Made available in DSpace on 2014-06-11T19:23:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-05-29Bitstream added on 2014-06-13T20:30:22Z : No. of bitstreams: 1 santos_irc_me_arafcf.pdf: 1670522 bytes, checksum: 94cf024bcd75478eee1c840ef55cc77f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A família das anonáceas é composta por muitos gêneros e espécies; dentre essas, a atemóia (Annona cherimola Mill. X Annona squamosa L.), resultante do cruzamento entre a fruta-do-conde (Annona squamosa L.) e a cherimóia (Annona cherimola Mill.). No Brasil, a atemóia vem despertando grande interesse na produção/comercialização dos seus frutos; no entanto um dos obstáculos enfrentados é a facilidade de escurecimento enzimático que a fruta apresenta. Esse tem como responsável a polifenoloxidase (PPO, E.C. 1.14.18.1); que sob diferentes condições de armazenamento e processamento de vegetais na sua fase póscolheita pode atuar sob substratos naturais e resultar na formação de compostos escuros, acarretando diminuição do valor nutricional, modificação das propriedades organolépticas e sensoriais, com consequente rejeição. Os objetivos desse trabalho foram isolar, purificar e caracterizar algumas propriedades da polifenoloxidase de atemóia. Condições de extração para a PPO foram estabelecidas e a enzima foi isolada por precipitação com sulfato de amônio e eluição em Sephadex G-100. Somente um pico de atividade foi eluído no processo de purificação com um fator de purificação de 7,12. O peso molecular determinado foi 82 kDa com valores ótimos de pH 6,0 e 7,0 para 4-metil catecol e catecol, respectivamente; sendo estável por 12 e 24 horas à incubação na faixa de pH 4,0-8,0. A temperatura ótima de atividade foi 35°C e 28°C para 4-metil catecol e catecol, respectivamente. Os valores calculados de energia de ativação (Ea) para esses substratos foram 87,29 cal/mol-1 e 180,97 cal/mol-1. As constantes cinéticas Km e Vmax foram 5,52mmol/L e 1428,57 UA/mL, para 4-metil catecol, e 79,3 mmol/L e 5000 UA/mL, para catecol. A relação Km/Vmax determinou uma maior afinidade da enzima pelo primeiro substrato. A enzima mostrou desprezível atividade... / The family of annonaceae is composed of many genus and species, among these, the atemoya (Annona cherimola Mill. X Annona squamosa L.), resulting from a cross between custard apple (Annona squamosa L.) and cherimoya (Annona cherimola Mill.). In Brazil, the atemoya is attracting great interest in the production / marketing of its fruits, however one of the obstacles faced is the ease of enzymatic browning that gives the fruit. This is as responsible for polyphenoloxidase (PPO, EC 1.14.18.1), which under different conditions of storage and processing plant in its post-harvest can act on natural substrates and result in the formation of dark compounds, causing decrease in nutritional value, modification of the organoleptic and sensory properties, with consequent rejection. The objectives of this study were to isolate, purify and characterize some properties of polyphenoloxidase from atemoya. Conditions for the extraction of PPO were established and the enzyme was isolated by precipitation with ammonium sulfate and elution on Sephadex G-100. Only one peak of activity was eluted in the process of purification with a purification factor of 7.12. The molecular weight of 82 kDa was determined with the optimum values of pH 6.0 and 7.0 for 4-methylcatechol and catechol, respectively. The enzyme was stable for 12 and 24 hours incubation in the pH range 4.0-8.0. The optimum temperatures for activity were 35 °C and 28 °C for 4-methylcatechol and catechol, respectively. The values of activation energy (Ea) for these substrates cal/mol-1 were 87.29 and 180.97 cal/mol-1. The kinetic constants Km and Vmax were 5.52 mmol/L and 1428.57 UA/mL for 4-methylcatechol, and 79.3 mmol/L and 5000 AU / mL for catechol. The Km/Vmax determined a higher affinity of the enzyme by the first substrate. The enzyme showed negligible activity for caffeic acid and chlorogenic as any for L-DOPA, catechin... (Complete abstract click electronic access below)

Made available in DSpace on 2016-12-08T16:44:47Z (GMT). No. of bitstreams: 1 PGPV13MA132.pdf: 590187 bytes, checksum: 07954870193d62f3303f0654bca77671 (MD5) Previous issue date: 2013-08-02 / Cold storage can induce the development of chilling injury in fruit of some apple cultivars, even when kept at temperatures above the freezing point. This study evaluated the increment of storage temperature for Gala mutation apples under controlled atmosphere (CA), as a method to reduce the development of internal browning, as well as the energy consumption for cooling. Experiments were conducted in 2011, with apples produced in Fraiburgo and São Joaquim, SC, and harvested at two maturity stages. Apples harvest in Fraiburgo were stored in experimental chambers of 0.150 m3, at -0.3 and 1.2 °C, and in commercial cold stores of 2050 m3, at 0.7 and 2 °C, while apples harvested in São Joaquim were stored in commercial cold stores of 578 m3, at 0.8, 1.4 and 1.9 °C. Fruits from all treatments were kept under CA condition, with O2 and CO2 partial pressures of 1.8 ± 0.2 kPa and 2.0 ± 0.2 kPa, respectively. Half of the fruit of each temperature treatment was exposed to the ethylene action inhibitor, 1-methylcyclopropene (1-MCP). Fruit were assessed in terms of firmness, soluble solids content (SSC), titratable acidity (TA) and the incidence of internal browning and skin cracking disorders, and of decay. Temperature treatments did not affect SSC and AT in all experiments. In most cases, apple stored at higher temperature kept better firmness. 