Evandro de Castro Melo

Evaluation of the chemical composition of Brazilian commercial Cymbopogon citratus (D.C.) stapf samples.

The concentration and the chemical composition of the essential oils obtained from different samples of Cymbopogon citratus were evaluated. Among the 12 samples investigated (11 dried leaf samples and fresh plant leaves), seven presented essential oil concentrations within the threshold established by the Brazilian legislation. The moisture content was also determined and the majority of the samples presented humidity contents near 12%. The GC and GC/MS analyses of the essential oils led to identification of 22 compounds, with neral and geranial as the two major components. The total percentage of these two compounds varied within the investigated sample oils from 40.7% to 75.4%. In addition, a considerable variation in the chemical composition of the analyzed samples was observed. The process of grinding the leaves significantly decreased (by up to 68%) the essential oil content, as well as the percentage of myrcene in the oils.

Análise e descrição matemática da cinética de secagem de folhas de capim-limão

As caracteristicas da secagem de folhas de Cymbopogon citratus (D.C.) Stapf em camada delgada, foram estudadas para a faixa de temperatura de 30-60 oC, utilizando-se modelos semi-teoricos e empiricos. O modelo de Midilli foi o que melhor descreveu as curvas de secagem. Os valores da difusividade efetiva variaram de 4 x 10-12a 3,9 x 10-11 m-2 s-1 para a faixa de temperatura avaliada. Os valores obtidos da difusividade efetiva mostraram uma dependencia de Arrhenius. O valor da energia de ativacao encontrado foi de 63,47 kJ mol- 1.

Modelagem matemática e parâmetros qualitativos da secagem de folhas de capim-limão [Cymbopogon citratus (DC.) Stapf]

The species Cymbopogon citratus, known as lemon grass, is widely used for medicinal purpose and in the pharmaceutical, food, cosmetic and perfumery industries. Due to the need for more specific knowledge of pre-processing management, this work aims to equate and analyze some drying aspects that allow preview the product quality alterations. The leaves from this species were cut at different lengths and dried at different temperatures. Different equations for modeling the drying curves were adjusted to the experimental data. The dried product was also evaluated for color and essential oil content. The results showed that the Modified Page model resulted in the best adjustment for the experimental data. The temperature of 50°C was the best for drying the species leaves, resulting in less essential oil loss and higher green color maintenance.

Cinética del secado de tomillo

Los objetivos del trabajo fueran estudiar la cinetica del secado de tomillo con posterior ajuste de diferentes modelos matematicos a los datos experimentales y determinar los valores de la difusividad efectiva y energia de activacion. Para el desarrollo del experimento de secado fueran utilizadas las temperaturas 30, 40, 50, 60 y 70 oC. El diseno experimental fue de bloques completamente aleatorizados, con tres repeticiones. Para el ajuste de los modelos matematicos a los datos experimentales fue realizado el analisis de regresion no lineal, por el metodo Simplex-Quasi-Newton. Los resultados mostraron que el modelo matematico de Page obtuve un mejor ajuste a los datos experimentales, los valores de los coeficientes de difusividad efectiva variaron entre 3,69 x 10-12 e 1,19 x 10-10 m2 s-1 y el valor de la energia de activacion fue de 77,16 kJ mol-1.

Quality parameters of Cymbopogon citratus leaves during ambient storage.

The effects of storage in different packages on the essential oil content and humidity of Brazilian lemon grass (Cymbopogon citratus) leaves were studied. Lemon grass leaves were dried at 50°C to moisture content of 11% (d.b.) and stored for one year in three different plastic and paper packages. Oil content and its principal compounds were isolated by the hydro-distillation method and analyzed by GC-FID as well as GC-MS every two months. The results showed a reduction in the oil content as well as a decrease in citral and myrcene in the plant for all packages during storage. Water concentration did not significantly vary during the period in the three packages.

Evaluation of Electrical Conductivity as a Quality Parameter of Lemongrass Leaves (Cymbopogon citratus Stapf) Submitted to Drying Process

This study aims to evaluate the quality of lemongrass plants after drying at different speeds (1.0, 1.5, 2.0 m s−1), temperatures (40, 50, 60, and 70°C), and drying air control systems (manual and automatic) using electrical conductivity as a parameter for evaluation. Firstly, we evaluated the time necessary for imbibitions of material in deionized water after drying for different air speeds and control systems. Secondly, the effect of temperature in fresh and dry plants was evaluated, comparing them with contents of essential oils and the quantity of ions leached by the electrical conductivity test. According to the results, the value of liquid diffusion increased with the increase of drying air temperature, and the value of activation energy was 62.84 kJ mol−1. The quality of lemongrass plants evaluated by the electrical conductivity test was inversely proportional to the increase in drying air temperature, and the levels of essential oils were higher in dry plants with lower drying air temperatures. The adaptation of the electrical conductivity methodology to lemongrass plants was effective. A period of 33 h of imbibitions of the material in deionized water was necessary to obtain consistent results from leaching of potassium ions. The electrical conductivity can be used as a quality parameter for drying of medicinal plants.

Remote environmental monitoring and management of data systems.

