The main purpose of this study was to improve the performance of microwave assisted drying. The osmotic treatment was used as pretreatment due to its inherent low energy requirement attributes. The vacuum was applied to microwave drying system to capture low temperature vaporization concepts. The whole process might be called "osmotically dehydrated microwave vacuum drying". Carrots and strawberries were selected to study as a representative of vegetables and fruits, respectively. / The laboratory scale microwave vacuum dryer was setup and the preliminary tests were done with carrots and strawberries. The occurrence of condensation of vapor in vacuum container was found during the drying trials. The location of the open-ended valve which controls the vacuum level was found to have an influence on the condensation. The re-location of valve which allowed air passage to the vacuum container was able to decrease the condensation. The input power for the microwave vacuum drying could not be greater than 1.5 W/g. The continuous use of input power caused the high temperature in the process. The pulse mode (on/off) was recommended for further studies. / Water removal and solid gain of osmotic treatment were considered as factors that affect the dielectric properties dielectric constant (epsilon') and the loss factor (epsilon"). The experiment was set up to investigate the influence of osmotic conditions to dielectric properties. Two osmotic agents, sucrose and salt, were used for carrots; but only sucrose was used for strawberries. The effects of variations in sucrose and salt concentrations, solution temperatures, and length of immersion time on the dielectric properties were studied. The empirical models were generated from response surface methodology (RSM) to predict epsilon' and epsilon" for the various ranges of osmotic conditions considered in this thesis. / As a consideration of the osmotic pre-drying treatment, it was considered appropriate to maximize water loss (WL) and minimize solid gain (SG). The parameter appropriate to study this situation was WL/SG. The optimum conditions of osmotic process to acquire the maximum ratio of WL/SG were investigated. The results of the optimum conditions for carrots were found to be sucrose concentration 50%(w/w), salt concentration 5%(w/w), temperature 20°C and immersion time 3 hours 38 minutes. The optimum conditions for strawberries were found to be sucrose concentration 60%(w/w), temperature 20°C and immersion time 24 hours. / The microwave vacuum drying was then studied as a technique combined with the osmotic pretreatment. The studies were performed on carrots and strawberries. The input power levels 1 and 1.5 W/g with different power modes (continuous, 45s on/15s off and 30s on/30s off) were experimentally studied with a certain condition of osmotic treatment, which was acquired from the previous study. Osmotic treatment prior to microwave vacuum of carrots showed the advantage in most cases; fast drying time, less energy consumption and superior quality aspects except the taste which was affected from the salt. The study of strawberries did not show great advantage of osmotic pretreatment. The drying time and energy consumption of the process with and without osmotic pretreatment were the same but the process with osmotic pre-treatment resulted in better quality of dried strawberries. / The microwave vacuum drying of carrots and strawberries after osmotic pretreatment did not show constant rate period in drying rate curve while the processes without osmotic treatment of strawberries showed longer constant rate period than those observed for carrot drying. According to these phenomena, thin layer models of Lewis and Henderson & Pabis were fitted to the observed data which showed excellent fit for the process without constant rate period, but Page's model was a good fit for both constant rate and falling rate period of microwave vacuum drying.

No description available.

