamento experimental, foi escolhido o ensaio de menor umidade, com 17% de maltodextrina e 24 horas de liofilização. A polpa apresentou características semelhantes às reportadas pela literatura, e uma concentração dos constituintes ocorreu com a desidratação da polpa. Quanto ao armazenamento, o ensaio controle (pó integral) teve uma vida útil de 60 dias, diferentemente do ensaio contendo maltodextrina que apresentou boas características durante todo período analisado. Além disso, a maltodextrina exerceu função protetora, evitando maiores perdas de constituintes químicos e reações físicas no produto, como menor taxa de aumento de higroscopicidade, umidade e atividade de água. As isotermas de adsorção foram características às do tipo III. Os modelos matemáticos de BET, GAB e Oswin foram os que melhor se ajustaram aos dados experimentais de sorção de umidade para o pó de cajá integral, e no pó da polpa de cajá com maltodextrina, o modelo de Henderson foi o que melhor se ajustou aos pontos experimentais do trabalho.
|
317 |
The development and preparation of a quality control dossier for registration of Artemisia Afra capsules for the treatment of chronic Asthma by the South African health products regulatory authoritySekhonyana-Khetsekile, Mabolaeng January 2018 (has links)
Magister Pharmaceuticae - Mpharm / The aim of this study was to determine quality control specifications needed for a dossier and an investigator's brochure of A. afra capsules, which can be used to motivate the registration and clinical testing of A. afra capsules in chronic asthma. The specific objectives were: (1) to establish the minimum product quality requirements for registration of A. afra capsules, (2) to prepare and pharmaceutically characterize a capsule product of A. afra freeze dried aqueous extract (FDAE) suitable for registration, and (3) to identify pharmaceutical product quality aspects of an investigator's brochure (IB) that would be appropriate for use in motivating a clinical trial of A. afra capsules in chronic asthma.
|
318 |
Secagem de pimenta dedo-de-moça (Capsicum baccatum var. pendulum) em secador convectivo horizontalVéras, Antonio Onias Mesquita 28 May 2010 (has links)
Made available in DSpace on 2016-06-02T19:56:39Z (GMT). No. of bitstreams: 1
3124.pdf: 1709285 bytes, checksum: 01aa5e6d0190ca5658a75e9fefae9b2b (MD5)
Previous issue date: 2010-05-28 / Financiadora de Estudos e Projetos / The cultivation of pepper is widespread in Brazil since its colonization. This plant, besides being much appreciated in the cuisine has proven pharmacological effects such as lowering cholesterol, inhibiting appetite and the presence of antioxidants such as ascorbic acid and beta-carotene. It is a product whose demand increases every year, but generally still produced handmade diminish the ability of producers to meet the needs of commerce. To contribute to improving the production of pepper dedo-de-moça, it was the behavior of this plant in analyzing the influence of drying process on the nutritional composition and physical qualities of the dried product. For this, drying kinetics were obtained and certain structural properties (apparent density, real density and porosity) as a function of moisture content during drying. Assessing the quality of the final product was performed by quantification of ascorbic acid and study of rehydration. The convective drying and freeze-drying was compared with respect to product quality parameters such as shrinkage, structural properties, vitamin C retention and rehydration characteristics. To describe the kinetics of drying and rehydration were used empirical and semiempirical equations. The characterization of the rehydration process was carried out from the indices that take account of the capacity of water absorption and loss of solutes. The use of seed from the drying of peppers to obtain seedlings was studied by checking the germination through standardized tests. The samples of convective drying at 60 ºC had the best results in terms of nutritional quality, rehydration characteristics and structural properties, comparing with those obtained from freezedrying. In assessing the use of seeds of peppers after processing to obtain new seedlings, the most suitable temperature was 40 oC to cause less damage to germination. / A cultura da pimenta está bem difundida no Brasil desde a sua colonização. Esse vegetal, além de ser muito apreciado na culinária possui efeitos farmacológicos comprovados como o de redutor do colesterol, inibidor do apetite e a presença de substâncias antioxidantes como o ácido ascórbico e o beta-caroteno. É um produto cuja demanda aumenta a cada ano, mas que a forma como é produzido continua, em sua maioria, artesanal diminuindo a capacidade dos produtores de atender às necessidades do comércio. Visando contribuir para o melhoramento da produção da pimenta dedo-de-moça, verificou-se o comportamento desse vegetal na secagem analisando a influência do processo na composição nutricional e qualidades físicas no produto seco. Para isso, foram obtidas as cinéticas de secagem e a determinação das propriedades estruturais (densidade aparente, densidade real e porosidade) em função do teor de umidade durante a secagem. A avaliação da qualidade do produto final foi realizada pela quantificação de ácido ascórbico e estudo da reidratação. A secagem convectiva foi comparada com a secagem em liofilizador com relação a parâmetros de qualidade do produto como encolhimento, propriedades estruturais, retenção de vitamina C e características de reidratação. Para descrever a cinética de secagem e de reidratação foram utilizados modelos empíricos e semi-empíricos. A caracterização do processo de reidratação foi realizada a partir dos índices que levam em conta a capacidade de absorção de água e a perda de solutos. Avaliou-se também o aproveitamento das sementes resultantes do processamento para obtenção de novas mudas através da verificação da capacidade germinativa por meio de testes padronizados. As amostras obtidas da secagem por convecção a 60oC tiveram os melhores resultados em termos de qualidade nutricional, características de reidratação e propriedades estruturais, comparando-se com aquelas obtidas da liofilização. Na avaliação do uso das sementes após o processamento das pimentas para obtenção de novas mudas, a temperatura mais adequada foi de 40oC por causar menos prejuízo a capacidade germinativa.
