Dissertations / Theses on the topic 'Hot air drying'

Thesis (M. Sc. (Agriculture)) --University of Limpopo, 2017
Tea is one of the most popular consumed beverages in the world, which has beneficial properties such as anti-oxidization, anti-carcinoma and preventing arteriosclerosis. The major essential components of catechins present in tea leaves, includes epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), epicatechin (EC), gallocatechin (GC) and catechin (C). Influence of time-based hot air drying method on chemical composition of the Jatropha zeyheri Sond, widely consumed in rural communities of Zebediela (Khureng village), Limpopo Province, South Africa, was investigated. Four treatments, namely; 0, 24, 48, and 72 hours, were arranged in completely randomised design (CRD), replicated five times. The study demonstrated that drying significantly increased total phenolic content, total antioxidant capacity and tannin content. It also demonstrated that drying significantly increased minerals elements; Mg, K, P, S, Al, Co, Mn, Si and Zn content and decreased Na, Ca and Ni and Zn quantities. Sodium-potassium ratio was very low across drying periods. Drying time did not significantly influence proximate chemicals; energy, protein, carbohydrates, ash and fibre content. Moisture and fat were significantly increased by drying period. Results of the study suggested that time-based hot air drying method improved the chemical composition of J. zeyheri, which has the potential of enhancing nutrition in marginal rural communities of Limpopo Province.

Banana (Musa acuminate) is a wholesome fruit that plays an important role in healthy diets and in international trade. However, many bananas are wasted and they in turn generate environmental problems as well as worsen the shortage of foods. This study aims at generating value to non-marketable fruits and at studying the effects of the drying process on the physico-chemical properties of banana. In the first part of this study, physical and chemical properties of banana were measured during ripening in order to establish predictive models between these properties and level of ripeness. To achieve this, changes in moisture content, peel color, texture, peel to pulp ratio, starch (resistant and non-resistant), mass loss, dielectric properties, total soluble solids, were measured at different stage of ripening. A hyperspectral imaging study was also conducted to validate these results. In the second part, experiments were conducted to assess the effects of maturity level and drying conditions on total, resistant and non-resistant starch contents in banana. Results obtained from the first part of this study were used to assess maturity level. The methods utilized to dry the banana slices were microwave with hot air or hot air alone, at different temperatures. Drying conditions were optimized. The hybrid drying system consisting of microwave with hot air was found to be superior to hot-air alone and the best drying temperature for unripe banana was found to be 65°C.
La banane (Musa acuminés) est un fruit sain qui joue un rôle important dans les régimes alimentaires équilibrées et dans le commerce international. Cependant, beaucoup de pertes sont encourues dans la manutention et la transformation des bananes ce qui génère des problèmes environnementaux et réduit sa disponibilité sur les marchés. Cette étude porte sur la valorisation des bananes déclassées et sur les effets du procédé de séchage sur ses caractéristiques physico-chimiques. Dans la première partie de l'étude, les propriétés physico-chimiques de la banane ont été mesurées à différents niveaux de maturité afin d'établir des modèles prédictifs. Pour y parvenir, la teneur en eau, la couleur de la peau, la texture, le rapport pulpe-peau, la teneur en amidon (résistant et non résistant), la perte de masse, les propriétés diélectriques, et la teneur en solides solubles totaux, ont été mesurés à différents stages de maturation. Une étude d'imagerie hyperspectrale a également été menée pour valider ces résultats. Dans la deuxième partie, des expériences ont été menées pour évaluer les effets du niveau de maturité et des conditions de séchage de la banane, sur la teneur en amidon (résistants, non-résistants t totaux). Les résultats obtenus dans la première partie de l'étude ont été utilisés pour évaluer le niveau de maturité. Les méthodes utilisées pour le séchage de tranches de bananes étaient soit : micro-ondes avec air chaud ou de l'air chaud seulement. Lors des essais, les séchoirs ont été opérées à des températures différentes et les conditions d'opération ont été optimisées. Le système de séchage hybride composé de micro-ondes avec air chaud a été jugé supérieur à l'air chaud seul et la température de séchage optimale pour la banane verte était de 65 ° C.

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.