Beef jerky is a dried meat snack which is rich in protein but of low calorific value. This ready-to- eat meat snack is in high demand among hikers, bikers and travelers due to its compact nature and nutritional value. The current processing methods such as smoke house and home dehydrators take 6-10 h. Increasing market for this shelf-stable meat product increases the need for alternate efficient processing method. Also, this meat snack market depends on its textural characteristics which denote the consumer acceptability. In this research, three different methods of drying beef jerky were examined. Influences of pH and salt on different characteristics of beef jerky were investigated using combined microwave-convection drying. Also, the effects of relative humidity and airflow rates in forced air thin layer drying on jerky processing were studied. Samples of beef jerky dried using a combined microwave-convection drier and thin layer drying unit were compared with samples dried in a smoke house. The results obtained showed that pH and salt content had a significant influence on drying, physical and textural characteristics of jerky. It was found that samples with low pH (5.15) and high salt content (3.28% (w/w)) dried faster than samples with high pH and low salt content due to their high drying rates. These samples had shown high shrinkage and weight loss compared to samples with pH 5.65 and 1.28% (w/w) salt content. Analysis of the textural characteristics such as tensile force, puncture force and texture profile showed that the samples with high pH and low salt content were comparably softer than the rest of the samples. Results of the effect of relative humidity and airflow rate in forced air thin layer drying on jerky processing showed that relative humidity and airflow rate influenced the drying, physical, chemical and textural characteristics of beef jerky. Combination of low relative humidity and high airflow rate showed desirable drying characteristics. However, samples dried at this combination showed high shrinkage and weight loss. The hardness of the beef jerky increased with increase in airflow rate and reduction in relative humidity. A comparison of the drying methods revealed that different drying methods produced different desirable properties. Combined microwave-convection drying was found to be efficient and very rapid (8.25 min). The low shrinkage and weight losses along with high drying rate obtained using this method would pave a way to fast and efficient processing. The color and textural characteristics were different from those of samples dried in a smoke house. Surprisingly, combined microwave-convection drying method produced softer beef jerky than thin layer and smokehouse methods. However, the commercially available jerky is tougher than the one dried using combined microwave-convection drying. The samples dried in a thin layer drier had comparable color and textural characteristics with samples dried in a smoke-house. Also, forced-air thin layer drying method reduced drying time of beef jerky from 7 to 3 h. The forced air thin layer drier has the potential to produce beef jerky with similar color and textural characteristics to commercially available smoke house dried samples.

Beef jerky is a dried meat snack which is rich in protein but of low calorific value. This ready-to- eat meat snack is in high demand among hikers, bikers and travelers due to its compact nature and nutritional value. The current processing methods such as smoke house and home dehydrators take 6-10 h. Increasing market for this shelf-stable meat product increases the need for alternate efficient processing method. Also, this meat snack market depends on its textural characteristics which denote the consumer acceptability. In this research, three different methods of drying beef jerky were examined. Influences of pH and salt on different characteristics of beef jerky were investigated using combined microwave-convection drying. Also, the effects of relative humidity and airflow rates in forced air thin layer drying on jerky processing were studied. Samples of beef jerky dried using a combined microwave-convection drier and thin layer drying unit were compared with samples dried in a smoke house. The results obtained showed that pH and salt content had a significant influence on drying, physical and textural characteristics of jerky. It was found that samples with low pH (5.15) and high salt content (3.28% (w/w)) dried faster than samples with high pH and low salt content due to their high drying rates. These samples had shown high shrinkage and weight loss compared to samples with pH 5.65 and 1.28% (w/w) salt content. Analysis of the textural characteristics such as tensile force, puncture force and texture profile showed that the samples with high pH and low salt content were comparably softer than the rest of the samples. Results of the effect of relative humidity and airflow rate in forced air thin layer drying on jerky processing showed that relative humidity and airflow rate influenced the drying, physical, chemical and textural characteristics of beef jerky. Combination of low relative humidity and high airflow rate showed desirable drying characteristics. However, samples dried at this combination showed high shrinkage and weight loss. The hardness of the beef jerky increased with increase in airflow rate and reduction in relative humidity. A comparison of the drying methods revealed that different drying methods produced different desirable properties. Combined microwave-convection drying was found to be efficient and very rapid (8.25 min). The low shrinkage and weight losses along with high drying rate obtained using this method would pave a way to fast and efficient processing. The color and textural characteristics were different from those of samples dried in a smoke house. Surprisingly, combined microwave-convection drying method produced softer beef jerky than thin layer and smokehouse methods. However, the commercially available jerky is tougher than the one dried using combined microwave-convection drying. The samples dried in a thin layer drier had comparable color and textural characteristics with samples dried in a smoke-house. Also, forced-air thin layer drying method reduced drying time of beef jerky from 7 to 3 h. The forced air thin layer drier has the potential to produce beef jerky with similar color and textural characteristics to commercially available smoke house dried samples.

