Reni Saath

Activity of some isoenzymatic systems in stored coffee grains.

Considering the worldwide consumption of coffee, it is natural that throughout the history many people have dedicated the research to markers that contribute somehow on gauging its quality. This research aimed to evaluate the biochemical performance of arabica coffee during storage. Coffee in beans (natural) and in parchment (pulped) dried in concrete terrace and in dryer with heated air were packed in jute bags and stored in not controlled environmental conditions. Enzymatic activities of superoxide dismutase, catalase, peroxidase, polyphenoloxidase, esterase and lipoxygenase in coffee grains were evaluated at zero, three, six, nine and twelve months by means of electrophoresis. Independently of the drying method, the activity of isoenzymatic complexes highlighted deteriorative processes in stored grains of coffee. The treatments 60/40o C and 60o C used to reduce the water content imposed a greater stress condition, accelerated metabolism of natural coffee in the storage with decreased activity of defense mechanisms due to latent damage in these grains. Natural coffees are more sensible to high drying temperatures and its quality reduces faster than pulped coffee in the storage.

Perfis proteicos e desempenho fisiológico de sementes de café submetidas a diferentes métodos de processamento e secagem

The objective of this work was to evaluate the protein profiles and physiological performance of coffee seeds subjected to different drying and processing methods. We evaluated processing by dry and wet routes, the drying methods: natural, on the patio, and artificial at 60oC, or at 60oC until 30% of moisture content and 40oC until 11% (wet basis). After processing and drying, the seeds were evaluated as to their physiological performance and subjected to biochemical analyses with electrophoresis of heat‑resistant LEA (late embryogenesis abundant) proteins and of the enzymes superoxide dismutase, catalase, peroxidase, esterase, polyphenol oxidase, isocitrate dehydrogenase, alcohol dehydrogenase, and malate dehydrogenase. The protein profile of coffee seeds is affected by the processing and drying methods. The coffee processed by wet route has higher tolerance to drying - shown by the higher activity of antioxidative enzymes and better physiological performance - than that processed by dry route. The activity of heat‑resistant proteins and antioxidant enzymes is a promising variable for the differentiation of the quality of coffee subjected to different postharvest management.

Microscopia eletrônica de varredura do endosperma de café (Coffea arabica L.) durante o processo de secagem

A manutencao da integridade das membranas celulares, entre outros eventos, e um forte indicativo de que a qualidade do cafe foi preservada na pos-colheita. Objetivou-se neste trabalho, analisar o efeito de diferentes metodos de secagem na manutencao da integridade da parede celular e da membrana plasmatica de cafe natural e cafe despolpado, buscando determinar as condicoes e o momento em que ocorrem as rupturas microscopicas. Os cafes foram submetidos a um periodo de pre-secagem em terreiro. Apos este, uma parcela de cada tipo de cafe foi desidratada no terreiro e, outra, a temperatura de 40oC e 60oC em secadores de camada fixa, monitorando-se a temperatura e o teor de agua ate 11% (bu). Nesse periodo, graos foram aleatoriamente amostrados e fragmentos do endosperma preparados para a microscopia eletronica de varredura, registrando-se diversas eletromicrografias, avaliando-se as alteracoes na membrana plasmatica da celula do endosperma dos graos de cafes em funcao do teor de agua e tempo de secagem. O citoplasma das celulas a 11% (bu) de teor de agua nao foi comprometido na secagem em terreiro e a 40°C; na secagem a 60°C, observou-se comprometimento nas estruturas celulares nos cafes com teor de agua de 20% (bu).