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Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG
The aim of this study was to evaluate the physical and chemical quality Curcuma Longa L. leaf submitted to three drying methods: hot air drying, freezedrying and microwave drying, as well as the study of kinetic drying methods by convection and microwave. For the kinetic study the leaves were dried by hot air (60 °C) and microwave drying (900W power). Mathematical modeling using various models was performed, as follows: Lewis, Page, Henderson and Pabis, Wang and Singh, and logarithmic models were used to adjust experimental kinetic data. The results showed that the drying time of microwave was 60 times lower than hot air drying. Page model was the best adjusted the drying kinetics data by both methods. The phenol content was higher in the dry leaf (185.42mg/100g-1±0,65) by microwave (p <0.05) than in the hot air dried leaf (183,76 mg/100g-1±0,60), showing phenolic content greater than three times the fresh leaf (54,88mg/100g-1±0,76). It was observed that the drying process does not influence the color variation (ΔE) of the dried leaf. To study the physical and chemical characterization of Curcuma longa L. leaves by studying the chemical composition of the fresh leaf, mineral composition, antinutritional factors and evaluation of the color change of fresh and dry leaf, they were dehydrated by methods microwave, hot air drying and freezedrying. The chemical composition showed appreciable amounts of protein (39,5g (100g) -1 ± 0.91), carbohydrates (44,74g (100g) -1 ± 1.04), total fiber (34,47g (100g) -1 ± 0.98), and soluble fiber (22,65g (100g) -1 ± 0.65), insoluble fiber (11,81g (100g) -1 ± 0.34), ash (13,81g (100g) - 1 ± 1.05), and low in lipids (2,47g (100g) -1 ± 0.12). The mineral composition showed higher amounts of Na, Mg, K, Ca, P, and Mn. Other minerals are Fe and Zn. It was observed low levels of nitrate 0.05 mg / g ± 0.00 (fresh leaf) and 0,46-0,47mg / g (dry leaves) and showed no cyanogenic compounds in its composition. It was observed that the drying process influence on color variation of the dry leaves, increasing the brightness, diminindo the intensity of green color and causing the change in the shade of green to yellowish green. To study the effect of different methods of preservation (hot air drying, in a microwave and freezedrying) the content of bioactive compounds and antioxidant capacity of turmeric leaves, they were dehydrated by drying in an oven (60 ° C) in microwaves (900 W) and lyophilizing (vacuum of 300 mmHg) until equilibrium moisture content (0.030 kgágua.kgsolido dry- 1 ). The content of total phenolics, tannins hydrolysates and condensates and antioxidant activity (DPPH scavenging, reducing and iron chelation) of dried and fresh Curcuma longa leaves were evaluated. The drying methods led to reduction of all the characteristics assessed on a dry basis (2.77 to 73.86%) and antioxidant capacity compared to fresh leaf (67 to 98%). The microwave drying was preservation method studied which produced the best dry leaves, based on the content of bioactive compounds and antioxidant capacity (top being 0.9 to 612% compared to other methods).
O objetivo desse trabalho foi avaliar a qualidade físico-química e caracterizar os compostos bioativos e capacidade antioxidante da folha da Cúrcuma Longa L. submetida a três métodos de secagem: estufa, liofilização e micro-ondas, assim como o estudo cinético pelos métodos de secagem por convecção e micro-ondas. Para o estudo cinético as folhas foram secas por convecção (temperatura de 60°C) e micro-ondas (potência de 900 W). Foi realizada a modelagem matemática utilizando vários modelos, sendo eles: Lewis, Page, Henderson e Pabis, Wang & Singh e logarítmico, ajustando os modelos aos dados experimentais cinéticos. Os resultados obtidos revelaram que o tempo de secagem por micro-ondas foi 60 vezes inferior ao de secagem convectiva. O modelo de Page foi o que melhor ajustou os dados de cinética de secagem pelos dois métodos. O conteúdo de fenólicos foi superior na folha seca (185,42mg/100g-1±0,65) pelo método micro-ondas (p<0,05) que na folha seca por convecção (183,76 mg/100g-1±0,60), apresentando conteúdo de fenólicos maior que três vezes o da folha in natura (54,88mg/100g-1±0,76). Observou-se que o processo de secagem não influenciou na variação de cor (ΔE) da folha seca. Para o estudo da caracterização física e química de folhas de Curcuma longa L. através do estudo da composição centesimal da folha fresca, composição de minerais, presença de fatores antinutricionais e avaliação da variação de cor da folha fresca e seca, estas foram desidratadas pelos métodos de micro-ondas, estufa e liofilização. A composição centesimal apresentou quantidades apreciáveis de proteínas (39,5g (100g)-1 ±0,91), carboidratos (44,74g (100g)-1±1,04), fibras totais (34,47g (100g)-1±0,98), sendo fibra solúvel (22,65g (100g)-1±0,65), fibra insolúvel (11,81g (100g)-1±0,34) , cinzas (13,81g (100g)-1±1,05), e baixo teor de lipídeos (2,47g (100g)-1±0,12). A composição mineral mostrou maiores valores de Na, Mg, Ca, K, P e Mn. Outros minerais foram Fe e Zn. Observou- se baixos teores de nitrato 0,05 mg/g±0,00 (folha fresca) e 0,46-0,47mg/g (folhas secas) e não apresentou compostos cianogênicos em sua composição. Observou-se que o processo de secagem influenciou na variação de cor das folhas secas, aumentando a luminosidade, diminindo a intensidade da cor verde e provocando a mudança da tonalidade verde para verde amarelada. Para o estudo do efeito de diferentes métodos de conservação (secagem em estufa, em micro-ondas e liofilização) no conteúdo de compostos bioativos e na capacidade antioxidante de folhas de cúrcuma, estas foram desidratadas por secagem em estufa (60ºC), em micro-ondas (900 W) e liofilização (vácuo de 300 mmHg) até umidade de equilíbrio (0,030 kgágua.kgsólido seco -1 ). O conteúdo de fenólicos totais, taninos hidrolisados e condensados e atividade antioxidante (sequestradora de DPPH, redução e quelação de ferro) de folhas cúrcuma secas e fresca foram avaliados. Os métodos de secagem provocaram redução de todas as características avaliadas, em base seca (2,77 a 73,86%) e capacidade antioxidante em relação à folha fresca (67 a 98%). A secagem por micro-ondas foi o método de conservação estudado que produziu as melhores folhas secas, com base no conteúdo de compostos bioativos e capacidade antioxidante (sendo superior de 0,9 a 612% em relação aos outros métodos utilizados).