Passive (static) and dynamic studies have shown aroma to be an important aspect of food quality, which can be used to differentiate, classify, and grade foodstuffs, and in some cases it can be used to predict other quality characteristics. Monitoring and control of food aroma changes during food processing can significantly improve the quality of the final product in terms of flavour, color, taste, and overall appearance. Hence, it is a prominent and urgent field of study in the post production systems. / Passive aroma detection of unprocessed foods and dynamic aroma detection during food processing was undertaken using a fast GC analyzer -- zNose. During the study on the passive aroma detection, the aroma of Chinese spirits (Fenjiu) and mango (Mangifera indica L.) fruits, (i.e., liquid and solid states, respectively) was analyzed. In the study of Chinese spirits, aroma profiles of Fenjiu liquor samples of different quality levels were acquired and used for quality classification and prediction. Measurements of dielectric properties of the samples were also conducted to estimate alcohol concentration. In the study of mango fruits, aroma changes of mango samples were monitored during their shelf life and used to evaluate mango quality. Ripening and rots were detected with 80% and 93% accuracy, respectively. / During the study of dynamic aroma detection, a real-time aroma monitoring and control system was developed for use during microwave drying. Aroma signals of a processed food item were detected with zNose and analyzed with a fuzzy logic algorithm to determine the optimal food drying temperature. Phase control was used to adjust the microwave power level to meet temperature requirements. Carrot (Daucus carota L.) and apple (Malus domestica Borkh) were selected as representatives of vegetables and fruits. In carrot drying, samples could be dried in a short time at high temperatures but the interior of some sample cubes was burnt. Drying at a lower temperature extended the drying process, but led to a great loss of aroma in the finished product.' The best results were obtained at 60°C. Based on these results, a fuzzy logic controller was designed and employed to control the drying process according to carrot aroma changes. To investigate the possibility of aroma improvement without zNose assistance, a linear control method was developed whereby a temperature control profile imitated the fuzzy logic control, but aroma control was not included. With these new control strategies, the carrot color and flavour were significantly improved and less time and power were consumed. Similar results were achieved when apple was microwave-dried. Apple aroma was monitored online during microwave drying processes and controlled with similar fuzzy and linear control strategies. Apple color, aroma, and overall appearance remained intact with the new strategies and less time and power were consumed. In contrast to the carrot drying, a different linear temperature profile was required for apple drying in terms of aroma retention.

The moisture contents of the final coal products from processing plants are often too high and do not meet the requirements of the client. In many cases, drying becomes a necessary step to control the moisture content. Conventional thermal drying is inefficient and is not environmentally friendly. This study investigates the application of microwaves as an alternative heat source for drying coal. The rate of drying was determined by the thermogravimetric analysis (TGA) technique. Several variables that have significant effects on the drying kinetics were investigated, including incident microwave power, initial moisture content and the sample mass. Microwave drying tests were performed under various conditions and the mass change was monitored continuously. The percentage mass loss, moisture fraction and drying rate were obtained for each experimental condition. The final temperature was measured and drying efficiencies were calculated. For comparison purposes, some conventional thermal drying tests were also carried out at temperatures ranging from 130 to 220oC and with coal masses ranging from 10g to 100g. The TGA results show that microwave drying has distinct advantages over conventional drying such as reducing the overall required time and increasing the drying efficiency. A multiple-regression analytical method was used for both microwave and conventional drying to find the best fit model among eleven different types. Finally, the sample mass, which proved to be the most dominant factor in microwave drying, was incorporated into the equation of the best fit model. / Thesis (Master, Mining Engineering) -- Queen's University, 2010-12-23 22:56:04.119

No description available.