|
319 |
Utiliza??o de embri?es liofilizados e flocos de Artemia na diversifica??o nutricional de p?s-larvas do camar?o marinho Litopenaes vannamei (Boone, 1931)Cavalcante, Pedro Herc?lio de Oliveira 19 May 2006 (has links)
Made available in DSpace on 2014-12-17T14:02:03Z (GMT). No. of bitstreams: 1
PedroHOC.pdf: 308732 bytes, checksum: f9e88debb287b72111d2b3aeb9898ae7 (MD5)
Previous issue date: 2006-05-19 / The objective of the current study was to evaluate the zootechnical performance (survival and growth) of Litopenaeus vannamei post-Iarvae fed an artificial shrimp diet supplemented with Artemia flakes or freeze-dried Artemia embryos. For that purpose, 20 culturing units were individually stocked with 50 shrimp post-Iarvae (average dry weight of 0,3 ? 0,03 mg) at a stocking density of 20 post-larvae per liter, and fed the experimental diets to satiation during 20 days. The experimental design consisted of four diets (T1, T2, T3 and T4) with five repetitions each. For treatments T1, T2 and T3, dietary supplements of 5mg of Artemia flakes (T1), freeze-dried Artemia embryos (T2), and of the commercial shrimp diet (T3) were offered 2 hours after the shrimp were initially fed the commercial shrimp diet. For treatment T4 (control), no additive was offered 2 hours after the initial feeding. Shrimp survival, absolut (GPA) and relative increase in weight (GPR), and specific growth rate (TCR) were used as evaluation criteria. After the experimental period, no significant statistical differences (p>0,05) in survival were observed. Regarding growth, the dietary treatment which used freeze-dried Artemia embryos as an additive (T2) presented the best results for GPA (6,7 ? 0,7 mg). There were no statistical differences within treatments T1, T3 and T4 (p>0,05). AIso, post-larvae fed freeze-dried embryos (T2) showed a relative increase in weight (2241,4%) which differed significantly (p<0,05) from T4(1911,7%) but not from T1 (1801,6%) or T3 (1946,7%). In conclusion, the results of the current study indicate that an artificial shrimp diet supplemented with freeze-dried Artemia embryos fulfils the nutritional requirements of post-larvae L. vannamei and promotes a better growth than diets not supplemented with Artemia flakes / O presente trabalho teve por objetivo avaliar o desempenho zoot?cnico (sobreviv?ncia e crescimento) de p?s-larvas de Litopenaeus vannamei alimentadas com dietas comerciais suplementadas com flocos ou embri?es liofilizados de Artemia. Para isso, durante um per?odo de 20 dias, cada uma das 20 unidades de cultivo foram estocadas com 50 p?s-larvas de peso seco m?dio inicial de 0,3 ? 0,03 mg (a uma densidade de 20 p?s-larvas por litro) e alimentadas de modo ad libitum. O desenho experimental foi inteiramente casualizado com quatro tratamentos (T1, T2, T3 e T4) com cinco r?plicas cada. Para os tratamentos T1, T2 e T3, 2 h ap?s a oferta inicial da ra??o comercial, um suplemento adicional de 5mg aditivo era ofertado. Os aditivos utilizados consistiram de Artemia em flocos (T1), embri?es liofilizados de Artemia (T2) e ra??o comercial (T3). Para o tratamento T4 (controle), n?o houve oferta de aditivo 2 h ap?s o arra?oamento. O protocolo experimental utilizou como crit?rios de avalia??o a sobreviv?ncia, o ganho de peso absoluto (GPA), o ganho de peso relativo (GPR) e a taxa de crescimento relativo (TCR). Ap?s o per?odo experimental, n?o foram observadas diferen?as estat?sticas significativas (p>0,05) para o crit?rio sobreviv?ncia. Para o crit?rio crescimento, o tratamento que utilizou embri?es de Artemia como aditivo (T2) para p?s-larvas de camar?o L. vannamei apresentou o melhor desempenho para o GPA (6,7 ? 0,7 mg). Os tratamentos T1, T3 e T4 n?o diferiram estatisticamente (p>0,05) entre si. Igualmente, as p?s-larvas alimentadas com embri?es liofilizados (T2) apresentaram ganho de peso relativo (GPR) de 2241,4%, o qual diferiu significativamente (p<0,05) do tratamento T4 (1911,7%), mas n?o dos tratamentos T1 (1801,6%) ou T3 (1946,7%). Em conclus?o, os resultados do presente estudo indicam que uma dieta artificial suplementada com embri?es liofilizados de Artemia atende ?s necessidades nutricionais das p?s-larvas de L. vannamei e promove um melhor crescimento em rela??o a dietas comerciais n?o suplementadas ou parcialmente suplementadas com flocos de Artermia
|
320 |
Desidratação de resíduos do processamento de maracujá-amarelo por diferentes metodologiasSilva, Neiton Carlos da 24 July 2015 (has links)
Brazil is one of the greatest producers of fruits in the world which involves the
generation of a large amount of agro-industrial residues whose potential still needs to be
better studied. The yellow passion fruit (Passiflora edulis f. flavicarpa) is rich in minerals,