Cette étude porte sur l'amélioration de la qualité de la tomate séchée par microondes assistés par air chaud (MOAC). Le principal but recherché est la préservation de la qualité de la tomate séchée en évitant notamment l'apparition de tâches noires qui souvent surviennent lors d'un chauffage microondes suite à une surchauffe locale du produit quand il devient sec. Pour ce faire, un système de séchage microondes assistés par air chaud avec la capacité de contrôler automatiquement la puissance spécifique a été développé sous labView®. Après une première étude où la puissance microondes appliquée est maintenue constante, une seconde stratégie de séchage MOAC, avec deux modes différents de régulation de la puissance spécifique, a été mise en oeuvre. Ces modes consistent à ajuster la puissance microondes appliquée à la masse du produit, représentative de la quantité d'eau restante. Dans le premier mode, l'adaptation est faite toutes les secondes (ajustement "continu") alors que dans le second mode, la puissance a été ajustée seulement chaque cinq minute (ajustement intermittent). L'ajustement permet de travailler avec un rapport puissance appliquée sur masse résiduelle du produit (puissance spécifique) constant. Tous les paramètres du procédé incluant la puissance appliquée on été enregistrés chaque seconde. De même, la température et la masse du produit sont mesurées chaque seconde. Le produit final a été caractérisé en réalisant des mesures de couleur, de texture, de structure ainsi que de taux résiduel de lycopène. La première étude sur le séchage MOAC réalisée à puissance constante (puissance spécifique variable), a produit des tomates avec des points chauds par endroit et plus de la moitié de la teneur en lycopène de la tomate est dégradée. En revanche, les tomates séchées par MOAC utilisant les deux modes de régulation du séchage, présentent une meilleure qualité en termes de couleur et de structures comparées à deux tomates séchées commerciales de référence (d'origine italienne et ivoirienne). Par ailleurs, l'observation de la structure des tomates par Microscopie Electronique à Balayage (MEB), a permis d'expliquer les changements observés au niveau de la texture de la tomate séchée. D'un point de vue chimique, le taux résiduel de lycopène de la tomate séchée par les modes de régulation (1 et 2) est situé respectivement entre 64,78 et 55,63% pour les puissances et températures d'air basses (3W/g-30°C) et entre 30,91 et 28,75% pour les puissances et températures d'air élevées (7W/g-50°C), contre 30,56 et 22,30% pour les tomates commerciales d'origine italienne et ivoirienne.

Ce travail de thèse porte sur l’étude de l’effet du traitement par champs électriques pulsés (CEP) sur différents procédés de séchage et de friture à partir de produits végétaux (pommes de terre et carottes). Les interactions entre différents modes de séchage et de prétraitement ont été étudiées. L’impact du traitement par CEP et du pré-séchage par l’air chaud ou pré-séchage par le vide sur la cinétique de friture et sur la qualité des produits frits ont été analysés. Le prétraitement par CEP entraîne une électro-perméabilisation des membranes cellulaires, ce qui favorise l’accélération des cinétiques de perte en masse (humidité). Les résultats montrent que le temps de séchage a été réduit significativement dans tous les procédés étudiés (séchage par l’air chaud, séchage par microonde, séchage sous vide). L’avantage du traitement par CEP se manifeste également par une diminution au niveau de la température interne du produit séché. Cette température basse présente un avantage notable dans la préservation des composés sensibles à la chaleur (caroténoïdes…). La couleur des échantillons prétraités par CEP puis séchés, gardent mieux la coloration initiale et présente une déviation réduite en termes de couleur après réhydratation. En ce qui concerne le procédé de friture, l’application du traitement par CEP montrent un avantage en termes de temps de friture mais également en termes de la teneur en huile absorbée. En effet, cette teneur en huile est moins élevée pour le cas des échantillons traités électriquement comparés aux échantillons non traités. La combinaison du CEP et du pré-séchage à l’air chaud (ou du pré-séchage sous vide) montre une réduction importante du temps de friture et également en terme de teneur en huile absorbée
This research project focuses on the effect of pulsed electric field (PEF) treatment on various drying and frying processes from plant products (potatoes and carrots). Interactions between different drying modes and pretreatment have been studied. The impact of PEF treatment and pre-drying by hot air or pre-drying by vacuum drying on frying kinetics and the quality of fried products were analyzed. PEF pretreatment results in electro-permeabilization of the cell membranes, which favors the acceleration of mass transfer processes. The results showed that the drying time was significantly reduced in all processes (hot air drying, microwave drying, vacuum drying). The advantage of the PEF treatment was also manifested by a decrease of the internal temperature of the product during drying. This lower temperature has a significant advantage in the preservation of heat-sensitive compounds (carotene, etc.). The dried sample pretreated by PEF could better retain the initial product color and had a reduced color deviation after rehydration. In regards to the frying process, the application of the PEF treatment showed not only an advantage in terms of the frying time but also in terms of oil content absorbed. The oil content of PEF treated sample was lower compared to untreated ones. Moreover, the combination of the PEF pretreatment and hot air pre-drying (or vacuum pre-drying) showed a synergistic efficiency on frying time and also in terms of oil content absorbed

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

碩士
國立中興大學
園藝學系所
106