1-MCP treatment increased the retention of fruit firmness, regardless of storage temperature. For apples produced in Fraiburgo, the development of decay was not affected by storage temperature in commercial cold storage, regardless of 1-MCP treatment. However, apples from São Joaquim not treated with 1-MCP were less affected by decay when stored at higher temperature. The increase of storage temperature reduced consistently the incidence of internal browning and skin cracking disorders in Gala apples. The lowest incidence of internal browning was observed in apples stored at higher temperatures and treated with 1-MCP. The results of this study show that the increase of storage temperature by 1.3 °C can result in energy saving by about 21% for ventilation, and by 50% for cooling / O armazenamento refrigerado pode induzir o desenvolvimento de danos por frio em maçãs de algumas cultivares, mesmo quando mantidas em temperatura superior ao ponto de congelamento. O presente estudo avaliou o aumento da temperatura de armazenagem de maçãs clones de Gala sob atmosfera controlada (AC), como método para redução do desenvolvimento de escurecimento da polpa e do consumo de energia para refrigeração. Experimentos foram conduzidos em 2011, com maçãs produzidas nas regiões de Fraiburgo e de São Joaquim, SC, colhidas em dois estádios de maturação. Maçãs colhidas em Fraiburgo foram armazenadas em câmaras experimentais de 0,150 m3, a -0,3 e 1,2 °C, e em câmaras comerciais de 2050 m3, a 0,7 e 2 °C, enquanto maçãs colhidas em São Joaquim foram armazenadas em câmaras comerciais de 578 m3, a 0,8, 1,4 e 1,9 °C. Frutos de todos os tratamentos foram mantidos sob AC com regimes de O2 e CO2 de 1,8±0,2 kPa e 2,0±0,2 kPa, respectivamente. Metade dos frutos de cada tratamento de temperatura foi tratada com o inibidor da ação do etileno, 1-metilciclopropeno (1-MCP). Os frutos foram analisados quanto a firmeza da polpa, o teor de sólidos solúveis (SS), a acidez titulável (AT) e a incidência dos distúrbios escurecimento da polpa e rachaduras, e de podridões. Os tratamentos de temperatura de armazenagem não influenciaram significativamente os teores de SS e a AT, em todos os experimentos. Frequentemente, maçãs armazenadas em temperaturas mais elevadas mantiveram melhor a firmeza da polpa. O tratamento 1-MCP aumentou a conservação da firmeza da polpa das maçãs, independentemente da temperatura de armazenagem. O desenvolvimento de podridões não foi afetado pela temperatura de armazenagem em maçãs de Fraiburgo armazenadas em câmaras comerciais, independentemente do tratamento com 1-MCP. No entanto, maçãs de São Joaquim, não tratadas com 1-MCP, foram menos afetadas por podridões quando mantidas na temperatura mais alta. O aumento da temperatura de armazenagem reduziu consistentemente a incidência de maçãs Gala afetadas pelos distúrbios escurecimento da polpa e rachaduras. A incidência de escurecimento da polpa foi menor nas maçãs armazenadas em temperaturas mais elevadas e tratadas com 1-MCP. Os resultados desse estudo mostram que o aumento da temperatura de armazenagem em 1,3 °C pode resultar em economia no consumo de energia em aproximadamente 21% para ventilação e 50% para refrigeração

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Um dos maiores problemas atuais da indÃstria de beneficiamento de castanha de caju, sÃo as amÃndoas que necessitam de re-despeliculagem, as amÃndoas do tipo âdurÃoâ, despeliculadas manualmente, ou com vapor convencional, tendo como inconvenientes a baixa produtividade de raspagem e o escurecimento das amÃndoas, fatores depreciativos de preÃo. Para solucionar esse problema, inicialmente foram realizados em nÃvel de laboratÃrio, ensaios de tratamento de amÃndoas despeliculadas e com pelÃculas de diÃmetro mÃdio à = 1,68 mm, com vapores provenientes de soluÃÃes de Ãcido tartÃrico (1%; 2% e 3%), Ãcido mÃlico (1%; 3% e 5%), cloreto de potÃssio (1%, 2% e 3%) e Ãgua nos tempos de exposiÃÃo de 1,2, 3, 4 e 5 minutos. Foram quantificados nos condensados dos vapores, provenientes do tratamento da pelÃcula, os compostos fenÃlicos totais e pigmentos hidrossolÃveis. Os compostos fenÃlicos totais tambÃm foram quantificados nos vapores apÃs os tratamentos das amÃndoas despeliculadas. Nas amÃndoas despeliculadas foram determinados a concentraÃÃo de hidroximetilfurfural (HMF) e a cor instrumental. Neste estudo, alÃm de quantificar os constituintes jà citados, foi de extrema importÃncia o entendimento acerca da