Polyphenoloxidase, leaching of potassium and quality of coffee picked at maturation stages

Abstract

Coffee (Coffea arabica L.) grains of catuaí red variety were harvested in the region of Lavras, MG, Brazil, in the green, sugarcane-green, cherry and dry-raisin stages of maturation in quantity of 100 kg of grains per stage. Samples of approximately 5 kg were milled and submitted to physical, physico-chemical, chemical and qualitative analyses. This experiment had the objective of determining the polyphenoloxidase activity, the potassium leaching, the beverage quality and the relationships between the parameters in coffee harvested at four maturation stages. Different behaviors were observed in relation to the contents of these components at the different stages of grain maturation. Coffee harvested in the cherry stage of maturation showed greater polyphenoloxidase activity of K. The grains harvested at the green stage of maturation showed high leaching of K, and low polyphenoloxidase activity, in the dry-raisin and sugarcane-green stages of maturation presented intermediate values for these parameters analyzed. The classifications of the coffees based on the polyphenoloxidase was unacceptable ("riada" and "rio" beverage) for coffees picked green; dry-raisin and sugarcane-green stages of maturation were classified as fine (soft drink and only soft drink) and cherry maturation stage as extra fine (strictly soft beverage). The classification of drink based on the cup test indicated no difference among the samples of the four stages of maturation (hard beverage).