In recent years, the average annual output of pineapple is about 440,000 metric tons, and there is a gradual increase. Although the sales volume has increased year by year in the past five years, it is only 5.5% of the annual output, so it is still mainly domestic sales. Pineapple is a tropical fruit that is not resistant to low temperature storage. Long-term storage at low temperatures can easily lead to cold damage, that is, internal browning, which seriously affects consumers'' perception. Therefore, further processing is required to improve the problem of not being able to withstand long-term storage. Drying is the most commonly used processing method. The drying rate and the quality after drying are factors that the producers use and consumers decide to purchase. Therefore, the test is carried out at different temperatures (45, 55, 65, 75 ° C) and thick- ness (0.5, respectively). Combined drying experiment of 1.0, 1.5, 2.0 cm). It can be obtained from the test results. The hot air drying of pineapple at 65 °C can effectively shorten the drying time to one day, and it has a slight browning phenomenon after proc- essing. Compared with 65 °C, it has a poor appearance color at 75 °C, due to high temperature or low temperature. Long-term processing has a browning phenomenon, so it is necessary to investigate the cause of browning during drying. In order to understand the activity changes of the enzyme at different temperatures, the pineapple pulp was soaked in 40, 50, 60, 70, 80 ° C distilled water for 30 minutes, and then the enzyme activity was investigated. Its enzyme activity, whether it is POD or PPO, decreases with increasing temperature and reaches a relatively low activity at 70 °C. In addition, after killing the cyanine at a high temperature of 80 ° C, it is dried at 75 ° C, and its appearance color is still dark brown. Therefore, it is inferred that browning of pineapple during hot air drying may belong to non-enzymatic browning. In order to reduce browning, pretreatment is required before drying, and osmotic dehydration is the most common pretreatment. Oxygen is blocked by the osmotic process to prevent enzymes and non-enzymatic reactions, while retaining the appe- arance color of the dried product. Shorten the effect of drying time. In this experiment, different sucrose (black sugar, granulated sugar, rock sugar, fine granulated sugar) was used as a penetrating agent to investigate the effect of different sucrose on the appea- rance after drying. From the test results, the refined granulated sugar and rock sugar have better appearance color, considering the cost problem. Refined sugar is used as a follow-up penetrant. The permeate concentration affects the time required for subse- quent processing. Therefore, the test is carried out by osmotic dehydration at 30°, 40°, 50°, 60°, 70° different sucrose concentrations for 4 hours. From the test results, 50% sucrose solution is obtained as the permeate. Dewatering at room temperature for 4 hours provides better processing benefits. Because the sugar enters the product during the osmotic process, resulting in poor food quality, this experiment additionally adds different additives( 2% salt, 2% vitamin C, 0.75% SD and 10% honey) to increase the flavor and investigate impact of its at appearance after drying. The test results can be obtained by adding 0.75% SD, 10% honey and 2% salt to have a better appearance. In terms of flavor, 10% honey is used as an infiltration pretreatment of pineapple to produce a pineapple with better eating quality. It can be obtained from the test results, and the sucrose permeate containing 10% honey is permeated and dehydrated at room temperature for 4 hours, and dried by hot air at 65 ° C to obtain a better dry appearance and edible quality.

碩士
大葉大學
食品工程學系碩士班
91
ABSTRACT In this research, Ming-jian flesh-reddened yams (D. alata L. var. purpurea (Roxb.) M. Pouch) (No.70R20) were studied. The flesh and skin of the yam tubers were blanched, freeze dried, and hot air dried. The antioxidant components of these samples were extracted using methanol . The antioxidant properties including the reducing power, the ferrous ion chelating power, and the free radical α, α-diphenyl-β-picryl-hydrazyl (DPPH) scavenging activity, were measured and compared with those of butylated hydroxyanisole (BHA) and alpha-tocopherol. In the analysis of reducing power, it was found that the reducing power of the yam flesh increased with the increase of the ratio of sample weight/solvent volume. Compared with BHA and alpha-tocopherol in the same concentration, the methanolic extracts of the yam flesh treated with different drying methods had the lowest value. The reducing power of the methanolic extract of the freeze dried yam skin had higher value. The reducing power of the methanolic extract of the hot air dried yam skin was good when the ratio of sample weight /solvent volume was 4mg/ mL. The methanolic extracts of yam after different drying treatments were still lower than BHA and alpha-tocopherol in the reducing power. In the analysis of ferrous ion chelating power, the methanolic extracts of the yam flesh dried by different treatments were the highest in ferrous ion chelating power with the value around 85%. BHA and alpha-tocopherol exhibited no ferrous ion chelating power. The methanolic extract of the hot air dried yam skin was stronger than freeze dried yam skin in the ferrous ion chelating power. The methanolic extracts of the yam skin after different drying treatments were had an increasing followed by decreasing clelating power as the ratio of sample weight/solvent volume increased. In the analysis of DPPH scavenging activity, BHA and alpha-tocopherol had the highest scavenging activity. The DPPH scavenging activity of the methanolic extracts of the yam flesh treated with different drying methods were getting greater with the increase of the ratio of sample weight /solvent volume. The methanolic extract of the freeze dried yam skin had a higher DPPH scavenging activity. With the increase of the ratio of sample weight /solvent volume, the DPPH scavenging activity of the hot air dried yam skin methanolic extract had higher scavenging activity and was close to alpha-tocopherol ,freeze dried yam skin methanolic extract lower than BHA.. In the analysis of antioxidant