Ce travail de doctorat consiste à valoriser les coproduits issus des industries d’agrumes par des technologies innovantes. Le pressage des agrumes produit des millions de tonnes de déchets par an dans le monde. Ces déchets (peaux, pulpes et pépins) sont généralement dédiés à l’alimentation animale ou bien éliminés par compostage ou incinération. Cependant leur contenu en molécules bioactives conduit à plusieurs voies de valorisation. Vu que les peaux constituent à peu près la moitié de la masse des déchets d’agrumes, les études ont été faites sur la valorisation des peaux de différents types d’agrumes. Les méthodes conventionnelles généralement utilisées pour l’extraction des molécules d’intérêt (extraction solide-liquide, hydrodistillation) présentent plusieurs désavantages tels que l’utilisation des solvants coûteux et toxiques, les longues durées d’extraction et la consommation élevée en énergie. Pour cette raison plusieurs technologies innovantes non thermiques telles que les Champs Electriques Pulsés (CEP), les Décharges Électriques de Haute Tension (DEHT) et les ultrasons (US) et thermiques comme les microondes (MO) et les infrarouges (IR) ont été testées dans ce travail de thèse, pour la valorisation des coproduits d’agrumes. Les agrumes entiers (oranges, pomelos, citrons) sont traités par les CEP à une intensité de 3 kV/cm et l’extraction du jus d’agrumes et des polyphénols a été réalisée par pressage. L’étude de la perméabilisation cellulaire induite par les CEP a été réalisée par plusieurs méthodes et a montré que les degrés d’endommagement diffèrent selon le type d’agrumes traités. L’électroporation des cellules, induite par les CEP a permis d’augmenter les rendements en jus après pressage et d’améliorer le passage des polyphénols des peaux d’agrumes dans le jus. Ce qui explique la possibilité d’obtention d’un jus riche en polyphénols en traitant les agrumes par les CEP avant leur pressage. Parmi les solvants testés pour l’extraction des polyphénols à partir des peaux d’agrumes, l’eau est le moins efficace. L’ajout de 20% de glycérol dans l’eau a modifié la polarité du milieu et a amélioré l’extraction des polyphénols. L’utilisation d’un mélange enzymatique a favorisé la libération des polyphénols piégés dans les polysaccharides. Les solvants eutectiques profonds préparés, ont été aussi efficaces que les mélanges hydro éthanoliques. Pour améliorer d’avantages l’extraction dans les différents solvants verts ou dans le mélange enzymatique, les peaux d’agrumes ont été prétraitées par les DEHT dans l’eau. L’effet mécanique des DEHT, capable de fragmenter les peaux a permis d’améliorer l’extraction des polyphénols 6 dans les différents solvants. L’intensification de l’extraction des polyphénols a été aussi réalisée par les IR et les US. L’extraction des polyphénols par les IR a été optimisée en ayant recours à la méthodologie de surface de réponse. Le chauffage par les IR n’a pas altéré les polyphénols extraits qui ont gardé des activités antifongiques et anti-mycotoxinogènes importantes. Le prétraitement des peaux d’agrumes par les IR sans solvant a fragilisé les structures cellulaires, ce qui a permis d’augmenter la diffusion des polyphénols durant le traitement avec les US. / This work consists of the valorization of citrus by-products with innovative technologies. Citrus pressing produces millions of tons of waste per year worldwide. This waste (peels, pulps and seeds) is generally dedicated to animal feed or eliminated by composting or incineration. However its content in bioactive molecules leads to several ways of valorization. Since peels present about half of the citrus waste mass, studies have been focused on the valorization of citrus peels by the extraction of bioactive compounds. Conventional methods generally used for the extraction of bioactive compounds (solid-liquid extraction, hydrodistillation) have several disadvantages such as the use of expensive and toxic solvents, long extraction times and high energy consumption. For this reason, several innovative non-thermal technologies such as Pulsed Electric Fields (PEF), High Voltage Electrical Discharges (HVED) and Ultrasounds (US) and thermal treatments such as microwaves (MO) and infrared (IR) have been tested for the valorization of citrus by-products. Whole citrus fruits (oranges, pomelos, lemons) were PEF treated at an intensity of 3 kV/cm, then citrus juice and polyphenols were extracted by pressing. The study of the PEF-induced cell permeabilization was conducted by several methods and showed that the degree of damage varied according to the type of the treated fruit. The electroporation of the cells induced by the PEF, allowed an increase the juice yields after pressing and improved the liberation of the polyphenols from the citrus peels into the juice. This explains the possibility of obtaining a juice rich in polyphenols by treating the whole fruits with PEF before pressing. Among the solvents tested for the extraction of polyphenols from citrus peels, water is the least effective. The addition of 20% glycerol to water changed the polarity of the medium and improved the extraction of the polyphenols. The