forma como ocorre o escurecimento na superfÃcie das amÃndoas, via reaÃÃo de Maillard e pela interaÃÃo dos pigmentos extraÃdos com esses vapores. Os resultados mostraram que os menores teores de pigmentos solÃveis, fenÃlicos totais extraÃdos da pelÃcula e a menor formaÃÃo de hidroximetilfurfural nas amÃndoas ocorreram nos tratamentos com Ãcido tartÃrico 1,0% - 1,0 minuto; Ãcido mÃlico - 1% - 1,0 minuto; cloreto de potÃssio 2,0% - 1 minuto e Ãgua - 1,0 minuto. Foi avaliado tambÃm o despeliculamento e a quebra em escala industrial nas amÃndoas durÃo com pelÃcula aplicando esses vapores citados, nos tempos e concentraÃÃes mencionados, mostrando os seguintes valores para as porcentagens de despeliculagem e quebra, respectivamente: Ãcido mÃlico: 50,24 - 28,37; Ãcido tartÃrico: 56,78 - 20,99; cloreto de potÃssio: 56,52 - 23,15 e Ãgua: 50,43 - 24,12. A anÃlise colorimÃtrica das amÃndoas tratadas com vapor de Ãcido tartÃrico a 1% - 1 min. mostrou que esta fonte de vapor, foi a que apresentou melhores resultados em todos os parÃmetros (L*, a* e b*), quando comparadas as amÃndoas padrÃo tipo 01 tratadas com vapor de Ãgua. Os resultados mostraram ainda que à mais vantajoso usar vapor de Ãcido tartÃrico em vez de vapor de Ãgua para aumentar o rendimento de despeliculagem e reduzir a quebra das amÃndoas de castanha de caju tipo âdurÃoâ. / One of the biggest challenges that faces the cashew nut processing industries today, is the kernels that needs to peel again, called durao kernels, manually peeled- with a low peeling yield or peeled with conventional water steam - which causes a noticeable browning, decreasing its commercial value. To solve this problem, were performed initially on a laboratory scale, peeled kernels and skin (à = 1,68 mm) from kernels were treated with steams from tartaric acid 1,0;2,0;3,0% ; malic acid 1,0;3,0;5,0 % ; potassium chloride 1,0;2,0 3,0% and water during 1,2,3,4 and 5 minutes. Was measured the condensed steam, from treatment of the skin, total phenolics and water soluble pigments. The total phenolics were also measured in the steams after treatment of peeled kernels. In kernel peeled, concentration hydroxymethylfurfural (HMF) and instrumental color, was determined. In this study, in addition to measuring the constituents already mentioned, was extremely important to the understanding of how browning occurs on the surface of kernels, the Maillard reaction and the interactions of the extracted pigments with their steams. The results showed that the lowest concentration of soluble pigments, total phenolics extracted from the skin and less formation of hydroxymethylfurfural in kernels occurred in treatment with tartaric acid 1,0% - 1,0 minute; malic acid 1,0% - 1,0 minute; potassium chloride 2,0% - 1,0 minute and water - 1,0 minute. The peeled and breaking on an industrial scale in kernels durao with skin applying these steams cited in times and concentrations mentioned, showing the following values for the percentages of peeling and breaking, was determined respectively - malic acid: 50,24 - 28,37; tartaric acid: 56,78 - 20,99; potassium chloride: 56,52 - 23,15 and water: 50,43 - 24,12. From the peeled kernel colorimetric analysis (L*, a*, b*) after treatments with the four steams in the times above mentioned, tartaric acid 1,0% - 1,0 minute showed the best values when compared with the colour parameter of the kernel exportation 01- standard. The results still showed that is more profitable to use tartaric acid steam instead of water steam to increase peeling yield and reduce kernel durao breaking.

Orientador: Hélia Harumi Sato / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-16T13:40:32Z (GMT). No. of bitstreams: 1 Paz_JanaiCristianeSantosNascimento_D.pdf: 1800600 bytes, checksum: 7cadb066c6097038fea7c86ca9f6c95f (MD5) Previous issue date: 2010 / Resumo: A reação de escurecimento enzimático ocorre em muitas frutas e vegetais quando certos compostos fenólicos são oxidados em reações catalisadas por enzimas como polifenoloxidase (PFO) (EC 1.14.18.1) ou peroxidases (POD) (EC 1.11.1.7). A ampliação das alternativas de conservação de frutas como a ameixa nacional Rubimel, cuja produção nacional tem aumentado nos últimos anos e da polpa de cacau, uma fruta de sabor exótico e muito agradável, muito consumida no Estado da Bahia, é necessária, pois possibilita a busca por mercado consumidor dos produtos derivados dessas frutas em regiões mais distantes, preservando a qualidade da fruta in natura. Este trabalho teve como objetivo caracterizar as enzimas polifenoloxidase e peroxidase presentes nas polpas de ameixa Rubimel e de cacau e estudar o efeito de alguns agentes antioxidantes na preservação da cor natural dessas polpas. O suco de ameixa Rubimel escureceu rapidamente após a extração. O extrato enzimático bruto obtido pela centrifugação da polpa de ameixa Rubimel apresentou atividade de polifenoloxidase (448U/g de polpa) e peroxidase (705U/g de polpa). Em estudo univariável (ensaio preliminar ao estudo do efeito combinado) a PFO do extrato bruto de ameixa