components of the methanolic extracts treated with different drying methods, the results showed that the freeze dried yam skin had the highest quantity of polyphenols with 33.05 mg per gram, which was 5.2 ~ 5.6 times higher than the yam flesh ,and was 1.6 times higher than the hot air dried yam skin. In the analysis of flavonoids, the freeze dried yam skin had the highest quantity. In the analysis of ascorbic acid, the freeze dried yam flesh had the highest quantity. Four yam samples treated with different drying methods were all lower in ascorbic acid. In the test of the storage stability, the yam samples treated with different drying methods did not have a great change in ascorbic acid, flavonoids, and polyphenols, after they had been stored for eight weeks. They also made no obvious change in color. In water quantity, the hot air dried yam samples had a greater change with the increase of the storage time. All the results showed that the methanolic extracts of the freeze dried yam skin had the highest quantities of flavonoids and polyphenols in the quantitative analysis of the antioxidant components. Besides, because of its good reducing power and DPPH scavenging activity, the yam skin classified as farming waste is worth studying to enhance its value. KEY WORDS: yam, yam flesh, yam skin, freeze dried, hot air dried, antioxidant properties.

碩士
國立屏東科技大學
食品科學系所
95
Dry longan (Euphoria longana Lam.) is not only a fruit with special color, flavor, and taste, but also a tonic medicine for curing some symptoms, such as weakness, fatigue, and anemia. The quality of dry longan is greatly affected by drying method. Thus, this study compare the moisture content, water activity, product size, chroma change, and volatile compounds in the dry longan made by two drying methods: traditional drying and hot air drying. Experimental results showed that the drying rate of pulp in the traditional drying method was lower than that in the hot air drying method. In addition, the moisture content in dried pulp made by the hot air drying method was higher than that made by the traditional drying method by 27.7%. The water activity in both whole longan and pulp reduced with time in both traditional and hot air drying process. The water activity in the dried whole longan and the dried pulp made by the hot air drying method was higher than that made by the traditional drying method by 20.9% and 17.3%, respectively. In the product size changes, after a 128-hour drying by using the traditional drying method, the length and width of whole longan reduced by 7.0% and 5.7% respectively; whereas the length and width of longan pulp reduced by 19.5% and 26.5% respectively. For hot air drying method, after a 34-hour drying, the length and width of whole longan reduced by 3.3% and 4.6% respectively; whereas the length and width of longan pulp reduced by 11.2% and 14.0% respectively. However, there was no positive correlation between the product size change and the moisture content change during drying process of the two methods. In the chroma change, the L value of both shell and pulp in the dry longan made by the traditional drying method reduced slowly and the a value and b value were increased. The trend of chroma changes in the shell and pulp was similar. As for the dry longan made by the hot air drying method, the chroma changes between shell and pulp was quite distinct. The L value of the shell quickly reduced first and then increased to a constant, and there was no significant change in both a value and b value. In appearance, the shell color of dry longan made by the traditional drying method was deeper than that made by the hot air drying method. In respect of the volatile compounds, we used solid phase microextraction and GC/MS to separate and the volatile compounds characterized. Eleven compounds were characterized in the dry longan made by the traditional drying method. The beta-caryophyllene was the major compound. Thus, such a drying method can help retain much more terpenes in the product. As to the dry longan made by the hot air drying method, at least ten compounds were identified. The beta-ocimene was the major. This drying method can retain much more sequiterpenes in the product. Thus, we conclude that the quality of the dry longan made by the traditional drying method is better than that made by hot air drying method.

碩士
國立宜蘭大學
食品科學系碩士班
98
This aim of this study was to evaluate microwave-assisted hot air drying on process energy efficiency and product quality of candied kumqua. The drying time and energy consumption and color, texture, volume shrinkage and sensory analysis of product were investigated. The result showed that 50℃ is the best temperature for hot air candied kumqua drying, but its color and sensory evaluation is poor. Candied kumquat by two stage hot air drying had the higher sensory evaluation scores, but its drying time and energy consumption increase 68.2% and 1.5%. 52.0% drying time and 21.3% energy can be saved when removing 10g water /kg kumquat by microwave-assisted drying, and the color (L) of product increase, the hardness increase 17.8%. 69.2% drying time and 47.0% energy can be saved when removing 100g water /kg kumquat by microwave-assisted drying, and the color value (L, a, b) of product increase, the hardness decrease 50.1%, the volume increase 7.0%. 72.8% drying time and 50.1% energy can be saved when removing 200g water /kg kumquat by microwave-assisted drying, and the color value (L, a, b) of product decrease, the hardness decrease 49.63%, the volume increase 9.5%. After 11 hours hot air drying and then removing 10g water /kg kumquat by microwave-assisted drying, the drying process could save 57.6% drying time and 30.5% energy. After 6.5 hours hot air drying and then removing 100g water /kg kumquat by microwave-assisted drying, the drying process could save 69.2% drying time and 40.7% energy. The candied kumqua removing 10g water /kg kumquat by microwave-assisted hot air drying had the highest appearance and the texture score, but in the taste aspect still had the highest score by two stage hot air drying product.