use of an enzyme mixture enhanced the release of the polyphenols related to the polysaccharides. Deep eutectic solvents have been as effective as hydroethanolic mixtures. To improve the yields and the kinetics of extractions in the different green solvents and in the enzyme mixture, citrus peels were pretreated with HVED in water. The mechanical effect of HVED, based on the fragmentation of the peels has improved the extraction of polyphenols in the various solvents. The intensification of polyphenols extraction was also conducted by IR and US. The extraction of polyphenols by IR was optimized using the surface response methodology. IR heating did not alter the extracted polyphenols which have significant antifungal and anti-mycotoxinogenic activities. The pretreatment of citrus peels with IR weakened the cell structures, increasing thus the diffusion of polyphenols during US treatment.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The pollution caused by heavy metals has been becoming a serious environmental problem. The use of biomass as sorbent material for the treatment of industrial effluent containing heavy metals arises as a promising alternative for the current technologies. The waste that contains these metals may cause damages to the environment and to the human health. Even chrome, which is a essential metal, can be harmful in high concentrations; therefore, the proposal of this work was to evaluate the capacity of adsorption of chrome, using as biosorbent orange (pêra rio) and jabuticaba produced in the region of Triângulo Mineiro and the green coconut shell (cocus nucífera). The synthetic effluent, prepared from potassium dichromate reagent, was treated with this material previously dried, grinded and separated by granulometric analysis. The process was carried out isothermally in jacketed batch reactors continuously agitated. The mixture polluted by chrome in its metal nature was treated for a period up to twenty four hours. It was analysed the influence of pH in the process, being tested 2, 6 and 10. The efficiency of the biosorbent material, its granulometry, the influence of pH and the equilibrium concentration were the variables evaluated. The isothermal equilibrium data were adjusted employing the linear models of Langmuir and Freundlich. It was verified that Freundlich s adsorption isotherm was the one that fitted the best with the equilibrium data. The data were also adjusted to the kinetic models of pseudo first-order and pseudo second-order, and the pseudo-second order was the most representative for the data. With respect to the kinetic parameters, the process is spontaneous, it is endothermic when coconut shells and jabuticaba are used and exothermic when orange peels are used. / A poluição por metais pesados vem se tornando um sério problema ambiental. O uso de biomassas como material sorvente para o tratamento dos efluentes industriais contendo metais pesados aparece como uma alternativa promissora às tecnologias existentes. Os rejeitos contendo estes metais, podem ocasionar danos ao meio ambiente e à saúde humana. Mesmo o cromo, que é um metal essencial, pode ser prejudicial em altas concentrações, por esse motivo a proposta desse trabalho foi avaliar a capacidade de adsorção de cromo empregando-se, como biossorvente, laranja (pêra rio) e jabuticaba produzida na região do Triângulo Mineiro e casca de coco verde (cocus nucífera). O efluente sintético, preparado a partir do reagente dicromato de potássio (K2Cr2O7), foi tratado com esse material previamente seco, triturado e separado a diferentes granulometrias. O processo foi realizado isotermicamente nas temperaturas de 25, 35 e 45ºC, em reatores batelada, encamisado e com agitação continua. A mistura contaminada por cromo em sua forma metálica (Cr+3 e Cr+6) era tratada por um tempo de até vinte quatro horas. Foi analisada a interferência do pH no processo, sendo testados os valores de 2, 6 e 10. A eficiência do material biossorvente, a granulometria, a interferência do pH e a concentração de equilíbrio foram as variáveis estudadas. A granulometria menor que 106μm e o pH ácido igual a 2 foram os que apresentaram melhores resultados. Os dados isotérmicos de equilíbrio foram ajustados utilizando-se os modelos lineares de Langmuir e Freundlich. Verificou-se que a isoterma de adsorção de Freundlich foi a que apresentou melhor ajuste aos dados de equilíbrio, indicando que não há uma interação entre os sítios ativos. Os dados também foram ajustados aos modelos cinéticos de pseudo primeira-ordem e pseudo segunda-ordem, sendo o de pseudo-segunda ordem mais representativo para os dados. Em relação aos parâmetros cinéticos, o processo é espontâneo, endotérmico quando se utilizam as cascas de coco e jabuticaba e exotérmico quando utiliza-se a casca de laranja em relação a entropia apresenta uma maior ordenação das moléculas na superfície da jabuticaba utilizada como adsorvente e uma desordem na superfície da laranja. Os biossorventes se mostraram eficientes na remoção de cromo total, embora em nenhum dos casos tenha sido atingido valores inferiores aos máximos permitidos por lei. / Mestre em Engenharia Química