Rubimel apresentou atividade ótima na faixa de temperatura de 30 a 35°C e pH 6,5 e estabilidade na faixa de pH 3,0 a 7,5, após incubação durante 24h a 5ºC ou 4h a 25ºC. A enzima foi completamente inativada após tratamento térmico a 70°C por 10 minutos ou a 80°C por 1 minuto. No estudo do efeito combinado do pH e da temperatura utilizando metodologia de superfície de resposta, verificou-se que, da mesma forma que os resultados do estudo univariável, a PFO de ameixa Rubimel apresentou maior atividade em pH 6,5 e na faixa de 30 a 35°C, sendo que a enzima mostrou menor atividade em valores de pH próximos a 4,0, quando incubada a 5°C como a 65°C. Em estudo univariável (ensaio preliminar ao estudo do efeito combinado) a POD do extrato bruto de ameixa Rubimel apresentou atividade ótima a 40°C e pH 4,0 e estabilidade na faixa de pH 2,5 a 5,5, após incubação durante 24h a 5ºC ou 4h a 25ºC. A POD foi completamente inativada após tratamento térmico a 70ºC por 10minutos. No estudo do efeito combinado do pH e da temperatura utilizando metodologia de superfície de resposta, observouse que a POD de ameixa Rubimel mostrou maior atividade em pH 5,0 e a 35°C, sendo que a enzima mostrou menor atividade em valores de pH próximos a 4,0, quando incubada a 5°C como a 65°C. A adição de N-acetil-L-cisteína ou glutationa na concentração final de 5mMol/L ou a adição das combinações: 5mMol de ácido ascórbico + 1,8 mMol de 4-hexil-resorcinol ou 5 mMol de ácido ascórbico + 3,4 mMol de L-cisteína, proporcionaram uma redução de 99% na atividade da PFO de ameixa Rubimel. O extrato bruto solúvel, obtido pela centrifugação da polpa de cacau, apresentou baixa atividade de PFO (72U/g de polpa de cacau) e maior atividade de POD (668 u/g de polpa de cacau). Em estudo univariável a PFO do extrato bruto solúvel da polpa de cacau apresentou atividade ótima a 20ºC e em pH 7,0 e maior estabilidade na faixa de pH 2,6 a 10, após 24h a 5ºC ou 4h a 25ºC. A enzima apresentou 13% da atividade inicial após tratamento a 70ºC por 10 minutos, sendo completamente inativada após tratamento térmico a 80ºC por 1 minuto. Em estudo univariável a POD do extrato bruto solúvel da polpa de cacau apresentou atividade ótima a 40 ºC e em pH 5,0. O tratamento da polpa de cacau com ácido ascórbico nas concentrações de 1 a 5 mMol/L, proporcionou uma maior redução na atividade de POD entre os agentes anti-escurecimento, em todas as concentrações testadas, sendo obtida uma redução na atividade de 99% e 100%, após armazenamento por 1h e 24h a 5ºC, respectivamente, com a adição de 5mMol/L de ácido ascórbico à polpa de cacau. O tratamento térmico em ebulição por 1 minuto reduziu 99% da atividade da POD da polpa de cacau e o tratamento térmico a 70ºC da polpa de cacau contendo 3mMol/L de ácido ascórbico e posterior armazenamento durante 24h a 5ºC resultou em completa inativação da POD / Abstract: The enzymatic browning reaction occurs in many fruits and vegetables when certain phenol compounds are oxidized in reactions catalyzed by enzymes such as polyphenol oxidase (PPO) (EC 1.14.18.1) and peroxidases (POD) (EC 1.11.1.7). A widening of the alternatives for the preservation of fruits such as the Rubimel plum, whose production in Brazil has increased in recent years, and of cocoa pulp, a fruit with an exotic and very agreeable taste, highly consumed in the State of Bahia, Brazil, is necessary because it enables one to search for consumer markets for products derived from these fruits in more distant regions, preserving the quality of the fruit in natura. The objective of the present work was to characterize the enzymes polyphenoloxidase and peroxidase present in the pulps of the Rubimel plum and cocoa, and study the effects of some antioxidants on the preservation of the natural color of the pulps.The juice of the Rubimel plum turns brown quickly after extraction. The crude enzymatic extract obtained by centrifugation of the Rubimel plum pulp showed PPO (448U/g of pulp) and POD (705U/g of pulp) activities. In a univariate study PPO (preliminary study preceding a study of the combined effect) the PPO in the crude extracts from the Rubimel plum showed optimum activity in the temperature range from 30 to 35°C at pH 6.5 and was stable in the pH range from 3.0 to 7.5 after 24 hours at 5°C or 4 hours at 25°C. The enzyme was completely inactivated after heat treatment at 70°C for 10 minutes or at 80ºC for 1 minute. In a study of the combined effect of pH and temperature using response surface methodology it was found that Rubimel plum PPO was most active at pH 6.5 in the temperature range from 30 to 35°C, and showed less activity at pH values close to 4.0 when incubated at 5°C and at 65ºC. In the univariate (preliminary study preceding a study of the combined effect) the POD in the crude extracts of the Rubimel plum showed greater activity at 40°C and pH 4.0 and stability in the pH range from 2.5 to 5.5, after incubation for 24h at 5ºC or 4h at 25°C. The POD was completely inactivated after heat treatment at 70°C for 10 minutes. In a study of the combined