碩士
國立宜蘭大學
食品科學系碩士班
99
The phenolic compounds, free and bound form, and antioxidant activities of immature calamondin (Citrofortunella mitis) peel were investigated after freeze drying and 150oC hot air drying by different solvents successive extraction, including hexane, ethyl acetate, hot water, alkaline hydrolysis and acid hydrolysis. Furthermore, the hot water extract of immature calamondin peel was treated with polyphenol oxidase activity. The phenolic compounds and antioxidant activity of resultant solution were analyzed and separated by semipreparative HPLC column. The separated fractions were subjected to the following assays antioxidant activity, tyrosinase inhibition activity, alphaamylase inhibition activity and xanthine oxidase inhibition activity. The results indicated that total phenoic contents of immature calamondin’s peel extract were 13659.53 ± 383.15 GAE mg / 100 g d.w., while 92% of it existed as free form. The compositions of flavonoids were investigated and 8823.33 ± 546.36 mg / 100 g d.w. of total flavonoids were found. Most of the flavonoids (about 99%) were free form in calamondin and 3’,5’-di-C-b-glucopyranosylphloretin and nobiletin were the two major components. However, the phenoic acid existed 95% as bound form and the major compounds were p-coumaric acid and ferulic acid. The antioxidant activity and total phenolic contents, no matter free from or bound from, of immature peel increased after 150oC drying. The total phenolic content of free form increased to 14951.37 ± 372.41 GAE mg / 100 g d.w. The highest free form phenoic contents of nobiletin and tangeretin were observed after drying with the levels of 4513.97 ± 174.20 and 2319.33 ± 90.42 mg / 100 g d.w, respectively. The free form phenolic compounds of diosmin, narrigin, hesperidin and 3’,5’-di-C-b-glucopyranosylphloretin were also found. On the other hand, the total phenolic contents of bound form increased to 1224.17 ± 110.39 GAE mg / 100 g d.w. after drying. p-coumaric acid, ferulic acid, sinapic acid and ellagic acid were found in calamondin peel, which the contents of p-coumaric acid and ferulic acid, the major two components, were 269.22 ± 32.01 and 365.11 ± 28.69 mg / 100g d.w.,respectively. Furthermore, the contents of bound form existed more ester linkage compounds than glycoside linkage compounds. This indicated that phenoic acid in immature peel were mainly in ester linkage compounds. The antioxidant activity of immature peel increased after 150oC drying. The scavenging effect on DPPH radical and the oxygen radical activity capacity of free form phenoic compounds was higher than bound form phenoic compounds, which of free form phenoic compounds were 15.65-47.92% / mg / mL and 486.80-1154.02 umole Trolox / g extract, respectively, and that of bound form phenoic compounds were 1.8-12.01% / mg / mL and 285.16-368.62 umole Trolox / g extract, respectively. The resultant solution of hot water extracts from immature calamondin peel reacted with polyphenol oxidase was separated and collected as four fractions (I-Ⅳ) by semipreparative reversed phase HPLC. The fraction I contained the highest alphaamylase inhibition activity with IC50 values of 0.55 ± 012 mg / mL, which equaled to 50% effect of the positive control (Acarbose). Meanwhile, Fraction I showed DPPH radical scavenging effect with values of 89.81 ± 1.79% / mg / mL and its IC50 closed to the value of Trolox. There are two main peaks, peak 1 and peak 2, were decteced in fraction Ⅰ. The peak 1 and peak 2 were proposed as major effective components on DPPH scavenging effect. The maximum UV absorption of peak 1 and peak 2 were 225, 238 and 288 nm, which was similar with 3’,5’-di-C-b-glucopyranosylphloretin. Therefore, peak 1 and peak 2 might probably the oxidation products of 3’,5’-di-C-b-glucopyranosylphloretin.