vitamins and fibers and its production generates a large number of by-products as peels and
seeds, which can reach 70% of the fruit weight. Within this reality, the methods of
dehydration stand out as an alternative to remove moisture of this material, preventing the
proliferation of microorganisms and creating opportunities for its reutilization. In this work, it
was studied the impact of four techniques of dehydration in the passion fruit s residue: hot air,
infrared, microwaves and freeze drying. In all was possible to obtain a material with
satisfactory final moisture levels, highlighting the use of microwaves as the most efficient in
terms of time. Dehydration by hot air was positively affected by velocity and temperature
conditions, but the bioactive compounds had impact of temperature and time (80oC and 7
hours). The temperature of 95oC was the most efficient for the moisture removal and contends
of bioactive compounds in the dehydration of infrared, but an overexposure to this radiation
beyond the observed limits must be avoided. The use of microwaves show that is possible to
obtain a material with good final quality and quickly, since intermediate levels of powers (480
W) are used to avoid over exposure. Freezer drying produced a final product with better
visual appearance but its great operation times and the final content of bioactive compounds
found wasn t better to other methods, in exception of pectin contents. Analyzing the bioactive
compounds, phenolics and flavonoids were positively impacted by dehydration, reach values
near and above of the residue in natura in all techniques. Citric acid showed deterioration in
all conditions observed, indicating its sensibility to thermal processes as much as freeze
drying. The ascorbic acid was strongly influenced by heat exposure an increased its levels,
except in the freeze drying samples. Overall, the best dehydration methodology was the
microwave technique, indicating a potential future use of this method in the use of passion
fruit residues. / O Brasil é um dos maiores produtores de frutas do mundo, o que implica na geração
de uma grande quantidade de resíduos agroindustriais cujo potencial ainda necessita ser
melhor estudado. O maracujá-amarelo (Passiflora edulis f. flavicarpa) é um fruto rico em
minerais, vitaminas e fibras e sua produção gera uma grande quantidade de subprodutos como
cascas e sementes, que podem chegar até 70% do peso do fruto. Dentro dessa realidade,
destacam-se as metodologias de desidratação como alternativa para remoção de umidade
desse material, impedindo a proliferação de micro-organismos e abrindo oportunidades para
seu posterior aproveitamento. Neste trabalho foram verificados os impactos de quatro
metodologias de desidratação no resíduo de maracujá: o uso de ar quente, infravermelho,
micro-ondas e liofilização. Em todos foi possível obter um material com níveis de umidade
final satisfatórios, destacando-se o uso de micro-ondas como o mais eficiente em termos de
tempo. A desidratação por ar quente se mostrou impactada positivamente pela velocidade e
temperatura de operação, mas os compostos bioativos sofreram maior impacto da temperatura
e do tempo (80oC e 7 horas). A temperatura de 95oC se destacou como a mais eficiente tanto
em remoção de umidade quanto nos teores de compostos bioativos para a desidratação por
infravermelho, mas verificou-se que uma superexposição a essa radiação além dos limites
observados deve ser evitada. O uso de micro-ondas indicou que é possível obter um material
final de qualidade e rapidamente, desde que sejam utilizadas potências intermediárias (480 W)
e evitado o excesso de exposição. A liofilização resultou em um produto final com melhor
aspecto visual, porém seus tempos de operação elevados e o nível de compostos bioativos
finais encontrados não obtiveram destaque perante os demais métodos, com exceção aos
teores de pectina. Quanto aos compostos bioativos, os fenólicos e flavonoides foram
impactados positivamente pela desidratação, atingindo valores próximos e superiores ao do
resíduo in natura em todas as metodologias. O ácido cítrico apresentou degradação em todas
as condições a que foi submetido, indicando a sensibilidade do mesmo tanto a processos
térmicos quanto à liofilização. Já o ácido ascórbico se mostrou fortemente influenciado pela
exposição ao aquecimento, apresentando aumento em seus teores, com exceção das amostras
liofilizadas. Globalmente, o melhor método de desidratação obtido foi o micro-ondas,
indicando um potencial uso do mesmo no aproveitamento do resíduo de maracujá. / Mestre em Engenharia Química
|
Page generated in 0.0515 seconds