This study is aimed to investigate the possibility of using halogen lamp-microwave combination oven for production of bread crumbs and to determine the drying conditions in this oven to produce bread crumbs with the highest quality. Bread crumb dough was dried from about 40.9% to 8% moisture content by conventional oven, microwave, infrared and infrared-assisted microwave drying. In the experiments 30%, 50% and 70% halogen lamp and/or microwave powers were used. As a control, conventional oven drying at 75&deg / C was used. Conventional drying time was reduced significantly with the usage of infrared, microwave and infrared-assisted microwave drying. Percent reduction in the drying time was found as 96.5-98.6% for microwave, 80.2-94.0% for infrared and 96.8-98.6% for infrared-assisted microwave drying. Contribution of microwave drying was about nine fold of that of infrared drying in infrared-assisted microwave drying. In conventional drying moisture content decayed exponentionally with time whereas in microwave drying it showed a linear decrease. Infrared and infrared-assisted microwave drying fitted the same non-linear model. Total color change values were lower in microwave and higher in infrared drying with respect to the conventional drying. When drying was done by infrared-assisted microwave drying similar color values with the conventionally dried bread crumbs were encountered. Microwave, infrared and infrared-assisted microwave drying methods were effective in increasing water binding capacity. As long as time and energy reduction and high quality were considered, the optimum condition in infrared-assisted microwave drying for production of bread crumbs can be selected as 50% microwave and 30% halogen lamp power.

Die Vakuum-Mikrowellentrocknung in Multimodekammern stellt eine Möglichkeit zur schnellen und fehlerfreien Trocknung von porösen Körpern dar. In der vorliegenden Arbeit wurden der Einfluss von spezifischer absorbierter Leistung, Kammerdruck, Probenlänge, Probendicke und Anfangsfeuchte auf die Trocknung von Schnittholz untersucht. In Abhängigkeit von Holzart und Anordnung konnten Trocknungsgeschwindigkeiten von bis zu 7 %/min erzielt werden. Die daraus resultierenden Trocknungszeiten ermöglichen die Nutzung einer kontinuierlichen Prozessführung, die die Beobachtung von einzelnen Brettern erlaubt. Die Ergebnisse der Arbeit erlauben eine Bewertung der Entwicklung von Feuchte- und Temperaturverteilung im Material bei Variation der genannten Parameter. Es werden Ansätze zur Steuerung eines kontinuierlichen Mikrowellentrocknungsprozesses und zur Gestaltung geeigneter Applikatoren vorgestellt. / One possibility to dry porous materials at high rates and without structural damage is vacuum microwave drying, a combination of low pressure and microwave application. The influence of specific absorbed power, pressure level, length and thickness of the sample and initial moisture content on drying was investigated by the example of wood. Drying rates of up to 7 %/min were reached depending on the wood species and the configuration. The resulting drying times are suitable to design a continuous process, which allows single board processing. The results of this work give the possibility to evaluate the development of moisture and temperature fields within the material during variation of the mentioned parameters. Basic approaches are discussed for the control of a continuous microwave drying process and for the qualified design of applicators.

