Avaliação do teor e da composição eo óleo essencial de Cymbopogon citratus e Thymys vulgaris submetidos a processos de secagem e armazenamento

• Autor(a) principal: Rocha, Ronicely Pereira da
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/695
• topic: Plantas medicinais; Capim-limão; Tomilho; Componentes químicos; Medicinal plants; Lemon grass; Thyme; Chemical components; CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA

Considering that, nowadays the experiments with drying of medicinal plants were carried out with the drying air temperature constant during whole process, aimed to evaluate in this work a new method of drying the leaves of lemon grass, in order to maximize the quantity and quality of essential oil of this specie and the preservation of this oil after storage. In addition, for the species in question, was evaluated the influence of plant age on the content and chemical composition of essential oil. Also was evaluated the effect of conventional drying (constant temperature) on quality of essential oil of thyme leaves. To achieve these goals were carried out, in a completely randomized design, the following experiments. Lemon Grass: In the first experiment,leaves were harvested at ages of 3, 6, 9, 12 months after planting, and evaluate the content and quality of essential oil in the different harvesting times. In the second, leaves of lemon grass, with 12 months of age, were dried using the new methodology: High Temperature and Short Time (HTST) drying that consisted in applying high temperatures (60, 70, 80, 90, 100 oC) in short periods of time (5, 10 and 15 minutes) at the beginning of drying and after constant temperature (50 oC) to finish the process. The content and composition of essential oils extracted from the specie, after being submitted to drying, were compared with values obtained from drying at 50 oC constant and with the fresh plant (controls). Also, the effects on each variable were analyzed as a function of temperature for each time. In a third experiment, the leaves from the drying tests HTST were stored for one year in packaging, polyethylene inside and kraft paper outside, and compared the values of content and chemical components of essential oil before (year 0) and after storage (year 1). Also was performed the comparison of these variables between treatments and as a function of temperature for each time. Thyme: Thyme leaves were dried using air heated at 30, 40, 50, 60 and 70 ºC to evaluate the quality of essential oil compared with the fresh plant. The experimental data of drying of both species were adjusted twelve mathematical models using simplex method and Quasi-Newton, using the program Statistica ® and determined the effective diffusivity by Fick's law and the activation energy by Arrhenius equation. The extractions of essential oils of the species studied were carried out in Clevenger and CO2 supercritical equipment, respectively, for lemongrass and thyme. The chromatography of both species, were conducted in a gas chromatograph (GC-MS and GC-FID). According to the results obtained, we can conclude that: 1) The mathematical models of the approximation of diffusion and Page were the ones that best fit the experimental data to describe the kinetics of drying the leaves of lemon grass and thyme, respectively; 2) For the drying of lemon grass leaves, the values of effective diffusivity coefficients ranged from 2.01 to 4.91 x 10-11 m2 s-1 for the drying experiments that have suffered previous drying (HTST) and was 3.24 x 10-11 m2 s-1 for the treatment of drying at 50 oC. These values for thyme ranged between 3.69 and 1.19 x 10-12 x 10-10 m2 s-1 for the temperatures studied; 3) The values of activation energy for the diffusion of water in the drying process of lemon grass were 10.87, 15.08 and 16.78 kJ mol-1 for the times of 5, 10 and 15 minutes, respectively. This value for thyme was 77.16 kJ mol-1 under the conditions studied; 4) The age of the plant did not influence statistically the amount of essential oil extracted from leaves of lemon grass, but caused significant alterations in the quality of this oil; 5 ) The essential oil content of the drying treatments HTST was not statistically different from the drying at 50 oC, but for all drying treatments (HTST and 50 oC) the essential oil in content decreased when compared with the fresh plant; 6) To dry lemon grass leaves are recommended the treatments HTST: 60 oC and 70 oC for 15 minutes, 80 oC and 90 oC for 10 minutes and 100 °C for 5 minutes in order to obtain the highest concentration of citral. For drying thyme air temperature indicated was 50 ºC; 7) No change in the content and main chemical components of lemongrass essential, when compared the these variables after the drying process (year 0) and after one year of storage (a year). However, drying at 80 oC for 10 minutes was the one that produced the highest concentration of citral in relation to other treatments HTST drying after a year of storage.