As instrumentation and measurement system technology develop, the demand for faster and more reliable data transfer increases. At the same time, data collection in field research is becoming more expensive given the necessity of the researcher’s on-site presence. This requires that researchers invest significant amounts of time on the acquisition of data, especially when points of collection are geographically stratified. The utilization of communication networks in instrumentation systems enables remote analysis of data in real-time, allowing researchers to explore more diverse uses for the data. Such systems can be easily utilized by multiple users, regardless of their location. The objective of this project was to develop a system for remote management of data transmission over diverse communication interfaces. This goal was achieved by developing a protocol system that allows remote storage, access, and transmission of data. In this case, the data used was obtained from previously implemented projects. With a standardized method of data storage, collected data takes a consistent form. Databanks created facilitate the inclusion and recuperation of information in an unequivocal format, allowing researchers to integrate the information efficiently in their research projects. Project activities can be easily and reliably managed, making possible a more organized execution of field studies and eliminating problematic manual registers.

Resistance to forced airflow through layers of composting organic material

The objective of this study was to adjust equations to estimate the static pressure gradient of airflow through layers of organic residues submitted to two stages of biochemical degradation, and to evaluate the static pressure drop of airflow thought the material layer. Measurements of static pressure drop in the layers of sugarcane bagasse and coffee husks mixed with poultry litter on day 0 and after 30 days of composting were performed using a prototype with specific airflow rates ranging from 0.02 to 0.13 m(3) s(-1) m(-2). Static pressure gradient and specific airflow rate data were properly fit to the Shedd, Hukill & Ives and Ergun models, which may be used to predict the static pressure gradient of air to be blown through the organic residue layers. However, the Shedd model was that which best represented the phenomenon studied. The static pressure drop of airflow increased as a power of the material layer thickness and showed tendency for decreasing with the biochemical degradation time of the organic material.

Avaliação das curvas de secagem de guaco (Mikania glomerata Spreng.) em secador de bandejas

This work aimed to evaluate different mathematical models to determine the curve of the drying of Mikania glomerata Spreng. . For the conduction of the experiment, a drier with forced ventilation was used, with 4 trays, using liquefied petroleum gas as heating source. Six drying treatments were carried out, that is, with hot air at 40, 50, 60, 70 and 80oC, as well as drying with air at room temperature. For all the treatments, the drying air speed, through the mass of plants, were kept at, approximately, 0.5 m s-1. For the adjustment of the mathematical models to the experimental data, nonlinear regression analysis was performed through the Quasi-Newton method, using the computational program STATISTICA 6.0®, and the values of the parameters of the models were estimated in function of the temperature of the drying air. But only the model considered by Midilli et al. presented satisfactory adjustment to describe the process of drying Mikania glomerata Spreng., regardless of the temperature of the drying air, while the model of diffusion approximation was suitable for room temperature and hot air at 60oC.

Mathematical modeling of the drying kinetics of the leaves of lemon grass (Cymbopogon citratus Stapf) and its effects on quality

espanolEl objetivo de este estudio fue evaluar el secado de la planta de hierba de limon (Cymbopogon citratus Stapf) a diferentes temperaturas de aire (40 °C, 50 °C, 60 °C y 70 °C) para ajustar los datos experimentales obtenidos con diferentes modelos matematicos y evaluar la calidad de la planta despues del secado. Un diseno completamente al azar (DCA) se utilizo con tres repeticiones para cada velocidad de secado y la temperatura del aire de secado. El contenido de aceite esencial extraido de la planta seca en 0,8 m s-1 y 1,3 m s-1 con sistema de control manual no se vio afectado por el proceso de secado, la temperatura del aire de secado tuvo una influencia negativa sobre la reduccion de los niveles del aceite esencial de la planta, el secado con control automatico de disminucion del contenido de aceite esencial para todas las velocidades estudiado en comparacion la planta fresca; incrementa el valor de la temperatura del aire de secado ha reducido significativamente el equipo de secado, el modelo matematico de Dos Terminos es adecuada para describir el proceso de secado de la planta de hierba de limon (Cymbopogon citratus Stapf), los valores de difusion aumento con el aumento de temperatura del aire de secado, mientras que el valor de la energia de activacion es 62.84 kJ mol-1. EnglishThe aim of this study was evaluate the drying of the lemon grass plant (Cymbopogon citratus Stapf) at different air temperatures (40 °C, 50 °C, 60 °C and 70 °C) to adjust the experimental data obtained with different mathematical models and assess the quality of the plant after drying. A completely randomized design (CRD) was used with three drying replications for each speed and temperature of the drying air. The essential oil content extracted from the dried plant at 0.8 m s-1 and 1.3 m s-1 with manual control system was not affected by the drying process; the temperature of the drying air had a negative influence on the levels of the essential oil of the plant; drying with automatic control decreased the essential oil content for all velocities studied compared to the fresh plant; increments in the temperature of the drying air significantly reduced drying time. The mathematical model of Two Terms is adequate to describe the drying process of lemon grass plant (Cymbopogon citratus Stapf); diffusion values increased with increasing temperature of the drying air, while the value of activation energy was 62.84 kJ mol-1.