In the process of drilling, the rock fragments generated by the drill are taken from the well to the surface by the drilling fluid. The drilling fluid used in Brazil is made by synthetic oil, it presents several advantages over other types of drilling fluid. However, it has the disadvantage of having high toxicity and low biodegradability, requiring a separation system of drilled cuttings contaminated with this drilling fluid. Currently, the responsible equipment for reducing these levels to the permitted by law is working under extreme conditions and residual levels generated are very close to permitted by environmental legislation. For this reason, the technique of microwave drying has been studied for use in remediation of drilled cuttings and has shown very promising because it presents high efficiency and low operational problems when it is compared to conventional equipment. Therefore, the aim of this work are to investigate the influence of various operating parameters of a microwave dryer, analyze the efficiency of the dryer microwave suited for this job and to obtain operational conditions and information for operating a industrial microwave operating in continuous flow. So were tested influence of temperature, flow rate of inert, initial fluid content, reuse of drilled cuttings, rock type, fluid type and mechanical agitation in microwave drying; tests of drying kinetics and the mapping drying inside the microwave were made. The results showed no difference in drying with the influence of inert flow and the type of fluid, but there was influence of drying temperature, the initial salt content, initial fluid content and rock type. Drying with agitation can increased the removal efficiency in 17 % with 27 mm of bed thickness, rocks with slow heating improve the removal efficiency, drilled cuttings with similar physical aspects have similar removal efficiency. The heating of rocks in the microwave depends strongly of the oxides content in its composition. The temperature control of the bed should be the upper limit of the boiling range of the hydrocarbons present in the drilling fluid. The mapping study showed that there are drying gradients inside the microwave, besides showing the intrusive effect of metals in the material, effect of the edges of the recipes and the position of exhaust fan. The equipment showed to be as efficient as others listed in the literature, which can reduce the levels of n-paraffin to below 1 % by mass. / No processo de perfuração de poços de petróleo, os fragmentos de rocha gerados pela broca, são transportados do fundo do poço até a superfície pelo fluido de perfuração. O fluido de perfuração mais utilizado no cenário brasileiro é o de base sintética, pois apresenta diversas vantagens com relação a outros tipos de fluido. Porém, apresenta a desvantagem de possuir alta toxicidade e baixa biodegrabilidade, necessitando de um sistema de separação para que o cascalho contaminado com esse fluido possa ser descartado no meio ambiente. Atualmente, o equipamento responsável pela redução destes teores até os limites permitidos por lei, opera de maneira sobrecarregada e os teores residuais alcançados estão muito próximos do permitido pela legislação ambiental. Por essa razão, a técnica de secagem por micro-ondas vem sendo estudada para ser utilizada na descontaminação de cascalhos contaminados com fluido de perfuração. Essa tecnologia mostra-se ser muito promissora, pois apresenta altas eficiências de remoção e menores problemas operacionais quando comparados aos equipamentos convencionais. Por isso, o objetivo deste trabalho é verificar a influência de algumas variáveis de operação de um secador micro-ondas de bancada adaptado para a descontaminação de cascalhos de perfuração. Além de verificar a eficiência desse equipamento e obter condições operacionais e informações suficientes para o projeto de um micro-ondas semi-industrial contínuo. Para isso, foram testadas as influências da temperatura, vazão de inerte, teor inicial de fluido, reutilização do cascalho, tipo de rocha, tipo de fluido e a presença da agitação mecânica na secagem por micro-ondas; foram feitos testes de cinética de secagem por micro-ondas e feito o mapeamento da secagem no interior do equipamento. Os resultados mostraram que não houve diferença na secagem por micro-ondas para diferentes vazões de inerte e tipo de fluido, porém houve influência da temperatura da secagem, do teor inicial de sal, do teor inicial de fluido e do tipo de rocha. A agitação mecânica aumentou a eficiência de remoção em 17% para um leito de 27 mm de espessura; o aquecimento lento de cascalhos melhoram a eficiência de remoção; cascalhos contaminados que apresentam aspectos físicos iguais apresentam eficiência de remoção semelhantes. O aquecimento de rochas no micro-ondas depende, fortemente, dos teores de óxidos em sua composição. A temperatura de controle do leito deve ser acima do limite superior da faixa de ebulição dos hidrocarbonetos presentes na base do fluido de perfuração. O estudo de mapeamento mostrou que há gradientes de secagem no interior do micro-ondas, além de mostrar o efeito intrusivo de metais no material e efeito das bordas do recipiente. O equipamento apresentou ser tão eficiente quanto outros reportados na literatura, podendo reduzir os teores de n-parafina até abaixo de 1%, em massa. / Mestre em Engenharia Química