碩士
國立中興大學
食品暨應用生物科技學系所
100
The objective of this study is to evaluate the effect of hot-air drying (85℃,65℃,45℃) and ethanol extraction concnetrations (95%,75%,50%,25% and 0% ethanol, which was denoted as E95, E75,E50,E25 and E0, respectively ) on the antioxidant properties、dietary fiber characteristics and emulsifying properties of the young fronds of Asplenium australasicum (J. Sm.) Hook. It was found that Increasing the temperature of hot-air drying process generally resulted in an initially decrease and finally increase in the total phenolic and flavonoids contents, and ABTS and NO radical scavenging activities. Furthermore, the total phenolic and flavonoids correlated with the reducing power and DPPH radical scavenging activity, and ABTS and NO radical scavenging activities correlated with chlorophyll content. In contrast, increasing the temperature of hot-air drying process resulted in a decreased in the chlorophyll content due to thermal degradation and superoxide anion radical scavenging activity. Functional properties such as swelling, solubility, water retention capacity(WRC), fat adsorption capacity (FAC) of the A. australasicum were found to be reduced by increasing the drying temperature. The hot-air dried A. australasicum showed significant surface activity. Moreover, the emulsifying activity of A. australasicum was influenced by the pH, oil/water ratio and concentration. A. australasicum hot-air dried at 45℃showed the highest emulsifying activity and good emulsion stability (>90%). Total phenolic , flavonoids and chlorophyll contents of A. australasicum were found to be increased with increasing the ethanol extraction concentration due to the hydrophobic nature of these compounds. p-coumaric acid and ferulic acid were the main bound phenolic acids of the alkali extract of A. australasicum, and their contents increased with increasing the ethanol extraction concentration. The E75 and E50 extracts showed the highest DPPH、ABTS radical scavenging activity and reducing power ; E50 and E25 extracts showed the highest NO radical scavenging activity; and E25 and E0 extracts showed the highest superoxide anion radical scavenging activity.

The general objective of this Ph.D. programme was to study and to optimize the development, in terms of process efficiencyand the product quality,of fruit-based dry products with intermediate water content through osmotic dehydration,or reduced water content by subsequent combination of this technique with other drying methods.The first part of the work focused on the osmotic dehydration (OD) of apple cubes and physalis. The adequacyof thefit of some mathematical models to describethe mass transfer kinetics inthe products was also studied.The objectives were to perform the OD of apple cubes and to study the effects of the solute (sucrose orsorbitol) and the concentration (40 and 60 °Bx) in the osmotic solution, the mass ratio ofsample to solution (1:4 or1:10), the temperature (25, 40 and 60 ºC), and the pressure (1 bar and 150 mbar) on the water loss (WL) and the solid gain (SG).Regarding physalis, the OD was performed with a mass ratio of sample to solution of 1:4 at 60 °C and the pressure was1 bar or150 mbar. Another objective was to evaluate the changes in the microstructure of the apple tissue after the osmotic treatment with sucrose orsorbitol. Thus, in the apple cubes, the sorbitol, the increase of the temperature and of the soluteconcentration in the osmotic solution resulted in an increase ofthe ODrate, but the mass ratio of the sample to the solution and the pressure did not affect the process. In the physalis, the initial WLrate increased when the vacuum was applied during the OD with sucrose and tended to increase with the use of sorbitol. At the end of the DO of apple cubes, it was observed,by microstructure analysis,that this process affected the size and shape parameters of plant cells and the changes were more pronounced in samples osmotically dehydrated with sorbitol. The OD process caused the shrinkage of the cells and,consequently,a reduction of volume, the plasmolysis and the folding of the cell walls.In the second part of the work, some drying methods were studied to obtain cut apple with reduced water content, namely hot air drying, microwave drying and freeze-drying.The effect of the osmotic pre-treatment with sucrose orsorbitol solutionswas also studied. For the best conditions of each method, the drying kinetics were compared amongthe different methods and the quality —water activity(aw), the colour, the total phenolic content(TPC), the antioxidant activity(AA)and the rehydration ability —of the dried apple cubes were evaluated.Theadequacyof thefit of some mathematical models to describe the water content during drying was also evaluated. Thus, the effect of the temperature (25, 55, 70 and 80 ºC) was studied on the hot air drying of osmotically dehydrated apple cubes (60 ºC, 60 ºBx sucrose orsorbitol solutions, mass ratio of sample to solution 1:4).In the microwave vidrying,the effect of the osmotic pre-treatment andthepower (160, 350, 500, 650, 750 and 850 W) on the WLkinetics of apple cubes was also evaluated. Finally, the WLkinetics of the freeze-drying of apple cubes were studied. Concerning thedried cut apple with reduced water content, the osmotic dehydration as pre-treatment before the hot air drying increased the drying rate and reduced the drying time. The osmotic agent did not affect the drying rate, but the use of sorbitol reduced more the drying time and the awof the final product.In the microwave drying, the increase of the power level reduced the drying time and this reduction was higherfor samples osmotically dehydrated with sorbitol. OD prior to freeze-drying did not present a relevant advantage and the awwas lower in non-treated samples. The type of drying and the pre-treatment did not affect the rehydration rate of the dried apple cubes, but the control samples presentedhigher equilibrium water content than the osmotically dehydrated ones.The OD and subsequent drying by hot air, microwave and freeze-drying, significantly decreased the TPC and the AA. These quality parameters of the osmotically dehydrated samples were not affected by the subsequent drying, but only by the OD.In order to compare the effect of the osmotic agent used in the OD on the consumer’sacceptance, the sensory analysis of hot air dried apple cubes pre-treated osmotically with sucrose orsorbitol was carried out. There was no difference in theresults and the final product was well accepted by consumers.Among the drying methods studied, microwave drying without osmotic pre-treatment produced dried apple cubes with good quality and in a short time. Sorbitol is a good alternative to sucrose as theagent in the osmotic pre-treatment of apple cubes and physalis. Furthermore, sorbitol isa prebioticwith health benefits.
O objetivo geral deste programa de doutoramento foi estudar e otimizar o desenvolvimento, a níveldaeficiênciadoprocesso e da qualidade, de produtos à base de frutos desidratados, de teor intermédio de água por desidratação osmótica, ou de teor reduzido de água por combinação desta técnica com outros métodos subsequentes de secagem.A primeira parte do trabalho incidiu na desidratação osmótica (DO) de cubos de maçã e fisális. A capacidade de ajuste de alguns modelos matemáticos em descrever as cinéticas de transferência de massa nos produtos também foi estudada. Os objetivos consistiram em realizar a DO de cubos de maçã e estudar os efeitos do soluto (sacarose ousorbitol) e da concentração (40 e 60 °Bx) na solução osmótica, da razão mássica amostra: solução (1:4 e 1:10), da temperatura (25, 40 e 60 ºC), e da pressão (1 bar e 150 mbar) na perda de água (PA) e no ganho sólidos (GS). Relativamente à fisális, a DO foi efetuada com uma razão mássica amostra: solução de 1:4, a 60 ºC e a pressão foi de1 bar ou150 mbar. Outro dos objetivos foi avaliar as alterações da microestrutura do tecido da maçã após o tratamento osmótico com sacarose e sorbitol. Assim, nos cubos de maçã, o sorbitol, o aumento da temperatura e o aumento da concentração do soluto na solução osmótica resultaram num aumento da velocidade da DO, mas a razão mássica amostra: solução e a pressão não afetaramo processo. Na fisális, a velocidade inicial de PAaumentou quando o vácuo foi aplicado durante a DO com sacarose e apresentou tendência a aumentar com o uso de sorbitol. No final da DO de cubos de maçã, observou-se, por análise da microestrutura, que este processo afetou os parâmetros de tamanho e forma das células vegetais e as alterações foram mais pronunciadas em amostras osmoticamente desidratadas com sorbitol. O processo de DO provocou o encolhimento das células e consequentemente uma redução de volume, a plasmólise e o dobramento das paredes celulares.Na segunda parte do trabalho,foram estudados métodos de secagem para obter maçã cortada com teor de água reduzido, nomeadamente a secagem a ar quente, a secagem por micro-ondas e a liofilização. Estudou-se também o efeito do pré-tratamento osmótico com soluçõesde sacarose e sorbitol. Para as melhores condições de cada método, foi efetuada a comparação das cinéticas de secagem entre os diferentes métodos e foi avaliada a qualidade —atividade da água(aw), cor, teorfenólico total(TFT), atividade antioxidante(AA)e capacidade de reidratação —dos cubos de maçã secos. A capacidade de ajuste de alguns modelos matemáticos para descrever o teor de água durante a secagem também foi avaliada. Assim, foi avaliado o efeito da temperatura (25, 55, 70 e 80 ºC) na secagem a ar quente de cubos de maçã osmoticamente desidratados (60 ºC, solução de sacarose ousorbitol a 60 ºBx, razão mássica amostra: solução 1:4). Na secagem por micro-ondas,foi também avaliado o efeito do pré-tratamento osmótico e da potência (160, 350, 500, 650, 750 e 850 W) na cinética de PAde cubos de maçã. Finalmente, estudou-se a cinética de PAde cubos de maçã na liofilização. No que diz respeito à maçã cortada seca comteor reduzido de água, a desidratação osmótica como pré-tratamento antes da secagem a ar quente aumentou a velocidade e reduziu o tempo de secagem. O agente osmótico não afetou a velocidade de secagem, mas a utilizaçãode sorbitol reduziu mais o tempo de secagem e a awdo produto final. Na secagem por micro-ondas, o aumento do nível de potência reduziu o tempo de secagem e esta redução foi maior para as amostras osmoticamente desidratadas com sorbitol. A DO antes da liofilização não apresentou uma vantagemrelevante e a awfoi menor em amostras semtratamentoosmótico.O tipo de secagem e o pré-tratamento não afetaram a velocidade de reidratação dos cubos de maçã secos, mas as amostras controlo apresentaram um teor de água de equilíbrio superioràs amostrasosmoticamente desidratadas.A DO e a secagem subsequente, por ar quente, micro-ondas e liofilização, diminuiram significativamente o TFT e a AA. Nas amostras osmoticamente desidratadas, estes parâmetros de qualidadenão foram afetados pela secagem subsequente, mas apenas pela DO. Com o objetivo de comparar o efeito do agente osmótico utilizado na DO na aceitação pelo consumidor, foi efetuada a análise sensorial de cubos de maçã secos a ar quente pré-tratados osmoticamente com sacarose ousorbitol. Não houve diferença nos resultados e o produto final foi bemaceite pelos consumidores.De entre os métodos de secagem estudados, a secagem por micro-ondas sem pré-tratamento produziu cubos de maçã secos deboa qualidade e numtemporeduzido. O sorbitol é uma boa alternativa à sacarose como agente no pré-tratamento osmótico de cubos de maçã e fisális. Para além disso, o sorbitol éum prebiótico com benefíciospara a saúde.