effect of pH and temperature using response surface methodology the POD of the Rubimel plum showed greater activity at pH 5.0 and 35°C, and less activity at pH values near 4 .0 when incubated at 5°C and at 65ºC. The addition of N-acetyl-L-cysteine or glutathione at final concentrations of 5 mMol/L or the addition of the combinations: 5mMol/L of ascorbic acid + 1.8 mMol/L of 4-hexyl-resorcinol or 5mMol/L ascorbic acid + 3.4mMol/L of L-cysteine, resulted in a 99% reduction in the PPO activity of the Rubimel plum. The soluble extract obtained by centrifugation of the cocoa pulp showed low PPO activity (72U/g of cocoa pulp) and high POD activity (668U/g of cocoa pulp). The PPO in the crude extract from cocoa pulp showed optimum activity at 20°C and pH 7.0, and stability in the pH range from 2.6 to 10.0, after 24 hours at 5°C or 4 hours at 25°C. The enzyme showed 13% of its initi al activity after treatment at 70°C for 10 minutes, being completely inactivated a fter heat treatment at 80°C for 10 minutes. In a univariate study the POD in the soluble crude extract from the cocoa pulp showed optimum activity at 40°C and pH 5 .0. The treatment of cocoa pulp with ascorbic acid at concentrations from 1 to 5 mMol/L, provided a greater reduction in POD activity than any of the other anti-browning agents tested, at all the concentrations tested, obtaining reductions in activity of 99% and 100%, respectively, after storage for 1 hour and 24 hours at 5°C, with the addition of 5mMol/L ascorbic acid to the cocoa pulp. Heat treatment in boiling water for 1 minute reduced the POD activity of cocoa pulp by 99% and treatment at 70°C for 30 minutes of cocoa pulp containing 3mmol / L of ascorbic acid and then stored for 24 hours at 5°C resulted in complete inactivation o f the POD / Doutorado / Doutor em Ciência de Alimentos

La conservation des mangues 4ème gamme est limitée par le brunissement enzymatique et la perte de fermeté dus aux différentes opérations de transformation. Cette thèse propose un nouvelle approche pour améliorer la conservation de mangues 4ème gamme : l’application de traitements thermiques par immersion et/ou la conservation sous atmosphère modifiée : passive ou active (5% O2 – 5 % CO2) ou des enrobages (chitosane). Ce travail a permis tout d’abord de déterminer un couple température / temps optimal: 50 °C / 30 min qui permet de maintenir la qualité de plusieurs variétés de mangue (Keitt, Kent, Tommy Atkins). Les effets du traitement thermique sur l’intensité respiratoire, la couleur, la fermeté, les teneurs en antioxydants : vitamine C, caroténoïdes et phénols totaux, et sur l’activité de plusieurs enzymes (pour la fermeté : PME, PG, b-GAL ; et pour la couleur : PPO et PAL) ont été étudiés. Ces travaux ont montré que durant 9 jours à 6 °C, le traitement thermique maintient principalement la couleur par réduction de l’activité de la PPO et réduit la perte en fermeté par réduction de l’activité des enzymes pectolytiques (PME et b-GAL). Par ailleurs, les atmosphères modifiées semblent moins efficaces pour le maintien de la couleur et de la fermeté des mangues 4ème gamme. L’association du traitement 50°C/ 30 min avec une conservation sous atmosphère modifiée apporte peu d’effets additionnels et a même parfois un effet inhibiteur / The storage of fresh-cut mangoes is limited by the enzymatic browning and the loss of firmness due to the various operations of process. This work proposes a new approache to improve the storage of fresh-cut mangoes by: application of heat treatments by dipping with, or not, a storage under modified atmosphere: passive or active (5% O2 - 5% CO2) or using coatings (chitosane). The first step of this work was to determine the traitement 50 °C/30 min as an optimal treatment which maintian the quality of several varieties of mango (Keitt, Kent, Tommy Atkins). Effects of the heat treatment on the respiratory intensity, the color, firmness, the contents antioxydants: vitamin C, carotenoids and phenols total, and on the activity of several enzymes (PME, PG, b-GAL: for firmness; and PPO and PAL for colour changes) were studied. This work showed that during 9 days at 6 °C, the heat treatment maintains mainly the color by reduction of the activity of PPO and reduces the loss in firmness by reduction of the activity of the pectolytic enzymes (PME et b-GAL). In addition, the modified atmospheres seem less effective for the maintenance of the color and the firmness of freshcut mangoes. Combination of heat treatment with a modified atmosphere storage and have less additional effects and has even sometimes an inhibiting effect

Mixed drinks have been used to take advantage of certain fruits, which individually have difficulties in processing, such as banana, whose derivatives in preparation of beverages has been affected by the high content of pectin, a tendency to browning and formation of colloids. Recently, fruits like pineapple have been used for reclamation of other fruit, because they have good acceptability, antioxidant capacity and improve color stability. The aim of this study was to develop and characterize a mixed drink based on pineapple and banana. In the first stage, we used a total factorial design to evaluate the viability of heat treatment at different temperatures (70, 80 and 90 oC) and processing times (30, 60 and 90 min), on the stability of physical-chemical parameters in pineapple banana juice (2:1 v/w). We selected the treatment with the best conditions, in terms of quality, and three final formulations were proposed, with the intention of proving the preservative power of pineapple juice when combined with banana (2:1 v/w). Formulations included a banana nectar pasteurized (NBP), a pasteurized mixed juice, as well as, a pasteurized and sulphited mixed juice (SMP and SMPS). Microbiological analysis (aerobic-mesophile, yeasts and molds) were held in refrigerated samples to ensure safety in the sensory test of acceptability. Raw materials were characterized for having high percentage of moisture and an important mineral content and total dietary fiber. Results obtained using factorial test showed viability for use of heat treatment at 70 °C for 30 min to minimize browning reactions and maintain physical-chemical stability during storage. Moreover, NBP samples showed more susceptibility of loss for quality parameters, with high temperatures affecting, undesirably, certain parameters, such as luminosity index, yellow index, TSS/TA ratio and total polyphenol contents. Also, NBP samples were more susceptible to microbiological contamination. SMP and SMPS samples showed less change for important parameters, such as color and TSS/TTA ratio, but were impossible maintain stability of polyphenol contents. SMP showed higher K content that those found in fresh pulps. Microbiological counts for refrigerated samples were 11 and 51 CFU/mL, for aerobic mesophile-and molds and yeasts respectively. Both, SMP and SMPS were no significant differences between scores obtained in sensorial acceptability test. Results confirm viability of using pineapple and banana fruits to develop not sulphited mixed drinks, which are microbiologically safe, show sensory acceptability and maintain good quality parameters during 30 days of storage. / Bebidas mistas têm sido usadas para aproveitar certas frutas, que individualmente tem dificuldades no processamento, como é o caso da banana, cujos derivados na elaboração de bebidas têm sido afetados pelo alto teor de pectinas, tendência ao escurecimento e formação de coloides. Recentemente, frutas como o abacaxi têm sido usadas para aproveitamento de outras frutas, já que apresenta boa aceitação sensorial, capacidade antioxidante e favorecem a estabilidade da cor. O objetivo deste estudo foi desenvolver e caracterizar uma bebida mista a base de abacaxi e banana. Na primeira etapa, foi usado um planejamento totalmente fatorial para avaliar a viabilidade do tratamento térmico, a diferentes temperaturas (70, 80 e 90 oC) e tempos de processamento (30, 60 e 90 min), sob a estabilidade dos parâmetros físico-químicos em bebida a base de abacaxi e banana (2:1 v/m). Selecionou-se o tratamento que manteve as melhores condições em termos de qualidade e foram propostas três formulações finais, com intenção de comprovar o poder conservante do suco de abacaxi quando combinado com banana (2:1 v/m). As formulações incluíram um néctar de banana pasteurizado (NBP), suco misto pasteurizado e suco misto pasteurizado sulfitado (SMP e SMPS). Análises microbiológicas (aeróbios-mesófilos, bolores e leveduras) foram realizadas em amostras refrigeradas para garantir a segurança no teste sensorial de aceitabilidade. As matérias primas caracterizaram-se por apresentarem alta percentagem de umidade e um conteúdo importante de minerais e fibra alimentar total. O resultado obtido para o teste fatorial mostrou a factibilidade do uso do tratamento térmico a 70 oC por 30 min para minimizar as reações de escurecimento e manter a estabilidade físico-química durante o armazenamento. Por outra parte, os NBP mostraram mais susceptibilidade à perda de parâmetros de qualidade, sendo que altas temperaturas afetaram negativamente certos parâmetros, como o índice de luminosidade, o índice de amarelo, relação SST/ATT e polifenóis totais. Os NBP também foram mais susceptíveis à contaminação microbiológicas. Os SMP e SMPS apresentaram poucas mudanças em certos parâmetros de importância, como cor e relação SST/ATT, mas não foi possível manter a estabilidade no teor de polifenóis. O teor de K em SMP foi maior que o presente nas polpas. A análises microbiológicas para amostras refrigeradas apresentaram contagens de 11 e 51 UFC/mL, para aeróbios-mesófilos e bolores e leveduras respetivamente. Tanto o SMP quanto o SMPS foram aceitos sensorialmente e não apresentaram diferenças significativas entre o grau de aceitação. Os resultados confirmam a viabilidade de uso de abacaxi e banana para desenvolver bebidas mistas não sulfitadas, microbiologicamente seguras, aceitáveis sensorialmente e com bons parâmetros de qualidade durante 30 dias de armazenamento.

