Physical characterization of coffee after roasting and grinding

Abstract

Flowability is an important characteristic of handling process for efficiency and reliability purpose of post-harvest operations, which are governed by the physical properties of the product. Physical properties determination is an important factor for formulation of machinery projects and sizing of post-harvest operations, which may impact considerably on the products quality, influencing directly the operation cost and company profit. Thus, the objective of this work was to evaluate and determinate some physical properties (repose angle, unit and bulk density, porosity and color coordinates, particle size, moisture content, water activity, angle of internal friction and effective angle of internal friction) of coffee, such as to evaluate the influence of different roast and grinding degrees over these properties. Crude grain coffee (Coffea canephora and Coffea arabica), dehulled and dried were used. These were roasted at two levels: medium light and medium-dark brown, which Agtron numbers are, respectively, SCAA#65 and SCAA#45. After roasting process, grains were grinded at three particle sizes (thin, medium and thick). Both particle size and roast degree significantly affected physical properties of coffee. Coffee samples roasted at medium dark level obtained lower values of moisture content, water activity, repose angle, bulk and real density. Coffee samples grinded at level thin presented an increase of angle of internal friction and effective angle of internal friction, repose angle, bulk and real density, porosity and decrease of water activity values.

Keywords

• Physical properties; Post-harvest; Flowability