Les dattes sont le siège d'attaques importantes d'insectes. La fumigation à l'aide de gaz toxiques est la réponse classique et efficace pour tuer ces insectes, mais celle-ci est peu respectueuse de l'environnement et incompatible avec le cahier des charges des dattes certifiées biologiques. Aussi, des alternatives de désinfestation par des procédés thermiques sont envisagées. Ces dans ce contexte, que s'inscrit le présent travail qui a pour but de développer des approches expérimentales et de modélisation pour évaluer l'impact de transfert de chaleur (convection thermique et ondes électromagnétiques) sur la désinfestation des dattes, tout en limitant leur brunissement. Pour y parvenir, un élevage d'insecte (Ephestia kuehniella Zeller) a été réalisé et une base de données originale du taux de survie des oeufs et larves est construite entre 46 et 75°C. Les deux modèles cinétiques retenus (ordre 1 pour les oeufs ; distribution de Weibull pour les larves) représentent bien le taux de survie des insectes en fonction de leur historique thermique. En parallèle, un modèle numérique de transfert d'énergie en 2D axisymétrique a été conçu et résolu par la méthode des éléments finis (Comsol). Il prend notamment en compte, les diverses parties d'une datte (pulpe, lame d'air, noyau) et la position de l'hôte-insectes dans la datte. Les propriétés diélectriques des insectes et de la datte ont été mesurées et injectées dans le modèle afin de simuler le couplage entre les transferts d'énergie, le taux de survie de la larve localisée dans la lame d'air, celui des oeufs à la surface des dattes, ainsi que de leurs interactions lors du chauffage et refroidissement. L'obtention d'un faible taux de survie d'une larve constitue l'élément limitant pour l'opération de désinfestation par convection. En revanche, c'est le taux de survie des oeufs qui devient l'élément limitant pour les traitements par ondes électromagnétiques. Eu égard à leurs surfaces spécifiques élevées, les oeufs ne s'échauffent pas suffisamment pour mourir pendant les traitements micro-ondes (915 MHz) à des champs électriques. Une désinfestation par micro-ondes ne présente un intérêt qu'en étant associée simultanément ou séquentiellement à un traitement de surface avec un fluide chaud (air, liquide, vapeur). En revanche, un transfert convectif intense (avec un liquide) utilisé seul risque d'aboutir à un brunissement superficiel trop important des dattes. Aussi, un traitement micro-ondes (1 290 V m-1) associé à une ventilation modérée (20 W m-2 K-1) à l'air chaud (60°C) permet en 180 s, d'obtenir un taux de survie d'insectes de 0,01% tout en limitant le brunissement. En revanche, cette opération combinée ne peut être mise de façon efficace qu'avec une bonne homogénéité de la teneur en eau des dattes. En effet, le facteur de pertes diélectriques de la pulpe de datte dépend fortement de la teneur en eau. / Date fruits are subject to major attacks by insect pests. Fumigation with toxic gases is the classic and effective response to insect infestation, but it is neither environmentally friendly nor compatible with organic date certification. Alternative forms of disinfestation by thermal processes are therefore considered. The present work aims to develop experimental and modelling approaches to evaluate the impact of heat transfer (convection and electromagnetic waves) on the disinfestation of dates, while limiting browning. To achieve this, a breeding population of insects (Ephestia kuehniella Zeller) was established and a database of survival rate of eggs and larvae between 46 °C and 75 °C constructed. The two kinetic models selected (first order for eggs and a Weibull distribution for larvae) accurately describe insect survival according to their thermal history. In parallel, a 2D axis-symmetric numerical model of energy transfer was designed and solved by the finite element method (Comsol). It takes into account the various parts of a date fruit (pulp, air layer and pit) and the position of an insect in the fruit. The dielectric properties of insects and date fruit were measured and used in the model in order to simulate the coupling between the energy transfer, the survival rate of larvae located in the air layer (between pulp and pit), that of eggs on the date surface, and their interactions during heating and cooling. Achieving a low survival rate of larvae is the limiting factor for disinfestation by convection, whereas in contrast, the survival rate of eggs becomes the limiting factor for treatment by electromagnetic waves. Due to their high specific surface area, the eggs do not become hot enough to die during microwave treatment (915 MHz) at an electric field . Disinfestation by microwaves is therefore only of interest if associated simultaneously or sequentially with a surface treatment using a hot fluid (air, liquid, vapour). In contrast, an intense convective transfer (with liquid) used alone may lead to unacceptable surface browning. A microwave treatment (1 290 V m-1) associated with moderate ventilation (20 W m-2 K-1) with hot air (60 °C) for 180 s achieves an insect survival rate of 0.01% while limiting surface browning. However, this combined operation is only effective if the water content of dates is homogeneous. Indeed, the dielectric loss factor of date pulp depends strongly on water content.