The majority of lakes on Earth are shallow, unproductive and located at high latitudes. These lakes are experiencing big changes due to climate change, where two environmental drivers operate simultaneously, browning and warming. How they affect lake ecosystems is not well understood. Here, I addressed this issue by using a theoretical and an experimental approach. In particular, I generated model predictions and compared them with the results of a realistic large-scale experiment, where browning and warming were manipulated in a factorial design. In addition, model outcomes were compared with data from 12 unproductive lakes sampled along a gradient of browning. Another novelty of my thesis is that it integrates benthic and pelagic food web components in the model and experimental approaches. I found that browning affected the resources availability for benthic and pelagic producers in the model and in the experiment. With browning, benthic primary producers became increasingly light limited and declined, while pelagic producers became less nutrient limited and increased. Pelagic nutrient limitation was alleviated by two non-exclusive mechanisms. Browning directly enriched the water with nutrients, and browning indirectly increased the nutrient flowing from the sediment to the pelagic habitat via suppression of benthic producers. To tease apart these two mechanisms I applied structural equation modeling (SEM). The indirect evidence by SEM suggests that both mechanisms contributed equally to the pelagic nutrient concentration in the experiment. Interestingly, a model food web with only primary producers shows similar qualitative behavior as a food web with grazers and carnivores included. This happens because carnivorous fish exert strong top-down control in the more productive habitat, which relaxes grazing pressure on primary producers and increases resource limitation in the adjacent habitat. Biomass of benthic and pelagic consumers followed the same pattern as their resources. The lake data were largely congruent with model expectations and supported the findings of the experiment. Furthermore, the model also predicted a negative relationship between total phosphorus and both primary and fish production, which was observed across the 12 lakes. Warming effects were more complex. The model predicts that warming effects should depend on browning and are expected to be strongest in the more productive of the two (benthic and pelagic) habitats. For example, at low levels of browning the biomasses of benthic algae and fish are expected to decline with warming, which was observed in the experiment. In contrast, observed warming effects at high levels of browning deviated from model expectations. The mechanisms by which browning and warming interactively affect lake food webs are still poorly understood. This thesis offers a conceptual foundation for their further study through the integration of within- and between-habitat interactions.

Litchi (Litchi chinensis Sonn.) is a commercially valued fruit mainly for its attractively red pericarp and exotic taste. However, the market value of the fruit is affected by pericarp browning, desiccation and postharvest decay. Current control measures include sulphur dioxide (SO2) fumigation, low temperature storage and high relative humidity (RH). Sulphur residues on fruit, moisture loss, altered taste and decay caused by Penicillium spp., limit the use of SO2 fumigation. Technology that can provide a potential alternative method to retain the quality of fruit is modified atmosphere packaging (MAP). In this study (Chapter 3), the effect of active and passive modified atmospheres on quality retention of litchi cultivars ‘Mauritius’ and ‘McLean’s Red’ was investigated. Results indicated that ‘McLean’s Red’ is more suitable for MAP technology than ‘Mauritius’. Lidding film–4 holes significantly reduced activity of oxidation enzymes, polyphenol oxidase (PPO) and peroxidase (POD), and retained higher pericarp colour. Lidding film–10 holes retained soluble solids concentration to titratable acidity ratio (SSC/TA) (~65), thereby preventing the loss of taste and litchi fruit flavour. In order to enhance the MAP technology further (Chapter 4), chitosan coating of fruit was also assessed. Chitosan (1.0 g L-1) combined with MAP effectively prevented decay, browning and pericarp colour loss in ‘McLean’s Red’. Chitosan (1.0 g L-1) integrated with MAP reduced PPO and POD activity, retained membrane integrity, anthocyanin content and pericarp colour. ‘McLean’s Red’ was found to be more suitable for the chitosan (1.0 g L-1) and MAP integrated treatment than ‘Mauritius’ in retaining overall quality. In addition, the effect of 1-methylcyclopropene (1-MCP) in combination with MAP was determined for both cultivars (Chapter 5). In this case 1-MCP (300 nL L-1) was most effective in preventing browning and retaining colour in both cultivars after 14 and 21 days of cold storage. The effect of 1-MCP (300 nL L-1) showed more potential on ‘McLean’s Red’ than ‘Mauritius’. At higher concentrations (500 and 1000 nL L-1), 1-MCP showed negative effects on membrane integrity, pericarp browning, PPO and POD activity in both cultivars. The effect of integrated postharvest treatments i.e. modified atmosphere packaging combined with chitosan and integrated MAP and 1-MCP as well as MAP and chitosan coating on foodborne bacterial pathogens (Escherichia coli O157:H7 and Staphylococcus aureus) spike-inoculated on litchi fruit surfaces, and Penicillium spp. decay were also investigated (Chapter 6). Results showed integrated MAP and chitosan (0.1 g L-1 and 1.0 g L-1) treatments significantly reduced high and low inoculums load of E. coli O157:H7 and S. aureus on litchi fruit after 21 days of cold storage. Integrated MAP and 1000 nL L-1 1-MCP resulted in higher disease severity. Integrated MAP and chitosan (0.1 g L-1 and 1.0 g L-1) treatments showed very good decay control. The total microbial population of the litchi fruit surface was also determined. Integrated MAP and 1.0 g L-1 significantly reduced the total microbial flora after 21 days of cold storage. / Dissertation (MSc)--University of Pretoria, 2010. / Microbiology and Plant Pathology / unrestricted

abstract: The popularity of solar photovoltaic (PV) energy is growing across the globe with more than 500 GW installed in 2018 with a capacity of 640 GW in 2019. Improved PV module reliability minimizes the levelized cost of energy. Studying and accelerating encapsulant browning and solder bond degradation—two of the most commonly observed degradation modes in the field—in a lab requires replicating the stress conditions that induce the same field degradation modes in a controlled accelerated environment to reduce testing time. Accelerated testing is vital in learning about the reliability of solar PV modules. The unique streamlined approach taken saves time and resources with a statistically significant number of samples being tested in one chamber under multiple experimental stress conditions that closely mirror field conditions that induce encapsulant browning and solder bond degradation. With short circuit current (Isc) and series resistance (Rs) degradation data sets at multiple temperatures, the activation energies (Ea) for encapsulant browning and solder bond degradation was calculated. Regular degradation was replaced by the wear-out stages of encapsulant browning and solder bond degradation by subjecting two types of field-aged modules to further accelerated testing. For browning, the Ea calculated through the Arrhenius model was 0.37 ± 0.17 eV and 0.71 ± 0.07 eV. For solder bond degradation, the Arrhenius model was used to calculate an Ea of 0.12 ± 0.05 eV for solder with 2wt% Ag and 0.35 ± 0.04 eV for Sn60Pb40 solder. To study the effect of types of encapsulant, backsheet, and solder on encapsulant browning and solder bond degradation, 9-cut-cell samples maximizing available data points while minimizing resources underwent accelerated tests described for modules. A ring-like browning feature was observed in samples with UV pass EVA above and UV cut EVA below the cells. The backsheet permeability influences the extent of oxygen photo-bleaching. In samples with solder bond degradation, increased bright spots and cell darkening resulted in increased Rs. Combining image processing with fluorescence imaging and electroluminescence imaging would yield great insight into the two degradation modes. / Dissertation/Thesis / Doctoral Dissertation Systems Engineering 2020

Thesis (M. Sc. (Horticulture)) -- University of Limpopo, 2019 / The South African Avocado Industry is continuously expanding with ‘Hass’ cultivar occupying the largest land and therefore, the most exported cultivar. Expansion of the industry implies an increased demand for irrigation water. However, South Africa is a water scarce country characterised by low and erratic rainfall, where fruit production relies heavily on irrigation. The agricultural sector is under an obligation to reduce water use due to the increasing demand for water by other economic sectors. Therefore, it must find efficient water use techniques to save water and ensure water availability for other economic sectors. Partial root-zone drying (PRD) is an irrigation technique which may lead to 50% reduction in water use, half of the root system is kept wet while the other half is left dry to a predetermined level of soil water depletion, the dry and the moist sides are alternated at regular intervals. During storage and transportation of fresh produce, low temperature is a post-harvest tool used to maintain quality, especially when fruit are destined for long distant export markets. This study investigated the effect of PRD and low temperature storage on post-harvest quality parameters of ‘Hass’ avocado fruit. The experiment was laid as a factorial arranged in randomised complete block design (RCBD). The treatment factors for chilling injury, electrolyte leakage and vascular browning were 2 x irrigation regimes (Full Irrigation (FI) vs. PRD) and 2 x storage temperatures (2.0 and 5.5°C). However, treatment factors for fruit weight loss, respiration rate, fruit firmness, ripening percentage and fruit skin colour were 2 x irrigation regimes (Full Irrigation (FI) vs. PRD), 2 x storage temperatures (2.0 and 5.5°C) and 4 ripening days (0, 2, 4 and 6 days). Mature ‘Hass’ avocado fruit were harvested from PRD and fully irrigated trees and thereafter fruit of each treatment were stored at 2.0 and 5.5°C for 28 days. Each treatment consisted of 6 replicates, with an exception of electrolyte leakage, whereby the experiment was replicated 4 times. After 28 days’ storage at 2.0 and 5.5°C, fruit were ripened at 21°C. The effect of PRD and low temperature storage was determined by evaluating the following physico-chemical fruit parameters during ripening: external chilling injury, electrolyte leakage, fruit weight loss, respiration rate, firmness, fruit skin colour and vascular browning. During ripening, ‘Hass’ avocado fruit stored at 2.0°C showed significantly higher incidences of external chilling injury symptoms compared with xiii 5.5°C, irrespective of irrigation treatment. Furthermore, an interaction between irrigation treatment and low storage temperature had a significant (P<0.05) effect on cell membrane electrolyte leakage. All evaluated fruit showed similar weight loss, irrespective of irrigation and storage treatment. Irrigation, storage temperature and ripening days did not have effect on respiration during ripening. Fruit reached the respiratory climacteric peak on the same day (day 2). Furthermore, there was no significant interaction effect (P˃0.05) on fruit firmness. However, PRD treated fruit showed slightly low firmness when compared with control fruit. ‘Hass’ avocado fruit harvested from PRD and fully irrigated trees and stored at 5.5°C ripened quicker compared to fruit stored at 2.0°C. There was no significant interaction effect (P˃0.05) on fruit skin lightness (L), chroma (C), hue angle (h°) and fruit eye colour due to irrigation and cold storage treatment. In general, fruit showed skin colour change from emerald green to approximately 75% coloured. Furthermore, irrigation and storage temperature did not have effect on vascular browning, however, there incidence was high on fruit stored at 2.0°C when compared with 5.5°C. The results of this study indicated that ‘Hass’ avocado fruit stored at 2.0°C was negatively affected by low temperature storage and this cold storage temperature is not recommended. PRD reduced water use during irrigation, however, its effect on post-harvest quality of ‘Hass’ avocado fruit subjected to 5.5°C must be further investigated before recommended for export markets. / Agricultural Research Council-Tropical and Subtropical Crops (ARC-TSC) and Agricultural Sector Education Training Authority (AgriSeta)