Microscopia eletrÃnica de varredura do endosperma do cafà (Coffea arabica L.) durante o processo de secagem / Scanning electronic microscopy in the endosperm of coffee (Coffea arabica L.) during the drying process.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

After harvesting the type of processing and drying method used and the storage conditions contribute to the final drinking quality of coffee. The maintenance of the integrity of the cellular membranes, among other events, is a strong indicator that the quality of the coffee was preserved after harvesting. Therefore, this work aimed to analyze the effect of different drying methods in the maintenance of the integrity of the cell walls and plasma membrane of natural and de-pulped coffee in order to determine the conditions and the moment that microscopic ruptures take place. De-pulped and natural coffees were submitted to the drying process under sun light and with heated air. Natural and de-pulped coffees were divided in different parcels under sun light and submitted to a pre-drying period. After this period, a parcel of coffee was mechanically dried and other parcel stayed under sun light to dry completely. The mechanical drying was performed in two dryers of fixed layers with heated air to 40ÂC and 60ÂC until the coffee reach the water content of 11%. For characterization of the drying kinetics, samples were taken every hour and had the water content determined. The temperatures of the mass of coffee were measured every 30 minutes. During drying coffee grains were randomly sampled and fragments of the endosperm were prepared for scanning electronic microscopy using the equipment LEO EVO 40 XVP. For each sample images were generated and registered digitally. In the electromicrographs generated were performed ultra-structural analyses and measurements in the cells, evaluating changes in the plasma membrane as well as variations in the cellular area in function of the water content and period of drying. From the results obtained we concluded that during drying under sun light and at the temperature of 40ÂC, the cytoplasm of the cells of the endosperm of coffee grains de-pulped and natural with 11% of moisture content was intact and the space between the plasma membrane and cell wall was empty. However, during the drying to 60ÂC, it was observed for natural and de-pulped coffees with water content of 20% that the cellular lumen was filled possibly as a consequence of leaching of part of the cellular content of the cytoplasm, indicating the changes in the cellular structures. The variation in the area of the cells of the endosperm of the coffee depends on the type of processing method and the drying conditions used, albeit the phenomenon of cell contraction and expansion differed in intensity and moment of occurrence. Those changes can be related to the changes in plasma membrane integrity. The largest rate of variation of the cytoplasm was observed when the grains were dried the temperature of 60ÂC, in the intermediate phase, with water content of 30% and 20%, where were observed changes in the cellular structure in this phase

ASSUNTO(S)

cafà despolpado integridade celular engenharia agricola rocessing cafà natural processamento integrity of the cellular drying methods natural coffee mÃtodos de secagem de-pulped coffee

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