Disinfestation using microwaves can be an alternate to chemical methods of killing insects in grain. A pilot-scale industrial microwave dryer operating at 2.45 GHz was used to determine the mortality of life stages of Tribolium castaneum (Herbst), Sitophilus granarius (L.) and Cryptolestes ferrugineus (Stephens) adults in wheat, barley, and rye. Grain samples of 50 g each at 14, 16, and 18% moisture content were infested with stored-grain insects. The samples were then exposed to microwave energy at 200, 300, 400, and 500 W for exposure times of 28 and 56 s. Complete (100%) mortality was achieved for adults of three insect species at 500 W, 28 s and at 400 W, 56 s in barley and wheat. In rye, complete mortality of adult T. castaneum and S. granarius was achieved at 400 W, 28 s and at 300 W, 56 s whereas for C. ferrugineus, complete mortality was achieved at 500 W, 28 s and at 400 W, 56 s. The average temperature of wheat, barley, and rye at 500 W and 28 s was around 80, 71 and 82oC, respectively, and moisture loss was 2.0, 1.9 and 2.5 percentage points, respectively. Among the life stages of T. castaneum in wheat, eggs were the most susceptible followed by larvae, and the least susceptible were the pupae and adults. Among the life stages of T. castaneum in barley and rye, eggs were the most susceptible and adults were the least susceptible with no significant difference between pupae and larvae. There was no significant difference in the mortality of adults at 14, 16, and 18% moisture content barley and rye and the life stages of T. castaneum and S. granarius in rye. Germination of seeds decreased with an increase in power level or exposure time or both. There was no significant difference in the quality characteristics of microwave-heated wheat and rye except for reduced flour yield in rye. The quality of the barley treated at 500 W, 28 s was the same as the control, whereas, there was significant decrease in the quality of barley treated at 400 W, 56 s. / May 2009

Disinfestation using microwaves can be an alternate to chemical methods of killing insects in grain. A pilot-scale industrial microwave dryer operating at 2.45 GHz was used to determine the mortality of life stages of Tribolium castaneum (Herbst), Sitophilus granarius (L.) and Cryptolestes ferrugineus (Stephens) adults in wheat, barley, and rye. Grain samples of 50 g each at 14, 16, and 18% moisture content were infested with stored-grain insects. The samples were then exposed to microwave energy at 200, 300, 400, and 500 W for exposure times of 28 and 56 s. Complete (100%) mortality was achieved for adults of three insect species at 500 W, 28 s and at 400 W, 56 s in barley and wheat. In rye, complete mortality of adult T. castaneum and S. granarius was achieved at 400 W, 28 s and at 300 W, 56 s whereas for C. ferrugineus, complete mortality was achieved at 500 W, 28 s and at 400 W, 56 s. The average temperature of wheat, barley, and rye at 500 W and 28 s was around 80, 71 and 82oC, respectively, and moisture loss was 2.0, 1.9 and 2.5 percentage points, respectively. Among the life stages of T. castaneum in wheat, eggs were the most susceptible followed by larvae, and the least susceptible were the pupae and adults. Among the life stages of T. castaneum in barley and rye, eggs were the most susceptible and adults were the least susceptible with no significant difference between pupae and larvae. There was no significant difference in the mortality of adults at 14, 16, and 18% moisture content barley and rye and the life stages of T. castaneum and S. granarius in rye. Germination of seeds decreased with an increase in power level or exposure time or both. There was no significant difference in the quality characteristics of microwave-heated wheat and rye except for reduced flour yield in rye. The quality of the barley treated at 500 W, 28 s was the same as the control, whereas, there was significant decrease in the quality of barley treated at 400 W, 56 s.

Disinfestation using microwaves can be an alternate to chemical methods of killing insects in grain. A pilot-scale industrial microwave dryer operating at 2.45 GHz was used to determine the mortality of life stages of Tribolium castaneum (Herbst), Sitophilus granarius (L.) and Cryptolestes ferrugineus (Stephens) adults in wheat, barley, and rye. Grain samples of 50 g each at 14, 16, and 18% moisture content were infested with stored-grain insects. The samples were then exposed to microwave energy at 200, 300, 400, and 500 W for exposure times of 28 and 56 s. Complete (100%) mortality was achieved for adults of three insect species at 500 W, 28 s and at 400 W, 56 s in barley and wheat. In rye, complete mortality of adult T. castaneum and S. granarius was achieved at 400 W, 28 s and at 300 W, 56 s whereas for C. ferrugineus, complete mortality was achieved at 500 W, 28 s and at 400 W, 56 s. The average temperature of wheat, barley, and rye at 500 W and 28 s was around 80, 71 and 82oC, respectively, and moisture loss was 2.0, 1.9 and 2.5 percentage points, respectively. Among the life stages of T. castaneum in wheat, eggs were the most susceptible followed by larvae, and the least susceptible were the pupae and adults. Among the life stages of T. castaneum in barley and rye, eggs were the most susceptible and adults were the least susceptible with no significant difference between pupae and larvae. There was no significant difference in the mortality of adults at 14, 16, and 18% moisture content barley and rye and the life stages of T. castaneum and S. granarius in rye. Germination of seeds decreased with an increase in power level or exposure time or both. There was no significant difference in the quality characteristics of microwave-heated wheat and rye except for reduced flour yield in rye. The quality of the barley treated at 500 W, 28 s was the same as the control, whereas, there was significant decrease in the quality of barley treated at 400 W, 56 s.

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Made available in DSpace on 2014-10-09T12:27:14Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:00Z (GMT). No. of bitstreams: 0 / O presente trabalho teve como objetivos realizar um levantamento para identificar a entomofauna associada a rações na cidade São Paulo/SP bem como avaliar o efeito da radiação gama em rações para alimentação de animais domésticos infestadas por pragas. Amostras de 20 lojas Pet Shop de diferentes regiões da cidade São Paulo/SP foram submetidas a triagens de 1 e 45 dias para coleta de insetos com auxilio de aspirador entomológico e peneiras de diferentes granulometrias. As espécies Sitophilus zeamais, Cryptolestes ferrugineus, Lasioderma serricorne e Oryzaephilus sp. apresentaram maior freqüência. Na avaliação dos efeitos da radiação gama utilizamos amostras de grãos de milho, sementes de girassol e mistura para roedores infestadas com insetos adultos das espécies Sitophilus zeamais, Lasioderma serricorne e Plodia interpunctella, após o periodo de 7 a 10 dias foram retirados os insetos e as amostras submetidas a doses crescentes de radiação gama. As espécies Sitophilus zeamais e Lasioderma serricorne foram submetidas as doses de 0,25 a 1,50kGy e a espécie Plodia interpuctella a doses de 0,10 a 2,0kGy. Decorridos 40 dias após irradiação avaliou-se o número de insetos emergidos. Os resultados dos bioensaios com Sitophilus zeamais como com Lasioderma serricorne demostraram que doses apartir de 0,5 kGy foram suficientes para causar letalidade dos ovos e larvas recém emergidas. Os resultados com a Plodia interpunctella a partir de 1,50 kGy, não emergiram insetos adultos, concluindo-se que essas doses foram suficientes para causar letalidade dos ovos e larvas. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP